KEY CONCEPTS AND PROCESS SKILLS

Transcription

1 Storing Waste to 2 50-minute sessions ACTIVITY OVERVIEW TA L K I N G I T O V E R The issue of nuclear waste disposal at Yucca Mountain, Nevada is used to introduce volcanoes and earthquakes to students. Student groups first read background information on nuclear waste. Then, they evaluate eight statements in order to determine whether each statement provides evidence that either supports or does not support Yucca Mountain as a storage site. Each student sorts the relevant evidence using a discussion web and then decides whether or not to recommend storing nuclear waste at Yucca Mountain. The concept of risk analysis is discussed. KEY CONCEPTS AND PROCESS SKILLS (with correlation to NSE 5 8 Content Standards) 1. Making decisions about complex issues invovlves trade-offs (i.e. giving up one thing in favor of another). One such issue is how to dispose of nuclear waste. (Perspectives 4, 5) 2. Identifying and evaluating relevant evidence is essential for thoughtful inquiry and good decison making (Inquiry 1, 2; History 2) 3. Risk analysis considers the type of risk, the frequency of the consequences, and the severity of the consequences. (Perspectives 4) KEY VOCABULARY active dormant extinct evidence nuclear waste risk trade-offs D-1

2 Activity 36 Storing Waste MATERIALS AND ADVANCE PREPARATION For the teacher 1 Scoring Guide: EVIDENCE AND TRADE-OFFS (ET) For each student 1 Student Sheet 36.1, Analyzing Evidence: Yucca Mountain 1 Student Sheet 36.2, Discussion Web: Yucca Mountain 1 Scoring Guide: EVIDENCE AND TRADE-OFFS (ET) (optional) *Not supplied in kit Masters for Scoring Guides can be found in Teacher Resources III: Assessment. TEACHING SUMMARY Getting Started 1. Introduce the issue of nuclear waste disposal at Yucca Mountain, Nevada. Doing the Activity 2. (LITERACY) Students groups work together to read statements and identify relevant evidence. Follow-Up 3. (ET ASSESSMENT) Discuss whether Yucca Mountain meets the general criteria for a good storage site. 4. Discuss the concept of risk analysis.if this works) BACKGROUND INFORMATION Radioactivity Radiation is energy released in the form of waves or particles (such as alpha, beta, and gamma radiation). Elements that release such energy are described as radioactive, and there are over 60 naturally-occurring radioactive elements. As a result, there are many natural sources of low levels of radiation, including radon gas, soil, and even outer space. Exposure to high levels of radiation or exposure to lower levels over long periods of time can increase the risk of cancer. In the U.S., most people receive an average annualbackground radiation dose of about 360 millirem (mrem) from a combination of both natural and manufactured sources. Radon gas is the primary natural source of natural radiation, and it accounts for about 200 mrem. Medical x-rays, the primary manufactured source, accounts for another 40 mrem. (A typical chest x-ray results in a 10 mrem dose.) D-2

3 Storing Waste Activity 36 Waste from Nuclear Power Plants Nuclear energy is the heat energy produced from the splitting of uranium atoms (known as fission) in a nuclear reactor. A nuclear power plant uses this heat to produce electricity. Nuclear power plants produce two types of radioactive waste: high-level and low-level. Nearly all high-level waste is from used fuel rods. Low-level waste includes tools and equipment that may contain small amounts of radioactive material. High-level waste is handled remotely and stored in steel-lined, concrete pools filled with water or in large steel-lined, concrete containers. Low-level waste may be stored or shipped to a disposal facility. The U.S. Nuclear Regulatory Commission (NRC) has established a dose limit to the general public from nuclear industry activities to 0.1 rem (100 mrem). This limit assumes that an individual must receive a whole-body dose of about 25,000 mrem before there is a significant increase in the risk of serious human health effects, and a dose of about 500,000 mrem before probable death as a result of radiological health effects. Government regulations also require that NRC licensees and U.S. Department of Energy contractors follow the radiation control concept known as as low as reasonably achievable. Yucca Mountain At the time of this book s writing in 2012, the U.S. Department of Energy had withdrawn its application for a license to build the Yucca Mountain long-term nuclear waste site. The decision was controversial, and led to lawsuits by South Carolina, Washington, and other entities. They maintained that the withdrawal of the application violates nuclear waste laws. Although the future of the Yucca Mountain site is uncertain, it is likely that scientific studies and political lessons learned will play a role in future recommendations for storing nuclear waste. REFERENCES Blue Ribbon Commission on America s Nuclear Future. (January 2012). Report to the Secretary of Energy. Retrieved January 30, 2012 from brc.gov Halstead, Robert J. (2000). Radiation Exposures From Spent Nuclear Fuel and High-Level Nuclear Waste Transportation to a Geologic Repository or Interim Storage Facility in Nevada (paper). State of Nevada Nuclear Waste Project Office, Carson City, NV. Available online at Nevada Seismological Laboratory. (March 14, 2003). FAQs on Seismicity Near Yucca Mountain (website). University of Nevada, Reno, NV. Retrieved August 2004 from Office of Civilian Radioactive Waste Management. Yucca Mountain Project (website). U.S. Department of Energy, Office of Respository Development, Las Vegas, NV. Retrieved August 2004 from Special Metals Corporation (March 2004). Inconel Alloy 22. (Publication number SMC-049) Special Metals Corporation, Huntington, WV. U.S. Geological Survey. (June 27, 1005) Earthquake Hazards Program: The Top Earthquake States Earthquakes, magnitude 3.5 and greater, (website). U.S. Department of Interior, Retrieved October 2005 from neic.usgs.gov/neis/states/top_states.html U.S. Nuclear Regulatory Commission. (2010). Motion to withdraw from Yucca Mountain application. U. S. Department of Energy. Retrieved January 4, 2012 from D-3

4 Activity 36 Storing Waste TEACHING SUGGESTIONS GETTING STARTED 1. Introduce the issue of nuclear waste disposal at Yucca Mountain, Nevada. Turn the lights on and off and ask, Where does the electricity that runs these lights come from? Explain that most electricity is generated in power plants. Power plants need energy to produce electricity, and that energy can be generated in different ways, such as the burning of fossil fuels like coal or from the heat released during nuclear reactions. Most methods have trade-offs. In the case of nuclear reactors, one of the trade-offs is the production of nuclear waste. This symbol represents an opportunity to elicit students ideas so the subsequent instruction can take into account students current understandings and experiences. Sometimes students ideas will reflect partial understandings and relevant everyday experiences that you can build on. In other cases, their ideas are inconsistent with scientific explanations, although sometimes consistent with everyday observations. The Teacher s Edition will provide additional information when this icon appears. For more information on identifying and addressing students ideas see Eliciting and Addressing Students Ideas in Teacher Resources II: Diverse Learners. Distinguish between the hazards related to nuclear reactors and nuclear waste. In the event of a meltdown of core fuel, a nuclear reactor can explode, rapidly releasing radioactive materials. Nuclear waste does not present a risk of explosion, but does pose a risk of release of radioactive material if the containers of waste were to leak. Stress that the risk from nuclear waste is not explosion, but the health effects of radioactive materials should they be released into the environment and be inhaled or ingested in food or drinking water. Summarize or have students read the student introduction and Challenge. Ask, Imagine that you planned to store nuclear waste somewhere in the United States. What do you think you would look for in a site? At this point, students may begin asking questions about nuclear waste. If they do, inform them that they will find out more during the activity. Encourage students to focus on the criteria, such as population density and the likelihood of natural hazards, that they would consider important in siting a nuclear waste storage facility. DOING THE ACTIVIT Y 2. (LITERACY) Students groups work together to read statements and identify relevant evidence. Have students work on the Procedure in groups of four. They should begin by reading the background information on nuclear waste found in the Student Book. Teacher s Note: After reading the background information, students may have additional questions about nuclear waste. As you respond, keep the focus on the storage of nuclear waste that already exists. The activity is not about the trade-offs of nuclear power plants as an energy source, the dangers of radiation, etc. This activity is intended to initiate students thinking about the earth and to begin to introduce them to the factors associated with the risk of earthquakes and volcanoes. (To have a meaningful discussion on topics such as the role of nuclear power plants as an energy source, it would be important to provide information about the trade-offs of other energy sources such as coal mining, the primary source of electrical energy in the U.S.) Hand out Student Sheet 36.1, Analyzing Evidence: Yucca Mountain. Each group should read each of the statements on Student Sheet 36.1 aloud and determine whether a statement provides evidence for or against storing nuclear waste at Yucca Mountain. Introduce or review the differences among extinct, dormant, and active volcanoes. Note that the terms are not exact, and the use of each term can vary among scientists. In general, volcanoes that are not expected to erupt ever again are considered extinct, while those that have not erupted for at D-4

5 Storing Waste Activity 36 least 10,000 years but may erupt again are considered dormant. A volcano is considered active if it is currently erupting, is showing signs (such as significant new gas emissions) that it is likely to erupt in the near future, or has erupted at any time during recorded history. Students are likely to have different ideas based on their interpretation of some of the statements. For example, one group may identify the Statement 5 (referring to a large earthquake that occurred in the area 50,000 years ago) as evidence for storing waste at Yucca Mountain since the most recent large earthquake occurred thousands of years ago. Another group may be concerned about the possibility of another large earthquake occurring in the area and identify the statement as evidence against storing waste at Yucca Mountain. After discussing the evidence provided by the statements, students are expected to sort the relevant evidence using a literacy strategy known as a discussion web. Students use the web found on Student Sheet 36.2, Discussion Web: Yucca Mountain, to sort evidence in order to make a decision. Depending on your student population, students can work individually, in pairs, or in groups to complete this step. Explain to students that they should not copy the statements directly, but should explain how the statement provides evidence for or against storing the waste at Yucca Mountain. Again, the individual interpretation that students make of the statements will determine what they write. Possible responses are shown on the next page. FOLLOW-UP 3. (ET ASSESSMENT) Discuss whether Yucca Mountain meets the general criteria for a good storage site. Begin a class discussion by reminding students what they initially considered important in a nuclear waste storage site. Ask, In what ways did Yucca Mountain meet or not meet your original criteria for a nuclear waste storage site? Encourage students to share both positive and negative aspects of this particular site, and to identify the trade-offs. For example, the fact that there are few people in the area is generally considered an advantage. But because the site is in a low-density region, it is far from many nuclear power plants and the waste must be transported long distances to be stored there. Use Analysis Question 1 to elicit additional student ideas about the issue. You may want to review student responses to Student Sheet 36.2 by having one student group that had more statements under the Yes column and one student group that had more statements under the No column each explain how they sorted the statements and why. Note that Question 1 can be assessed using the EVI- DENCE AND TRADE-OFFS (ET) Scoring Guide. You may find it helpful to review the expectations for a Level 3 response prior to assigning the question. If you anticipate that your students may have difficulty answering this question, you may want to use or construct a writing frame to guide their writing (see the Literacy section of Teacher Resources II: Diverse Learners). 4. Discuss the concept of risk analysis. Use the questions as an opportunity to discuss the concept of risk analysis. While storing nuclear waste nearby increases the risk of radiation exposure, it does not mean that it is certain to happen. Determining the level of risk involves identifying how likely the event is to happen. For example, each year more children under the age of 14 are injured from playing sports than from motor vehicle accidents. Using this data, you could conclude that the risk of injury from sports is greater than that from cars. You may want to use this example to discuss how people s perception of risk influences their decision-making (perception of risk vs. probability). When making a decision, people often evaluate the likelihood that something will happen, as well as the trade-offs involved. For example, even though participating in sports increases the risk of injury, most people determine that the level of risk is worth the pleasure of participating. Most people prefer to have low levels of risk for actions in which they may D-5

6 Activity 36 Storing Waste Possible Responses to Student Sheet 36.2 Statements (for teacher reference) Evidence or Opinion? Should nuclear waste be stored at Yucca Mountain? Yes No 1. Yucca Mountain receives about 19 cm (7.5 inches) of rain per year. The average rainfall per year for the United States is 87.6 cm (34.5 inches). Yucca Mountain is a relatively dry area, so there is a lower risk of nuclear waste containers being damaged by water. 2. To reach Yucca Mountain, nuclear waste would be shipped from or through 43 states. Transporting waste through so many states increases the possibility of an accident in a densely-populated area. 3. Evidence suggests that the last time a very destructive earthquake (6.5 on the Richter scale) occurred in the Yucca Mountain area was about 50,000 years ago. 4. Las Vegas, a city of almost 1/2 million people, is located 161 km (100 mi) from Yucca Mountain. 5. No one lives in the Yucca Mountain area. Yucca Mountain is intended to safely store nuclear waste for 10,000 years; it is unlikely that another large earthquake will occur during that period since one has not occurred for 50,000 years. In case of a severe accident, Las Vegas may not be affected since it is farther than the anticipated contamination zone. No one lives in the immediate vicinity, and thus the area would be safer in case of an accident. Some nuclear waste can be dangerous for 250,000 years. It is possible that another large earthquake could occur within that time period and result in an accident. Las Vegas is a large city that could become contaminated if accidentally released radiation was spread by air or water. 6. There is significant opposition to the site among citizens of Nevada. People who live nearby are against the site. 7. In the U.S., Nevada has the fourth highest number of earthquakes per year (after Alaska, California, and Hawaii). Yucca Mountain is in Nevada, an area of frequent earthquakes. Earthquakes could result in damage to containers or to the storage site, and result in the accidental release of radiation. 8. Yucca Mountain was formed from the eruptions of a volcano that is now extinct. There are seven dormant volcanoes within 43 km (27 mi) of Yucca Mountain. The risk of volcanoes causing an accident is low, since the volcano that formed Yucca Mountain is extinct and the nearby volcanoes are dormant. The risk of volcanoes causing an accident is high, since this is an area of past volcanic activity and there are nearby volcanoes that have the potential to erupt. 9. Nye County, where Yucca Mountain is located, supports the Yucca Mountain site. People in the county are for the site. 10. One reason for considering Yucca Mountain is that the earth material in this region tends to absorb contaminants. This might help to prevent waste from spreading in the event of leakage from the waste containers. The earth at Yucca Mountain might prevent people from being exposed to radiation. D-6

7 Storing Waste Activity 36 have little control or perceive little benefit. The storage of nuclear waste is such an issue. A low-probability event with high-stakes consequences (such as an earthquake, tsunami, or accidental exposure to high levels of radiation) may be perceived to carry more risk than a higher-probability event with high-stakes consequences (such as a severe car accident), even if there is data to the contrary. Ask, Imagine that you live in Las Vegas, Nevada. Would you consider Yucca Mountain a good site for storing nuclear waste? Why or why not? Encourage students to consider how evaluating risk may not only depend on relevant evidence, but also on how much emphasis is placed on pieces of evidence, and on the perspective of the individual. SUGGESTED ANSWERS TO QUESTIONS 1. What other information would you like to have before you make a decision about a proposed long-term nuclear waste site, such as Yucca Mountain? Be sure to explain how this information would be helpful. Students are likely to have many questions. Encourage students to make a list of their questions and identify those that will be answered in the unit, such as the ones listed below. How likely are large earthquakes and/or volcanic eruptions at the Yucca Mountain site? Can the waste be buried very deep to avoid it being affected by these type of hazards? What is likely to happen to this area in the future? You may also wish to provide class time for students to use the links provided on the SEPUP website to gather more information. Regardless of whether you gather additional information or not, some students may insist that they still need more information before making a decision about the issue. Be sure to remind students that people usually have to make decisions based the available information, and that students are expected to do the same in this activity. Explain that it is possible that they may change their ideas in the future. 2. (ET ASSESSMENT) Do you think that one or two sites deep in the ground would be better than the current situation? Explain by a. stating your decision. b. supporting your decision with as many pieces of evidence as you can. c. discussing the trade-offs of your decision. Level 3 Response I think deep storage would be better than the current situation. Right now, waste is at the surface at over 100 nuclear power plants. This waste might leak and get into the air or water. If there were an accident at a site, it could be bad. Burying the waste deep underground and in a remote area would keep it away from people. And one or two sites would be easier to control. One trade-off is that the waste would have to be moved long distances. And people in the area might fight a site that holds so much of the country s waste. 3. What role do you think each of the following should play in the selection of a long-term nuclear waste site? a. Scientific evidence Students might suggest that scientific evidence should play a role in determining sites that might be suitable, based on the weather, type of land, risk of leakage of waste, and other risks, such as earthquakes. b. Social or political concerns Many will think that local concerns about the site should play a major role, while others might think that scientific reasons should trump local concerns. Accept all answers, but encourage students to explain their thinking. Based on students answers to this question, have a class discussion on the complexity of identifying and developing one or a few suitable sites. D-7

