Geologic Time

Front

What era accounts for 90% of Earth's history?

Back

Precambrian

Front

What event typically marks the end of an Era?

Back

A Mass Extinction

Front

What is the oldest known organism on the geologic time scale?

Back

Trilobites

Front

True or False: Scientists determine the beginning and end of geologic time units based on the appearance or disappearance of life.

Back

True

Front

Which period is closest to the present day?

Back

Tertiary

Front

Define the Precambrian era.

Back

The Precambrian era is the earliest part of Earth's history, covering about 90% of the geological time scale, before the Cambrian period.

Front

What significant event occurred at the end of the Paleozoic era?

Back

The Permian-Triassic extinction event, the largest mass extinction in Earth's history.

Front

What are trilobites?

Back

Trilobites are extinct marine arthropods that existed during the Paleozoic era and are among the earliest known complex life forms.

Front

What is the significance of the Cambrian explosion?

Back

The Cambrian explosion marks a rapid diversification of life forms and the appearance of most major animal phyla.

Front

What is the Mesozoic era known for?

Back

The Mesozoic era is known as the age of reptiles, including dinosaurs, and the emergence of mammals and birds.