Clue's to Earth Past

Fossil
remains, imprints, or traces of prehistoric organism

permineralized remains
fossil in which the spaces inside are filled with minerals

carbon film
thin film of carbon residue preserved as fossil.

mold
cavity in a rock

cast
copy of an original object

index fossil
remains of species that existed on Earth for short periods of time

principle of superposition

states in undisturbed rock layers, the oldest rocks are on the bottom and the young ones nearer the surface

relative age

age of something in comparison to other things

 unconformity
gasps in rock sequences

absolute age
age, in years, of a rock or other object.

radioactive decay
the process of breaking down

half-life
time it takes for half of atoms in the isotope to decay

radiometric dating
processes use to calculate the absolute age of rock

uniformitarianism
the principles states of Earth procceses ocurring today are similar to those occurring today