Geologic time rock dating methods

The Phanerozoic Eon began 570 million years ago and continues today.This time scale, from the Decade of North American Geology, is widely used in North America.

This format is useful, but it tends to conceal the immense span of time, over 85 percent of Earth’s history, within the Precambrian. Its crust is continually being created, modified, and destroyed.These ages, usually called radiometric ages, are used in conjunction with relative dating principles to determine at least an approximate age for most of the world’s major rock formations.The 4.55 billion-year geologic time scale is subdivided into different time periods of varying lengths.The principal evidence for the antiquity of Earth and its cosmic surroundings is: The oldest rocks on Earth, found in western Greenland, have been dated by four independent radiometric dating methods at 3.7-3.8 billion years.Rocks 3.4-3.6 billion years in age have been found in southern Africa, western Australia, and the Great Lakes region of North America.