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Earth’s History

Earth’s History. Ch 4. IAN pg 28. 4.1 What are Fossils?. Mold. Mold vs. Cast. Cast. 1. 2. 3. 4. Which Fossils are Molds? Which are Casts?. 7. 6. 8. 5. 9. 11. 10. 12. IAN pg 29. IAN pg 29. IAN pg 30. Mammoth Article & Reflections.

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Earth’s History

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  1. Earth’s History Ch 4

  2. IAN pg 28 4.1 What are Fossils?

  3. Mold Mold vs. Cast Cast

  4. 1 2 3 4 • Which Fossils are Molds? • Which are Casts? 7 6 8 5 9 11 10 12

  5. IAN pg29

  6. IAN pg29

  7. IAN pg 30 Mammoth Article & Reflections Why is it important for geologists to preserve the mammoth tusk? How can geologists use the mammoth tusk to learn about the ice age in North America? How might this discovery impact the company who owns the construction site where the tusk was found? How might this discovery impact the city of Seattle?

  8. IAN pg 31 4.1 Fossils EQ: What are fossils? A: the preserved remains, or traces, of living things EQ: How do Fossils Form? A: 1. living things die 2. buried in sediment 3. hardens into rock 4. preserves the shape of the organism NOTE about what becomes a fossil: • Mostly hard body parts fossilize: teeth, bones, woody stems, shells, seeds • Soft parts usually decay: skin, leaves, etc

  9. IAN pg 31 4.1 Fossils EQ: What are the types of Fossils? • a. Molds: most common type of fossil; an organism gets buried in sediment, decays and leaves a hollow impression b. Casts: when sediment fills a mold and hardens to make a solid copy of the organism • Petrified fossils – when the remains of an organism “turn to stone” / petrify. • Carbon films – an extremely thin coating of carbon on a rock; can preserve leaves & insects • Trace Fossils – fossils of trails, burrows, footprints, and activities of ancient life. • Preserved Remains – an entire organism preserved in amber/tree sap, or ice.

  10. IAN pg 31 4.1 Fossils More Vocabulary: • Paleontologist – scientist who studies fossils • Evolution– changes in an organism/species over time • Extinct– no longer exists on Earth and will never exist again EQ: What do fossils show? • History of Life • Past environments on Earth • How organisms change (evolve) over time.

  11. IAN 32 4.2 Riddle Activity 5 Directions: 1. Read the story and clues below. Carefully observe the picture. 2. On the bottom half of IAN 31, write down who you think was the last person to take a cookie and explain WHY! DO NOT SHARE YOUR RESPONSE!

  12. Relative Dating – Who Dunit? IAN pg 32 Conclusions to Who dunit?

  13. IAN pg 33 4.2 Relative Age of Rocks • EQ: How old are rock layers? • A: the Law of Superposition, which determines the relative age of rocks, states that in undisturbed, horizontal layers of sedimentary rock, the youngest rock is on top and oldest at the bottom. • Methods used for determining the age of Rock layers: • Relative age • Law of superposition • Intrusions and Extrusions of igneous rock • Faults • Index fossils • Absolute age - scientists use Radiometric Dating.

  14. IAN pg 33 • EQ: How can Rock Layers Change? • Answer: Gaps in the Geologic Timerecord, and Folding can change the position in which the rock layers appear. • Gaps in the Geologic Time record • Unconformity – the surface where new rock layers meet much older rock layers that were exposed after erosion; shows where rock layers have been lost due to erosion. • Folding – when forces inside the Earth bend and fold rock layers so much that they can completely turn over. In this case, the youngest layer can be on the bottom. See virtual animation:How unconformities are made in the rock layers see pictures: http://www.marlimillerphoto.com/SrU.html

  15. IAN pg 34 Rock Layers – Playdoh LAB

  16. IAN pg 34 Rock Layers – Playdoh LAB

  17. IAN pg 34 Rock Layers – Playdoh LAB

  18. IAN pg 34 Picture of a Real Intrusion!

  19. IAN pg 34 Photo of a REAL Fault Line

  20. What are Index Fossils? Click link to demo : index fossils and relative age Identify the index fossils. Infer: why don’t all the locations have all 4 layers of rock?

  21. IAN 35 Relative Age of Rocks

  22. IAN 35 Relative Age of Rocks

  23. IAN 35 Relative Age of Rocks

  24. IAN 35 Relative Age of Rocks

  25. IAN 35 Relative Age of Rocks 1 3 2 4

  26. IAN 35 Relative Age of Rocks 3 1 2

  27. IAN 35 Relative Age of Rocks 1 2

  28. IAN 35 Relative Age of Rocks

  29. IAN 36 QUIZ: 4.1-4.3 Vocabulary

  30. 4.3 Radioactive Dating IAN pg 38 Review Notes And textbook answers corrections

  31. IAN pg 37 Notes EQ: What is Radioactive Decay? • A: When the atoms of one element break down to form the atoms of another element • Half-Life - the time it takes for half of the radioactive atoms to decay.