8 Activity 36 Storing Waste 4. Reflection: Would you agree to have nuclear waste stored near where you live? Why or why not? Student responses will vary. Generally, students are unlikely to want to have nuclear waste stored near where they live because of the increased risk to human health and safety. This attitude is often called NIMBY, or not in my backyard. D-8

9 Name Date Analyzing Evidence: Yucca Mountain Statements Evidence or Opinion? For Against 1. Yucca Mountain receives about 19 cm (7.5 inches) of rain per year. The average rainfall per year for the United States is 87.6 cm (34.5 inches). 2. To reach Yucca Mountain, nuclear waste would be shipped from or through 43 states. 3. Evidence suggests that the last time a very destructive earthquake (6.5 on the Richter scale) occurred in the Yucca Mountain area was about 50,000 years ago. 4. Las Vegas, a city of almost 1/2 million people, is located 161 km (100 mi) from Yucca Mountain. 5. No one lives in the Yucca Mountain area. 6. There is significant opposition to the site among citizens of Nevada. 7. In the U.S., Nevada has the fourth highest number of earthquakes per year (after Alaska, California, and Hawaii) The Regents of the University of California 8. Yucca Mountain was formed from the eruptions of a volcano that is now extinct. There are seven dormant volcanoes within 43 km (27 mi) of Yucca Mountain. 9. Nye County, where Yucca Mountain is located, supports the Yucca Mountain site. 10. One reason for considering Yucca Mountain is that the earth material in this region tends to absorb contaminants. This might help to prevent waste from spreading inthe event of leakage from the waste containers. Issues and Earth Science Student Sheet 36.1 D-9

10 Name Date Discussion Web: Yucca Mountain YES Should nuclear waste NO be stored at Yucca Mountain? 2012 The Regents of the University of California Issues and Earth Science Student Sheet 36.2 D-11

11 Volcanic Landforms to 1 50-minute session ACTIVITY OVERVIEW M O D E L I N G Students consider the constructive nature of volcanoes as they model the effects of two different kinds of volcanic eruptions. Students then apply what they have learned about volcanoes to the nuclear waste storage scenario. KEY CONCEPTS AND PROCESS SKILLS (with correlation to NSE 5 8 Content Standards) 1. Creating models is one way to understand and communicate scientific information. (Inquiry: 1) 2. Volcanoes can be a constructive force that results in the formation of new landforms, such as mountains. Differences in volcanic eruptions result in the different shapes of volcanic mountains. (EarthSci: 1) KEY VOCABULARY landform magma model D-13

12 Activity 37 Volcanic Landforms MATERIALS AND ADVANCE PREPARATION For the class 1 sample of basalt rock 1 sample of pumice rock For each group of four students 1 vial of baking soda 1 60-mL bottle of less gassy magma (red), containing food coloring, vinegar, and guar gum 1 60-mL bottle of more gassy magma (colorless), containing vinegar 1 cup of water 1 plastic volcano model with base 1 clear, colorless plastic tube 1 rubber stopper 1 white plastic scoop 1 30-mL graduated cup * paper towels and/or a sponge * meter sticks (optional) For each student * 1 pair of safety goggles 1 Literacy Student Sheet 1, Keeping a Science Notebook (optional) *Not supplied in kit If you prefer not to provide students with the bottles of magma, you (or a student assistant) can dispense the appropriate amount to each group as needed. The master for Literacy Student Sheet 1, Keeping a Science Notebook, can be found in the Literacy section of Teacher Resources II: Diverse Learners. SAFETY Both types of magma contain dilute acid (vinegar, also known as acetic acid). Students should wear safety goggles, avoid direct contact with skin and eyes, and wash their hands after completing the activity. D-14

13 Volcanic Landforms Activity 37 TEACHING SUMMARY Getting Started 1. Introduce the purpose of scientific modeling in this activity. Doing the Activity 2. (LITERACY) Students model eruptions of less gassy and more gassy magma. Follow-Up 3. Discuss the strengths and weaknesses of the volcano model.if this works) BACKGROUND INFORMATION Volcanoes Molten rock below the surface of the earth is known as magma. Temperatures in the earth's upper mantle are high enough to melt rocks with the lowest melting temperatures into small blobs of magma. These blobs collect, rise through fractures in the earth, and sometimes re-collect in larger pockets a few miles beneath the earth s surface. As pressure in these pockets builds, magma forces its way upward and may eventually break though the earth s crust, resulting in a volcanic eruption. The accumulation of rock formed from the cooling magma around a vent at the surface of the earth can form a conical landform known as a volcano. Magma is primarily a liquid composed of oxygen, silicon, aluminum, iron, magnesium, calcium, sodium, potassium, titanium, and manganese. It often contains crystals, fragments of surrounding (unmelted) rocks, and dissolved gases. After its eruption onto the earth s surface, magma is called lava. Lava is bright red when it pours out of a vent but soon changes to dark red, gray or black as it cools and solidifies. Hotter, less gassy lava containing abundant iron and magnesium is fluid and flows more quickly, while cooler, more gassy lava, higher in silicon, sodium, and potassium, is more viscous and flows more slowly. All magmas contain dissolved gases. As these gases rise to the surface to erupt, the pressure is reduced either quietly or explosively. If the lava is a thin fluid, the gases may escape easily. But if the lava is thick and highly viscous, the gases will not move freely but will build up tremendous pressure, and ultimately escape with explosive violence. Gases in lava may be compared with the gas in a bottle of a carbonated soft drink. If you put your thumb over the top of the bottle and shake it vigorously, the gas separates from the drink and forms bubbles. When you remove your thumb abruptly, there is a miniature explosion of gas and liquid. The gases in lava behave in somewhat the same way. Their sudden expansion causes the violent explosions that release large pieces of solid rock as well as lava, dust, and ashes. REFERENCES Tilling, Robert I. (1997). Volcanoes. Washington, D.C.: U.S. Geological Survey. D-15

14 Activity 37 Volcanic Landforms TEACHING SUGGESTIONS GETTING STARTED 1. Introduce the purpose of scientific modeling in this activity. Explain that scientists use models simplified representations of reality to examine aspects of the natural world. Depending on the quality and purpose of the model, models can be used to explain and predict natural processes. There are many types of scientific models, including physical models, mathematical models, and computer models. In this activity, students will use a physical model to investigate volcanic eruptions. Ask students whether they agree or disagree with the following statement: All volcanic eruptions are the same. If they agree, ask them to explain the aspects of volcanic eruptions that are the same. If they disagree, ask them to explain the aspects of volcanic eruptions that differ. Then, have students read the introduction and Challenge. Highlight that the force of an eruption is affected by the amount of gas in the magma. In this activity, students will model how the differing amounts of gas in magma can affect an eruption. DOING THE ACTIVIT Y 2. (LITERACY) Students model eruptions of both less gassy and more gassy magma. Review how to set up the pieces of the volcano model. Be sure to demonstrate Procedure Steps 12 and 13 doing these steps quickly and correctly is more likely to result in a successful eruption. Encourage students to practice those steps prior to the use of any of the chemicals. Note that students are expected to keep a science notebook throughout this course, and are expected to record their observations for this activity in their science notebook. If necessary, review Literacy Student Sheet 1, Keeping a Science Notebook, before beginning the activity. Distribute the materials and have students complete the Procedure. Emphasize that careful measurements are important in conducting the activity. If students are having difficult with producing an eruption in Procedure Part B, it may be that they are using too much baking soda. Too much baking soda on the stopper can result in the reaction occurring before the students have had a chance to turn the model right-side up and place it on a table. You may also want to have students use meter sticks to measure the height of the exploding volcano top (rubber stopper) when modeling the more gassy magma. After students have completed their trials, pass around a sample of basalt and a sample of pumice. Both are igneous rocks (a concept that was introduced in Unit B, Rocks and Minerals ). Basalt is fairly dense compared to pumice, because pumice often contains spaces where gas was once trapped inside it. In response to Procedure Step 18, students are apt to predict that basalt is more likely to have formed from (a) less gassy magma and pumice is more likely to have formed from (b) more gassy magma. Sample Response to Table 1, Observing Eruptions Type of Eruption Trial 1 Trial 2 Less gassy magma Red magma slowly oozed out of the top of the volcano and ran smoothly down the sides Red magma slowly oozed out of the top of the volcano and ran smoothly down the sides More gassy magma Rubber stopper popped off Nothing happened D-16

15 Volcanic Landforms Activity 37 FOLLOW-UP 3. Discuss the strengths and weaknesses of the volcano model. Use Questions 1 and 2 to compare the two different eruptions. Ask, What do you think the rubber stopper represented? Students may imagine that the rubber stopper formed the top of a volcano and that the large amount of pressure caused it to completely blow off. This sometimes happens in the case of extremely violent volcanic eruptions. Inform the class that once magma has erupted onto the earth s surface, it is called lava. More gassy magma tends to result in lava that flows less smoothly; this type of magma causes greater pressure to build up within a volcano and results in more explosive eruptions. Use Question 3 to emphasize that, while people often consider volcanoes destructive, they can be constructive forces that result in the formation of new landforms such as mountains or islands (such as the Hawaiian islands). Most Americans considered Mount St. Helens, Washington, simply a mountain (and not a volcano) until it erupted in Students will have an opportunity to see video footage of this eruption in Activity 42, The Theory of Plate Tectonics. Use Question 4 to discuss the strengths and weaknesses of this volcano model. Ask, What caused the more gassy magma to explode so violently? The chemical reaction between the baking soda and vinegar resulted in the formation of a gas. Because the vial was stoppered, the pressure inside the vial increased as more gas was produced. When the pressure was high enough, it caused the rubber stopper to pop off. Emphasize that while volcanic eruptions are a result of pressure building up underground, the pressure is not a result of chemical reactions, as in the model. This is one limitation of the model: it uses chemical reactions to model the buildup of pressure. SUGGESTED ANSWERS TO QUESTIONS 1. a. Describe the similarities and differences between the eruptions of less gassy and more gassy magma. In both types of eruptions, a chemical reaction resulted in a volcanic eruption. Both eruptions caused magma and gases from inside the volcano model to be released. The eruption of the less gassy magma released a red, bubbly lava. The eruption of the more gassy magma released a gas. With the less gassy magma, the eruption was gentle and the lava flowed smoothly, running along the sides of the volcano model. The more gassy magma caused a more explosive eruption that sometimes resulted in the rubber stopper popping off. b. Which type of magma produced a more explosive eruption? In general, the more gassy magma produced a more explosive eruption. 2. Over time, there have been both very explosive and less explosive eruptions in the Yucca Mountain area. Which type(s) of volcanic rock might you find there? Explain your reasoning. You might find both basalt and pumice. The basalt might be there from a less explosive eruption of less gassy magma, and the pumice might be there from a more explosive eruption of more gassy magma. 3. Imagine a volcano erupting many times over a period of years. Which of the following landforms is most likely a result of volcanic eruptions: a valley, a mountain, or a canyon? Explain. A mountain. As volcanoes erupt, magma from deep in the earth is brought to the surface. As it cools, it forms new rocks. Over time, these rocks build up to form a mountain. (When the top of a volcanic mountain is destroyed during an explosion, it may form a crater that collects water over time, forming a lake such as Crater Lake in Oregon.) D-17

16 Activity 37 Volcanic Landforms 4. What were the strengths and weaknesses of the volcano model? Hint: Think about ways in which the model did or did not represent real volcanic eruptions. The model was strong in simulating certain aspects of a volcano, such as underground magma and a resulting eruption. The volcano model also modeled two different types of eruptions: a gentle eruption of less gassy magma and a more violent eruption of more gassy magma. The variation among different trials was an accurate representation of variation among eruptions of different volcanoes. One important weakness is that volcanoes erupt as a result of pressure, not as a result of chemical reactions (as in the model). Even with more gentle eruptions, such as the one modeled in Procedure Part A, the eruption is a result of the build up of pressure. In some cases, this pressure is released slowly, resulting in a less explosive eruption. In addition, the shape of the volcano model represented a single volcano shape (with a single vent), which did not change as a result of the eruptions or the subsequent lava flow. D-18

17 Beneath the Earth s Surface 40- to minute sessions ACTIVITY OVERVIEW 38 R E A D I N G Students describe how deep they think nuclear waste should be buried and what they would observe if they could travel to the center of the earth. Students then read about volcanoes and the interior of the earth. They use information about the layers of the earth to construct a scaled, labeled diagram of the earth s interior. Then, they compare this diagram with the one they made prior to the reading. KEY CONCEPTS AND PROCESS SKILLS (with correlation to NSE 5 8 Content Standards) 1. Volcanoes can be a constructive force that results in the formation of new landforms, such as mountains. Differences in volcanic eruptions result in the different shapes of volcanic mountains. (EarthSci: 1) 2. The earth is made of up different layers (crust, mantle, outer core, inner core). Each of these layers has distinct properties. (Earth Sci: 1) 3. The crust and the solid upper layer of the mantle are known as the lithosphere. (Earth Sci: 1) 4. (MATHEMATICS) A scale can be a useful tool for creating a realistic model of the earth. KEY VOCABULARY core (inner core, outer core) crust dormant extinct lava lithosphere magma mantle scale cinder cone (optional) composite volcano (optional) cross-section (optional) shield volcano (optional) volcanologist (optional) Note: May also be spelled as vulcanologist. D-19

18 Activity 38 Beneath the Earth s Surface MATERIALS AND ADVANCE PREPARATION For the teacher 1 color transparency, Layers of the Earth 1 Scoring Guide: UNDERSTANDING CONCEPTS (UC) * 1 overhead projector * 1 apple (optional) * 1 paring knife (optional) * 1 red marker (optional) For each pair of students * 1 calculator colored pencils (optional) For each student 1 Student Sheet 38.1, Talking Drawing 1: Beneath the Earth s Surface 1 Student Sheet 38.2, Talking Drawing 2: Beneath the Earth s Surface (Version 38.2a or 38.2b) 1 metric ruler * 1 compass (optional) 1 Scoring Guide: UNDERSTANDING CONCEPTS (UC) (optional) *Not supplied in kit There are two versions of Student Sheet 38.2, Talking Drawing 2: Beneath the Earth s Surface. Student Sheet 38.2a is slightly easier, since it provides concentric circles for students to fill in (and it does not require a compass). Student Sheet 38.2b is slightly more difficult, as students are expected to use a ruler and a compass to draw the layers to scale. Decide which version you plan to use prior to making copies. Masters for Scoring Guides may be found in Teacher Resources III: Assessment. TEACHING SUMMARY Getting Started 1. (LITERACY) Students illustrate their preconceptions of the earth s size and structure. Doing the Activity 2. (LITERACY) Students read about the earth s structure. Follow-Up 3. (MATHEMATICS) Students draw and label a scaled diagram of the earth s structure. 4. (UC ASSESSMENT) Students compare their initial drawings to their scaled diagrams. D-20

19 Beneath the Earth s Surface Activity 38 TEACHING SUGGESTIONS GETTING STARTED 1. (LITERACY) Students illustrate their preconceptions of the earth s size and structure. Remind students that scientists agree that the safest way to store nuclear waste is to store it underground. Inform students that they are going to think about how deep they think that the waste should be stored. First, they need to reflect on what they think about the inside of the earth. Ask students to close their eyes and think about the following: Imagine taking a glass elevator to the center of the earth. What would you see? Student Sheet 38.1, Talking Drawing 1: Beneath the Earth s Surface, is a literacy strategy that encourages students to reflect on their current understanding. Distribute Student Sheet 38.1 and explain that this sheet is another type of model a conceptual model. The large circle with the dot at its center is intended to represent a physical object: the earth. Explain that students should draw what they think the earth is like as a cross-section of the earth s radius. You can illustrate the concept of a cross-section by creating yet another model: cut an apple in half down the middle and use a marker to draw a red line from the outer edge to the center. You can also refer to the drawing found in the introduction to the activity in the Student Book. You may also want to refer to other common items, such as a hard-boiled egg, an orange, or a watermelon, as models. Have students complete Student Sheet 38.1, including the estimation of the distance to the center of the earth and have them place an X at the depth that they think nuclear waste should be stored. If students are having difficulty with the sheet, you may want assign them partners so that they can do the work in pairs, but do not answer their questions about the accuracy of an idea. The purpose of this strategy is to elicit student thinking. You may want to prompt students with questions such as: Do you think the inside of the earth is completely solid? If so, what kind(s) of solid material do you think is there? If not, what type of substance(s) do you think is there? What do you think the temperature(s) inside the earth might be? Encourage students to describe the materials they think they would see, smell, and feel (such as temperature). When most students have completed Student Sheet 38.1, elicit some of their basic preconceptions about the structure of the earth by having them share their diagrams and descriptions. Students are likely to grossly underestimate the distance to the center of the earth, but at this point do not comment on the accuracy of the estimates. Instead, identify the range of student responses. DOING THE ACTIVIT Y 2. (LITERACY) Students read about the earth s structure. Use the Stop, Listen, and Write literacy strategy to read the text aloud to the class (see the Literacy section of Teacher Resources II: Diverse Learners). In this strategy, the teacher reads a section of text aloud. Students then write down what they heard (i.e. understood) from the passage; they may also choose to follow along with the written text (if students do this, be sure to have them close their books prior to writing). If students are good readers, you may want to read aloud for a select period of time, such as three minutes. If students have difficulty understanding scientific information, you may want to stop in order to allow the students to write after each paragraph. Be sure to answer any questions that students may have about the meaning of the reading, either after each passage or after completing the entire text. You can use Question 1 to review the categories and units used in Table 1: Layers of the Earth, in the Student Book. To help students understand the high temperatures found inside the earth, point out that room temperature is often close to 25 C (77 F). D-21

