What is Geologic Time?

This webpage of the National Park Service (NPS) and United States Geological Survey (USGS) discusses geologic time and what it represents. Beginning about 4.6 billion years ago and ending in the present day, this site exhibits (to scale) the various eras, periods, eons, and epochs of Earth's history with a downloadable geologic time scale available. Links provide maps of what the Earth looked like at various times in its history, as well as a description of how scientists developed the time scale and how they know the age of the Earth.

This description of a site outside SERC has not been vetted by SERC staff and may be incomplete or incorrect. If you have information we can use to flesh out or correct this record let us know.

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Grade Level: College Lower (13-14), High School (9-12), Middle (6-8)Keywords: Phanerozoic Eon, Precambrian, Archean, Proterozoic, Paleozoic Era, Mesozoic Era, Cenozoic Era, Cambrian Period, Ordovician Period, Silurian Period, Devonian Period, Carboniferous Period, Permian Period, Triassic Period, Jurassic Period, Cretaceous Period, Tertiary Period, Quaternary Period, Paleocene Epoch, Eocene Epoch, Oligocene Epoch, Miocene Epoch, Pliocene Epoch, Pleistocene Epoch, Holocene Epoch