Geologic Record

Front

What is absolute age in geology?

Back

The age of rock determined by radiometric dating.

Front

Which rock layer is typically the youngest?

Back

The top layer of sedimentary rock.

Front

Why are trilobites considered good index fossils?

Back

They are abundant, widespread geographically, and only lived for a short time.

Front

What principle do geologists use to determine the relative ages of rock layers?

Back

The law of superposition.

Front

What is the current estimated age of Earth based on radiometric dating?

Back

About 4.6 billion years old.

Front

What is the law of superposition?

Back

In undisturbed sedimentary rock layers, the oldest layers are at the bottom and the youngest are at the top.

Front

What is radiometric dating?

Back

A method used to date rocks and minerals using the decay of radioactive isotopes.

Front

What are index fossils?

Back

Fossils that are used to define and identify a particular time period in the geologic time scale.

Front

What is the significance of carbon dating?

Back

A method for determining the age of an object containing organic material by measuring the amount of carbon-14 it contains.

Front

What does the term 'geologic time scale' refer to?

Back

A system of chronological dating that relates geological strata to time.