20 Activity 38 Beneath the Earth s Surface If appropriate, inform students that denser substances sink relative to less dense substances. Students can think of the core as the bottom (center) of the earth, as it contains the most dense material. The crust can be considered the top of the earth and it is made up of the least dense material. Explain that when the earth was forming, these materials were even hotter and more fluid. These conditions allowed the lower density materials that make up the crust to rise to the top and the higher density materials to sink to the bottom. Today, the mantle is still fluid enough to allow a slow upward movement of less dense material and a slow downward movement of more dense material. FOLLOW-UP 3. (MATHEMATICS) Students draw and label a scaled diagram of the earth s structure. Hand out the appropriate version of Student Sheet 38.2, Talking Drawing 2: Beneath the Earth s Surface, and have students complete Questions 3 and 4 on it. Decide whether it would be best for students to work individually, in pairs, or even as a whole class. Remind them to measure and draw their layers from the surface down; some students may accidentally measure from the center outward (as opposed to down from the surface). If students are unfamiliar with the concept of a scale, describe some scaled models that students may have seen. For example, solar system models, action figures, miniature animal replicas, model ships, model trains, and miniature doll houses may all be created to scale. If the model is to scale, each part of the model has a size that is accurate relative to another part. For example, the doorway of a miniature doll house would be about the same size relative to the size of the room as a doorway in a full size house. If a model is not to scale, parts of it may be too large or too smaller relative to other parts. For example, certain action figures have waists that are not to scale. If such an action figure were the height of a real man or a woman, its waist would be out of proportion to that of a real person, with the circumferance of its waist closer to that of a typical human arm than a human waist. Some students may need additional help in determining the scale. If appropriate, model how to calculate the scale for the class, or inform them that 1 cm equals 800 km. Encourage them to calculate the scaled depth of each layer independently and to draw and label them on Student Sheet Teacher s Note: The depth of each layer was rounded to allow for the creation of a suitable scale. The mantle has a depth closer to 2,900 km (compared to the 2,800 km listed in the Student Book) and the depth of the crust varies considerably over the surface of the earth. It can be up to 100 km deep, though it has an average depth of km. 4. (UC ASSESSMENT) Students compare their initial drawings to their scaled diagrams. Project the color transparency, Layers of the Earth, and use it to summarize the major features of the earth s structure. Prior to assigning Question 5, which is an assessment opportunity, review student work on Student Sheet Determine whether the students have drawn the layers to scale and labeled them correctly. If not, you may want to provide students with an opportunity to revise their work before assigning Question 5. Have students complete Question 5 individually. Encourage students to identify what they have learned about the structure of the earth. Note that Question 5 can be assessed using the UNDERSTANDING CONCEPTS Scoring Guide. You may find it helpful to review the expectations for a Level 3 response prior to assigning the question. SUGGESTED ANSWERS TO QUESTIONS 1. Which layer(s) of the earth is (or are) a. the hottest? The inner core. b. at the earth s center? The inner core. c. completely solid? The crust and inner core. D-22

21 Beneath the Earth s Surface Activity Copy the five words shown below. outer core lithosphere crust upper mantle solid a. Look for a relationship among the words. Cross out the word or phrase that does not belong. b. Circle the word or phrase that includes all the other words. c. Explain how the word or phrase you circled is related to other words in the list. The lithosphere is made up of the crust and upper mantle, and is solid. Your teacher will give you Student Sheet 38.2, Talking Drawing 2: Beneath the Earth s Surface. Use it and the information from the Reading to answer Questions 3 and Answer Parts a h to create a scaled drawing of the earth s layers on Student Sheet If you have time, you may want to color in the different layers. a. How far is to the center of the earth in kilometers (km)? Record this distance on Student Sheet Approximately 6,400 km. b. Use a ruler to measure and record the distance from the earth s surface to its center in centimeters (cm). The distance is 8 cm. c. How many kilometers will a single centimeter will represent? This is called a scale. Calculate and record your scale. Hint: You will need to divide the distance to the center of the earth in kilometers by the distance in centimeters. One centimeter will represent 800 km (6,400/8 = 800). d. Record the lowest depth of each earth layer in kilometers. See table below. Earth Layer e. Use your scale and a calculator to determine the scaled depth of each earth layer in centimeters. f. Use a ruler to measure the depth of each layer, starting from the earth s surface. Draw a circle at each depth. Hint: After drawing the other layers, sketch the approximate location of the crust. g. Label each layer with its name, state, and temperature. h. Label the lithosphere. Be sure to record its actual depth in km. See the color transparency, Layers of the Earth, for a key to Parts f h. (The scaled depth of the lithosphere is 0.12 cm, or slightly more than 1 millimeter.) Note that it is not necessary to draw a circle to identify the inner core, since the line delineating the lower margin of the outer core simultaneously identifies the outer margin of the inner core. 4. At Yucca Mountain, nuclear waste will be stored at a depth of about 0.3 km (300 meters, or 1,000 feet). a. In which layer of the earth will the waste be stored? The crust. Depth below the Earth s Surface (km) Scaled Depth below the Surface (cm) Crust Mantle 2, Outer Core 5, Inner Core 6,400 8 b. Place an X on that layer of your drawing on Student Sheet You may want to place an X in the crust shown on the color transparency, Layers of the Earth. D-23

22 Activity 38 Beneath the Earth s Surface 5. (UC ASSESSMENT) Compare your drawing on Student Sheet 38.1, Talking Drawing 1: Beneath the Earth s Surface, with your drawing on Student Sheet Describe the earth s interior and explain how your understanding of it has changed. Student descriptions of the earth s interior should reflect the information on the color transparency, Layers of the Earth. When comparing their drawings, it is likely that students will have identified the distance to the center of the earth as being a smaller distance than the actual; described greater or fewer earth layers than there are; imagined the composition and/or state of the layers differently; and underestimated (or not described) the high temperatures found inside the earth. Level 3 Response: The center of the earth is about 6,400 km deep and it gets hotter as you go down. Before, I thought it was 500 km deep and that it would get colder. The earth is made up of the crust, mantle, outer core, and inner core. The crust is much thinner than the other layers and is made up of rocks. The upper part of the mantle is solid and the lower part is liquid. The upper mantle and crust are called the lithosphere. The core is divided into the outer and inner core and they are both made of iron and nickel. The other core is liquid and the inner core is solid. The major changes are that my new diagram has more layers, temperatures, and I used to think the earth was solid rock. D-24

23 Name Date Talking Drawing 1: Beneath the Earth s Surface 1. Imagine taking a glass elevator to the center of the earth. Draw what you see. Be sure to label your drawing. 2. I think the distance to the center of the earth is: kilometers (km). 3. Place an X at the depth you think nuclear waste should be stored. Label the depth in kilometers (km). Glass Elevator Center of the earth 2012 The Regents of the University of California Issues and Earth Science Student Sheet 38.1 D-25

24 Name Date Talking Drawing 2: Beneath the Earth s Surface Distance to the earth s center (actual): kilometers (km) Earth Layer Crust Depth below the Earth s Surface (km) Scaled Depth below the Surface (cm) Distance to the earth s center (measured): Mantle centimeters (cm) Outer Core Scale: 1 cm = km Inner Core Surface Center of the earth 2012 The Regents of the University of California Issues and Earth Science Student Sheet 38.2a D-27

25 Name Date Talking Drawing 2: Beneath the Earth s Surface Distance to the earth s center (actual): kilometers (km) Earth Layer Crust Depth below the Earth s Surface (km) Scaled Depth below the Surface (cm) Distance to the earth s center (measured): Mantle centimeters (cm) Outer Core Scale: 1 cm = km Inner Core Surface Center of the earth 2012 The Regents of the University of California Issues and Earth Science Student Sheet 38.2b D-29

26 Earth Time to 1 50-minute session ACTIVITY OVERVIEW I N V E S T I G AT I O N Students are introduced to the age of the earth as they place important events in the earth s history into one of four time periods. They compare their ordering with that of modern geologists. KEY CONCEPTS AND PROCESS SKILLS (with correlation to NSE 5 8 Content Standards) 1. The earth is over four billion years old, and different events have occurred on earth during different periods of time. (EarthSci: 1) 2. Fossils provide important evidence about how life and environmental conditions on Earth have changed over geological time. (EarthSci: 2) KEY VOCABULARY geological time (thousands, millions, billions of years ago) paleontologist reptile D-31

27 Activity 39 Earth Time MATERIALS AND ADVANCE PREPARATION For the teacher 1 Transparency 39.1, Locator Map: Appalachian Mountains 1 Transparency 39.2, Event Timeline 1 Transparency 39.3, Geologic Time Scale (optional) * 1 overhead projector For each group of four students 1 set of 10 Events on Earth cards 1 Student Sheet 39.2, Paleontology Student s Notes * 1 set of four large index cards (optional) For each student 1 Student Sheet 39.1, Ordering Events * sticky notes, such as Post-Its (optional) *Not supplied in kit Do not copy Student Sheet 39.1 and 39.2 on the same sheet of paper, because Student Sheet 39.2 contains information that should only be provided later in the activity. Teacher s Note: The concept of geological time is further explored in the Evolution unit of Issues and Life Science, part of SEPUP s three-year middle school program. TEACHING SUMMARY Getting Started 1. Students identify which of three events happened thousands, millions, and billions of years ago. Doing the Activity 2. Students work together to place events in one of four time periods. Follow-Up 3. Discuss how different groups organized the events in the history of the earth. D-32

28 Earth Time Activity 39 BACKGROUND INFORMATION The Geologic Time Scale The geologic time scale, shown in an abbreviated form on Transparency 39.3, Geologic Time Scale, divides the history of the earth into a series of non-overlapping time periods. (However, the time periods are organized hierarchically: for example, the Jurassic is a period contained within the Mesozoic.) The time scale does not divide the history of the earth into blocks of equal duration. Instead, the boundaries are defined by the first or last appearance of certain fossils in the fossil record (called index fossils ). Many of these boundaries were defined and named long before scientists were able to determine the actual ages of the fossils (in millions of years ago) with any degree of accuracy. The beginning and end of each boundary have been determined precisely only recently, through the use of radiometric dating. The assigned dates continue to change somewhat as technology improves and new fossil localities are discovered, which leads to the redefinition of boundaries. The names of the three major divisions of the last 550 million years Paleozoic, Mesozoic, and Cenozoic are derived from word roots meaning old animals, middle animals, and new animals, because it is in these time periods that multicellular diversity exploded. Many of the names for the smaller divisions are derived from the name of the geographic region where their characteristic rocks or fossils were first described or where they are particularly abundant (e.g., the Devonian is named after Devon, a town in England; the Jurassic is named after the Jura Mountains in France). D-33

29 Activity 39 Earth Time TEACHING SUGGESTIONS GETTING STARTED 1. Students identify which of three events happened thousands, millions, and billions of years ago. Teacher s Note: Some students may have religious beliefs that are in conflict with the information provided in this activity. If this is a concern for your students, remind them that in every subject area they are expected to be responsible for information relevant to that subject area. The information presented in this activity is based on the most current scientific research. In science class, students are expected to knowledgeable about such scientific information. Explain that scientists use evidence from rock layers, and the radioactive decay in rocks, to accurately date when various fossils have formed and also when certain major events on earth have occurred. Introduce the activity and the concept of geological time by listing the following three events on the board. One of these events occurred (or can be dated to) thousands of years ago, one occurred (or can be dated to) millions of years ago, and one occurred (or can be dated to) billions of years ago. If necessary, you may need to review the concept of extinction. You may also need to explain an Ice Age as a period of time when glaciers covered large portions of the earth s surface. Students can imagine that the ice sheets of the Arctic, instead of being restricted to the North Pole, came down and covered large portions of North America, Europe, and Asia. Events Extinction of 90% of marine life on earth The last Ice Age Age of oldest fossil Ask students to write in their science notebooks which event they think occurred when. (Alternatively, provide each student with three sticky notes with one time period (e.g. thousands, millions, billions) on each note and have students post their ideas on the board.) Some students may be concerned about having the right answer. If so, explain that the goal at this time is for students to share their ideas, whether they are correct or not. After students have had an opportunity to record their individual ideas, ask for a show of hands (or summarize the trend of the sticky notes) to determine when most students think 90% of the earth s marine life became extinct, etc. Then share with the class the relative time period of each event: The last Ice Age happened thousands of years ago. There was a mass extinction of the earth s marine life millions of years ago. The oldest fossil is billions of years old. Place these events in the correct order on the board. Point out that by placing these events in order, you have created a chronological timeline. Let students know that they will be expected to do something similar in this activity. Explain that scientists who study the history of the earth known as paleontologists refer to periods of thousands, millions, and billions of years as geological time. DOING THE ACTIVIT Y 2. Students work together to place events in one of four time periods. Hand out Student Sheet 39.1, Ordering Events. Be sure that students understand that they are to place each event in one of the four time periods in the first column only. The last column will be used later in the activity. You may wish to review the relative age of the time periods that students will be working with. Less than 50 million years ago refers to the most recent period, while more than 500 million years ago is the oldest period. It may help some students to write down youngest at the top of the page and oldest at the bottom. Before handing out the Events on Earth cards, review any information that may be unfamiliar to D-34

30 Earth Time Activity 39 students. For example, the Appalachian Mountains are a mountain chain in the eastern U.S. that extend from Maine to northern Georgia. Use Transparency 39.1, Locator Map: Appalachian Mountains, to show students their location in modern North America. Students are expected to be familiar with reptiles, cold-blooded, air-breathing vertebrates with scales that typically lay eggs. Turtles, snakes, lizards, and crocodiles are all reptiles. Hand out the Events on Earth cards to each group of students. Remind groups that they should work together to determine which events happened during which time period. You may wish to create a set of four index cards for each group, listing the four time periods on Student Sheet Students can then use the index cards to arrange the Events on Earth cards within a particular time period. After students have organized and recorded the events in their table, hand out Student Sheet 39.2, Paleontology Student s Notes, to each group. Students can use this information to rearrange the cards and record the revised order in the last column of Student Sheet FOLLOW-UP 3. Discuss how different groups organized the events in the history of the earth. Discuss students work during the activity by sharing responses to Analysis Question 1 and asking, Did you place the cards in different time periods than paleontologists? What made you think that a particular event occurred sooner or later than it did? Student responses will vary, and may elicit student misconceptions. If so, clarify their ideas as necessary. Display Transparency 39.2, Event Timeline, and share with the class the approximate dates of the various events presented on the cards. Explain that in addition to using longer periods of time, geologists use names instead of numbers to refer to these dates. The last column of Transparency 39.2 provides the names of four geological time periods. Point out that the time periods that students used to group the events roughly corresponds to four time periods used by geologists: Precambrian, Paleozoic, Mesozoic, and Cenozoic. You may want to use Transparency 39.3, Geologic Time Scale, to describe geological time periods in greater detail. Relate Transparency 39.2 to the events used to introduce the activity: Some fossils of blue-green algae (cyanobacteria) have been dated at about 3.5 billion years old, which is in the Precambrian period. The beginning of the Paleozoic was marked by a dramatic increase in the number of animal phyla (including the evolution of land plants, reptiles, fish, and insects) and a mass extinction occurred near the end of the Paleozoic, about 248 million years ago. One group of organisms that became extinct at that time were the trilobites, marine arthropods characterized by a three-lobed exoskeleton. There have been several ice ages in the earth s history; the most recent ended about 10,000 years ago, during the Cenozoic. Use responses to Question 2 to review the concept of geological time. Point out that paleontologists use different measurements of time than most people do in everyday life. Because these periods of time are so long (i.e. thousands, millions, and billions of years), they are referred to as geological time. Question 3 provides an opportunity to connect the concept of geological time to the issue of storing nuclear waste in Yucca Mountain, and can be used to evaluate whether students have a correct understanding of geological time. More than one student response may be considered correct, though any acceptable response should be supported by accurate information and logical reasoning. Question 4 addresses the common student misconception that early humans ( cave men ) and dinosaurs co-existed. Help students synthesize the activity by using Question 5 to have them reflect on what they learned in this activity. D-35

