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Understanding Geologic Time

Understanding Geologic Time. Fossils. Preserved remains of living things Formed in sedimentary rock Paleontologist – One who studies fossils. hms-beagle.com. Kinds of Fossils. Petrified Mold and Cast Carbon Film Trace Fossil Preserved Remains. topnews.in. Petrified.

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Understanding Geologic Time

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  1. Understanding Geologic Time

  2. Fossils • Preserved remains of living things • Formed in sedimentary rock • Paleontologist – One who studies fossils hms-beagle.com

  3. Kinds of Fossils • Petrified • Mold and Cast • Carbon Film • Trace Fossil • Preserved Remains topnews.in

  4. Petrified • Organism dies and is covered by sediment • Water with minerals seep into space • Minerals replace all or part of organism statesymbolsusa.org

  5. More Petrified Samples pdphoto.org

  6. Mold and Cast • Most common type of fossil • Two part process Mold then Cast • Mold • Organism dies and is covered by sediment • Hollow area created where organism was • Cast • Minerals or sediment fill mold of organism and solidify • Copy of shape of organism

  7. Mold and Cast petrifiedwoodmuseum.org

  8. Carbon Film • Organism dies, covered by sediment • Thin coating of carbon left on rock • Finely detailed biosci.ohio-state.edu

  9. Trace Fossil • Evidence of organisms activities • Not actual organism • Examples • Footprints • Burrow • Trail http://www.pdphoto.org

  10. Preserved Remains • Organism is preserved in some material • Tar • Rancho La Brea Tar Pits • Amber • Hardened sap from tree • Frozen • Woolly Mammoth found in glacier http://www.dailytelegraph.com.au

  11. Uses for Fossils • Evidence of history of life on Earth • What appeared when/chronological record • Evidence for how life has changed over time • How organisms evolved • Evidence of past climate • What was Earth’s climate like and how has it changed

  12. Aging Rocks • Relative Age • A comparative age between other known ages • Relates to age of surrounding rocks • Younger than, older than, etc. • Absolute Age • Indicates the number of years since rocks formation • Based off age of radioactive isotopes and their half lives

  13. Clues to Ages of Rocks • Law of superposition • Igneous rock • Faulting • Index Fossils prehistoricplanet.com

  14. Law of Superposition • Horizontal sedimentary rock • Oldest rock at the bottom • Each higher layer younger cosscience1.pbworks.com

  15. Igneous Rock • Intrusion • Hardens underground • Younger than rock around or beneath it • Rock around it had to be there already to form • Extrusion • Hardens on the surface • Rock below extrusion is older • Rock had to be there already to form on

  16. Which is Oldest/Newest? en.wikibooks.org

  17. Index Fossil • Helps determine relative age of rock • Widely distributed organism • Organism existed for a short duration • Match rock layers geology.ohio-state.edu

  18. Gaps in Geologic Record • Unconformity • Gap in geologic record • Older layer touches newer layer where middle layers are missing • Does not conform to the law of superposition lams.slcusd.org

  19. Radioactive Dating • Using radioactive decay of material to determine age of material • Only good on igneous rock, why? • Unstable atoms decompose to form new atoms of different element • Carbon – 14 Nitrogen – 14 • Potassium 40 Argon - 40

  20. Half Life • Rate at which radioactive elements decay • Amount of time for half of atoms to decay visionlearning.com

  21. Age of the Earth • 4.6 Billion Years Old • Based off of Earth and Moon being roughly same age • Moon rock age at 4.6 byo • Oldest Earth rock known ~ 4 billion years old

  22. Geologic Time Scale • Divide geologic time into units • Precambrian time and 3 Eras • Eras are divided into periods • Periods are divided into epochs

  23. emc.maricopa.edu

  24. Precambrian Time 544 mya – 4.6 bya • 3.5 bya earliest fossils of life • Single-celled organisms similar to bacteria • 2.5 bya earliest photosynthesis • Produce atmosphere of oxygen sleepingdogstudios.com

  25. Paleozoic Era 245 mya – 544 mya • Paleo = ancient or early • Zoic = life • Life explodes in Cambrian Period (invertebrates) • Life reaches land • Silurian Period – plants • Devonian Period – animals • Mass extinction 95% life in oceans disappeared • Do not know cause http://www.palaeos.org

  26. Mesozoic Era 66.4 mya – 245 mya • Meso = middle • Age of the dinosaur • Mammals appear • Pangaea begins to break up • Land organisms diversify • Flying reptiles • Flowering plant • Mass extinction at end • Meteor hits Earth at Yucatan Peninsula dinosaurland.com

  27. Cenozoic Era present – 66.4 mya • Ceno = recent • Age of mammals • With dinosaur extinction rapid radiation of mammals occupying new niches • Earth’s climate was warm then cooled (Ice age) • Homo sapiens ~100,000 years ago oceanleadership.org

  28. http://www.geo.ucalgary.ca

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