  32. IAN pg 37 Notes EQ: What is radioactive dating? • A: finding the absolute age of a rock by calculating: • the amount of radioactive element in the rock • comparing it to the amount of the new stable element it turned in to • comparing it to the known half-life of that element • Two methods of Radioactive Dating • Potassium –Argon Dating – great for dating ancient rocks • Carbon 14 Dating - used to date fossils or rocks less that 50,000 yrs old

  33. Textbook check pg 153 To find the percent of radioactive element remaining, divide the # in the dark blue bar by 2. • Half-Life - the time it takes for half of the radioactive atoms to decay. • Answers: • )100 / 2 = 50% • )50 / 2 = 25% • )25 / 2 = 12.5% • )12.5 / 2 = 6.25 % To find the light blue portion of the bar, calculate 100 - dark blue% ANSWER: 100-6.25% = 93.75%

  34. Textbook check pg 154 3 • HOW OLD IS THE ROCK if it has only 12.5% of Potassium-40 in it? • How many half lives past to get down to 12.5% ? _______ • Use the table on pg. 154 to look up how long it takes to reach a half-life in potassium-40. ________________________________ • To find the AGE of the Rock: • Half lifeX Number of half lives passed • ANSWER: 3 x 1.3 billion years = 3.9 billion years old 1.3 Billion Years

  35. Textbook check pg 154 • To find the AGE of the Fossil or Rock: • Half lifeX Number of half lives passed • HOW OLD IS THE FOSSIL if it has 1/16 carbon-14 in it? • THINK: If is has only 1/16 Carbon left, what percent is that? • 1÷ 16 = .625 x 100 = 6.25% • SOLVE: If the fossil only has 6.25% Carbon-14 left, how many half lives have passed? (See graph text 153) • Number of half-lives passed? __________ • Half life of Carbon 14? ____________________________ • Solve: _________________ X _____________________ =____________________ 3 5730 years 3 half lives 22920 years 5730 years

  36. IAN pg 38 Notes EQ: How do scientists find Earth’s Age? • A: scientists use radioactive dating and evidence from rocks on the Earth and the moon • What did we find? • Using rocks on Earth that haven’t changed much since Earth formed, we calculated Earth is at least 3.8-4.28 billion years old • Using Moon rocks, we have more information and we have inferred that the Earth is about 4.6 billion years old

  37. IAN pg 38 The teacher will answer your questions here. DO NOT WRITE in this section In this column EXPLAIN 3 things you learned about radioactive decay from the notes and from the penny lab or gizmo lab List 2 questions about radioactive decay from the notes and from the penny lab or gizmo lab that you are still unsure about Play the Carbon dating game online at Phet and tell me one more thing you learned.

  38. Bell Work IAN pg 40 Label IAN pg 40 as follows: • Line 1 - 4.4 Geologic Time • Line 2 – Bell work: Making Connections Then Do the following:(NOTE - do not use more than the top 1/3 of the page) • “create a timeline to show your life from birth to present.” • It must include the following: • The day you were born • When you started Junior High • Present day • Then go back and add 3 of your favorite events that occurred in your life (note dates on timeline like month and year)

  39. Your timeline vs. Earth’s Timeline Imagine that I asked you to create a timeline for the earth, and not just for you, as a single person on earth. Tell me several things that would be different about the Earth’s Timeline What things would you use to mark as events on earth’s timeline?

  40. Earth’s Geologic Timeline Tear out text page 160 and trim it like this. Glue it like a page extension on IAN page 40

  41. Earth’s Geologic TimelineFrom the beginning (start at the bottom of the picture) How Long did Precambrian Time Last? Calculate as follows: 4,600 • 542 • 4,058 million years

  42. Earth’s Geologic TimelineFinish Calculating the whole page Review of Answers: Quarternary=1.6 million years Neocene = 21.4 million years Paleogene = 43 million years Cretaceous = 80 million years Jurassic = 54 million years Triassic = 51 million years Permian = 48 million years Carboniferous = 60 million years Devonian = 57 million years Silurian = 28 million years Ordovician = 44 million years Cambrian = 54 million years Precambrian = 4,058 million years

  43. 4.4 Geologic Time IAN notes pg 39

  44. The Clock of Eras: another way to represent time • Describe the job of an analog clock • Name the parts of an analog clock and describe their function • Teacher intro the Clock of Eras and contrast with standard clock

  45. Precambrian Time Real Time = 3.957 Billion Years Clock comparison: 10 hours 32 minutes Midnight to 10:32am

  46. Real Time = 295 million years more Clock comparison: It is now 11:19am

  47. Real Time = 183 million more years Clock comparison: It is now 11:48am

  48. Real Time = 65 million more years Clock comparison: It is now 11:58am

  49. IAN pg 39 NOTES EQ: What is the Geologic Time Scale? A: A record of the geologic events and the evolution of life forms on Earth as shown in the fossil record Why is it necessary to have a geologic time scale? • The time span of Earth’s past is so long, the scale provides a useful model of events in chronological order.

  50. IAN pg 39 NOTES How is Geologic Time Divided? • The geologic Time Scale is determined by studying rock layers and index fossils. • Using the fossil record, scientists identify major changes in Life Formsand mark the beginning and end of that time period.

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