Library Guides: Geology: Geologic Time

About Geologic Time

Geologists have determined that the Earth is more than 4.5 billion years old, based on radiometric age dating. The following links connect to information on geologic time, including several geologic time scales, and resources about the concept of geologic time.

Geologic Time Scale
A geologic time scale focusing on the Americas available from the Geological Society of America.
International Chronostratigraphic Chart
A geologic time scale developed by the International Union of Geological Sciences, originally published in Episodes, which is provided by the International Commission on Stratigraphy.
Geologic Mnemonics
A collection of geology related mnemonic devices from a site in the European Union. Includes geologic time as well as devices for remembering other geologic facts (Mohs hardness scale, grain size and the order of crystallization of minerals from a magma).
EarthViewer
EarthViewer is an interactive website from HHMI that can be used to explore the history of the Earth.
ChronoZoom
ChronoZoom, which requires a current Silverlight plug-in, allows users to tour Big History, the history of the Earth from the Big Bang to the present, including the history of the Big Bang, cosmos, Earth & life, human pre-history and human history.
Time: It's Like, So Deep
A web resource on geologic time developed by the Smithsonian Institution.
Phanerozoic Geologic Time Chart
A geologic time scale from the British Geological Survey.
Geological Timeline
A resource about geological time developed by the British Geological Survey that includes an interactive geologic time line.