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30 Cards in this Set

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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