Subdivisions
Since few geological traces of this period remain on Earth there is no official subdivision. However, the Lunar geologic timescale embraces several major divisions relating to the Hadean and so these are sometimes used in a somewhat informal sense to refer to the same periods of time on Earth.
The Lunar divisions are:
- Pre-Nectarian, from the formation of the Moon's crust up to about 3,920 million years ago
- Nectarian ranging up to about 3,850 million years ago, in a time when the Late Heavy Bombardment, according to that theory, was in a stage of decline.
There is a recently proposed alternative scale published in 2010 by Solid Earth, a new open access journal. The article proposes the addition of the Chaotian and Prenephelean Eons preceding it and divides the Hadean into three eras with two periods each. The Paleohadean era consists of the Hephaestean (4.5-4.4 Ga) and the Jacobian periods (4.4-4.3 Ga). The Mesohadean is divided into the Canadian (4.3-4.2 Ga) and the Procrustean periods ({{4.24.1 Ga). The Neohadean is divided into the Acastan (4.1-4.0 Ga) and the Promethean periods (4.0-3.9 Ga).
Read more about this topic: Hadean