Hadean

The earliest eon of Earth's geologic history, spanning from the planet's formation about 4.6 billion years ago to about 4.0 billion years ago, named for the hellish conditions of a molten, heavily bombarded early surface with no rock record of its own preserved on Earth today. Includes the Hadean eon entity alone; no era, period or epoch is formally nested within it in the standard geologic time scale, since the rock record the time scale is built from does not begin until the eon ends. Belongs here: the Hadean eon and nothing else, the oldest interval on the geologic time scale. Does not belong here: the Archean eon that follows, defined by the appearance of the first preserved continental crust that closes the Hadean.