Geologic Time Review

Front

What is radiometric dating?

Back

The process of measuring the absolute age of rocks, minerals, and fossils by measuring the concentrations of radioactive isotopes and their decay products.

Front

What is an unconformity in geology?

Back

A boundary between layers of sediment or sedimentary rock that represents an interruption in the deposition of sediment, including an interruption that involves partial erosion of the older layer.

Front

What happens to unstable radioactive isotopes over time?

Back

They decay to form more stable isotopes at a predictable rate.

Front

What do geologists mean when they refer to an unconformity in rock?

Back

An interrupting boundary between layers of sedimentary rock.

Front

Which layer is most likely the oldest in a geologic formation?

Back

Layer C.

Front

What is the principle of superposition?

Back

In an undeformed sequence of sedimentary rocks, the oldest layers are at the bottom and the youngest layers are at the top.

Front

What is a fossil?

Back

The preserved remains or traces of ancient organisms, often found in sedimentary rock.

Front

What is the significance of index fossils?

Back

Index fossils are used to define and identify specific time periods in the geologic time scale.

Front

What is the geologic time scale?

Back

A system of chronological dating that relates geological strata to time, used by geologists and other Earth scientists.

Front

What is absolute dating?

Back

A method of determining the exact age of a rock or fossil in years, often using radiometric techniques.