11.6 An Overview of Earth History

Question 1

Cambrian explosion

Answer 1

The tremendous increase in the variety of organisms on Earth that occurred over a time span of 20 – 25 million years at the beginning of the Cambrian Period.

Question 2

Eon

Answer 2

The longest division on the geologic time scale, such as Phanerozoic Eon.

Question 3

Epoch

Answer 3

A division of a period on the geologic time scale, such as the Pleistocene or Eocene Epochs.

Question 4

Era

Answer 4

A division of an eon on the geologic time scale, such as the Mesozoic or Paleozoic Eras.

Question 5

Geologic column

Answer 5

An ordered arrangement of rock layers from oldest to youngest. The geologic column is a concept and does not exist in its entirety at any one place in Earth’s crust.

Question 6

Mass extinction

Answer 6

A time in Earth history when many species go extinct at the same time.

Question 7

Period

Answer 7

A division of an era on the geologic time scale, such as the Ordovician and Jurassic Periods.

Question 8

Principle of fossil succession

Answer 8

The principle which states that fossils occur in a specific order in the geologic record.