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Chapter 8b – Earth History

Chapter 8b – Earth History. Earth’s age is between 4.53 and 4.56 billion years old. A difficult to fathom length of time. To put this in perspective:

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Chapter 8b – Earth History

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  1. Chapter 8b – Earth History Earth’s age is between 4.53 and 4.56 billion years old. A difficult to fathom length of time. To put this in perspective: Yard is the distance from King’s nose to his index finger. If all of earth’s history is on that yard stick, then if the King files his fingernail once, he just removed all of human history.

  2. Geologic Time Scale Geologists and Paleontologists divide relative time into “zones” that reflect differing earth characteristics. Eon: Largest interval of geologic time. Four Hadean – 4.5 to 4.0 billion years ago Archean – 4.0 to 2.5 billion years ago Proterozoic – 2.5 to 0.542 billion years ago Phanerozoic – 0.542 billion to present

  3. Geologic Time Scale - Eras The Phanerozoic Eon is divided into three Eras based on the major life types. Paleozoic Era – Ancient Life: “Age of Invertebrates” Mesozoic Era – Middle Life: “Age of Reptiles and Dinosaurs” Cenozoic Era – Recent Life: “Age of Mammals” Eras are further divided into Periods based on additional distinctions of life.

  4. Geologic Time Scale - GSA

  5. Geologic Time Scale – Encyclopedia of Life Let’s divide earth history into a nine volume encyclopaedia. Each volume would comprise 500 million years. Let’s make each volume have 500 pages. Each page would then represent 1 million years. A very long time, but very short compared to the age of earth.

  6. Geologic Time Scale – Volume 1 Volume 1 - 4.5 billion to 4.0 billion No rocks of these ages present on Earth. Why? 500 million years of intense meteorite bombardment. Plate tectonics. Erosion of old rocks Oldest evidence that there were rocks is 4.42 billion years before present. Zircon.

  7. Geologic Time Scale – Volume 1 Evidence of meteorite bombardment. Age of Earth determined from lunar rocks and meteorite radiometric ages.

  8. Geologic Time Scale – Volume 2 Volume 2 - 4.0 billion to 3.5 billion No oxygen in atmosphere. Considerable evidence. Sedimentary minerals Volcanic gases H2O, CO2, SO2, CH4, NH3 Hotter earth because of higher CO2 Sun produces less heat 3.8 billion – earliest evidence of life Carbon isotope evidence – life is lazy? Requires self replication – DNA from RNA?

  9. Geologic Time – Hydrothermal Vent

  10. Geologic Time – Tube Worms Thermophile bacteria at the bottom of the food chain.

  11. Geologic Time Scale – Volume 3 Volume 3 – 3.5 billion to 3.0 billion Nothing new.

  12. Geologic Time Scale – Volume 4 Volume 4 – 3.0 billion to 2.5 billion Stromatolite

  13. Geologic Time Scale – Volume 4 Stromatolite

  14. Geologic Time Scale – Volume 4 At 2.5 billion years before present something really great is about to occur!

  15. Geologic Time Scale – Volume 5 Volume 5 – 2.5 billion to 2.0 billion Banded Iron Formations are found all over Earth. First oxygen producing photosynthesis More efficient! Oxygen is a deadly poison! Botulism Gangrene How to safely get rid of deadly O2? Combine it with ferrous iron (Fe2+)

  16. Geologic Time Scale – Banded Iron Formation Alternating layers of magnetite iron and red chert.

  17. Geologic Time Scale – Volume 5 continued Volume 5 – 2.5 billion to 2.0 billion Major advance in evolution at about 2.2 billion years ago. Prokaryote bacteria – reproduces by fission (asexual reproduction) Eukaryote bacteria – reproduces by mixing DNA from two individuals (sexual reproduction). Advantage: genetic diversity!

  18. Geologic Time Scale – Volume 6 Volume 6 – 2.0 billion to 1.5 billion Nothing new.

  19. Geologic Time Scale – Volume 7 Volume 7 – 1.5 billion to 1.0 billion Nothing new.

  20. Geologic Time Scale – Volume 8 Volume 8 – 1.0 billion to 0.54 billion A great disaster? Or the best thing to have ever happened? Photosynthesis is using up CO2 and creating O2 in earth’s atmosphere. Temperatures drop. Snowball Earth 716 million years before present.

  21. Drop Stone

  22. Snowball Earth

  23. Snowball Earth Earth is frozen over to the very low latitudes. What color is earth? What is earth’s reflectivity? 0.1 albedo vs. 0.8 albedo for oceans Will earth ever de-ice? Unlikely. Except earth is currently not frozen. What could have happened?

