The Archean eon, from about 4 billion to 2.5 billion years ago, is the time when the first continents grew and the oceans settled into their basins. The atmosphere had almost no free oxygen and the planet was hotter inside than it is today.
Life appears in the rock record during the Archean: layered mats of microbes called stromatolites are known from about 3.5 billion years ago, and by the end of the eon photosynthesis may already have been releasing oxygen.
Explore this era on the timeline
Key events of the Archean
4 events are on the timeline for this era; these are among the most notable, in date order.
- from about 3.92 billion years ago to 3.85 billion years agoNectarian
- about 3.48 billion years agoEarly evidence of life: stromatolites
- from about 3.2 billion years ago to 1.1 billion years agoEratosthenian
- from about 2.99 billion years ago to 2.84 billion years agoPongola glaciation