2. Geologic History

3. Quickwrite: In 2-3 sentences answer one of the questions below: How do you think scientists know which fossils are older and which fossils are younger? What do you think causes mass extinctions?

4. Topic: Relative Dating Objectives: Day 1 of 3 To learn how scientists use relative dating techniques to put geologic events in order To learn how to apply the laws of geology (the law horizontality, law of superposition, law of cross-cutting relationships) to relative dating

5. Relative Dating The concept of dating rocks by putting geologic events in order It does not give an exact age of rocks 3. 2. 1. 8. 7. 5. Magma Intrusion 4. Fault cuts through

6. Relative Dating The concept of dating rocks by putting geologic events in order It does not give an exact age of rocks 3. 2. 1. 4. Magma Intrusion 8. 7. 5. Fault cuts through

7. What is Relative Dating? The concept of dating rocks by putting geologic events in_______ 3. 2. 1. 4. Magma Intrusion 8. 7. 5. Fault cuts through Answer Bank Younger gap Top after Bottom Order flat

8. Law of Superposition 3. 2. 1. In layers of deposited sedimentary rock, the oldest rock layers are at the bottom and the rock layers become younger toward the top

9. Law of Superposition Principle of Superposition: States that the oldest rock layers are at the bottom and the rock layers become younger toward the top

10. The law of Superpostion: Old rocks formed on the bottom and young rocks are at the top Young rocks are at the top Old rocks are at the bottom

11. What is the Law of Superposition? 3. 2. 1. In layers of deposited sedimentary rock, the oldest rock layers are at the ____ and the rock layers become younger toward the ____ Answer Bank Younger gap Top after Bottom Order flat

12. Law of Horizontality L a w o f H o r i z o n t a l i t y : R o c k s f a l l i n t o p l a c e f o r m i n g f l a t, h o r i z o n t a l l a y e r s

13. Sediments are originally deposited in flat horizontal layers. If the rocks are folded or are laying at a steep angle, they must have been disturbed or tilted after they were originally deposited. 3. 2. 1. 3. 2. 1.

14. What is the Law of Horizontality? Sediments are originally deposited in ____ horizontal layers. If the rocks are folded or at an angle, they must have been disturbed _____they were originally deposited. 3. 2. 1. 3. 2. 1. Answer Bank Younger gap Top after Bottom Order flat

15. Unconformities Think of layers of rock as pages of a history book If we remove pages, the book is incomplete An unconformity is when layers of rock are missing 3. 2. 1. 3.

16. Unconformities: Here’s how it works!!!! 3. 2. 1. 5. 4. 3. Unconformity (weathering and erosion create a gap in geologic time)

17. Unconformities An unconformity is a gap in rock layers due to erosion and weathering or a break in the depositing of sediments (missing rock layers) 3. 2. 1. 3.

18. What is an Unconformity? An unconformity is a ____ in rock layers due to erosion and weathering or a break in the depositing of sediments (missing rock layers) 3. 2. 1. 3. Answer Bank Younger gap Top after Bottom Order flat

19. 2. 1. 4. Magma Intrusion 5. Fault cuts through Law of Cross Cutting Relationships The law of cross cutting relationships states that a fault line or an igneous intrusion must be younger than the rock it cuts across.

20. 3. 2. 1. 4. Magma Intrusion 5. Fault cuts through What is the Law of Cross Cutting Relationships? A fault line or an igneous intrusion must be _____ than the rock it cuts across. Answer Bank Younger gap Top after Bottom Order flat

21. Practice: Start with the oldest rock and work your way to the youngest C B A D Magma Intrusion H G E Fault cuts through Young 1. 2. 3. 4. 5. 6. 7. 8. Old F A B C D E F G H C B A D Magma Intrusion H G E Fault cuts through F

22. Summary: The law of ______ states that Sediments are deposited in flat horizontal layers When rock layers are missing in the geologic record we call it an _______ The law of ____ ____ relationships states that A fault line or an igneous intrusion must be younger than the rock it cuts across. Answer Bank unconformity horizontality Cross-cutting superposition

23. Quickwrite: In 2-3 sentences answer one of the questions below: How do you think scientists know the earth is 4.6 billion years old??? If you shook up 100 pennies in a box, how many do you think would be heads???? How many do you think would be tails????

24. Topic: Absolute Dating Objectives: Day 2 of 3 To will how scientists use absolute dating to determine the exact age of rocks I will know the concept of half life and radioactive decay

25. Absolute Rock Dating How do we know the earth is 4.6 billion years old? How do we know when dinosaurs lived? Thankfully, we can answer those questions by using Absolute Dating Absolute Dating is a method used by geologists to determine the age of a rock or fossil By analyzing the properties of atoms in rocks and fossils we can get a really accurate date for when the rock or fossil formed

26. What is Absolute Dating? Absolute Dating is a method used by geologists to determine the exact _____ of a rock or fossil It is different from relative dating because it gives an exact age Answer Bank Element Age determine decay

27. Radioactive Decay Radioactive Decay: The decay of an atom of one element to form another element, an example would be when uranium becomes lead or carbon 14 becomes Nitrogen For Example, after uranium-238 loses two protons and neutrons it becomes Lead- 206 which is stable and no longer changes UraniumLead

