The Archean Eon
The Archean is one of the four principal eons in earth history. It is subdivided up into 4 parts.
- The first of these is the Eoarchean 4,000-3,600 M.A.. Eoarchean is made up of two Greek words Eos (dawn) and archaios (ancient).
- During the Eoarchean the earth is thought to have a firm crust for the first time, how ever many spots of the crust were not fully formed.
- This was followed by the Paleoarchean from 3,600 - 3,200 M.A.. the name derives from the greek word “palaios” meaning ancient.
- During this period the first supercontinent Vaalbara formed. While Vaalbara was forming, between 3,200-3,500 M.A. 4 meteor strikes happened. High temperatures caused by the meteorites hitting earth forced sediments into small glassy spherules.
- The third phase is the Mesoarchean 3200 M.A. - 2,800 M.A. fossils in australia shows that stromatolites lived on the earth.
- Supercontinent vaalbara broke up during the end of this phase 2,800 M.A..
- The fourth and final phase of Archean is neoarchean 2,800 - 2,500 M.A.. Oxygenic photosynthesis first evolved during this era, which led to the oxygen catastrophe later in the paleoproterozoic. The supercontinent kenorland formed during this period, 2,700 M.A..