31 Activity 39 Earth Time SUGGESTED ANSWERS TO QUESTIONS 1. How did your group s original order of events differ from that of paleontologists? Explain. Some student groups may have had particular difficulty placing the oldest rock and the formation of the Appalachian Mountains in the correct order and/or time period. 2. Would units of time such as minutes and hours be useful in measuring events in earth s history? Why or why not? No, because events in earth s history have happened over such a long time period that it would be impractical to use smaller measurements in time. A time period of 195,000 years ago, when the most recent Event on Earth card occurred, is equivalent to 102 billion minutes, or 1.7 billion hours. It would not be feasible to discuss events that occurred million and billions of years ago in terms of minutes and hours. 3. Some nuclear waste may be radioactive for 250,000 years. Would you consider this to be a long or short period in geological time? Explain your reasoning. This is a relatively short period of time in geological time, which is measured in thousands, millions, and billions of years. Yucca Mountain itself is about 40 times older than the period of time in which such nuclear waste may be radioactive. Some students may consider this to be a long period of time, since it is slightly longer than the age of the oldest Homo sapiens fossils (195,000 years ago). This means that some nuclear waste will be radioactive for a period of time longer than modern humans have existed on the earth. 4. Your younger brother tells you about a television show he watched where humans ride dinosaurs instead of cars. He says he wishes he could go back to the time when people lived with dinosaurs. Based on what you learned in this activity, what do you tell him? In real life, dinosaurs and humans did not exist on the earth at the same time. Dinosaurs became extinct between 50 and 250 million years ago (about 65 million years ago). The oldest modern human fossil is only thousands of years old. That means that dinosaurs became extinct millions of years before evidence of the first modern human. Human co-exist with dinosaurs only in fantasy or science fiction. 5. Reflection: How did first placing these events in order yourself help you to understand Earth s history? Hint: Think about how your understanding of events in geological time has changed. Student answers will vary. Students are likely to observe that it helped them identify information that they did not know or misunderstood, such as: the age of the earth when certain groups of animals first evolved or became extinct fossils can form before a species becomes extinct fossil evidence of modern humans is very recent in geological terms the sequence of events in earth s history D-36

32 Locator Map: Appalachian Mountains 2012 The Regents of the University of California Issues and Earth Science Transparency 39.1 D-37

33 Event Timeline 2012 The Regents of the University of California Issues and Earth Science Transparency 39.2 D-39

34 Geologic Time Scale 2012 The Regents of the University of California Issues and Earth Science Transparency 39.3 D-41

35 Name Date Ordering Events Events on Earth: Time Period Events on Earth: Original Order Revised Order Less than 50 million years ago million years ago million years ago 2012 The Regents of the University of California More than 500 million years ago Issues and Earth Science Student Sheet 39.1 D-43

36 Name Date Paleontology Student s Notes Time Period Events on Earth Less than 50 million years ago Fossil evidence of first modern humans (Homo sapiens) Yucca Mountain formed million years ago Dinosaurs became extinct Age of reptiles million years ago Fossil evidence of first reptiles Fossil evidence of first land plants Appalachian Mountains began to form More than 500 million years ago Fossil evidence of first life on the earth Oldest rock 2012 The Regents of the University of California Earth formed Issues and Earth Science Student Sheet 39.2 D-45

37 The Continent Puzzle to 1 50-minute session ACTIVITY OVERVIEW I N V E S T I G AT I O N Students use puzzle pieces representing the earth s continents in order to begin to investigate the idea of continental drift. Teacher s Note: Activity 40 is an exploratory activity only. It is the first of three activities that considers evidence for the movement of continents. These three activities are then followed by additional activities that investigate plate tectonics. You may wish to limit detailed explanations of continental drift and plate tectonics until after Activity 42, The Theory of Plate Tectonics. KEY CONCEPTS AND PROCESS SKILLS (with correlation to NSE 5 8 Content Standards) 1. Creating models is one way to understand and communicate scientific information. (Inquiry: 1) 2. The earth is over four billion years old, and different events have occurred on earth during different periods of time. (EarthSci: 1) 3. Fossils provide important evidence about how life and environmental conditions on the earth have changed over geological time. (EarthSci: 2) 4. The continents are part of large lithospheric plates that have moved over geological time and continue to move at a rate of centimeters per year. (EarthSci: 1, 2) KEY VOCABULARY continent geological time Pangea D-47

38 Activity 40 The Continent Puzzle MATERIALS AND ADVANCE PREPARATION For the teacher 1 Transparency 39.2, Event Timeline 1 Transparency 40.1, World Map 1 Transparency 40.2, Puzzle Key (with individual pieces cut apart) * 1 globe (optional) * 1 overhead projector For each group of four students 1 set of 7 World Puzzle pieces 1 Student Sheet 40.1, Earth s Surface Through Geological Time For each student 1 completed Student Sheet 39.1, Ordering Events *Not supplied in kit Cut apart a copy of Transparency 40.2, Puzzle Key, so that you can move the individual puzzle pieces around on an overhead projector. You can use the paper copy of the transparency as a reference. TEACHING SUMMARY Getting Started 1. Read the introduction in the Student Book. 2. Discuss the continents on the earth. Doing the Activity 3. Students work together to put the puzzle together. Follow-Up 4. Discuss what the puzzle suggests about the history of the earth.if this works) REFERENCES Kious, W. Jaquelyne, and Tilling, Robert I. U.S. Geological Survey. (1996). This Dynamic Earth: The Story of Plate Tectonics (online edition). Retrieved November 2004 from pubs.usgs.gov/publications/text/historical.html D-48

39 The Continent Puzzle Activity 40 BACKGROUND INFORMATION Fossil Evidence Glossopteris was a fern-like plant that grew during the late Paleozoic era (which ended about 245 million years ago). First discovered from fossils in 1824, it is now considered to be a gymnosperm (a seed plant that bears naked seeds, such as conifers and ginkgos). Glossopteris had tongue-shaped leaves and was about 3.7 meters (12 ft) tall. Fossil remains of the plant have been found in southern Africa, South America, Australia, India, and Antarctica. Before the proposal of continental drift, scientists had difficulty understanding how the seeds of the Glossopteris plant could have been transported to all these locations by wind or water currents, because the seeds were considered too large and heavy. Mesosaurus was a small aquatic reptile during the Permian period (280 to 248 million years ago) and its fossils have been found both in southern Brazil and in South Africa. Scientists could not easily explain this distribution of fossils either before the idea of continental drift was introduced because, although Mesosaurus could swim, it was considered too small (about half a meter long, less than 2 ft) to have been able to swim all the way across the ocean. Cynognathus was a mammal-like reptile that had four legs and a short tail. It was about the size of a wolf (1.5 m, or about 5 ft long). It lived during the early to middle Triassic period (about million years ago) and its fossils have been found in South Africa and Argentina. Lystrosaurus was a mammal-like reptile with four legs and a short, stubby tail during the Triassic period ( million years ago). It was a plant eater, about 1 meter (3 feet) long, and it is estimated to have weighed about 90 kilograms (200 pounds). Fossils of Lystrosaurus have been found in South Africa, Asia (including India), Europe, and Antarctica. Rock Evidence Modern scientific studies (including the use of radiometric dating and the identification of magnetic striping) show similarities between the age and sequence of rock layers on different continents. For example, there are many similarities between 550 million-year-old rocks found in both northeast Brazil and western Africa. This suggests that the two continents were joined together for some period of time prior to 550 million years ago. Mountain belts of similar ages also appear to line up when the continents are placed together. The oldest portions of the Appalachian Mountains, extending from the northeastern part of the United States through eastern Canada, match up with the Caledonides mountains of Ireland, Britain, Greenland, and Scandinavia. A younger part of the Appalachians lines up with mountains of similar age in Africa and Europe. D-49

40 Activity 40 The Continent Puzzle TEACHING SUGGESTIONS GETTING STARTED 1. Read the introduction in the Student Book. The introduction foreshadows the next few activities and may help in providing students with more context for the activity. After reading the introduction, ask students to imagine Hawaii as a cold snowy place, millions of years in the future: What would the discovery of fossilized palm trees tell people about the past climate of the area? Such fossils would suggest that the area was once much warmer. In a similar way, scientists have been able to use the extinct plant Glossopteris to deduce that the climate of some parts of the world are very different today than they were in the past. Point out that this fern-like plant could only grow in warm, wet climates. 2. Discuss the continents on the earth. Ask the class, In which part of the world (or which country) do we live? Which continent is our country in? The United States is part of the North American continent. Use examples of familiar countries to remind students that countries in different parts of the world are on different land masses, or continents. The Student Book contains a world map with each of the continents labeled. You may wish to use it or Transparency 40.1, World Map, to review the continents or simply ask students to list the world s continents. Both Europe and Asia are part of the same land mass, which is sometimes referred to as Eurasia. Note that while the country of India is identified for reference, it is not a continent it is part of the continent of Asia. Ask students if they can name the large areas on the map that are not labeled. Students may recognize some of the world s oceans, as well as Greenland (which is a country that is part of the North American continent), and the Arctic (which is not a continent and is primarily made up of huge ice sheets). Point out that the perspective on a map makes Greenland appear much larger than it is. It is actually smaller than Australia. If you have a globe, use it to show this difference in size. Also, point out to students that Antarctica is an island slightly larger than Australia with a circular shape. Again, the perspective of the map skews its shape, making it apper to be a long sliver of land. If you have a globe, use it to show the students the actual shape of Antarctica. DOING THE ACTIVIT Y 3. Students work together to put the puzzle together. Explain that because Greenland is not a continent and is not an essential element of the geological process the activity is modeling, it is not a part of the puzzle that students will be doing. Teacher s Note: This activity uses stylized continent shapes to introduce and model the movement of continental land masses over geological time. It is possible to cut out the shape of the continents along the modern land margins and attempt to match them, but it is difficult to create an exact match because the angles, as well as some of the boundaries, have changed since the continents were joined. Provide each group of students with a set of World Puzzle pieces. Students are first expected to use the world map in the Student Book to identify what each puzzle piece represents. They represent the seven continents and one country. The continents represented are: North America South America Africa Australia Antarctica Europe and Asia (1 puzzle piece for both) The country represented is: India You may want to review the key to the symbols found on the puzzle pieces. They show the locations D-50

41 The Continent Puzzle Activity 40 where fossils of certain extinct organisms have been found, as well as the location of mountain ranges that have similar rock layers. (Research in these fields continues, and paleontologists continue to find fossils of extinct species with similar ages and distributions on continents that were once connected.) When students are ready to begin Procedure Part B, provide each group with a copy of Student Sheet 40.1, Earth s Surface Through Geological Time. FOLLOW-UP 4. Discuss what the puzzle suggests about the history of the earth. After students have completed the activity, have a student use transparent puzzle pieces (from Transparency 40.2, Puzzle Key, ) to demonstrate how the puzzle is put together. Encourage students to use the markings on the puzzle pieces to determine where these fossils have been found and to compare what they know about the climate of the place today with what it might have been in the past. Use Transparencies 40.1 and 40.2, in conjuction with Questions 1 and 2, to review how the pieces model modern land masses. One puzzle piece represents two continents: Europe and Asia. Highlight that one of the pieces does not represent a continent, but rather a country (India). Point out that India is often referred to as a subcontinent and that its northern border is marked by the Himalayan mountain chain, which contains the highest mountains on earth (including Mount Everest and K2). You can point this out if you have a globe or a world map that shows topographic features. Use Question 3 to discuss why the distribution of fossils suggests that the continents were once joined. The seeds of the Glossopteris plant are considered too heavy to have been distributed by wind or water. Mesosaurus was a freshwater reptile (which would not be expected to swim across saltwater oceans), and is considered too small to have successfully swum between South America and Africa. As land reptiles, neither Cynognathus nor Lystrosaurus would be expected to cross the great oceanic distances between South America and Africa (Cynognathus) or Africa, Antarctica, and India (Lystrosaurus). Ask, This activity used puzzle pieces to model large land masses. Do you think the puzzle pieces are a good model for the continents? Why or why not? Students are likely to point out that the sizes and shapes of the puzzle pieces are not identical to the outline of the continents. If the continents (along with India) were arranged from largest to smallest by land area, they would be listed as follows: Eurasia (without India), Africa, North America, South America, Antarctica, Australia, and India. Also, the projection of the map found in the Student Book makes it difficult to match some of the puzzle pieces to continents (e.g. Antarctica). Finally, one of the pieces did not represent a continent but a country. Other students may point out that the model is adequate since the general shape of large land masses was kept the same and that the pieces contained data that corresponded to findings on these land masses. In addition, the pieces provided evidence related to fossils and mountain ranges. SUGGESTED ANSWERS TO QUESTIONS 1. Describe what has happened to land on the surface of the earth over the past 425 million years. Land masses on the earth s surface have moved and changed shape over time. About 425 million years ago, some of the percursors to today s continents were joined in a large land mass known as Gondwanaland, with some land masses that are currently near the equator near the south pole and some that are currently near the poles near the equator. Between 425 and 230 million years ago, all of the land joined together to form Pangea. Since then, Pangea has broken apart to form the arrangement of the continents seen on the earth today. One of the smaller pieces eventually connected with the Asian continent; today that land mass is the country of India. D-51

42 Activity 40 The Continent Puzzle 2. There are seven continents and there were seven puzzle pieces. But not every puzzle piece represented a continent. Why do you think this is? Hint: Think about how you used the pieces to model changes on the earth s surface. The continents of Europe and Asia are and have been part of a single land mass over the past 230 million years, so they could be represented by a single piece. The continent of Asia, however, was formed from two land masses: a part that was connected to the European continent and a part that today forms the country of India. Since the Indian land mass broke off from Pangea separately and later connected to Asia, it is represented by its own piece: this piece was used to more accurately model how land masses have moved on the earth s surface over geological time. 3. What types of evidence did the puzzle provide about change on the earth s surface? The puzzle provided evidence related to fossil distribution, mountain ranges with similar rock layers, and the shape and position of the continents. 4. a. Look at the information in Table 1, Approximate Time Period of Some Extinct Organisms. [in Student Book] On Student Sheet 39.1, Ordering Events, record when each of these organisms lived. You may want to use Transparency 39.2, Event Timeline, to demonstrate when each organism should be recorded. Glossopteris grew during the Mesozoic as well as the end of the Paleozoic, Mesosaurus lived during the Paleozoic, Cynognathus lived during the early Mesozoic, and Lystrosaurus existed during the Mesozoic as well as the end of the Paleozoic. b. Pangea began to break apart about million years ago. Record this event on Student Sheet You may want to use Transparency 39.2, Event Timeline, to demonstrate when this event should be recorded. The break-up of Pangea began during the Mesozoic. c. Which of the extinct organisms listed in Table 1 lived on Pangea before it broke apart? All of them (Glossopteris, Mesosaurus, Cynognathus, and Lystrosaurus). D-52

43 World Map 2012 The Regents of the University of California Issues and Earth Science Transparency 40.1 D-53

44 Puzzle Key 2012 The Regents of the University of California Issues and Earth Science Transparency 40.2 D-55

45 Name Date Earth s Surface Through Geological Time 2012 The Regents of the University of California Issues and Earth Science Student Sheet 40.1 D-57

46 Continental Drift to minute sessions ACTIVITY OVERVIEW TA L K I N G I T O V E R Students evaluate evidence related to continental drift. They first determine which statements constitute evidence, and they then identify the statements that support this idea of continental movement. KEY CONCEPTS AND PROCESS SKILLS (with correlation to NSE 5 8 Content Standards) 1. The continents are part of large lithospheric plates that have moved over geological time and continue to move at a rate of centimeters per year. (EarthSci: 1, 2) 2. Fossils provide important evidence about how life and environmental conditions on earth have changed over geological time. (EarthSci: 2) 3. Tracing the history of science demonstrates how individuals contributed to the development of modern scientific ideas, and reveals important interactions between science and society. (History: 3) KEY VOCABULARY continental drift evidence D-59