28. What is Radioactive Decay? The decay of an atom of one element into another _____ ex. uranium becomes lead Answer Bank Element Age determine decay

29. Parent and Daughter Material In the example of Uranium and Lead, which one is the Parent material and which one is the daughter material? Uranium becomes Lead and is therefore the parent material Lead is the stable daughter product Uranium is the parent material Lead is the daughter material

30. Half-Life Half life is the time it takes for half of the of the parent material to decay For example, if I had one pound of Uranium it would take 4.5 billion years for half of it to decay Therefore, we would only have half of what we started with after 4.5 billion years have passed How much would we have after another 4.5 billion years have passed?

31. What is Half life? Half life is the time it takes for half of the of the parent material to _____ Example: Lead Answer Bank Element Age determine decay

32. Who thinks they understand half-life? 1) What is the half life of uranium-238? 2) According to this diagram, how much uranium remains after 4.5 Billion years? Lead? 3) After 9 billion years, how much uranium is left? Lead?

33. = parent material = daughter material ½ life = 50,000 yrs 50,000 yrs 100% Parent Material 50,000 yrs 50% Daughter Material 50% Parent Material 75% Daughter Material 25% Parent Material 87.5% Daughter Material 12.5% Parent Material Number of Half Lives Amount of Parent Material 75 100 50 25 50,000 yrs 123450

34. Old vs. Young Rock We use Uranium half life to measure the age of the earth, which is very old But, how would we measure something that is younger, like tree rings or artifacts from an ancient land? Because Carbon-14 ( a radioactive form of carbon) has a half-life of 5,730 years, we can use it to date rocks that are much younger (unlike uranium, which has a half-life of 4.5 billion years) After 5,730 years Carbon-14 will decay into stable Nitrogen

35. Radiometric Dating To a geologist who studies rocks in order figure out earth’s history, these radioactive elements that decay are like a clock ticking away, keeping track of time since that’s passed since earth formed Radiometric Dating: A dating method that uses the rate of decay of radioactive atoms in rocks by the amount of parent and daughter product to determine the absolute age of a rock

36. What is Radiometric Dating? Dating method that uses the rate of decay of radioactive atoms in rocks by the amount of parent and daughter product to _____ the absolute age of a rock Answer Bank Element Age determine decay

37. Summarize: Read the following scenario to complete the answer below: A piece of coal (made of carbon) from a cave man’s fire is found to have about 50% Carbon-14 and 50% Nitrogen. The half life of Carbon-14 is 5730 years. Carbon-14 is the _____ material and Nitrogen is the _____material The caveman’s coal and fire is ______years old Scientist’s use _____dating to determine the absolute ____of rocks and fossils Answer Bank Parent age Daughter radiometric 100% Carbon-14 5,730years 50% Carbon-14 50% Nitrogen

38. Quickwrite: In 2-3 sentences answer one of the questions below: Where do you think all the oxygen in our atmosphere came from? How long do you think Humans have on this planet for???? Considering the age of the earth 4.6 BYO, When do you think life first appeared??

39. Topic: Geologic Time Objectives: Day 3 of 3 I will know the major geologic events that have transformed our earth I will know the geologic time scale and it’s major divisions

40. The geological time scale is the geologic history of the planet from formation to the present. It is starts with large divisions of time called eons and is subdivided into successively smaller units such ass eras and period The geologic time scale is based on dominant lifeforms, and mass extinction events Geologic Time Scale

41. Some of the major time eras include the: Precambrian Oceans and atmosphere form Paleozoic Invertebrates, plants and fish are the dominant forms of life Mesozoic Reptiles are the dominant forms of life Cenozoic Mammals are the dominant forms of life Precambrain “Age of Water and Atmosphere” “Age of Plants, fish, and invertebrates” “Age of Reptiles” Paleozoic Mesozoic Cenozoic “Age of Mammals”

42. What is the Geologic Time Scale? Time scale from the beginning of earth to present It is broken time divisions such as Eras, & Periods that are based on the ____record, dominant life forms, and mass ____events Answer Bank Extinction 90% Meteorites Explosion Fossil Oxygen Humans Photosynthesis

43. It was a harsh environment. Meteorites bombarded our earth And volcanoes spewed out gases Our oceans slowly formed over millions of years As volcanoes released steam One of these gases was steam or (H 2 O) 4.6 billion years ago Earth Forms CO 2 N2N2 H2OH2OH2OH2OH2OH2O This was what our planet was like for 4 billion years--90% of earth’s History Scientists call this period the Precambrian Precambrian During the Precambrian, our oceans and atmosphere formed along with other important events Steam cooled and condensed into clouds, These clouds Released precipitation (rain) for millions of years, eventually forming our oceans Welcome to Earth 4.6 Billion Years ago

