What happened during this time?
Beginning of Archean dated to the oldest rocks found on Earth
Recent discoveries have pushed back the earliest dated rocks to about 4.0 billion years old
Earth moderately warm
Sun 30% cooler than today,
Earth's geological activity was much greater, creating warmer climate
Earth was hotter than it is today, its mantle may have contained less water because mantle minerals hold onto less water at higher temperatures (Dong et al. 2021)
Assuming that the mantle currently has more than 0.3-0.8 times the mass of the ocean, a larger surface ocean might have existed during the early Archean.
At that time, the mantle was about 1,900-3,000 degrees Kelvin (2,960-4,940 degrees Fahrenheit), compared to 1,600-2,600 degrees Kelvin (2,420-4,220 degrees Fahrenheit) today.
If early Earth had a larger ocean than today, that could have altered the composition of the early atmosphere and reduced how much sunlight was reflected back into space (Dong et al. 2021)
These factors would have affected the climate and the habitat that supported the first life on Earth.
Formation of proto-continents
When continents appear is under debate, but there is evidence of continental drift
These original proto-continents no longer exist; remnants found in cratons
Cratons are areas of ancient rock that survive on some continents
Appear when the overlying rock (mostly volcanic igneous rock) is buried deep, but not deep enough to be re-melted.
Heat and pressure converts it into metamorphic rock.
These are areas where the crust has thickened, with fresh igneous rock on top and metamorphic rock beneath (though folding of the crust can obscure this relationship).
Complexity of life in the ocean hints at a greater continental mass during this time
"...if there was life in the ocean, you need some amount of continental weathering taking place to deliver phosphorus so the organisms can live." (Satkoski 2016)
Earth has a reducing atmosphere
The Great Oxidation Crisis event
Oxygen produced by bacteria (see below) oxidized rocks and iron in the oceans,
Increase in atmospheric oxygen for a very long time. Atmospheric oxygen did not begin to rise significantly until billions of years after photosynthesis first began.
Origin of prokaryotic organisms, probably bacteria
Oldest direct evidence found in Western Australia (3.43 Ga)
First organisms were likely non-photosynthetic, utilizing methane, ammonia or sulfates for their energy needs
Origin of the Archaea, and then toward the end of the eon, their decline.
Colonial stromatolites appear and proliferate