47 Activity 41 Continental Drift MATERIALS AND ADVANCE PREPARATION For the teacher 1 Scoring Guide: UNDERSTANDING CONCEPTS (UC) 1 Scoring Guide: ORGANIZING SCIENTIFIC IDEAS (SI) 1 Transparency 40.2, Puzzle Key * 1 overhead projector For each student 1 Student Sheet 41.1, Analyzing Evidence: Continental Drift 1 Student Sheet 41.2, Writing Frame: Continental Movement (optional) 1 Scoring Guide: UNDERSTANDING CONCEPTS (UC) (optional) 1 Scoring Guide: ORGANIZING SCIENTIFIC IDEAS (SI) (optional) *Not supplied in kit Masters for Scoring Guides can be found in Teacher Resources III: Assessment. TEACHING SUMMARY Getting Started 1. Use the introduction in the Student Book to explain the concept of continental drift. Doing the Activity 2. Students evaluate evidence on Student Sheet Follow-Up 3. Relate continental drift to previous activities. 4. (UC, SI ASSESSMENT, LITERACY) Students write a paragraph on continental drift. D-60

48 Continental Drift Activity 41 BACKGROUND INFORMATION Alfred Wegener and Continental Drift The idea of continental drift was first proposed by German meteorologist Alfred Wegener. In December 1910, he wrote in a letter to his future wife: Doesn t the east coast of South America fit exactly against the west coast of Africa as if they had once been joined? This is an idea I ll have to pursue. By 1915, he had published the first edition of The Origin of Continents and Oceans, a book in which he outlined his ideas about continental drift and described the evidence in support of it. In a revised third edition, published in 1922, he wrote: Geological evidence shows that about 300 million years ago, all of the continents were joined together. I will refer to this supercontinent as Pangea, meaning all lands. It appears that Pangea began to break up about 200 million years ago. Wegener relied on several lines of evidence described in the Student Book, including the distribution of fossils of the same geological age along different shores, similar rock layers along the edges of different continents, evidence of past glacial activity, and the relationship among mountain ranges on different continents (including similar rock strata and the presence of coal beds). He also noted the distribution of specific rock types, in order to determine the range of different climate zones in the geologic past. He found that these zones occupied different positions than today. For example, coral reefs indicate a tropical climate, and today coral reefs are distributed in a zone around the equator parallel to the poles. Evidence of coral reefs in geological history would indicate either that this tropical zone was not parallel to the ancient poles or that the continents themselves moved, leaving the climate zones parallel to the ancient poles. Wegener proposed the latter as evidence for continental drift. Wegener s ideas about continental drift were not widely accepted during his lifetime. He suggested that the earth s spinning on its axis caused the continents to move and to plow through the ocean floor, and many geologists of the time were not convinced by this explanation of the mechanism of continental drift. They countered that the amount of force needed to overcome the resistance of rock layers found on the ocean floor made this mechanism improbable. Since Wegener s time, advances in science have led to additional evidence that supports his idea that the continents have moved, and continue to move and to the proposal of a more convincing mechanism for this movement. Some of these advances are described on Student Sheet Other advances include new understandings related to sea-floor spreading and the magnetic properties of rocks. Today, elements of the idea of continental drift have become part of the larger theory of plate tectonics, which is introduced in the next activity. REFERENCES Hughes, Patrick. (April 1, 1994) The Meteorologist Who Started a Revolution. Weatherwise, Vol. 47, p. 29. Heldref Publications, Washington, D.C. D-61

49 Activity 41 Continental Drift TEACHING SUGGESTIONS GETTING STARTED 1. Use the student introduction to explain the concept of continental drift. Explain that the idea that the continents were once joined together was first suggested over 100 years ago by a German scientist named Alfred Wegener. He suggested that the continents were once joined in a single land mass that eventually broke apart into pieces that slowly drifted away from each other. This idea is known as continental drift. DOING THE ACTIVIT Y 2. Students evaluate evidence on Student Sheet Hand out Student Sheet 41.1, Analyzing Evidence: Continental Drift. Explain to students that they have a three part task: (1) Determining which statements constitute evidence; (2) Identifying the pieces of evidence that support and the pieces that contradict the idea that continents have moved; and (3) Explaining how each piece of evidence supports or contradicts this idea. Students are instructed to decide what constitutes evidence and what does not. If students have difficulty with the concept of evidence, use everyday examples, such as the type of evidence used in a court of law. In some cases, evidence is direct (a person is observed trespassing, for example), while in other cases the evidence is indirect (a person left a unique shoeprint in the mud on the property). If students have difficulty deciding what is or is not evidence, work as a class to evaluate one of the statements. After determining which statements provide evidence and which do not, students are instructed to cross out the statements that they believe are not evidence. While student responses will vary, Statements 3 and 7 do not provide any evidence and can be crossed out. Seven statements (1, 2, 5, 6, and 8 10) provide evidence in support of the theory. Statement 4 is more challenging. It makes a claim about the size of the continents that is relative (they are large) in order to support the idea that the continents have never moved. Some students may agree, while others may dispute the claim by pointing out that Australia is a relatively small continent and it could move. FOLLOW-UP 3. Relate continental drift to previous activities. After students have completed the Procedure, use Question 1 to discuss how particular statements provided evidence for continental movement. Display Transparency 40.2, Puzzle Key. Discuss how the fossil and rock layers provide evidence for continental movement. You may want to refer to Statement 10 (about earthworm fossils) and go back to Procedure Step 5 and the Key to Symbols on the World Puzzle of Activity 40, The Continent Puzzle, in the Student Book to review some of the fossil evidence that has been found to date. Note that this information will be presented again in the next activity. 4. (UC, SI ASSESSMENT, LITERACY) Students write a paragraph on continental drift. Be sure to review Question 1 before assigning Question 3. Question 1 provides an opportunity to determine if students understand the evidence and how it supports continental movement. When assigning Question 3, explain to students that they should write a complete paragraph. You may want to have them write a first draft and then continue to revise their work. If students need additional support, provide Student Sheet 41.2, Writing Frame: Continental Movement. Student responses can be used to assess their understanding of the movement of continents using the UNDERSTANDING CONCEPTS (UC) Scoring Guide and/or can be assessed for clear and logical communication using the ORGANIZING SCIENTIFIC IDEAS (SI) Scoring Guide. D-62

50 Continental Drift Activity 41 SUGGESTED ANSWERS TO QUESTIONS 1. On Student Sheet 41.1, you identified statements that provide evidence in support of continental movement. Explain how each of these statements supports the idea that continents have moved. Students are likely to have identified some, if not all, of the following statements: Statement 1 supports the idea that continents moved because it shows that the same kind of plant was found in different parts of the world. Since plants can t move, one explanation is that these different parts of the world were once connected. (Note that the unlikelihood of the seeds of the Glossopteris plant being distributed by wind or water should have come up in the follow-up discussion of the previous activity.) Statement 2 supports the idea that the continents have moved, because it helps explain why places with warm climates today could have had cold climates in the past. It also proposes the formation of a single large ice sheet at that time rather than several different ice sheets. Statement 5 supports the idea that continents have moved because it shows a pattern of geological features in line with the suggested single land mass. Statement 6 supports the idea that continents have moved because it is highly unlikely that rock layers in two different parts of the world, affected by different forces, formed exactly the same sequence of layers and fossils if they had not been joined. Statement 8 supports the idea that continents have moved because it shows how precisely two of the continents could have once been attached. (If they were not attached, how could they fit so well?) Statement 9 supports the idea that continents have moved because it shows that the continents are now moving. This means that they could have moved in the past. Over billions of years, a few centimeters per year could result in a distance of thousands of kilometers. Statement 10 supports the idea that continents have moved because it shows the same worm fossil in different parts of the world. One explanation for finding the same worm fossil in places that are so far apart and have such different climates today is that these areas were connected and had the same climate. 2. Look again at Student Sheet Have people other than Wegener contributed to the evidence in support of continental movement? Explain. On Student Sheet 41.1, three other people are decribed as having contributed evidence in support of continental movement: Eduard Seuss, Alexander du Toit, and Edward Bullard. In addition, other people have likely contributed to this idea but are not named on Student Sheet For example, the work involved in taking satellite measurements and finding Megascolecina fossils is not attributed to any individual(s). Students may also correctly assume that other scientists have contributed to work begun by one scientist (such as Wegener) or have gone on to new research that provides additional evidence. 3. (UC, SI ASSESSMENT)Imagine that you have been asked to write an encyclopedia entry about the movement of continents. Write a paragraph about continental movement, describing the history of this idea and citing as many pieces of evidence as you can. Level 3 UC Response: Continental drift is the idea that all of the continents were once joined together to form a single piece of land. This land broke into pieces and the continents drifted apart. This idea was first suggested by Alfred Wegener in He called the single continent Pangea. Today, there are many different kinds of evidence that support the idea of continental movement. The evidence includes: (1) satellites show that the continents are still moving; (2) the outlines of some of the continents match really well; and (3) fossils of extinct plants and worms are found in different parts of the world that are believed to have been connected in the past. D-63

51 Name Date Analyzing Evidence: Continental Drift Is it evidence? Statements Does it support the idea that the continents have moved? Yes No Yes No : Geologist Eduard Seuss points out that fossils of the Glossopteris plant are found in southern Africa, South America, Australia, Antarctica, and India. 2. Wegener examines the location of tiny rocks and the direction of grooves formed by large glaciers scraping across southern areas of Africa, South America, Australia, Antarctica, and India. He concludes that if all these places were fitted together, they would form a continuous ice sheet expanding outward in all directions. 3. Frankfurt News, January 6, 1912: Announcement that German scientist Alfred Wegener will speak at the Geological Association meeting. 4. Popular Geology magazine, March 12, 1912: Continents are so large they must always have been where they are. 5. Wegener observes that a South American mountain range in Argentina lines up with an ancient African mountain range in South Africa when the two continents are placed together. He writes: It is just as if we were to refit the torn pieces of a newspaper by matching their edges and then check whether the lines of print ran smoothly across. If they do, there is nothing left but to conclude that the pieces were in fact joined in this way The Regents of the University of California : Geologist Alexander du Toit observes rock layers on the western coast of Africa in the following sequence: basalt rock, shale containing fossil reptiles, coal layers containing Glossopteris fossils, rocks containing Mesosaurus fossils, and shale. He discovers an almost identical sequence of rock layers on the eastern coast of South America : Geologist Baily Willis calls Wegener s theory a fairy tale. He says it seems impossible that the continents could move : Geologist Edward Bullard uses computers to match coasts of South America and Africa. They match extremely well at an ocean depth of 1,000 meters s: Satellites and lasers are used to measure the movement of continents. They continue to move at an average of about 2 cm (0.8 in) per year. 10. Fossils of Megascolecina earthworms are found in South America, Africa, India, and Australia, as well as the islands of Madagascar and New Guinea. Issues and Earth Science Student Sheet 41.1 D-65

52 Name Date Writing Frame: Continental Movement Continental drift is the idea that This idea was first suggested by in (year). He called the single large continent. Today, there are many different kinds of evidence that support continental movement. The evidence includes: The Regents of the University of California 3. Issues and Earth Science Student Sheet 41.2 D-67

53 The Theory of Plate Tectonics to minute sessions ACTIVITY OVERVIEW V I E W A N D R E F L E C T Students watch two video segments on the history of the development of plate tectonics, beginning with Wegener s idea of continental drift. They use Student Sheet 42.1 to review key ideas presented in the video. KEY CONCEPTS AND PROCESS SKILLS (with correlation to NSE 5 8 Content Standards) 1. The earth is over four billion years old, and different events have occurred on earth during different periods of time. (EarthSci: 1) 2. The continents are part of large lithospheric plates that have moved over geological time and continue to move at a rate of centimeters per year. (EarthSci: 1, 2) 3. The movement of the earth s plates can produce earthquakes and volcanoes, and result in the formation of mountains over geological time. (EarthSci: 1) 4. Fossils provide important evidence about how life and environmental conditions on the earth have changed over geological time. (EarthSci: 2) 5. Tracing the history of science demonstrates how individuals contributed to the development of modern scientific ideas, and reveals important interactions between science and society. (History: 3) KEY VOCABULARY continental drift lithosphere plates plate tectonics theory D-69

54 Activity 42 The Theory of Plate Tectonics MATERIALS AND ADVANCE PREPARATION For the teacher * 1 Computer with Internet access or downloaded video segments * 1 Projection device or monitor connected to the computer For each student 1 Student Sheet 42.1, Plate Tectonics Video *Not supplied in kit The teacher page of the Issues and Earth Science website entry for Activity 42 provides links to the video segments required for this activity. These segments are provided on the Teachers Domain website (teachersdomain.org), and are titled Plate Tectonics: The Scientist Behind the Theory, and Plate Tectonics: Further Evidence. The first time you use Teachers Domain, you will need to sign in for a free account. The video segments can be viewed as streaming video directly from the website. Some can also be downloaded. TEACHING SUMMARY Getting Started 1. Review the questions in the Student Book and on Student Sheet Doing the Activity 2. Students view the video and use Student Sheet 42.1 to take notes. Follow-Up 3. (LITERACY) Review the idea that plate tectonics describes the movement of lithospheric plates.if this works) BACKGROUND INFORMATION Theory In everyday language, the term theory is often used to refer to an idea about how things work. The idea may or may not have any basis in fact and can often be proven wrong, sometimes very easily. In science, a theory is a thoughtful, testable explanation of all relevant observations. Scientists use theories to explain natural phenomena. A scientific theory is one that explains observations and can predict future observations. It is testable and can be refuted if contradicted by other observations. A good theory can accommodate new findings and sometimes even anticipate them. For example, in 1869, Dmitri Mendeleev organized the 63 known elements into a table based on their properties, called the periodic table. He used his table to predict that there were still-undiscovered elements that would have properties that would complete his table. Over the next seven years, the discovery of 3 new elements proved his predictions as well as his theory about the relationship between elements and their properties. Theories evolve as more evidence is collected. For example, the theory of the atom has been refined as new evidence has been gathered about atomic behavior. REFERENCES D-70 Public Broadcasting Service (PBS). A Science Odyssey Short Trip: I Feel the Earth Move (video). United States, 1998.

