Early Earth

Early Earth is loosely defined as encompassing Earth in its first one billion years, or gigayear (Ga, 10⁹ y),^[1] from its initial formation in the young Solar System at about 4.55 Ga to some time in the Archean eon in approximately 3.5 Ga.^[2] On the geologic time scale, this comprises all of the Hadean eon, starting with the formation of the Earth about 4.6 billion years ago,^[3] and the Eoarchean, starting 4 billion years ago, and part of the Paleoarchean era, starting 3.6 billion years ago, of the Archean eon.

This period of Earth's history involved the planet's formation from the solar nebula via a process known as accretion. This time period included intense meteorite bombardment as well as giant impacts, including the Moon-forming impact, which resulted in a series of magma oceans and episodes of core formation.^[4] After formation of the core, meteorites or comets may have delivered water and other volatile compounds to the Earth in a "late veneer".^[5] Although little crustal material from this period survives, the oldest dated specimen is a zircon mineral of 4.404 ± 0.008 Ga enclosed in a metamorphosed sandstone conglomerate in the Jack Hills of the Narryer Gneiss Terrane of Western Australia.^[6] The earliest supracrustals (such as the Isua greenstone belt) date from the latter half of this period, about 3.8 Ga, around the same time as peak Late Heavy Bombardment.