  24. Snowball Earth Thaws Out Are volcanoes still erupting? What do they erupt? CO2? Why is CO2 important?

  25. Snowball Earth Environmental Stress First multi-cellular life evolves. Burrowing organisms. Change from fissile shales to siltstones that have no layering.

  26. Snowball Earth Environmental Stress First multi-cellular life evolves. Burrowing organisms. Change from fissile shales to siltstones that have no layering.

  27. Geologic Time Scale – Volume 9 Volume 9 – 0.54 billion (542 million) to present Phanerozoic Eon The “good stuff” Only 1/9 of earth history (11%) Abundant life seen as fossils

  28. Geologic Time Scale – Phanerozoic Volume 9 – 0.54 billion (542 million) to present Phanerozoic Eon The “good stuff” Only 1/9 of earth history (11%) Abundant life seen as fossils Divided into three Eras

  29. Geologic Time Scale – Paleozoic Paleozoic Era Cambrian Period – first abundant life as seen in the fossil record. Hard parts. Trilobite Brachiopod

  30. Geologic Time Scale – Paleozoic Ordovician Period – waterworld (bad movie). Jawless fish.

  31. Geologic Time Scale – Paleozoic Silurian Period – Jawed fish.

  32. Geologic Time Scale – Paleozoic Silurian Period – First land plants. Falling sealevel Major development. Surrounded by nutrients vs. Separate systems above and below earth.

  33. Geologic Time Scale – Paleozoic Devonian Period – Age of Fishes. First tetrapods (amphibians) from lobe-finned lungfish. First seed plants (conifers). Insects migrate onto land. Mississippian – sea-level rises. Amphibians everywhere. Pennsylvanian – sea-level drops. Amphibians in trouble. Reptiles evolve amnoionic (hard-shelled) egg. Yippee! Permian – First mammal-like reptiles. Greatest extinction of life ever. 80-95% of all species become extinct.

  34. Geologic Time Scale – Mesozoic Following the extinction of most species of invertebrates, reptiles become the advanced organisms. Three periods of the Mesozoic. Triassic – Pangaea begins to break apart. Species are isolated and development of new species occurs. Reptiles dominate early Triassic. Dinosaurs evolve towards end of Triassic and dominate land. Reptiles still dominate the world’s oceans.

  35. Dinosaur vs. Reptile Dinosaur Reptile

  36. Dinosaurs Warm Blooded? Were dinosaurs warm or cold blooded? The ratio of oxygen-18 to oxygen-16 can be used as a thermometer. Oxygen isotope studies of large (pelvic) vs. small (finger) bones of cold and warm blooded organisms indicate: Some dinosaurs were warm-blooded. Some dinosaurs were cold-blooded.

  37. Dinosaurs Warm Blooded? Were dinosaurs warm or cold blooded? Reptiles are cold blooded. Birds are warm blooded.

  38. Jurassic During the Jurassic dinosaurs dominate land. Jurassic Park dinosaurs are not Jurassic in age. They are Cretaceous! Why? Birds evolve from the dinosaurs. Atlantic Ocean begins to fully form.

  39. First Feathers

  40. Cretaceous First flowering plants. Bird and bees proliferate. Why? One of the strangest means of symbiotic reproduction.

  41. Cretaceous Cretaceous mammals are small burrowing organisms.

  42. Cretaceous Mammals .

  43. Cretaceous-Tertiary Extinction At the end of the Cretaceous, beginning of the Tertiary the dinosaurs and many other organisms become extinct. • Climate warming and • drying for 10 Mybp. • 2. Deccan Traps volcanic • eruption. Adds CO2. • Shiva? • 3. Chicxulub Impact.

  44. Cenozoic There are now new environmental niches for the mammals to evolve and come to dominate Earth. The “Age of Mammals”. Mammals dramatically increase in size since they don’t have to live in burrows any more. Some large mammals move back into the oceans. Whales.

  45. Whales How do we know they were originally land mammals and not fish? Vestigial legs and pelvis.

  46. Linked Horse and Grass Evolution At the beginning of the Cenozoic horses evolved first in mid-North America which was heavily forested.

  47. Horse Evolution Lots of places for horses to hide from predators.

  48. Horse Food What did early horses eat? We can tell from teeth. Browsers versus grazers. Is it easier to eat grass or leaves?

  49. Horse Food What did early horses eat? We can tell from teeth. Browsers versus grazers. Is it easier to eat grass or leaves? You’re right! It’s easier to eat and digest leaves than grass.

  50. Forests Replaced by Grasslands Over millions of years there are fewer trees and more grass covered meadows. Harder for horses to hide from predators. How to escape? Run faster? How to accomplish this? Fewer leaves to eat? Eat grass! How?

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