Geologic time scales
Named divisions of geologic time used to specify relationships among geologic units and structural features
- Geologic time scale bookmark [More info]
- This printable bookmark was designed for use with USGS activities at the 2nd USA Science and Engineering Festival, held April 26-29, 2012.
- Compilation of various geologic time scales [More info]
- Preliminary report comparing various geologic time scales. Text is HTML or plain text format, and colored compilation chart in Excel format.
- Divisions of Geologic Time - Major Chronostratigraphic and Geochronologic Units [More info]
- A summary of the divisions of geologic time intended to provide a consistent time scale to be used in communicating ages of geologic units in the United States.
- Geologic time online edition [More info]
- Booklet giving general explanations of geologic time, major divisions of geologic time, relative and radiometric time scales, index fossils, and the age of the earth.
- Fossils, rocks, and time [More info]
- Booklet describes how paleontologists use the identification of fossils to recognize rocks of the same or different ages.
- Precambrian Time - The Story of the Early Earth [More info]
- Explains what we know about the early history of the earth and how we study the deposits formed during that time to understand the formation of the earth and life.