Mesoarchean Era

What happened during this time?

Geophysical

• Free oxygen present in the oceans, possibly formed from cyanobacteria around 3.2 billion years ago (Satkoski et al., 2015)

• Evidence for chemical weathering of rocks leading to soil formation that occurred in the presence of O2 at least 3.02 billion years ago (Deane & Crowley, 2014)

• The oldest known glaciation event, Pongola, starts toward the end of this period (~2.9 Ga)

• Extensive cratonization events have never been repeated in the history of the Earth.

  • The first supercontinent, Vaalbara, broke up during this time

  • The Supercontinent, Ur, may have originated during this time (~3.1 Ga)

  • Ur existed for a very long time, joining with other cratons to later form Rodinia and, even later, Pangaea.

• Atmospheric oxygen levels remained very low as the oxygen continued to be used up in oxidizing minerals on the earth's crust and in the sea

  • Oldest Banded Iron-Ore formations are from this time

Biological

• First direct evidence of life on Earth

  • Anaerobic prokaryotes

  • Diversification of stromatolites on Earth

• Possible microbial life on land by 3.0 Ga (Retallack et al., 2016)

• Potentially complex microfossils of photosynthetic microplankton (House et al., 2013)

• "The process of cumulative complexification," which led to an endosymbiotic event and eukaryotic origins, may have started as early as 2.9 Ga (Kay et al., 2025)