History of the Earth Vocab

Front

Age of a rock compared to others

Back

Relative Age

Front

Age of a rock in years since formation

Back

Absolute Age

Front

Geologic principle stating that in horizontal sedimentary rock layers, each layer is older than the one above and younger than the one below.

Back

Law of Superposition

Front

Preserved remains or traces of an organism from the past

Back

Fossil

Front

A gap in the geologic record where rock layers are lost due to erosion.

Back

Unconformity

Front

Process where radioactive nuclei break down, releasing particles and energy

Back

Radioactive Decay

Front

Determining the age of an object using the half-life of radioactive isotopes

Back

Radioactive Dating

Front

Record of geologic events and life forms in Earth's history

Back

Geologic Time Scale

Front

One of 3 long time units between the Precambrian and now

Back

Era

Front

Unit of geologic time dividing eras

Back

Period