Geologic Time Vocab

Front

Oldest rocks at the bottom, younger rocks on top in undisturbed layers.

Back

Principle of superposition

Front

Remains, imprints, or traces of prehistoric organisms that indicate their existence and lifestyle.

Back

Fossils

Front

Time for half of a radioactive isotope to decay.

Back

Half-life

Front

Thin film of carbon residue preserved as a fossil.

Back

Carbon film

Front

Principle stating current Earth processes resemble those in the past.

Back

Uniformitarianism

Front

Calculating absolute age of rock by measuring parent isotope to daughter product ratio and knowing half-life.

Back

Radiometric dating

Front

Age of a rock or object, determined by material properties.

Back

Absolute age

Front

Fossils with spaces filled by groundwater minerals.

Back

Permineralized remains

Front

Remains of species that existed briefly, were abundant, and help geologists date rock layers.

Back

Index fossil

Front

Type of body fossil forming in rock when an organism with hard parts decays, leaving a cavity.

Back

Mold