55 The Theory of Plate Tectonics Activity 42 TEACHING SUGGESTIONS GETTING STARTED 1. Review the questions in the Student Book and on Student Sheet As a class, read Questions 1 3 in the Student Book. While students may already be able to answer the questions in part (prior to seeing the video), reviewing the questions will help focus their viewing. Hand out Student Sheet 42.1, Plate Tectonics Video. The student sheet is intended to help students identify the key ideas presented in the video and can be used to help answer the questions in the Student Book. As a class, read aloud the questions on Student Sheet Review any words that may be confusing. DOING THE ACTIVIT Y 2. Students view the video segments and use Student Sheet 42.1 to take notes. Show the segments on continental drift and plate tectonics from the Teachers Domain website. The two segments together are approximately 6 minutes. Then have students answer as many questions on Student Sheet 42.1 as they can. Show the video segments again. The purpose of showing the videos again is to allow students to pick up on missed ideas and to give them an opportunity to process the significant amount of information presented in these short segments. This strategy will also help support the understanding of students who are less proficient in English or who have special needs. Have students complete Student Sheet You may wish to review answers to the student sheet, which are shown below. 1. a. an idea 2. All of the statements should be checked. 3. c. The continents were once part of a single land mass called Pangea. 5. b. The earth s crust is made of large pieces, called plates, that have moved over time. 6. c. Old crust is destroyed and new crust is formed at plate boundaries. 7. a. California is located in an area where two plates are sliding past each other. 8. true Teacher s Note: The video describes plates as moving at a rate of 2 inches per year. Different plates move at different rates and in different directions. Later in the Student Book, the continent of North American plate is described as moving away from the plate containing Europe at a rate of 2 cm per year. FOLLOW-UP 3. (LITERACY) Review the idea that plate tectonics describes the movement of lithospheric plates. Discuss Questions 1 3 with the class. Question 3 is a literacy strategy that can be completed as a class. Encourage students to suggest at least one idea in each part of the Venn diagram before working together. This will help them process their own understanding of the similarities and differences between these ideas. Although the video usually refers to the earth s crust, the tectonic plates extend down into the upper mantle. Have students re-read the introduction to the activity to reinforce the idea that it is the entire lithosphere (crust and upper mantle) that is moving, and not just the continents. If students have completed Unit B, Rocks and Minerals, ask, How does plate tectonics help explain the rock cycle? Plate tectonics explains how rocks can melt into magma (when solid parts of the earth s lithosphere are pushed down into hotter layers of melted magma) and why magma is forced up into the surface of the earth (to release pressure formed from the moving of plates). 4. b. volcanoes D-71

56 Activity 42 The Theory of Plate Tectonics SUGGESTED ANSWERS TO QUESTIONS 1. Why were scientists surprised to find coal in the Arctic? Coal is formed in warm wet climates (such as swamps) when large amounts of plants die and are buried over geological time. Today, the Arctic is a cold, snowy area. It is surprising to find the fossil remains of a material that formed in a climate so different than that of the present-day Arctic. 2. Think about what you learned from the video about where volcanoes are most likely to occur. Based on this information, do you think that the risk of a volcanic explosion at Yucca Mountain is high or low? Explain. 3. (LITERACY) a. The idea of continental drift eventually led to the modern theory of plate tectonics. To help you remember similarities and differences between these two ideas, create a larger version of the Venn diagram shown below in your science notebook. b. Compare continental drift and plate tectonics by recording unique features of each idea in the circle with that label. Hint: Think about what you have learned about these ideas in the last few activities. c. Record features that are common to both these ideas in the space that overlaps. The risk is low, since volcanoes are most likely to occur at plate boundaries. Possible features that students may record in their Venn diagrams are listed in the table below. Possible Responses to Analysis Question 3 Continental Drift Both Plate Tectonics Describes continents Continents rearrange (join together and drift apart) Original idea Proposed by Alfred Wegener in 1915 Occur over geological time Land was once all connected in supercontinent known as Pangea Land masses have moved over the earth s surface Relies on evidence from fossils and rock layers Describes the earth s plates (i.e. including crust under oceans) Lithosphere is destroyed and formed at plate boundaries Modern theory supported by additional evidence such as satellite measurements of continental movement Helps explain earthquakes, volcanoes, mountain formation D-72

57 Name Date Plate Tectonics Video 1. When Alfred Wegener first noticed that the continents fit together like puzzle pieces, this was: a. an idea b. a theory c. proof of continental drift 2. Check every piece of evidence that Alfred Wegener used to develop and support his ideas: Fossils of the lizard-like Mesosaurus were found in both Brazil and South Africa. Maps of the continental shelf below the ocean s surface show how Africa and South America fit together. There are glacier marks in South Africa. Coal has been found on Arctic islands. 3. Continental drift is the idea that: a. the earth s crust has cooled and contracted over millions of years. b. sections of the earth s crust have collapsed underwater, leaving continents. c. the continents were once part of a single land mass called Pangaea. 4. During World War II, what did scientists discover on the ocean floor? a. fossils b. volcanoes c. a new species of shark 5. Plate tectonics is the idea that: a. the earth s crust is made of large pieces, called plates, that cannot move. b. the earth s crust is made of large pieces, called plates, that have moved over time. c. the continents float on the oceans like plates The Regents of the University of California 6. Which of the following statements about the earth s crust is true? a. The earth s crust moves around but is never destroyed. b. Old crust falls into the oceans and is destroyed by ocean currents. c. Old crust is destroyed and new crust is formed at plate boundaries. 7. Why are there so many earthquakes in the state of California? a. California is located in an area where two plates are sliding past each other. b. The ground in California contains a lot of sand and is very unstable. c. Large ocean currents sometimes collide with the coast of California. 8. True or False: The plates keep moving and are still moving today. Issues and Earth Science Student Sheet 42.1 D-73

58 Measuring Earthquakes to minute sessions ACTIVITY OVERVIEW M O D E L I N G Students model how a seismograph records earthquakes as they explore the relationship between earthquakes and plate boundaries. KEY CONCEPTS AND PROCESS SKILLS (with correlation to NSE 5 8 Content Standards) 1. Creating models is one way to understand and communicate scientific information. (Inquiry: 1) 2. The continents are part of large lithospheric plates that have moved over geological time and continue to move at a rate of centimeters per year. (EarthSci: 1, 2) 3. The movement of the earth s plates can produce earthquakes and volcanoes, and result in the formation of mountains over geological time. (EarthSci: 1) KEY VOCABULARY earthquake plates Richter scale seismograph seismogram fault (optional) D-75

59 Activity 43 Measuring Earthquakes MATERIALS AND ADVANCE PREPARATION For the teacher 1 Scoring Guide: GROUP INTERACTION (GI) 1 Transparency 43.1, Earthquake Strength * 1 overhead projector For each group of four students 1 seismograph model 1 black marker * 4 sheets of plain paper 8 toothpicks For each student * 1 pair of safety goggles 1 Scoring Guide: GROUP INTERACTION (GI) (optional) *Not supplied in kit This activity provides an opportunity to assess students on their ability to work in groups. You can use the GROUP INTERACTION (GI) Scoring Guide to assess students ability to work as a group and respectfully consider each other s ideas. Masters for Scoring Guides can be found in Teacher Resources III: Assessment. SAFETY Remind students to pay attention to the other people and objects in the vicinity when moving the different parts of the seismograph model. If students have long fingernails that could potentially scratch the hands of other students, demonstrate how to hold the seismograph so that nails are pointed away from the hands of other group members. TEACHING SUMMARY Getting Started 1. Introduce the seismograph model. Doing the Activity 2. (GI ASSESSMENT) Students model earthquakes. Follow-Up 3. Apply observations from the model to plate tectonics.if this works) D-76

60 Measuring Earthquakes Activity 43 BACKGROUND INFORMATION Earthquakes An earthquake is the sometimes violent vibration of the earth s surface that follows a release of energy in the earth s lithosphere. This energy can be generated by a sudden dislocation of segments of the lithosphere, by a volcanic eruption, or even by manufactured explosions. The largest earthquakes, and many smaller ones, are a result of movements within the rocks of the lithosphere. The tectonic plates that form the outer surface of the earth continue to move. Sometimes the movement is gradual, while at other times, the plates are locked together, unable to release accumulating energy. Eventually the plates break free, causing an earthquake. The lithosphere may first bend and then, when the stress exceeds the strength of the rocks, break and snap to a new position. In the process of breaking, vibrations called seismic waves are generated. These waves travel outward from the source of the earthquake along the surface and through the earth at varying speeds, depending on the material through which they are moving. Earthquakes can be destructive in many ways. Earthquakes that occur beneath the ocean floor sometimes generate tsunamis, like the one that affected southeast Asia in December Other earthquakes can cause landslides or liquefaction of the soil. The region where an earthquake s energy originates is known as the focus, with the focus of most earthquakes occurring in the earth s crust or upper mantle. Deep earthquakes may originate up to 700 kilometers (435 miles) below the suface, which is still only 10% of the depth to the center of the earth s core. Earthquakes are also commonly located by their epicenter, which is the point on the earth's surface directly above the focus. A fracture in the earth s surface, along which two blocks of the crust have slipped, is known as a fault. Faults are usually described by how the blocks move in relation to each other. Geologists have found that earthquakes tend to reoccur along faults, which reflect zones of weakness in the earth's crust and which are often found on or near tectonic plate boundaries. Scientists use machines called seismographs to measure earthquakes. A seismograph is designed to address that fact that when the ground moves, so does the seismograph. These machines usually contain a large suspended mass (which tends to remain at rest) attached to a recording structure. A seismograph records the difference in motion between the earth s surface and the suspended mass. Since a single seismograph can only record motion in a single direction, most sites contain several seismographs (including one that can measure vertical motion). REFERENCES Shedlock, Kaye M., and Pakiser, Louis C. (1994) Earthquakes. Washington, D.C.: U.S. Geological Survey. U.S. Geological Survey. (August 17, 2005) Earthquake Hazards Program: Earthquakes: Frequently Asked Questions (website). U.S. Department of the Interior. Retrieved August 2005 from earthquake.usgs.gov/faq/plates.html D-77

61 Activity 43 Measuring Earthquakes TEACHING SUGGESTIONS GETTING STARTED 1. Introduce the seismograph model. Ask students if any of them have experienced an earthquake. If so, have the student describe what it felt like. (If you are in an earthquake-prone area, it is likely that many students will want to share their experiences. You may want to limit this discussion to no more than 5 minutes.) If no one in your class has experienced an earthquake, you may want to share the following U.S. Geological Survey description: Generally, during an earthquake you first will feel a swaying or small jerking motion, then a slight pause, followed by a more intense rolling or jerking motion. The duration of the shaking you feel depends on the earthquake's magnitude, your distance from the epicenter, and the geology of the ground under your feet. Use the Student Book introduction to review the concept of a seismograph and a seismogram. DOING THE ACTIVIT Y 2. (GI ASSESSMENT) Students model earthquakes. Demonstrate how to set up the seismograph model and then explain how to use the model to produce a seismogram. The model requires a large surface to support all of the moving parts. If you do not have large tables available, you may want to have students work with the model while sitting on the floor. In either case, remind students to be aware of the location of other students and to use the model correctly and safely. You may also want to review seating arrangements so that each role is conducted properly. The illustration after Procedure Step 2 of the Student Book illustrates how students can work together to use the seismograph model. The two people pushing Plates A and B (the Plate Holders) should be seated next to each other. The Data Recorder should sit at a right angle on their right-hand side (so that the paper tray is easily pulled). The Observer should sit on their left-hand side. This ensures that no one is facing Plate B as it is pushed away from the Plate B Holder. Some students may be concerned that they will not be able to conduct their role properly, but use this as an opportunity to explain this as the reason that each student will perform his or her role two times in a row. Each group of four will conduct a total of eight trials, and every student will have a chance to produce two seismograms by pushing Plate B twice. Although it is the Data Recorder who will ensure that the seismogram is recorded, the actual data will be a result of the Plate B Holder pushing the model and breaking the toothpick. It is not necessary for every trial to produce valid data (i.e. a good seismogram). Distribute the materials and have students complete the Procedure. You may wish to assess how well students are working together using the GROUP INTERACTION (GI) Scoring Guide. Remind students to write their observations of the seismograph model, the seismogram, and the force required to break the toothpick in their science notebooks. Encourage them to compare their observations to previous trials. FOLLOW-UP 3. Apply observations from the model to plate tectonics. Have students take a few minutes to discuss Question 1 in their groups. Then, hold a full class discussion of Questions 1 and 2 and review the model. Display Transparency 43.1, Earthquake Strength, and point out that there are different ways of measuring the strength of an earthquake. One approach is quantitative and the other qualitative. Introduce or review the Richter scale, which is used to quantitatively rate the strength, or magnitude, of an earthquake at the point where the rocks break, and the Mercalli scale, which is used to qualitatively rate the damage done, or intensity, of the earthquake at a particular place on the surface. Each increase of 1 on the Richter scale is equal to a D-78

62 Measuring Earthquakes Activity fold increase of released energy. Point out that there is a general correspondence between the Richter and Mercalli scales. However, an earthquake with a higher Richter value can do little or no damage if it occurs far enough away and vice versa an earthquake with a lower Richter value can do considerable damage if it occurs very close by. Ask, Did your seismograms provide you with enough information to compare the strength of your earthquakes? Answers will vary. Some students may observe that the wavy line was more pronounced when the earthquake was more intense, while others may not see any significant relationship, except that a wavy line (vs. a straight line) was recorded when the earthquake occurred (when the toothpick broke). Ask, How can modeling earthquakes help you understand plate tectonics? Explain that the movement of the lithospheric plates requires enormous amounts of energy and that this energy can build up. When it is released all at one time, this energy causes earthquakes. This explains the frequency of earthquakes along plate margins. SUGGESTED ANSWERS TO QUESTIONS 1. What similarities and differences did you observe among your group s 8 seismograms? Student responses will vary. In general, several of the seismograms should show a straight line, followed by one or more waves, and again more of the straight line. This corresponds to the initial pulling by the Data Recorder (when there was no plate movement), followed by the breaking of the toothpick as Plate B was pushed past Plate A, and finally a straight line again as the sudden motion ended. Students are likely to have seismograms with varied kinds of data, including situations in which very little data was recorded (the pen was no longer touching the paper), the mark went off the paper (an extremely violent movement of the plates), a single straight line (either because the Data Recorder forgot to say Start, or because the Plate B Holder could not break the toothpick before the length of paper ran out), and so on. 2. a. What did each half of the seismograph model represent? A plate on the earth s surface. b. What did the toothpick represent? (Hint: Reread the introduction to this activity.) Underground rock. When rock layers that are stuck together by the high pressures beneath the earth s surface, they tend to resist motion until a critical force is applied. c. When did an earthquake occur? It occurred when: the Data Recorder began pulling the paper tray. Plate B was first pushed. the toothpick broke. The earthquake occurred when the toothpick broke. d. What type of plate movement did you simulate? plates colliding plates sliding past each other plates pulling apart The activity simulated plates sliding past each other. 3. Describe what the seismogram looked like a. when there was little or no movement It recorded a straight line. b. when the toothpick broke. It recorded one or more wavy lines that were perpendicular to the straight line. 4. This activity modeled an earthquake occuring along a plate boundary. What do you think are the strengths and weaknesses of this model? Strengths of this model include the sudden earthquake motion that occurs when the toothpick snaps, the recording of this movement as a seismogram, and earthquakes resulting from the movement of sliding plates. Weaknesses of this model include the use of people s hands to move the plates and the paper, the use of a toothpick to provide resistance instead of rock, and the lack of quantitative data. D-79

63 Earthquake Strength 2012 The Regents of the University of California Issues and Earth Science Transparency 43.1 D-81

64 Mapping Plates to 1 50-minute session ACTIVITY OVERVIEW P R O B L E M S O LV I N G Students compare the sizes and shapes of continents with those of plates as they color in the continents and trace plate boundaries. The relationship between plate boundaries, earthquakes, and volcanoes is reinforced as students use earthquake and volcano data to both plot and draw missing plate boundaries. Students then label the major plates and use directional data to draw arrows showing the direction that they are moving. KEY CONCEPTS AND PROCESS SKILLS (with correlation to NSE 5 8 Content Standards) 1. The crust and the solid upper layer of the mantle are known as the lithosphere. (Earth Sci: 1) 2. The continents are part of large lithospheric plates that have moved over geological time and continue to move at a rate of centimeters per year. (EarthSci: 1, 2) 3. The movement of the earth s plates can produce earthquakes and volcanoes, and result in the formation of mountains over geological time. (EarthSci: 1) KEY VOCABULARY continent lithosphere plates risk D-83

65 Activity 44 Mapping Plates MATERIALS AND ADVANCE PREPARATION For the teacher 1 color transparency, Layers of the Earth 1 Transparency 44.1, Key to Plate Boundaries 1 metric ruler * 1 overhead projector For each student 1 Student Sheet 44.1, Anticipation Guide: Mapping Plates 1 Student Sheet 44.2, Plate Boundaries * 1 light-colored pencil (such as yellow) * 1 dark marker (such as purple) *Not supplied in kit TEACHING SUMMARY Getting Started 1. (LITERACY) Elicit student ideas about the earth s plates using Student Sheet Doing the Activity 2. Students complete Student Sheet Follow-Up 3. ( LITERACY) Students revisit their initial ideas as they discuss the movement of the lithospheric plates.f this works) REFERENCES Smithsonian National Museum of Natural History. (n.d.) Global Vulcanism Program: Volcanoes of the World, Find a Volcano by Region (website). Retrieved August 2005 from VolcanoWorld, University of North Dakota Department of Space Studies. (2001) Volcano World Volcano Index (website). Retrieved August 2005 from volcano.und.edu/vwdocs/volc_images/sorted_by_region.html D-84

