Fossils

the remains or traces of once living organisms

• fossils

• trace fossils

• index fossils

a record of the activity of an organism which could be in the form of footprints, tracks, a burrow, scratches, or fossilized dung

• index fossil

• amber fossil

• trace fossil

the method of finding the absolute age of rock based on comparing the amounts of unstable, radioactive particles in a sample

• radiometric dating

• radioactive decay

• half life

the impression of the body shape left in the sediment after an organism's tissues decompose

• cast fossil

• mold fossil

• index fossil

the principle that the geologic events and phenomena that happen today also happened in the past and that they apply everywhere in nature

• uniformitarianism

• law of superposition

• mass extinction

relates to whether a rock layer is older or younger than other rock layers

• uniformitarianism

• half life

• relative age

the process where certain unstable particles that make up matter in rocks and living organisms change into different stable particles at a constant rate

• half life

• radiometric dating

• radioactive decay

fossils used to estimate the absolute age of all the rock layers in which they are formed

• index fossils

• fossil records

• mold fossils

when all members of a species die out

• mass extinction

• half life

• extinction

when water seeps into the impression of a mold fossil and the minerals from the water harden it

• index fossil

• cast fossil

• amber fossil