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