Geologic Time Review

Front

What do geologists mostly study to develop the geologic time scale?

Back

Geologists study rock layers and index fossils to develop the geologic time scale.

Front

What is the term for the time it takes for half of a radioactive element's atoms to decay?

Back

The term is half-life.

Front

True or False: Invertebrates were Earth's earliest multicellular organisms.

Back

True.

Front

What is the name for all time before the Cambrian explosion of life?

Back

It is called Pre Cambrian Time.

Front

What is the largest division of time on the geologic time scale?

Back

The largest division is called an eon.

Front

What are index fossils?

Back

Index fossils are fossils of organisms that were widespread but only existed for a short period of time, used to date rock layers.

Front

What is the significance of the Cambrian explosion?

Back

The Cambrian explosion marks a period of rapid diversification of life forms on Earth.

Front

What is radioactive dating?

Back

Radioactive dating is a method used to determine the age of an object by measuring the amount of radioactive isotopes it contains.

Front

What is an unconformity in geology?

Back

An unconformity is a surface that represents a gap in the geologic record, where rock layers are missing.

Front

What is the difference between an era and a period in the geologic time scale?

Back

An era is a larger division of time than a period; periods are subdivisions of eras.