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Fossils Chapter 21
Fossils <ul><li>Remains or traces of once living organisms </li></ul><ul><li>Tells scientists when, where and how organism...
Types
Petrified Remains <ul><li>Hard, rock-like parts replaced by mineral (calcium) </li></ul><ul><li>Bones, Tree trunks </li></ul>
Carbonaceous Film <ul><li>Carbon Deposits </li></ul><ul><li>Coal, oil, Natural gas </li></ul>
Molds and Casts <ul><li>Remains Covered </li></ul><ul><li>Sediments Harden </li></ul><ul><li>Water dissolves object </li><...
Original Remains <ul><li>Entire (or part) of organism is preserved </li></ul><ul><li>Amber (Tree Sap), Ice, Bog (swamp) </...
Trace Fossils <ul><li>Not actually the remains of the organism, but evidence it has been there </li></ul><ul><li>Footprint...
How do we figure out age?? <ul><li>Absolute Age-  Exact age </li></ul><ul><ul><li>Example 3412 years old or 15 years old <...
Relative Age <ul><li>Best guess of age </li></ul><ul><li>Index Fossils- Fossils from species that lived for short periods ...
Geode
Absolute Dating <ul><li>True Age </li></ul><ul><li>Radioactive Decay- Breakdown of unstable isotopes into stable atoms </l...
Radiation <ul><li>Alpha ( α )- blocked by newspaper </li></ul><ul><ul><li>2(p + )&2n=mass# decrease by 4, atomic # decreas...
Isotopes <ul><li>Unstable- Parent isotope </li></ul><ul><li>Stable- Daughter </li></ul>
Half-Life <ul><li>Amount of time needed to breakdown half of the parent material into daughter material </li></ul><ul><li>...
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Fossils Lecture

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Transcript of "Fossils Lecture"

  1. 1. Fossils Chapter 21
  2. 2. Fossils <ul><li>Remains or traces of once living organisms </li></ul><ul><li>Tells scientists when, where and how organism lived </li></ul><ul><li>Formation </li></ul><ul><ul><li>Normal- Organism decays (deer on road) </li></ul></ul><ul><ul><li>MUST keep organism from rotting </li></ul></ul><ul><ul><ul><li>Quick burial (sand, mud, tree sap, etc) </li></ul></ul></ul><ul><ul><ul><li>Hard parts (bones, wood, etc) </li></ul></ul></ul>
  3. 3. Types
  4. 4. Petrified Remains <ul><li>Hard, rock-like parts replaced by mineral (calcium) </li></ul><ul><li>Bones, Tree trunks </li></ul>
  5. 5. Carbonaceous Film <ul><li>Carbon Deposits </li></ul><ul><li>Coal, oil, Natural gas </li></ul>
  6. 6. Molds and Casts <ul><li>Remains Covered </li></ul><ul><li>Sediments Harden </li></ul><ul><li>Water dissolves object </li></ul><ul><li>Mold Remains </li></ul><ul><li>Cast- Sediment fills mold and hardens </li></ul>
  7. 7. Original Remains <ul><li>Entire (or part) of organism is preserved </li></ul><ul><li>Amber (Tree Sap), Ice, Bog (swamp) </li></ul>
  8. 8. Trace Fossils <ul><li>Not actually the remains of the organism, but evidence it has been there </li></ul><ul><li>Footprints, Burroughs, etc </li></ul>
  9. 9. How do we figure out age?? <ul><li>Absolute Age- Exact age </li></ul><ul><ul><li>Example 3412 years old or 15 years old </li></ul></ul><ul><li>Relative Age- Approximate Age </li></ul>
  10. 10. Relative Age <ul><li>Best guess of age </li></ul><ul><li>Index Fossils- Fossils from species that lived for short periods of time and were wide spread across the world </li></ul><ul><li>Rock Layers- </li></ul><ul><ul><li>Law of Superposition- “above position” </li></ul></ul><ul><ul><ul><li>In UNDISTURBED layers of rocks, the oldest layers are on the bottom and younger layers on top </li></ul></ul></ul><ul><ul><ul><li>Think about a clothes hamper </li></ul></ul></ul>
  11. 11. Geode
  12. 12. Absolute Dating <ul><li>True Age </li></ul><ul><li>Radioactive Decay- Breakdown of unstable isotopes into stable atoms </li></ul><ul><li>Isotope- Variation in number of neutrons in an atom’s nucleus </li></ul><ul><li>Carbon- 2 isotopes </li></ul><ul><ul><li>C 12 - 6p and 6 n=12 </li></ul></ul><ul><ul><li>C 14 - 6p and 8n=14 </li></ul></ul><ul><ul><li>C 14 is unstable </li></ul></ul>
  13. 13. Radiation <ul><li>Alpha ( α )- blocked by newspaper </li></ul><ul><ul><li>2(p + )&2n=mass# decrease by 4, atomic # decrease by 2 </li></ul></ul><ul><li>Beta ( β )- Blocked by brick wall </li></ul><ul><ul><li>1 e -= no change in mass # </li></ul></ul><ul><ul><li>Electron is from neutron (p& e - )causing Atomic # to increase by 1 </li></ul></ul><ul><li>Gamma ( γ ) Blocked only by lead! </li></ul><ul><ul><li>Photon </li></ul></ul>
  14. 14. Isotopes <ul><li>Unstable- Parent isotope </li></ul><ul><li>Stable- Daughter </li></ul>
  15. 15. Half-Life <ul><li>Amount of time needed to breakdown half of the parent material into daughter material </li></ul><ul><li>Carbon 14- 5730 years </li></ul><ul><li>Uranium- 4.5 billion years </li></ul><ul><li>Potassium 40- 1.3 billion years </li></ul><ul><li>Which would you use to date the planet? </li></ul>
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