Richard A. Robison | Britannica

Richard A. Robison

Contributor

BIOGRAPHY

Gulf-Hedberg Professor of Geology, University of Kansas, Lawrence. Coauthor of Fossil Invertebrates.

Primary Contributions (2)

Articles

A detailed geologic time scale chart displaying Earth's history from the Hadean Eon over 4.5 billion years ago to the present, organized by eons, eras, periods, epochs, and ages with color-coded columns and corresponding dates in millions of years.

Paleozoic Era

Paleozoic Era, major interval of geologic time that began 538.8 million years ago with the Cambrian explosion, an extraordinary diversification of marine animals, and ended about 252 million years ago with the end-Permian extinction, the greatest extinction event in Earth history. The major…

Cambrian Period