Aims: November 1, 2016 SWABT explain the absolute age of rocks using radiometric dating. Agenda 1. Do Now 2. Class Notes 3. Guided Practice 4. Independent Practice 5. Practicing our AIMS: Homework: HE.3 Absolute Age How will you help our class earn all of our S.T.R.I.V.E. Points? 1
Aim Check: 2
SCIENCE 8 Absolute Age EH.3 Name: Date: Homeroom: Earth s History Shoooo I m GROWN! OBJECTIVES: By the end of class, students will be able to SWABT explain the absolute age of rocks using radiometric dating DO NOW 1. The smallest particle of an element that retains all of the properties of that element is called A. a nucleus B. a molecule C. an atom D. an electron 2. Which atomic particle has a positive charge? A. electron B. proton C. neutron D. nucleus 5. Draw your own model of an atom with 4 protons, 3 neutrons, and 4 electrons Label the protons, neutrons, and electrons by writing the letter P, N, or E inside the particle. Label the nucleus by circling its location. 3. An electron has what type of charge? A. neutral B. negative C. positive D. debit 4. What is the nucleus? A. location of the protons and electrons B. location of the neutrons and electrons C. location of the neutrons and protons D. location of the electrons and protons 3
NOTE TAKING 201: CLASS NOTES How to Date a Planet Earth owes its youthful appearance to: 4
The issue with rocks being remade: Compare and contrast: Zirconium atoms radioactively decay into 5
How to Date a Dead Thing How many carbon atoms are in your body: Carbon-14 atoms are important: Carbon-14 formed: All living things have It takes about for into of Carbon-14 decay 6
For samples older than 50,000 years: 7
IN SUMMARY ABSOLUTE AGE: To determine the absolute ages of fossils and rocks, scientists analyze isotopes of radioactive elements. ISOTOPES: o Most isotopes are stable and stay in their original form. o Other isotopes are RADIOACTIVE DECAY: o The unstable radioactive isotope is called the o The stable isotope is called the The rate of radioactive decay is constant, so scientists can compare the amount of parent material with the amount of daughter material to date rock. o If you know the rate of decay for a radioactive element in a rock, you can figure out the absolute age of the rock. HALF-LIFE: o After every half-life, the amount of parent material 8
Guided Practice 9
Independent Practice Directions: For each key term, explain the big idea to a kindergartener. Then, draw a picture to illustrate the word. Term Concept Picture ABSOLUTE AGE RADIOACTIVE DECAY HALF-LIFE 10
Directions: Read and ANNOTATE each question before you solve the problem. The table describes several methods scientists can use to date rock layers and fossils. A geologist wants to date several samples. Descriptions are provided for each sample. Because sampling can be expensive and time consuming, the geologist only wants to use the dating methods that are likely to provide a reliable date. Select the boxes to show all methods that can be used to date each sample. Method 1 Method 2 Method 3 Method 4 A deeply buried sample of limestone A piece of wood from a Native American cliff dwelling A shallowly buried sample of shale that contains oyster and snail fossils A dinosaur bone found in a sandstone layer that sits between two layers of basalt 11
BEAST MODE! Directions: Read and ANNOTATE the information before you solve the problem. Environmental Radiation Read the following paragraphs, and complete the exercises below. It may be surprising, but every day you are exposed to natural radiation from the environment in which you live. This natural radiation, which is often called background radiation, comes from a number of different sources. COSMIC RAYS Cosmic rays are high-speed particles that enter Earth s atmosphere from space. Some of the rays come from the sun, but most have their origins in other parts of the galaxy and beyond. On average, about 100,000 cosmic-ray particles pass through each person every hour. RADIATION FROM EARTH Some of the elements found in Earth are radioactive. Uranium and radium, which occur naturally on Earth, decay, producing radioactivity. The radioactive particles and waves may come directly from Earth s surface, or they may be released into the air, where they can be inhaled. Each hour, tens of thousands of atoms disintegrate in a person s lungs and release radioactivity. RADIATION FROM ORGANISMS Organisms use elements that contain trace amounts of radioactive isotopes. Inside the body, these isotopes release radiation as they decay. For example, the element carbon is used by every organism. A very small percentage of Earth s carbon is carbon-14, a radioactive isotope. In a similar way, potassium contains trace amounts of radioactive potassium-40. Every hour, about 15 million potassium-40 atoms disintegrate inside our bodies, releasing radioactive particles or waves. EXERCISES 1. What are three common sources of natural background radiation? 2. Why do living organisms release radiation? 3. Describe two ways that radiation is released from Earth. 4. Name two radioactive isotopes found in living organisms. 12
