Geologic Time 2
Terms
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- Fossil
- the evidence or remains of once living plants or animals.
- type of rock fossils most likely found
- sedimentary, limestone
- type of organism most likely to form fossils
- things with bones/cartilage/shells(most often)
- original preservation
- the soft and hard parts of plant and animal remains that have not undergone any kind of change since the organisms death
- locations likely to resulting in original preservation
- are uncommon because their preservation requires extradionary circumstances such as freezing, drying out, or oxygen free environments
- examples of original preservation
- mummified remains,tar pits;amber-insects in tree sap
- altered hard parts
- when all organic material has been removed and teh hard parts of a plant or animal have been changed either by mineral replacement or by recrystalization
- examples of altered hard parts by permineralization
- petrified wood
- examples of altered hard parts by recrystalization
- shells or corals
- permineralization
- process by which pore spaces are filled in with mineral substances
- molds
- are formed when the original shell parts of an organism within a sedimentary rock are weathered and eroded; hollowed out impression
- casts
- a cavity becomes filled with minerals or sediments to create a cast of the organism
- index fossils
- remains of plants or animals that can be used by geologists to correlate rock layers over large geographic areas or to date a particular rock layer
- trace fossils
- indirect evidence of plant and animal life
- examples of index fossils
- trilobites, dinosaurs
- examples of trace fossils
- worm trails, burrows, footprints, gastroliths, and coprolite
- coprolite
- fossilized remains of solid waste
- gastrolith
- smooth round rocks that dinasours have in stomach for digestion
- amber
- insects in tree sap
- conditions required for fossils to form
- quickly burried, little to no water or oxygen so decay is slow
- objects that can be dated using tritum
- water, ice
- objects that can be dated using C-14
- wood, bones, shells, organic
- objects taht can be dated using uranuim
- rocks, minerals
- general half life of tritium
- 12.3 years
- general half life of C-14
- 5730 years
- general half life of uranium
- 7.04 million years
- general half life for potassium
- 1.3 billion years
- how the original amount of parent isotope is determined
- cut it in half each times
- amount of parent isotope remaining after one half life
- 1/2
- amount of parent isotope remaining after two half lives
- 1/4