G RA D E 7 S C I E N C E

TERMS FOR GEOLOGIC TIME

GEOLOGIC TERMS

• Absolute age:

• Era:

• The numeric age of a layer of rocks or fossils. Absolute age can be determined using radiometric dating.

• The second largest division of time in the Geologic Time Scale, e.g. Mesozoic.

GEOLOGIC TERMS

• Eon:

• Fauna:

• Flora:

• The largest division of time in the Geologic Time Scale, e.g., Phanerozoic.

• The animals of a given region or period.

• The plants of a given region or period.

GEOLOGIC TERMS

• Fossil Record:

• Geologic Time Scale:

• All of the fossils that have existed throughout Earth’s history, whether they are in the ground or are in a museum.

• A vertical timeline representing events in Earth’s history. The Geologic time scale is divided into blocks of time that represent great changes in Earth’s biodiversity.

GEOLOGIC TERMS

• Law of Superposition:

• Period:

• The formation of new rock layers on top of older ones. This allows us to determine the relative age of rocks and fossils. “Super” refers to over and “position” refers to place.

• The third largest division of time in the Geologic Time Scale, e.g. Cretaceous.

GEOLOGIC TERMS

• Radiometric dating:

• Relative age:

• A method used to determine the absolute age of a rock by using the rock’s chemistry.

• The age of a rock layer, or the fossils it contains, compared to other layers.