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Earth’s History

Earth’s History. 4.6 Billion years ago Earth was formed. The theory of Uniformitarianism created by J ames Hutton as he studied Earth’s history States: Earth is an always changing place The same forces that work today were at work in the past. Uniformitarianism. Eons 

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Earth’s History

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  1. Earth’s History

  2. 4.6 Billion years ago Earth was formed

  3. The theory of Uniformitarianism created by James Hutton as he studied Earth’s history • States: • Earth is an always changing place • The same forces that work today were at work in the past Uniformitarianism

  4. Eons  The 1st Two Eons are not broken down any further • Era only the Phanerozoic Eon • Period  • Epoch only the end of the Phanerozoic Eon Earth’s History is divided into sections

  5. Eons – • Hadean ~ 4.6 – 3.9 billion years ago • Archeozoic (Archean) ~ 3.9 – 2.5 billion years ago • Proterozoic Eon ~ 2.5 billion years ago to 540 mya • Phanerozoic ~ 540 mya through today

  6. "Rockless Eon" - The solidifying of the Earth's continental and oceanic crusts • No rocks on the Earth are this old, except for meteorites. • During Hadean time, the Solar System was forming, probably within a large cloud of gas and dust around the sun Hadean Eon

  7. "Ancient Life" - The first life forms evolve - one celled organisms. Blue-green algae, archaeans, and bacteria appear in the sea • Atmosphere has a low level of oxygen Archeozoic (Archean) Eon

  8. Broken into 2 periods • No name for the 1st period • First multicellular life: colonial algae and soft-bodied invertebrates appear • Oxygen build-up in the Mid-Proterozoic. • 2nd period is Vendian/EdiacaranPeriod ~600 to 540mya • Vendian biota (Ediacaran fauna) multi-celled animals appear, including sponges • A mass extinction occurred • The continents had merged into a single supercontinent called Rodinia Proterozoic Eon

  9. This Eon is also know as the Eon of “Visible Life”, we know a lot about the history at this point so it is broken down accordingly • We will see organisms with skeletons or hard shells • Time period is 540 MYA through today Phanerozoic Eon

  10. Eras • Paleozoic Era ~ 540 to 248 mya • We will see fish and winged insects • Mesozoic Era ~ 248 to 65 mya • Age of the Reptile • This is when we see the dinosaurs • Cenozoic Era ~ 65 mya through today • Age of the Mammal • Eras are broken into Periods • Periods are broken into Epochs Phanerozoic Eon

  11. First mammals Deer, pigs, horses, dogs Grass is common Phanerozoic EonCenozoic EraTertiary Period

  12. The first humans (Homo sapiens) evolve • Mammoths, mastodons, saber-toothed cats, giant ground sloths • A mass extinction of large mammals and many birds happened about 10,000 years ago, probably caused by the end of the last ice age Phanerozoic Eon Cenozoic EraQuaternary Period Pleistocene Epoch

  13. This is where we are TODAY!! • Human civilization Phanerozoic Eon Cenozoic EraQuaternary Period Holocene Epoch

  14. http://www.timetoast.com/timelines/63215

  15. How do Scientists find out about Earth’s Past? • What type of Scientist studies Earth’s Past?

  16. Paleontologists study the Earth's past biosphere and current biosphere. Paleontology is the study of prehistoric life, including organisms' evolution and interactions with each other and their environments (their paleoecology) • An Anthropologist is a scientist who studies prehistoric people and their culture • An Archeologist is a scientist who studies past human life and culture by the recovery and examination of remaining material evidence, such as graves, buildings, tools, and pottery • As well as Biologists, Chemists Types of Scientists

  17. Traces or remains of living things from long ago • Fossils can give us clues to Earth’s past • Types of fossils: original remains, natural evidence, fossils in rocks Fossils

  18. Fossils that are the actual body parts (skin, muscle, bones, hair) • Conditions prevent decomposition • Ice – BEST preserver, large mammoths • Amber – harden resin of trees, insects • Tar- thick, oily liquid, large mammoths Fossils Original remains

  19. Fossils Original remainsIce- Mammoth found in Siberia

  20. Fossils Original remainsAmber – about 40 mya

  21. Fossils Original remainsTar – fossils found in tar pits

  22. Tree Rings – the width of the rings can give clues to the climate • Wide width = a wet season, good for growth • Thin width = dry season, may give hint to years of famish • Ice Core – vertical timeline of Earth’s atmosphere • Air content in different layers gives clues to temperature • Debris can give clues to volcanic eruptions Fossils Natural Evidence

  23. FossilsNatural Evidence – Tree Ring

  24. FossilsNatural Evidence – Ice Core

  25. ONLY in Sedimentary rocks, conditions have to be right • Traces of the hard parts of an organism • 4 types • Molds and Casts • Petrified Wood • Carbon Films • Trace Fossil Fossils in Rocks

  26. Mold is a visible shape left in sedimentary rock • Over time sediment buries an organism • The soft parts decay first, then the hard parts decay • Leaving a hollow space to fill with minerals, which makes a Cast of the organism Fossils in Rocks Molds and Casts

  27. Fossils in Rocks Molds and Casts

  28. A fallen tree that has been covered with sediment • Over time minerals replace the wood part of the tree/ the cells Fossils in Rocks Petrified Wood

  29. ALL living organisms contain carbon • Sometimes when an organism dies it leaves behind the carbon – a visible layer • You are able to see the soft parts Fossils in Rocks Carbon Film

  30. Evidence of an organism’s presence • Foot prints • Dwellings • Feces Fossils in Rocks Trace fossils

  31. So that brings us back to the question…How do Scientists KNOW how old the Earth is?

  32. Relative Age • Rock Layers • Index Fossils • Absolute Age • Radioactive Dating Finding the Age of Rocks

  33. The age of an event or object in relationship to something else Relative Age

  34. Sedimentary Rock Layers • Undisturbed layers the youngest layer will be on the top Relative Age

  35. Sedimentary Layers that have been disturbed by folding…follow the layers Relative Age

  36. Sedimentary Layers that have been disturbed by igneous rock…the igneous rock will be younger than the rock it goes through, but the sedimentary on top of that will be younger Relative Age

  37. Index Fossils – fossils of organisms that lived in many areas and existed ONLY during a specific time Relative Age

  38. How to use Index Fossils

  39. The ACTUAL age of an object or organism • Scientists use a process called Radioactive Dating – using the half-Life of radioactive elements • Used mostly with igneous rock • This process can NOT be used on sedimentary rocks (Why?) • Also used for organisms - Carbon Absolute Age

  40. Everything is made of Atoms • The Atoms of many elements exist in various forms • Some breakdown, and the way they breakdown is predictable • The time it takes for half of the atoms in a sample to change from an unstable form to a new form is called Half-Life • Each element has its own unique Half-Life Radioactive Dating

  41. Half-Life

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