Plate Tectonics Investigation Exploration A Look at a watch or clock with a second hand in the classroom. 1. What evidence of movement do you see on the clock face? 2. What other movement do you know takes place on the clock face although you cannot see it? 3. How do you know that this movement of the hour hand takes place? Exploration B 1. Obtain two cans of window glazing, a small pan, water, and a hot plate. 2. Place one can of window glazing in a refrigerator overnight. 3. Obtain the can of window glazing from the refrigerator the following day. 4. Touch the glazing and make some observations. 5. What observations did you make? 6. Place the other can of glazing in a pan of water and place the pan on a hot plate. 7. Make some observations of the glazing after it has been heated. 8. What observations did you make? Exploration C 1. Obtain a beaker or clear glass saucepan, instant chicken soup mix, water, and a hot plate. 2. Heat the chicken soup in a beaker or saucepan on the hot plate. 3. What observations can you make as the chicken soup heats up? Idea Questions Use complete sentences to answer the following questions. 1. How do you think exploration A relates to the idea of plate tectonics and the changing earth? Plate Tectonics Page 1
2. What differences did you observe in the cold and heated glazings from exploration B? 3. How is the heated glazing like the material that makes up the mantle? 4. What observations did you make in exploration C? 5. How do you think exploration C relates to plate tectonics and the changing earth? 6. What special properties and phenomena seen in the mantle support the theory of plate tectonics? Expansion A Reading on the theory of plate tectonics. Although you may think of the ground as solid and immovable, it is actually moving. The surface of the Earth is actually divided into about a dozen rigid, but moving plates. Some of the plates, such as the North American Plate and the Eurasian Plate, are moving apart. The Indian Plate is colliding with the Eurasian Plate. Some plates may slide past each other, such as the Pacific Plate and the North American Plate. These moving plates make up the part of the Earth known as the lithosphere. It is about 100 kilometers thick and is made basically of the igneous rock basalt. The continents have a composition more like that of the igneous rock granite. Because granite is less dense than basalt, continents occur only as pieces embedded in the surface of the more dense lithosphere. The lithosphere plates rest on a layer of the Earth known as the asthenosphere. It contains rock material that is partially melted. As a result, this layer is able to flow in the form of a large and slow moving current. Within these currents, material expands and rises upon heating but contracts and sinks upon cooling. When these currents rise, new material arrives at Earth s surface and pushes older material aside. This push drives the lithospheric plates apart. Where cooler, denser currents are sinking, the lithospheric plates are pulled together. All through time, people noted the similarities in the shape of the west coast of Africa and the east coast of South America. The suggestion was made that perhaps the two continents had once been part of a larger continent that had broken and moved apart. This idea was the start of a theory called continental drift. The most famous version of the theory was proposed in 1912 by Alfred Wegener. His theory was scorned and Plate Tectonics Page 2
ridiculed until the 1960 s. At that point, there were discoveries about volcanoes and earthquakes that lean support to Wegener s continental drift theory. This theory was expanded and became the study of plate tectonics. As stated above there are different ways that plates may move. Diverging boundaries are places where two lithospheric plates are diverging or moving apart. At the boundaries of some areas, the plates are sliding past each other. In California, the North American Plate and the Pacific Plate are sliding past each other along the San Andreas Fault. A fault is a break or crack in the Earth s crust along which movement has occurred. The average rate of movement along the San Andreas fault is five centimeters per year, but some areas have not moved for over a century. These are thought to be the most likely places for future earthquakes. Converging boundaries occur when two plates come together. Two continents may collide and create a collision boundary. The collision may cause the lithosphere at the boundary to be pushed up into a mountain range. The two continents that collided will become one larger continent. The Himalayan Mountains are the result of a collision boundary that is still forming today. A subduction boundary is a special form of a converging boundary. This is when one plate plunges down below another plate. Expansion B The movements of plates are classified three ways. Where one plate meets another, a plate boundary is formed. A converging (colliding) boundary forms when two plates are moving together. The edge of one plate may sink below another producing great heat and pressure. This in turn may lead to volcanoes and earthquakes. Also, huge rock layers may buckle and fold at these boundaries, forming mountains. A diverging (spreading) boundary is found where plates are moving apart. Volcanoes and earthquakes are also found along these boundaries. Fault (sliding) boundaries occur when two plates are rubbing past each other. A fault is a crack in the earth. When the rocks move past each other, earthquakes occur. 1. With your teacher s assistance, draw diagrams illustrating two plates that are converging. Include the three types of plate convergence. 2. Draw a diagram illustrating two plates that are diverging. 3. Draw a diagram illustrating two plates that are faulting. Plate Tectonics Page 3
