Are thr remains, imprints, or traces of prehistory organisms.
Are the fossils in which the spaces inside are filled with minerals from groundwater.
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Carbon film
A thin film of carbon residue is left, forming a silhouette of the original organism.
Mold
The hard part might decay or dissolve leaving behind a cavity rock.
Cast
Mineral-rich water or other sediment might enenter the cavity, form ew rock, and produce a copy of the orginal object.
Index fossils
Are the remains of species that existed on Earth for relatively short periods of time, were abundant, and were widespread geogrephically.
Principle of superposition
The oldest rocks are on the bottom and the rocks become progressively younger toward the top.
Relative Age
Something is its age in comparison to other things.
Unconformities
Gaps in rock sequence.
Absolute age
Age, in years, of a rock or other object.
Radioactive decay
Process os breaking down.
Half-life
The time it takes for half of the atoms in the isotope to decay.
Radiometric dating
Measure the ratio of a pafrent isorope to daughter product in a mineral and by knowing the half-life of the parent.
Unoformitarianism
Scottish scientist James Houtson used it.
Permineralized remains
