Are fossils in which the spaces inside are filled with minerals from groundwater.
A silhoutte of the original organism.
A cavity in the rock.
A type of body fossil that forms when crystals fill a mold or sediments wash into a mold and harden into rock.
Are the remains of species that existed on Earth for relatively short periods of time, were abundant, and were widespread geographically.
States that in undisturbed rock layers, the oldest rocks are on the bottom and the rocks become progressively younger toward the top.
The age of something compared with other things.
Gap in the rock layer that is due to erosion or periods without any deposition.
Age, in years, of a rock or other object; can be determined by using properties of the atoms that make up materials.
Process in which some isotopes break down into other isotopes and particles.
Time it takes for half the atoms of an isotope to decay.
Process used to calculate the absolute age of rock by measuring the ratio of parent isotope to daugher product in a mineral and knowing the half-life of the parent.
Principle stating that Earth processes occuring today are similar to those that occured in the past.
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