Expansion C 1. Partially fill a sink or dishpan with water. 2. Open up a dry washcloth in your hand. 3. Does the washcloth feel light or heavy? 4. Moisten one edge of the washcloth in the water. 5. Gently place the washcloth so that it floats on the water surface. 6. Observe the washcloth carefully (especially at its edges) as it starts to sink. 7. What observations did you make? 8. Remove the washcloth from the water and open it up in your hand. 9. Is the mass of the washcloth the same as, less than, or greater than when it was dry? 10. How did the washcloth s density change? 11. What effect did this change in density have on the washcloth? 12. How does this expansion relate to plate tectonics? Expansion D 1. Obtain an audiotape, scissors, metric ruler, plastic tape, and a bar magnet. 2. Cub six short pieces, each about 2.5 cm long, from a length of audiotape. 3. Tape one end of each piece to a flat surface. The pieces should be spaced about 1 cm apart and line up lengthwise in a single line. 4. Touch a bar magnet s north pole to the first piece of audiotape. 5. Reverse the magnet and touch its south pole to the next piece. 6. Repeat steps four and five until you have applied the magnet to each piece of audiotape. 7. Sweep one end of the magnet about 1 cm above the line of audiotape pieces. 8. Observe what happens. 9. What observations did you make? 10. What characteristic of the ocean floor did you observe as you swept the magnet along the line of audiotape pieces? Plate Tectonics Page 4
11. Draw a diagram depicting this characteristic of the ocean floor. Expansion E Sea floor spreading Scientists have gathered considerable evidence to suggest that the ocean floor is spreading in certain areas. We will build a model to help understand this process since it is difficult to observe. 1. Obtain scissors, a metric ruler, two sheets of unlined paper, and a colored marker or pencil. 2. Draw stripes across one sheet of paper, parallel to the short sides of the paper. The stripes should vary in spacing and thickness. 3. Fold the paper in half lengthwise and write the word start at the top of both halves of the paper. Using the scissors, carefully cut the paper in half along the fold line to form two strips. 4. Lightly fold the second sheet of paper into eighths. Then unfold it, leaving creases in the paper. Fold this sheet in half lengthwise. 5. Starting at the fold, draw lines 5.5 cm long on the middle crease and the two creases closest to the ends of the paper. 6. Now carefully cut along the lines you drew. Unfold the paper. There should be three slits in the center of the paper. 7. Put the two stripe d strips of paper together so their start labels touch one another. Insert the start ends of the strips up through the center slit and then pull them toward the side slits. 8. Insert the ends of the strips into the side slits. Pull the ends of the strips and watch what happens at the center slit. 9. Practice pulling the strips through the slits until you can make the two strips come up and go down at the same time. 10. What feature of the ocean floor does the center slip stand for? 11. What prominent feature of the ocean floor is missing from the model at this point? 12. What do the side slits stand for? 13. What does the space under the paper stand for? 14. What do the stripes stand for? Plate Tectonics Page 5
15. How does this expansion relate to plate tectonics and the sea-floor? 16. Explain how differences in density and temperature provide some of the force needed to cause sea-floor spreading and subduction? Expansion F The purpose of this expansion is to help you become familiar with the tectonic plates throughout the world. Materials Colored pencils and Map of the World Procedure: 1. Using the reference map on pages R60 and R61 in the appendix of the textbook, shade in the general boundaries of the world s mountain ranges with a black pencil. Be sure to include the Himalaya Mountains, Alps, Andes Mountains, and Rocky Mountains. 2. Using the map on pages R62 and R63 in the appendix of the textbook, draw in the boundaries of the lithospheric plates. Label each plate using a black pencil. Include the different types of plate boundaries shown on the map and the directions of plate movement. Feel free to come up with your own symbols, but make sure you include a key or legend for the plate boundaries. Shade in each plate using a different color for each plate. Questions: 1. What is the pattern as to the boundaries of the tectonic plates? 2. Where are most of the mountain ranges located in relation to the lithospheric plates? 3. What features are located where plates meet in the ocean and form a diverging boundary? Plate Tectonics Page 6
Reading & Note Taking Assignment Expansion G Cornell Notetaking Two Column Notetaking Before Reading Pages 610 to 642: Obtain a sheet of notebook paper and divide into two parts by drawing a vertical line about 2 to 3 inches from the left edge of the paper. During and After Reading: As you read each subsection, list the subtitles in the reading on the left side of the line on your sheet of paper as you read. Jot the important details to the right side of each subtitle as you read about each subtitle. Read and take notes over only those subsections below. Note the number of notes required to earn full points for this expansion. After Reading: Your teacher will spend class time discussing what you read. Add important points you missed and take out points you feel do not have much importance. 58 Total Notes x 2 Points Each + 4 Free Points = 120 Points 1. The lithosphere is made up of many plates 1 2. Continents join together and split apart 2 3. Evidence for Continental Drift Fossils 2 4. Evidence for Continental Drift Climate 4 5. Evidence for Continental Drift Geology 2 6. Pangaea and Continental Drift 1 7. Evidence from the Sea Floor Sea-Floor Spreading 1 8. Evidence from the Sea Floor Age of the Sea Floor 2 9. Evidence from the Sea Floor Ocean Trenches 2 10. Causes of Plate Movement 4 11. Putting the Theory Together 3 12. Tectonic plates have different boundaries 3 13. The sea floor spreads apart at divergent boundaries 2 14. Mid-Ocean Ridges and Rift Valleys 1 15. Sea-Floor Rock and Magnetic Reversals 9 16. Continents split apart at divergent boundaries 1 17. Hot spots can be used to track plate movements 2 18. Math in Science Tracking Tectonic Plates 1 19. Tectonic plates push together at convergent boundaries 3 20. Continental-Continental Collision 2 21. Oceanic-Oceanic Subduction 3 22. Oceanic-Continental Subduction 3 23. Tectonic plates scrape past each other at transform boundaries 1 24. The theory of plate tectonics helps geologists today 3 Expansion H Video: Plate Tectonics Plate Tectonics Page 7