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1. Warm-Up

1. Warm-Up. Which layer is the oldest? Layer F Which layer is the youngest? Layer G Which layers are younger than C? Layers B, A, G What does the “law of superposition” state? In undisturbed rock, the oldest rock layers are at the bottom. Standard 1.c.

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1. Warm-Up

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  1. 1. Warm-Up • Which layer is the oldest? • Layer F • Which layer is the youngest? • Layer G • Which layers are younger than C? • Layers B, A, G • What does the “law of superposition” state? • In undisturbed rock, the oldest rock layers are at the bottom. Flores

  2. Standard 1.c Evidence suggests that early earth was very different from the earth today. Flores

  3. 2. Rock Record • Scientists call sedimentary layers the “rockrecord” because they contain pieces of Earth’s history. • Using relative dating & radioactive dating, these rock layers were put in chronological order on the geologictimescale. • The geologic time scale is divided into 4 major divisions of timecalled Eras: • Precambrian, Paleozoic, Mesozoic, Cenozoic . Flores

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  5. 3. The Precambrian Rock Record • Geologists know little about early Precambrian time because most rocks were destroyed by erosion or plate tectonics. • Relative dating is difficult because these rocks rarely contain fossils. • Yet major geologic events occurred during the Precambrian. Flores

  6. 4. The Precambrian • The Precambrian begins 4.5 billion years ago with Earth’s formation. • As earth grew, its gravity increased, pulling in high-velocity meteorites. • So much heat was created that earth melted. • Melting allowed elements to differentiate, forming the crust, mantle, and core. Flores

  7. 4. The Precambrian • 4 billion years ago, energy from Earth’s interior powered platetectonics. • The first landmasses grew by the accretion of granite rock. • As the crust cooled, volcanoesoutgassed water vapor, CO2, Nitrogen, and other trace gases. Flores

  8. 4. The Precambrian • 3.5 billion years ago, the first life forms appear in the oceans. • Red & greenalgae use CO2 & release oxygen through photosynthesis. • Oxygen combined with iron, forming large deposits of rust. • 2 billion years ago, oxygenaccumulated in the atmosphere once iron & oxygen stopped reacting. Flores

  9. 4. The Precambrian • As Earth cooled, water vapor condensed & precipitated. • The rain evaporated, but helped speedup the cooling of Earth’s surface. • The rain, which continued for millions of years, slowly formed the oceans that covered which 90% of Earth. • Great rains reduced water vapor & dissolved CO2, leaving a nitrogen-rich atmosphere. Flores

  10. 4. The Precambrian • 700 million years ago, Earth experiences its first iceage. • The cold climate causes a massextinction. • Rodinia, the first supercontinent is formed. • 650 million years ago, Rodinia moves towards the poles, breaking apart. Flores

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  12. 5. Paleozoic Era • 400 million years ago, the ozonelayer forms, protecting the surface from UV radiation. • Landforms moved near the equator. • Temperatures warm, sparking the CambrianExplosion. • Many new groups of organisms evolved in a relatively short time. • Invertebrates: no back bones • Vertebrates: backbones • Arthropods: external skeleton • More than 600 known trilobites species Flores

  13. 5. Paleozoic Era • Landmasses push southward, forming Gondwana. • Vertebrates continue to evolve in the oceans with the appearance of the jawlessfish. • Life evolves onto land with the first landplants. • They added more oxygen into the atmosphere. Ostracoderms Flores

  14. 5. Paleozoic Era • 410 million years ago, landmasses collide, forming Laurasia across the equator. • Its climate is hot and dry. • Mossesand tree ferns develop the 1stforests. • Little competition from other land animals allow insects & amphibians to evolve. • A mass extinction affects the jawless fishes. Ichthyostega Had massive shoulders and seven hind digits Flores

  15. 5.Paleozoic Era • Land masses collide forming the Appalachian mountains. • Landmasses merge to form the supercontinent Pangaea. • Vast swamps develop in tropical climates. • Reptilesevolve from amphibians. Flores

  16. 5. Paleozoic Era • Conifers become abundant. • Mammal-like reptiles evolve. • Legs, skulls, and jawbones similar to mammals. • 250 million years ago, volcanic eruptions cause a mass extinction, killing 96% of all species. Dimetrodon 10 ft. Long Flores

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