You Do: REVIEW! (Comps are Nov 16-17!) 1. What caused the interior of Earth to separate into layers? A. a decrease in the rate of rotation of Earth B. the gravitational pull on materials of varying densities C. variations in heating by the Sun due to Earth s tilt D. collisions with meteors and comets 2. In the picture, magnetic reversals are indicated by dark and light bands. How can scientists tell when the reversals of the magnetic field occurred? A. by measuring the types of minerals that aligned to Earth s magnetic field in the different bands B. by measuring the thickness of the different bands of the oceanic crust C. by measuring how far the ocean floor band is from the mid-ocean ridge D. by measuring the strength of Earth s magnetic field recorded in the oceanic crust 3. Compared to the surrounding material, the mantle plumes that cause hot spots rise toward Earth s surface from the core-mantle boundary because they are A. hotter and less dense B. hotter and more dense C. cooler and less dense D. cooler and more dense 4. Which plate boundary feature is associated with the plate movement shown in the figure? A. continental rift valley B. mid-ocean ridge C. high folded mountain D. strike-slip fault 13
5. Which kind of rock is produced by heat and pressure, without completely melting? A marble, a metamorphic rock B sandstone, a sedimentary rock C granite, an intrusive igneous rock D pumice, an extrusive igneous rock 6. Broken pieces of rock are deposited into piles and are cemented together by other minerals. What type of rock has been formed? A chemical sedimentary B clastic sedimentary C rippled sedimentary D organic sedimentary 7. You are planning a hike across Sloan s Island from west to east, as shown. Which part of your hike would be steepest? A. From point P to point Q B. From point Q to point R C. From point R to point S D. From point T to point U 8. Foliated and non-foliated rocks are both types of rocks A. igneous B. sedimentary C. metamorphic D. biochemical 14
Science 8 Name: SKILL SNAPSHOT Date: Homeroom: EH.3: Absolute Age Quick Notes: Read and ANNOTATE each question before you solve the problem. Like A Scholar? Yes No Redo? Yes No Directions: Examine the graph below. Support your selection by finding evidence to support your answer OR evidence to support why another is incorrect. Start your explanation with The evidence shows that 1. Circle one the graph when there is 50% pf the parent isotope left. Question 2. The age you circled is called the Supporting evidence A. daughter B. isotope C. half-life D. radiometric age 3. If a sample had about 25% of the parent isotope left, how many half-lives would you expect the sample has gone through? A. 1 half-life B. 2 half-lives C. 4 half-lives D. 25 half-lives 15
Directions: Support your selection by finding evidence to support your answer OR evidence to support why another is incorrect. Start your explanation with The evidence shows that Question 4. Which of the following is absolute dating? A. The fossil I found is younger than a trilobite fossil B. Mr. Searles is younger than his sister. C. CCA is 9 years old. D. That tree was here before that building. Supporting evidence CONCEPT CHECK 5. What is the best description of sea-floor spreading? A. When continents move over time. B. The process of magma pushing up to the surface of the ocean and forming new crust that pushes old crust away. C. When two tectonic plates collide. D. When the ocean floor gets smaller. $$ BONUS $$ Directions: Estimate the age of each sample based on the number of parent and daughter atoms given. Use the graphs provided. (HINT: You can use either the Percentage of Parent Atoms OR the Percentage of Daughter Atoms to find your answer on the graph) Sample Number Number of Parent K-40 Number of Daughter Ar-40 1 6 14 Total Number of Atoms % of Parent % of Daughter Estimated Age of Sample 2 2 18 3 1 9 16