Scale: 1 pixel = 2 km. 5-degree grid; Lambert Conformal Conic Projection, Center 30N 000EW
|Copernican: Beginning with the formation of the
bright crater Copernicus, about 1.1 Ga. Formation of bright ray
Eratosthenian: Begins with the formation of the crater Eratosthenes. Fresh but non-rayed craters and late mare eruptions. 1.1 to 3.1 Ga.
Imbrian: Begins with the formation of the Imbrium Basin. Includes most mare eruptions. 3.1 to 3.8 Ga.
Nectarian: Begins with the formation of the Nectaris Basin, and includes most of the major impact basin events. 3.8 to 3.9 Ga.
pre-Nectarian: Before 3.9 Ga
Mare Imbrium (Sea of Rains) gives its name to the Imbrian Epoch. Formation of the Imbrium Basin was nearly the last major basin event (Mare Orientale came later), and the largest near-side impact. Several hundred million years later, magma welled upward and flooded the near-side impact basins but very few of the far-side basins. Since the mare eruptions, cratering has been much less intense. It's interesting and fortunate that just about the time Earth begins to have a readable geologic history, geologic history all but stops on the Moon. We can presume Earth suffered an early battering comparable to the Moon, but most of the evidence on Earth has been lost.
Created 11 April 2014, Last Update
12 March 2015
Not an official UW Green Bay site