44. 4.6 billion years ago Earth Forms CO 2 Precambrian Another gas given off by volcanoes is Carbon Dioxide (CO 2 ) These microscopic phytoplankton absorbed CO 2 from volcanoes and through Photosynthesis released Oxygen (O 2 ) into our atmosphere Another important event during the Precambrian was the appearance of the first single celled forms of life These phytoplankton were very important Because they helped create an oxygen rich atmosphere for life to thrive in About 2 billion years ago, primitive microscopic single celled forms of life called Phytoplankton began to fill the oceans Remember the recipe for Photosynthesis is: CO 2 + H 2 O  O 2 + C 6 H 12 O 6 O2O2 O2O2 O2O2 As Oxygen fill our atmosphere, Our skies eventually became Blue

45. How did our atmosphere become rich in oxygen? Primitive phytoplankton and algae bacteria called stromatolites released oxygen into our atmosphere through _____ about 2 bya Answer Bank Extinction 90% Meteorites Explosion Fossil Oxygen Humans Photosynthesis

46. Precambrian 3.8 bya- first oceans form 2 bya- oxygen rich atmopshere forms 3.5 bya- 1 st single celled forms of life Major Geologic Events of the Precambrian Era 1.1bya-1 st continent Rhodinia forms 1.3 bya- first multi celled forms of life 4.5 bya- Moon forms

47. What are major geologic events of the Precambrian Era? 3.8 bya- oceans form 3.5 bya- 1st single celled forms of life 2 bya- ____ rich atmosphere forms 1.3 bya- 1st multi celled forms of life 1.1bya-1st continent Rhodinia forms Answer Bank Extinction 90% Meteorites Explosion Fossil Oxygen Humans Photosynthesis

48. Some of these animals included trilobites, ammonites (squid like creatures with shells) Paleozoic Era The Paleozoic Era witnessed an explosion of life Very shallow seas covered most of the earth Precambrian Paleozoic Through out these shallow seas lived some of the first complex forms of life Including: invertebrates (shell fish), fish and plants

49. Precambrian Major Geologic Events of the Paleozoic Era Paleozoic

50. Precambrian Paleozoic 570 mya- Explosion of life 536 mya- 1st fish & invertebrates appear 513 mya- First land plants appear 322 mya- First reptiles appear 245 mya- Mass Extinction 90% of all life Major Geologic Events of the Paleozoic Era

51. What are major geologic events of the Paleozoic Era? 570 mya- _____ of life 536 mya- 1 st fish & invertebrates 513 mya- 1 st land plants 322 mya- 1 st reptiles appear 245 mya- Mass Extinction ___% of all life Answer Bank Extinction 90% Meteorites Explosion Fossil Oxygen Humans Photosynthesis

52. Mesozoic Era The Mesozoic Era was the age of reptiles & witnessed the evolution of the largest animals to have ever walked the earth Precambrian Paleozoic Mesozoic The dinosaurs would eventually go extinct and give rise to modern day birds

53. Mesozoic Era The Mesozoic Era witnessed an explosion of life Precambrian Paleozoic Mesozoic

54. Dinosaur Demise There is mounting evidence that a large meteorite impact slammed into earth 65 mya ending the Cenozoic era This impact would have caused widespread devastation and fires

55. Dinosaur Demise Ash and smoke from fires could have blocked out enough sunlight changing the global climate; decimating and wiping out the cold blood reptiles

56. Precambrian Major Geologic Events of the Mesozoic Era Paleozoic Mesozoic

57. Precambrian Paleozoic Mesozoic 200 mya- First Mammals appear 180 mya- Pangea breaks up 160 mya- First Birds appear 65 mya- Mass extinction 60% of all life perishes 200 mya- First Mammals appear Major Geologic Events of the Mesozoic Era

58. What are major geologic events of the Mesozoic Era? 200 mya- 1 st Mammals 180 mya- Pangea breaks up 160 mya- 1 st Birds 65 mya- Mass extinction 60% of all life perishes including dinosaurs due to large ______collision Answer Bank Extinction 90% Meteorites Explosion Fossil Oxygen Humans Photosynthesis

59. Cenozoic Era With Dinosaurs gone, Mammals would inherit the earth and dominate the land Large mammals thrive such as Horses, Mammoths, and Primates Mankind would evolve and inhabit the earth expanding it’s population Many Ice Ages came in went causing the extinction of many large mammals Precambrian Paleozoic Mesozoic Cenozoic Cenozoic

60. Precambrian Paleozoic Mesozoic Major Geologic Events of the Cenozoic Era

61. Precambrian Paleozoic Mesozoic Cenozoic Cenozoic 45 mya- One of the largest Ice ages occur 7 mya- First Human Ancestors appear 300,000 ya- Modern humans appear

62. What are major geologic events of the Cenozoic Era? 45 mya- Major ice age event 7 mya- 1st Human ancestors appear 300,000ya- 1st modern ____ Present- your writing this down!!!!! Answer Bank Extinction 90% Meteorites Explosion Fossil Oxygen Humans Photosynthesis

63. Summarize: List the events in order: Oldest  to youngest Mammals dominate the earth Mass extinction 90% of all life wiped out Reptiles dominate the earth Explosion of life Phytoplankton create oxygen rich atmosphere Mass extinction 65% of all life wiped out including dinosaurs