permineralization		unconfomity that exists between horizontal rock layers and rock layers that are tilted or folded
relative		ideal sequence of rock layers that contain all known fossils and rock formations
isotopes		"old life"
geologiccolumn		type of trace fossil
mold		insects are often preserved in this
mummificaiton		preserved feces
tarpits		four major parts of the geologic time scale
eons		the process where an unstable isotope changes into a stable isotope
angular		atoms of the same element with different masses
Mesozoic		an index fossil
trilobite		missing part or gap in the geologic column
fossil		most of the fossils of saber-toothed cats are found here
decay		object created when a mold is filled with sediments that become rock
uniformitarianism		a process in which mineral fill in the pore spaces of an organism's tissue
amber		process where organisms do not decay because the bacteria that feeds on the dead organism can't live without water
unconformity		principle that states that the younger rock layers lie above older rock layers in undisturbed sequences
index fossil		the time it takes for one half of a radioactive sample to decay
Paleozoic		era where reptiles dominated
trace		trace fossil of shelters made by animals
superposition		dating technique that establishes the age of an object
caprolites		type of fossil where the animal's acitivity is preserved
Cenozoic		priniciple that states that the geological processes that are acting on the Earth today are the same as those that acted upon the Earth in the past
burrows		dating technique that uses the principle of superposition to determine if an object or event is older or younger than another object or event
half-life		era where mammals dominated
cast		fossils of organisms that lived during a relatively short, well defined time period
petrification		naturally preserved evidence of life
absolute		a cavity in ground where a plant or animal was buried
track		occurs when an organism's tissue is completely replaced by minerals