The Mesoarchean era is thought to be the birthplace of modern-style plate subduction, based on geologic evidence from thePilbara Craton in westernAustralia.[3][4] Aconvergent margin with a modern-styleoceanic arc existed at the boundary between West and East Pilbara approximately 3.12 Ga. By 2.97 Ga, theWest Pilbara Terrane converged with and accreted onto the East Pilbara Terrane.[4] Asupercontinent,Vaalbara, may have existed in the Mesoarchean.[5]
Analysis ofoxygen isotopes in Mesoarcheancherts has been helpful in reconstructing Mesoarchean surface temperatures.[6] These cherts led researchers to draw an estimate of an oceanic temperature around 55-85°C[7] (131-185 Fahrenheit), while other studies ofweathering rates postulate average temperatures below 50°C (122 Fahrenheit).
The Mesoarchean atmosphere contained high levels of atmosphericmethane andcarbon dioxide, which could be an explanation for the high temperatures during this era.[6] Atmosphericdinitrogen content in the Mesoarchean is thought to have been similar to today, suggesting that nitrogen did not play an integral role in thethermal budget of ancient Earth.[8]
ThePongola glaciation occurred around 2.9 Ga, from which there is evidence of ice extending to a palaeolatitude (latitude based on the magnetic field recorded in the rock) of 48 degrees. This glaciation was likely not triggered by the evolution of photosynthetic cyanobacteria, which likely occurred in the interval between the Huronian glaciations and the Makganyene glaciation.[9]
Microbial life with diverse metabolisms expanded during the Mesoarchean era and produced gases that influencedearly Earth'satmospheric composition.Cyanobacteria producedoxygen gas, but oxygen did not begin to accumulate in the atmosphere until later in theArchean.[10] Small oases of relativelyoxygenated water did exist in some nearshore shallow marine environments by this era, however.[11]
Glacial period – Interval of time within an ice age that is marked by colder temperatures and glacier advances
Ice age – Period of long-term reduction in temperature of Earth's surface and atmosphere
Last glacial period – Period of major glaciations of the Northern Hemisphere (115,000–12,000 years ago)Pages displaying short descriptions of redirect targets
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