Geologic time scale


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Geologic time scale

  1. 1. Geologic Time Scale
  2. 2. Measuring Time <ul><li>The Earth has existed for 4.6 billion years </li></ul><ul><li>The geologic time scale divides all those years into sections </li></ul><ul><li>Like how your science book is divided into Units, then Chapters, then Sections, then Pages </li></ul><ul><li>Each section is unique because it shows a specific change in life or in the Earth’s surface </li></ul>
  3. 3. Giving Time a Name <ul><li>The largest sections are called “eons” </li></ul><ul><li>“ Eons” are divided into “eras” (the 2 nd largest section) </li></ul><ul><li>“ Eras” are divided into “periods” </li></ul><ul><li>Then “periods” are divided into “epochs” </li></ul><ul><li>Usually the oldest sections are shown on the bottom and the most recent sections are shown on the top </li></ul>
  4. 4. How is Time Divided? <ul><li>Major changes in Earth’s history mark the boundaries between the sections </li></ul><ul><li>Most sections have been divided because a major organism developed or went extinct. </li></ul>
  5. 5. Precambrian Time
  6. 6. Pre- Cambrian Time <ul><li>Oldest and Longest Time Period </li></ul><ul><li>Almost 90% of Earth’s History </li></ul><ul><li>From beginning of Earth (4.6 billion years ago) to 540 Million years ago </li></ul><ul><li>Oldest rocks are the deepest rocks </li></ul><ul><li>Ores are deposited (iron, silver, gold) </li></ul>
  7. 7. Paleozoic Era <ul><li>Began 542 million years ago and ended 251 million years ago </li></ul><ul><li>Divided into 6 periods </li></ul><ul><li>Many new life forms appeared during the 1 st period, the Cambrian Period = “Cambrian Explosion” </li></ul><ul><li>For the first time on Earth, organisms had hard parts (shells, exoskeletons) </li></ul><ul><li>Some organisms that were alive during this period still exist today (ferns and salamanders) but they were giants! </li></ul>
  8. 8. Phanerzoic Eon, Paleozoic Era <ul><li>Paleo- (Latin) ancient; -zoic (Latin) animals/ life </li></ul><ul><li>Hard shelled animals appear </li></ul><ul><li>Pangea formed </li></ul><ul><li>Plants begin to grow on land </li></ul><ul><li>“ Age of Fish” large fish populate oceans </li></ul><ul><li>Amphibians (frogs) go to land </li></ul><ul><li>Insects appear </li></ul>
  9. 9. Permian Extinction <ul><li>The largest mass extinction happened 251 million years ago </li></ul><ul><li>Marked the end of the Paleozoic Era and the start of the Mesozoic Era </li></ul><ul><li>Scientists are not sure what caused this mass extinction (maybe climate change & volcanoes) </li></ul><ul><li>90% of ocean life and 78% of land life died </li></ul><ul><li>Reptiles and amphibians survived! </li></ul>
  10. 10. Paleozoic Con’t <ul><li>Pennsylvanian Period- very large swamps which later become coal </li></ul><ul><li>Appalachian Mountains Form </li></ul>
  11. 11. Mesozoic Era
  12. 12. Mesozoic Era <ul><li>Began 251 million years ago </li></ul><ul><li>Surviving reptiles and amphibians evolved into many other species (like dinosaurs) = “Age of Reptiles” </li></ul>
  13. 13. Mesozoic Era <ul><li>Meso- “middle” -zoic “animals/life” </li></ul><ul><li>Breakup of Pangea </li></ul><ul><li>Age of Reptiles- dinosaurs and reptiles rule planet </li></ul><ul><li>Rocky Mountains form </li></ul>
  14. 14. Cretaceous-Tertiary Extinction <ul><li>Another mass extinction happened 65 million years ago </li></ul><ul><li>Marked the end of the Mesozoic Era and the beginning of the Cenozoic Era </li></ul><ul><li>All of the dinosaurs and half of the other animals & plants went extinct </li></ul><ul><li>Scientists think an asteroid hit Earth, the dust clouds blocked out the sun, plants died, then herbivores, then carnivores. </li></ul>
  15. 15. Mass Extinction <ul><li>Dinosaurs are killed by meteorite </li></ul><ul><li>Animals and plants change </li></ul><ul><li>90% of all species that have ever lived are now extinct </li></ul>
  16. 16. Cenozoic Era
  17. 17. Cenozoic Era <ul><li>Began 65 million years ago and continues today </li></ul><ul><li>Scientists know the most about this Era because the fossils are in the top rock layers and are easier to find </li></ul><ul><li>Land & climate has changed a lot </li></ul><ul><li>What big change will happen that will end this era & start the next? </li></ul>
  18. 18. Cenozoic Era <ul><li>Ceno- “new”; -zoic “life” </li></ul><ul><li>Last 45 million years </li></ul><ul><li>Age of Mammals- Humans evolve </li></ul><ul><li>Ice Ages </li></ul><ul><li>Flowering Plants </li></ul><ul><li>Colorado Plateau and Sierra Nevada Mountains formed </li></ul>