66 Mapping Plates Activity 44 TEACHING SUGGESTIONS GETTING STARTED 1. (LITERACY) Elicit student ideas about the earth s plates using Student Sheet Students began to investigate plate tectonics from a historical perspective by first considering the idea of continental drift. They know scientists believe that the earth s continents were once connected as a result of plate movement and that plate tectonics describe the movement of the earth s lithosphere. This activity is intended to help synthesize the relationship between continents (which students have frequently seen on world maps) and the plates referred to in plate tectonics. Remind students that, unlike continental drift (which referred only to continents), plate tectonics refers to the movement of lithospheric plates. These plates include the earth s crust and extend down into the uppermost part of the upper mantle. You may want to use the color transparency, Layers of the Earth, to review this idea. Begin by asking, In Activity 40, The Continent Puzzle, what did the puzzle pieces represent: continents or plates? They represented continents. Remind students that the theory of plate tectonics does not just describe the movement of continents, but the entire surface of the earth, which is broken up into numerous plates. Hand out Student Sheet 44.1, Anticipation Guide: Mapping Plates. You may want to read the statements aloud and clarify any questions students might have about their meaning. Instruct each student to record whether they agree or disagree with each statement by placing a + or in the Before column. Explain that they will have a chance to revisit these statements after the activity, to examine whether their ideas have changed or remained the same. DOING THE ACTIVIT Y 2. Students complete Student Sheet Students should use a light-colored pencil to shade in all of the continents and a dark marker to trace the boundary lines. They can then use the data in the Student Book to plot places where earthquakes have occurred and volcanic mountains exist. By connecting these points (generally from top to bottom and left to right), they will create lines that approximate the missing South American plate boundaries. Students are expected to be able to label the eight major plates with their names, since they correspond to the names of the continents (and the country of India.) If necessary, remind students to use their notes or the map from Activity 40, The Continent Puzzle, to help them with this step. You may need to guide some students on how to draw arrows pointing northeast, southeast, or northwest. Remind students that the map on Student Sheet 44.2 represents the earth, which is a sphere. The Pacific plate seen on the left side of the map extends throughout the Pacific Ocean, which is also depicted on the right side of the map in this projection. You may want students to fold over the right and left margins of the student sheet to try to create a paper tube that matches the North American and Pacific plates on either side of the map. When reviewing the map with students, you may want to identify key locations on the map such as the equator (0 latitude), the Prime Meridian (0 longitude), The Tropics of Cancer and Capricorn (about +23 N and -23 S latitude respectively), the International Date Line (about +180 longitude) and the north and south poles (+90 N and -90 S latitude respectively). FOLLOW-UP 3. (LITERACY) Students revisit their initial ideas as they discuss the movement of the lithospheric plates. After they finish the activity, have students complete Student Sheet 44.1 by either agreeing or disagreeing with the statements in the After column. Students are then expected to explain how the activity gave them evidence to support or change D-85

67 Activity 44 Mapping Plates their ideas. Be sure to discuss student responses and review the accuracy of each statement. Final Responses to Student Sheet The surface of the earth is divided into more than 50 large plates. 2. All of the earth s plates are about the same size The plates include the lithosphere under the oceans. 4. All of the earth s plates are moving in the same direction. 5. The edges of continents are the same as the boundaries of plates. Statement 1: There are fewer than 50 large plates shown on Student Sheet The number of large plates is closer to 20. Statement 2: The plates are different sizes. For example, the Indian plate is much smaller than the Eurasian plate. Statement 3: True. The plates include both continental and oceanic lithosphere, as shown by the plate boundaries extending into and throughout the oceans. Use the color transparency, Layers of the Earth, to highlight the idea that the lithospheric plates extend deep into the earth and that both continents and oceans rest on the upper surface of these plates. Statement 4: Different plates are moving in different directions. For example, North America is moving west, while Eurasia is moving east. Statement 5: While some of plate boundaries are found along continent edges (such as western North and South America), many plate boundaries do not match the boundaries of continents. The eastern coast of the U.S. is one example. out the distance involved. Explain that a large amount of energy is required to move a land mass as large as the North American plate even such a small distance. Understanding the amount of force required to move a plate helps explain the huge amount of energy released during large earthquakes. Inform students that not all plates are moving at the same speed. The rate may vary from 1 10 cm per year. Ask, How far will a plate move in 100 years? A plate will move between 100 1,000 cm, or 1 10 meters. SUGGESTED ANSWERS TO QUESTIONS 1. Are the sizes and shapes of the continents the same as the sizes and shapes of the plates? Support your answer with a specific example from Student Sheet While there is some similarity with those continents whose boundaries are close to the plate boundary, most continents and plates have differing sizes and shapes. For example, the Australian continent appears to be about one-third of the size of the plate that it is a part of, and the boundary edges are very different. Other examples may refer to ideas such as: Several plates contain entire continents and the adjacent ocean floor, such as the African plate, and are much larger than the continent itself. Eurasia is made up of several plates, including the Indian, Arabian, and part of the North American plate. Several (oceanic) plates are smaller than continents (such as the Caribbean and Philippine plates). Now that students have a sense of the large size of earth s plates, remind them that the North American and Eurasian plates are moving apart at a rate of 2 cm per year. Hold up a metric ruler and point D-86

68 Mapping Plates Activity Look again at Table 2, Some Major Earthquakes and Volcanoes in Central and South America, on the previous page [in the Student Book]. In terms of geological time, would you consider these volcanoes and earthquakes to have occurred recently or a long time ago? Explain. Geological time spans billions of years. The amount of time that has passed since the last occurrence of the listed earthquakes and volcanoes is only a little over one hundred years, a very recent period in geological time. 3. What is the relationship between earth quakes, volcanoes, and plate boundaries? Earthquakes and volcanoes occur more frequently along plate boundaries than on other parts of the earth s surface. In this activity, students used earthquake and volcano data to plot plate boundaries. 4. In Activity 36, Storing Waste, you learned that Nevada has the fourth highest number of earthquakes per year in the U.S. Which state would you predict to have a higher risk of earthquakes: Washington or Texas? Why? Washington, because it is closer to a plate boundary than Texas. 5. In Activity 40, The Continent Puzzle, the country of India was a separate puzzle piece. Use the information on Student Sheet 44.2 to help you explain why. India is part of the Indian plate, while most of Eurasia is part of the Eurasian plate. Since these continents are a part of two different plates, they moved separately over the surface of the earth. Having a separate puzzle piece for India meant that the individual movement of both of these plates could be modeled in Activity 40. D-87

69 Key to Plate Boundaries 2012 The Regents of the University of California Issues and Earth Science Transparency 44.1 D-89

70 Name Date Anticipation Guide: Mapping Plates Before starting the activity, mark whether you agree (+) or disagree ( ) with each statement below. After completing the activity, mark whether you agree (+) or disagree ( ) with each statement below. Under each statement, explain how the activity gave evidence to support or change your ideas. Before After 1. The surface of the earth is divided into more than 50 large plates. 2. All of the earth s plates are about the same size. 3. The plates include the lithosphere under the oceans The Regents of the University of California 4. All of the earth s plates are moving in the same direction. 5. The edges of continents are the same as the boundaries of plates. Issues and Earth Science Student Sheet 44.1 D-91

71 Name Date Plate Boundaries 2012 The Regents of the University of California Issues and Earth Science Student Sheet 44.2 D-93

72 Understanding Plate Boundaries 40- to minute sessions ACTIVITY OVERVIEW 45 R E A D I N G Students read about how the theory of plate tectonics helps explain earthquakes, volcanoes, and mountain ranges. They use a literacy strategy known as a DART (directed activity related to text) to organize the information presented in the reading. KEY CONCEPTS AND PROCESS SKILLS (with correlation to NSE 5 8 Content Standards) 1. Volcanoes can be a constructive force that result in the formation of new landforms, such as mountains. Differences in volcanic eruptions result in the different shapes of volcanic mountains. (EarthSci: 1) 2. The crust and the solid upper layer of the mantle are known as the lithosphere. (Earth Sci: 1) 3. The continents are part of large lithospheric plates that have moved over geological time and continue to move at a rate of centimeters per year. (EarthSci: 1, 2) 4. The movement of the earth s plates can produce earthquakes and volcanoes, and result in the formation of mountains over geological time. (EarthSci: 1) 5. Land forms are the result of constructive and destructive forces. Constructive forces include lithosphere deformation, volcanic eruption, and deposition of sediment, while destructive forces include weathering, and erosion. (Earth Sci: 1) KEY VOCABULARY convergent divergent lithosphere magma subduction transform hot spot (optional) D-95

73 Activity 45 Understanding Plate Boundaries MATERIALS AND ADVANCE PREPARATION For each student 1 completed Student Sheet 44.2, Plate Boundaries 1 Student Sheet 45.1, Directed Reading Table: Understanding Plate Boundaries *Not supplied in kit TEACHING SUMMARY Getting Started 1. Use Figure 1 to discuss the location of earthquakes and volcanoes on the earth. Doing the Activity 2. (LITERACY) Students read about how plate tectonics helps explain earthquakes, volcanoes, and mountain ranges. Follow-Up 3. Review the constructive and destructive forces that shape the surface of the earth.if this works) BACKGROUND INFORMATION Types of Plate Boundaries The size of the earth has stayed the same during the past 600 million years, and has probably not changed since soon after it first formed 4.6 billion years ago. This implies that the formation of new crust must be happening at the same rate as crust destruction. Crustal formation and destruction occurs at plate boundaries, where plates are moving against each other. The movement of these plates can usually be described by one of three types of motion: transform, divergent, or convergent. 1. Transform (sliding): The area between two plates sliding horizontally past each other is called a transform boundary. These types of plate boundaries are generally associated with faults and shallow earthquakes. Most transform boundaries are found on the ocean floor, though a few well-known ones, like the San Andreas fault zone in California and the Alpine fault in New Zealand, occur on land. 2. Divergent (spreading): Divergent boundaries occur where plates are moving apart and new lithosphere is being created by magma pushing up from the mantle. In the ocean, this process is called sea floor spreading, and on land, rift valleys are formed. Both earthquakes and volcanoes are common along this type of boundary. D-96

74 Understanding Plate Boundaries Activity 45 The mid-atlantic ridge, which marks the boundary between the North American and Eurasian plates and the South American and African plates, is one example of a divergent boundary. It is currently spreading at an average rate of 2.5 cm per year, or 25 km every million years. Seafloor spreading over the past million years has caused the Atlantic Ocean to grow from a narrow body of water between the continents of Europe, Africa, and the Americas into the large ocean that it is today. 3. Convergent (colliding): The type of convergence that takes place between plates depends on the kind of lithosphere involved. Convergence can occur between two continental plates, between an oceanic and a continental plate, or between two oceanic plates. When two continental plates collide, the lithosphere tends to buckle and be pushed upwards or sideways. This can result in the formation of tall mountain ranges. The Himalayan mountain range, which is a result of the Indian and Eurasion plates colliding, is a good example of this type of plate boundary. When an oceanic plate is involved, one plate may descend beneath the other, in part due to the higher density of oceanic plates relative to continental plates. The location where the plate descends is called a subduction zone, and both earthquakes and volcanoes are common in this zone. REFERENCES Anderson, D. L. (2009). Plate tectonics, platonics, and logic. Retrieved January 7, 2012, from MantlePlumes website, Kious, W. Jaquelyne, and Tilling, Robert I. U.S. Geological Survey. (1996). This Dynamic Earth: The Story of Plate Tectonics (online edition). Retrieved November 2004 from pubs.usgs.gov/publications/text/historical.html McNutt, M.K. (2006). Another nail in the plume coffin? Science, 313, U.S. Geological Survey. (2012). Magnitude 9.0 Near the east coast of Honshu, Japan. (Website). U.S. Department of the Interior. Retrieved January 4, 2012, from D-97

75 Activity 45 Understanding Plate Boundaries TEACHING SUGGESTIONS GETTING STARTED 1. Use Figure 1 to discuss the location of earthquakes and volcanoes on the earth. The Student Book contains a map that shows the location of individual earthquakes and volcanoes. Ask students to spend some time looking at the map and ask them questions such as: Is there an even distribution of earthquakes and volcanoes over the surface of the earth? No. There are regions where there are high concentrations of earthquakes and volcanoes, and when these are plotted on a map, they appear to form lines over the surface of the earth. What do you observe about the pattern of earthquakes and volcanoes on the earth? Where do they occur? Both earthquakes and volcanoes can be seen occurring in some of the same areas. There are a high number of both phenomena around the western edge of the Pacific Plate (known as the Ring of Fire ) as well as on the western coast of North and South America. How does this map compare to the plate boundaries you mapped on Student Sheet 44.2, Plate Boundaries? The pattern of earthquakes and volcanoes outline many of the same plate boundaries that were mapped on Student Sheet Inform students that the theory of plate tectonics helps explain this pattern of earthquakes and volcanoes, and students will find out more in the reading. DOING THE ACTIVIT Y 2. (LITERACY) Students read about how plate tectonics helps explain earthquakes, volcanoes, and mountain ranges. Directed Activities Related to Text (DART) is a literacy strategy in which students are provided with a structured activity related to the reading that helps them process written information. Student Sheet 45.1, Directed Reading Table: Understanding Plate Boundaries, is a DART that guides students to identify and summarize important points from the text. Hand out Student Sheet If your students are good readers, you may wish to assign the reading for homework. Sample Response to Student Sheet 45.1 Type of Plate Motion Scientific Term for Boundary Type At this type of plate boundary, which of the following geological processes are likely to occur? earthquakes volcanoes mountain formation At this type of plate boundary, what happens to the lithosphere? It is: formed destroyed neither Example of this type of plate boundary Sliding transform earthquakes neither boundary between Pacific plate and North American plate off west coast of California Spreading divergent earthquakes, volcanoes, volcanic mountain formation Colliding convergent earthquakes, volcanoes, mountain formation formed destroyed boundary in middle of Atlantic Ocean between North American and Eurasian plates and between South American and African plates boundary between Indian and Eurasian plates; boundary between western edge of South American plate and adjacent Nazca plate, Juan de Fuca plate boundary, boundary between Pacific Plate and continental plate east of Japan. D-98

76 Understanding Plate Boundaries Activity 45 FOLLOW-UP 3. Review the constructive and destructive forces that shape the surface of the earth. Before discussing the Analysis Questions, be sure to review responses to Student Sheet Then discuss Question 1. Ask, Think back to Unit C, Erosion and Deposition. What is another way that new landforms can take shape over time? This can happen through the process of deposition. Ask, Mountain formation often occurs at plate boundaries. What forces did you learn about in Unit C that contribute to the break down of landforms over time? This can happen through the process of erosion and weathering. Highlight the idea that the surface of the earth is constantly changing as a result of constructive and destructive forces. Constructive forces include lithosphere deformation, volcanic eruption, and deposition of sediment, while destructive forces include weathering and erosion. Analysis Questions 2 and 3 relate the types of boundaries in this reading to the plate boundaries that the students mapped on Student Sheet 44.2, Plate Boundaries. Question 4 provides an opportunity to reinforce the relationship between plate tectonics and the rock cycle. SUGGESTED ANSWERS TO QUESTIONS 1. Describe two ways in which the movement of lithospheric plates can result in the formation of mountains. One way is when two continental plates collide and the rock is pushed upward, as with the Himalayan mountains. Another way is when the lava from volcanic eruptions builds up around a vent and forms a volcanic mountain, like those seen at divergent boundaries and subduction zones. 2. On Student Sheet 44.2, Plate Boundaries, you drew the boundaries of large, lithospheric plates. Use information from this reading to identify and label a. a transform boundary A transform boundary is located in California between parts of the Pacific and North American plates. b. a divergent boundary A divergent boundary is located in middle of the Atlantic Ocean between the North American and Eurasian plates as well as between the South American and African plates. c. a convergent boundary A convergent boundary is located between the Indian and Eurasian plates, as well as between the western edge of the South American plate and the adjacent Nazca plate (this is also a subduction zone). 3. Yucca Mountain is located close to H6 on Student Sheet 44.2 Which type of boundary is closest to it? The transform boundary located in California between parts of the Pacific and North American plates. 4. In Unit B, Rocks and Minerals, you learned about three different types of rocks: igneous, metamorphic, and sedimentary. Which type of rock would you expect to find along a divergent plate boundary? Explain. Igneous, because igneous rocks are formed from the cooling of magma. One way that magma reaches the surface of the earth is through volcanoes. Volcanoes tend to form at divergent plate boundaries as the lithosphere thins and molten magma erupts onto the surface. D-99

77 Name Date Directed Reading Table: Understanding Plate Boundaries Type of Plate Motion Scientific Term for Boundary Type Sliding Spreading Colliding 2012 The Regents of the University of California At this type of plate boundary, which of the following geological processes are likely to occur? earthquakes volcanoes mountain formation At this type of plate boundary, what happens to the lithosphere? It is: formed destroyed neither Example of this type of plate boundary Issues and Earth Science Student Sheet 45.1 D-101

78 Convection Currents 40- to 1 50-minute session ACTIVITY OVERVIEW 46 L A B O R AT O R Y Students explore the mechanism behind plate motion as they investigate convection currents. KEY CONCEPTS AND PROCESS SKILLS (with correlation to NSE 5 8 Content Standards) 1. The earth is made of up different layers (crust, mantle, outer core, inner core). Each of these layers has distinct properties. (Earth Sci: 1) 2. The continents are part of large lithospheric plates that have moved over geological time and continue to move at a rate of centimeters per year. One theory is that convection currents within the earth's mantle drive this plate motion. (EarthSci: 1, 2) KEY VOCABULARY convection current magma mantle D-103

79 Activity 46 Convection Currents MATERIALS AND ADVANCE PREPARATION For the class * supply of warm water * supply of cold water For each group of four students 2 9-oz. plastic cups (or other large containers) 1 plastic syringe 1 plastic cup with circular depression 1 small vial with 2-holed cap 1 bottle of red food coloring * paper towels and/or a sponge *Not supplied in kit Make sure you have plenty of both warm and cold water available. This investigation will work if students use the 9-oz plastic cups provided, but works better if they use larger containers, such as 500-mL beakers. The vial snaps into the base of the plastic cup with the circular depression. In some cases, it is a very tight fit and the vial must be forcefully pushed into place. You may want to check your materials and snap the two pieces together prior to conducting this activity with the class. SAFETY This activity requires the use of warm water. However, extremely hot (e.g. boiling) water is not required; warm tap water will work fine, though it helps to use water that is warm enough so that it doesn t cool down too rapidly. Allow very hot water to cool slightly before allowing students to use it. Review classroom expectations for safety during this activity. TEACHING SUMMARY Getting Started 1. Students read the introductory text in the Student Book. Doing the Activity 2. Students investigate convection currents. Follow-Up 3. Discuss how differences in temperature cause convenction currents. D-104

80 Convection Currents Activity 46 TEACHING SUGGESTIONS GETTING STARTED 1. Students read the introductory text in the Student Book. Have students read the introduction and Challenge. Explain that convection is the circulation of a fluid due to differences in temperature. Students will investigate the formation of a convection current by mixing warm and cold water in two different trials. They will observe which trial results in the formation of a convection current. DOING THE ACTIVIT Y 2. Students investigate convection currents. Demonstrate how to use the equipment, particularly the small vial that fits into the plastic cup. Make clear to students that the 2-holed cap must face up when the vial is snapped into place. Help students as needed. You may need to provide assistance in recording observations. Students may find it helpful to construct a quick sketch of the movement of the colored water. Have students complete the investigation. After adding cold water to the warm water in the vial in Trial 1, the warmer, less dense red water should flow out of the holes in the vial and rise above the top of the colder water in the cup. When warm water is added to cold water in the vial in Trial 2, nothing should happen, since the colder, denser water is already below the hot water. If the cup is accidentally moved during Trial 2, it is possible that some of the cooler, red water will flow out of the vial. If this happens, it should appear to settle at the bottom of the cup. FOLLOW-UP 3. Discuss how differences in temperature cause convenction currents. guide students understanding of convection currents. Ask students to share their responses, and discuss how the differences in water temperature resulted in the formation of a convection current. Explain that convection currents require a source of heat. Remind students that the temperature of the earth s layers increases with depth. You may want to have students turn to Table 1, Layers of the Earth, at the end of the Reading in Activity 38, Beneath the Earth s Surface, to compare the relative temperatures. Since the core is much hotter than the mantle, it would continue to heat magma in the mantle as it began to cool and sink. Scientists hypothesize that the source of the earth s heat is either the radioactive decay of naturally-occurring radioactive elements within the earth s core, or residual heat from the formation of the earth, 4.6 billion years ago. SUGGESTED ANSWERS TO QUESTIONS 1. a. Did both trials result in the movement of water? Why or why not? Discuss your ideas with your group. Only Trial 1, in which the warm water was placed in the vial, resulted in the movement of water (the warm water rose upward and outward). There was no movement of water in Trial 2. This is because warm water rises and cold water sinks. In Trial 2, the warm water was already on top and the cold water was already at the bottom. b. What do you think is necessary for a convection current to form? It is necessary for warm water to be at the bottom (heated from below) and the cooler water to be sitting above it. It is the rising of warm water and its resulting displacement of the cool water that results in the formation of a convection current. Analysis Questions 1 and 2 are intended to help D-105

81 Activity 46 Convection Currents 2. Compare the results of your two trials. When warm and cold water are mixed, what happens to a. the warm water? It rises to the top. b. the cold water? It sinks to the bottom. 3. Imagine that hotter magma is lying beneath an area of cooler magma deep in the mantle. What do you predict will happen? Be as specific as you can and explain your reasoning. The hotter magma would rise and the cooler magma would sink. This would results in a current. In this activity, water was used to model magma, so I think what happens to water will happen to magma. 4. What do scientists believe cause plates to move? Convection currents within the earth s mantle caused by differences in temperature of magma within the mantle. D-106

82 Spreading Plates 40- to 1 50-minute session ACTIVITY OVERVIEW COMPUTER 47 SIMULATION Students utilize a computer simulation to investigate what happens when the earth s plates move apart. Students investigate the rate of this change on earth as they set the simulation to run for different time periods from 10 years to 20 million years. KEY CONCEPTS AND PROCESS SKILLS (with correlation to NSE 5 8 Content Standards) 1. The earth is over four billion years old, and different events have occurred on earth during different periods of time. (EarthSci: 1) 2. The continents are part of large lithospheric plates that have moved over geological time and continue to move at a rate of centimeters per year. One theory is that convection currents within the earth's mantle drive this plate motion. (EarthSci: 1, 2) 3. The movement of the earth s plates can produce earthquakes and volcanoes, and result in the formation of mountains over geological time. (EarthSci: 1) 4. Creating models is one way to understand and communicate scientific information. (Inquiry: 1) KEY VOCABULARY divergent (spreading) geological time lithosphere mantle plates D-107

83 Activity 47 Spreading Plates MATERIALS AND ADVANCE PREPARATION For the teacher 1 color transparency, Plate Motion Simulation: Screen Shots 1 transparency of Student Sheet 39.2, Paleontology Student s Notes * 1 overhead projector For each pair of students * 1 computer with access to SEPUP Plate Motion Simulation For each student 1 Student Sheet 47.1, Spreading Plate Observations *Not supplied in kit Both this activity and the next require student teams to access the SEPUP Plate Motion Simulation with a computer. You may also choose to conduct both computer-related activities in a single period, depending on computer availability. Activity 47 emphasizes geological time, while Activity 48 investigates additional types of plate boundaries. You may want to do the computer activities first in order to familiarize yourself with the simulation and the potential pitfalls that students may encounter while using the software. You may want to reserve a computer lab, so that students may work in small groups. The simulation is available from the Issues and Earth Science student page of the SEPUP website, as well as on the CD provided with the course materials. You may wish to bookmark the SEPUP website on each computer. TEACHING SUMMARY Getting Started 1. Use screen shots on color transparency to introduce SEPUP s Plate Motion computer simulation. Doing the Activity 2. Students use computers to simulate spreading plates. Follow-Up 3. Students summarize the changes that they observed.f D-108

84 Spreading Plates Activity 47 TEACHING SUGGESTIONS GETTING STARTED 1. Use screen shots on color transparency to introduce SEPUP s Plate Motion computer simulation. The color transparency, Plate Motion Simulation: Screen Shots, shows two of the computer screens that students will see during the simulation. Display it and point out any of the following points that are relevant to your class: The first screen shows a cross-section of the earth s plates at an angle. Each plate can move in one of three directions.students can only pick a direction for Plate 1, because selecting a direction for Plate 1 will automatically set a direction for Plate 2. In this activity, students should select the arrow point to the left, which will result in a divergent boundary. (They will investigate the other directions in the next activity.) After selecting and recording the direction of plate movements, students should click on the SEE PLATES OVER TIME button at the bottom of the screen. Selecting this button will lead to the second screen. The second screen again shows a cross-section of the earth. The earth s surface, lithosphere (crust and upper mantle), and lower mantle can all be seen. The large red arrows indicate the direction of plate movement. They will disappear as the simulation runs. The small yellow arrows show the movement of convection currents in the earth s mantle. It is these convection currents that drive plate motion. They will continue to move during the simulation. Explain to the students that this activity requires excellent observation skills. Students will need to be familiar with the Legend to identify what is happening in the simulation, and will need to make careful observations in order to identify small changes. Point out the legend found on the bottom left-hand of the Screen Shots transparency. Review what each symbol represents. Emphasize the importance of noting the different colors that may appear. For example, if areas of blue appear, it indicates the presence of water. Remind students that the mantle is made up of molten magma, so the red color of the mantle indicates magma. Two different colors are used to represent the two different types of lithosphere. (The color of the earth s surface will vary depending on the features being observed.) DOING THE ACTIVIT Y 2. Students use computers to simulate spreading plates. Hand out Student Sheet 47.1, Spreading Plate Observations. Students should record any changes to the land and water that they observe during the different time periods. If students are having difficulty, remind them that they can replay a period of time repeatedly until they have had a chance to make their observations. If you are concerned that students are not making complete observations, use Sample Response to Student Sheet 47.1 on the next page to review the types of observations (such as changes to the lithosphere or movement of magma into the lithosphere) that you expect students to observe. You may also want to have students draw their observations. The simulation models the convection currents that move within the mantle. Remind students that there are no arrows within the mantle rather, large amounts of magma move in a somewhat circular pattern that is best visualized using arrows. Students have to select a time period for the simulation to run before they can select the RUN button. D-109

85 Activity 47 Spreading Plates Sample Response to Student Sheet 47.1 Period of Time Changes to land, such as: earthquakes volcanoes mountains valleys lithosphere Changes to water, such as: appearance of water formation of oceans or lakes change in direction of rivers 10 years nothing happens except mantle convection nothing happens except mantle convection 100 years a single earthquake slight spreading movement of continental lithosphere 1,000 years several earthquakes along divergent boundary slight indentation (rise) of magma into center of continental lithosphere none none 1 million years 5 million years 20 million years several earthquakes increased indentation (rise) of magma into center of continental lithosphere appearance of a valley on earth s surface many earthquakes magma beginning to rise to surface (through lithosphere) appearance of a valley on earth s surface oceanic lithosphere begins to form along divergent boundary lot of earthquakes underwater volcanoes form along divergent boundary as magma rises to surface two large volcanic islands form at top of screen oceanic lithosphere is clearly visible at center of spreading boundary none small amount of water appears in center of valley valley fills with water, resulting in what could either be a lake or an ocean FOLLOW-UP 3. Students summarize the changes that they observed. Have students summarize the changes that they observed, as described below. Be sure to emphasize the relationship between plate movement, earthquakes, and volcanoes. Changes to the land: Earthquakes occur continuously over geological time. As the plates spread apart, a valley formed and new lithosphere formed along the margins. Small volcanoes began to appear in the center of the valley, eventually forming a few volcanic islands. Changes to the water: Water came in and covered a lot of the new land. It looked like a large lake or ocean. Remind students that divergent boundaries occur where plates are moving apart and new lithosphere is being created by magma pushing up from the mantle. In the ocean, this process is called sea floor spreading, and on land, rift valleys are formed. You may want to remind students that they observed spreading plates that have volcanoes along divergent boundaries during the video, I Can Feel the Earth Move. Scientists discovered volcanoes on the ocean floor and eventually realized that the line of volcanoes marked an area where two plates were D-110

86 Spreading Plates Activity 47 spreading apart. Students mapped part of this boundary when then plotted the eastern boundary of the South American plate in Activity 44, Mapping Plates. You may want to discuss the computer simulation as a model by identifying some of its strengths and weaknesses. For example, one strength of the simulation is that it models some of the events that occur at different types of plate boundaries over different periods of time. One weakness is that it does not differentiate among earthquakes by depth or magnitude; in general, earthquakes at divergent boundaries tend to be shallow and weaker. Today, many divergent boundaries are found underwater at mid-ocean ridges. In the simulation, the divergent boundary occurs on land and begins to form a rift valley. A rift valley may be below sea level, and water may eventually flow into it. Over time, this can result in the formation of a lake or ocean. (Another limitation of the simulation is that some students may have identified this body of water as a river.) Students can imagine that a similar process may have occurred with the breakup of Pangea (in which South America and Africa were once connected) and the resulting formation of the Atlantic Ocean. Today, there is a large rift valley along the eastern edge of Africa known as the Great Rift Valley. The northern part of this rift forms the Jordan River valley as well as the Red Sea. A photo of this region of the rift can be seen in the Student Book. Discuss Question 1 to reinforce the idea that the water in the simulation comes from somewhere else on the earth (and is not magically created). Discuss the ways in which the water can appear, as described in the suggested answer to Question 1. Questions 2 and 3 emphasize the role of geological time. Use a transparency of Student Sheet 39.2, Palentology Student s Notes, to review the amount of time simulated in the computer model versus the length of geological time students considered in Activity 39, Earth Time. While 20 million years is a long period of time in the context of the simulation, it is not a very long period of time in the history of the earth, which is over 4 billion years old. Review student responses to Question 4. After students have identified one or more events, discuss student responses as a class and attempt to put all the events in a single order. You may need to watch the simulation again to do so (and you may find that certain events happen almost simultaneously). SUGGESTED ANSWERS TO QUESTIONS 1. In the simulation, you saw water collect between spreading plates: where does this water come from? It comes from the surrounding regions and from rain. It flows into the region between the plates because this region is a lower elevation than the surrounding areas. For example, ask students to imagine digging a large deep hole next to a lake and then creating a deep channel between the two. If the level of water in the lake was higher than the hole, water would flow into the hole. In other cases, an area may fill with water over time through the accumulation of rain. Students may have seen large areas of pooled water after a sudden or large rainstorm. If the water accumulates faster than it evaporates or filters into the ground, a new body of water can be created. 2. In the simulation, how many years passed before you observed major changes to the earth s surface? It took at least one million years for a narrow valley to form and it took five million years to observe bigger changes, such as a wider valley and the formation of the first volcano. 3. There are seven continents on earth today. How many do you predict there will be a. in 1,000 years? Explain. There would still be seven continents because plates don t move very far in 1,000 years. At a rate of 1 10 cm per year, a plate would move 1,000 10,000 cm ( km). b. in 20 million years? Explain. Students responses will vary, but it may be possible to see some change in the shape and possibly the number of continents by that time. At a rate of 10 cm per year, a plate D-111

87 Activity 47 Spreading Plates could move up to 2,000 kilometers in 20 million years. Today, Senegal (in Africa) and Brazil (in South America) are about 2,575 km apart. Still the change would not be at the scale of the breakup of Pangea, which occurred about 200 million years ago. 4. a. List at least three things that happen as plates spread apart. Possible responses include: a valley forms, volcanoes erupt, earthquakes occur, water flows into the area from other parts of the earth, volcanic islands form, oceanic lithosphere begins to form, and a lake or ocean forms. b. Place these events in order by numbering them. One possible order is shown below. Earthquakes occur. A valley forms as the lithosphere thins. Oceanic lithosphere begins to form. Water flows into the area from other parts of the earth. Volcanoes erupt. A lake or ocean forms. Volcanic islands form. D-112

88 Name Date Spreading Plate Observations Direction of Plate Movement (circle one arrow for each plate) Plate 1 Plate 2 Period of Time Changes to land, such as: earthquakes volcanoes mountains valleys lithosphere Changes to water, such as: appearance of water formation of oceans or lakes change in direction of rivers 10 years 100 years 1,000 years 1 million years 2012 The Regents of the University of California 5 million years 20 million years Issues and Earth Science Student Sheet 47.1 D-113

89 Other Types of Plate Motion 40- to minute sessions ACTIVITY OVERVIEW COMPUTER 48 SIMULATION Students use a computer simulation to investigate what happens when the earth s plates collide as well as slide past each other. They then compare the similarities and differences among the three types of plate boundaries: sliding (transform), spreading (diverging), and colliding (converging). KEY CONCEPTS AND PROCESS SKILLS (with correlation to NSE 5 8 Content Standards) 1. The earth is over four billion years old, and different events have occurred on earth during different periods of time. (EarthSci: 1) 2. The continents are part of large lithospheric plates that have moved over geological time and continue to move at a rate of centimeters per year. One theory is that convection currents within the earth's mantle drive this plate motion. (EarthSci: 1, 2) 3. The movement of the earth s plates can produce earthquakes and volcanoes, and result in the formation of mountains over geological time. (EarthSci: 1) KEY VOCABULARY convergent (colliding) divergent (spreading) geological time lithosphere mantle magma subduction transform (sliding) D-115