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The Mesoarchean (, also spelled Mesoarchaean) is a
The Mesoarchean era is thought to be the birthplace of modern-style plate subduction, based on geologic evidence from the Pilbara craton in western
Mesoarchean (chronostratigraphy scale)
*03 Geological eras Precambrian geochronology {{Geochronology-stub
geologic
Geology () is a branch of natural science concerned with Earth and other astronomical objects, the features or rocks of which it is composed, and the processes by which they change over time. Modern geology significantly overlaps all other Eart ...
era in the Archean Eon, spanning , which contains the first evidence of modern-style plate subduction and expansion of microbial life. The era is defined chronometrically and is not referenced to a specific level in a rock section on Earth.
Tectonics
The Mesoarchean era is thought to be the birthplace of modern-style plate subduction, based on geologic evidence from the Pilbara craton in western Australia
Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...
. A convergent margin with a modern-style oceanic arc
A volcanic arc (also known as a magmatic arc) is a belt of volcanoes formed above a subducting oceanic tectonic plate,
with the belt arranged in an arc shape as seen from above. Volcanic arcs typically parallel an oceanic trench, with the arc lo ...
existed at the boundary between West and East Pilbara approximately 3.12 Ga. By 2.97 Ga, the West Pilbara Terrane converged with and accreted onto the East Pilbara Terrane. A supercontinent, Vaalbara, may have existed in the Mesoarchean.
Environmental conditions
Analysis ofoxygen isotopes
There are three known stable isotopes of oxygen (8O): Oxygen-16, , Oxygen-17, , and Oxygen-18, .
Radioactive isotope, Radioactive isotopes ranging from to have also been characterized, all short-lived. The longest-lived radioisotope is with a ...
in Mesoarchean cherts has been helpful in reconstructing Mesoarchean surface temperatures. These cherts led researchers to draw an estimate of an oceanic temperature around 55-85°C while other studies of weathering rates postulate average temperatures below 50°C.
The Mesoarchean atmosphere contained high levels of atmospheric methane and carbon dioxide, which could be an explanation for the high temperatures during this era. Atmospheric dinitrogen content in the Mesoarchean is thought to have been similar to today, suggesting that nitrogen did not play an integral role in the thermal budget of ancient Earth.
The Pongola glaciation occurred around 2.9 Ga, triggered by the evolution of atmospheric photosynthesis.
Early microbial life
Microbial life with diverse metabolisms expanded during the Mesoarchean era and produced gases that influenced early Earth'satmospheric composition
Atmospheric chemistry is a branch of atmospheric science in which the chemistry of the Earth's atmosphere and that of other planets is studied. It is a multidisciplinary approach of research and draws on environmental chemistry, physics, meteorol ...
. Cyanobacteria
Cyanobacteria (), also known as Cyanophyta, are a phylum of gram-negative bacteria that obtain energy via photosynthesis. The name ''cyanobacteria'' refers to their color (), which similarly forms the basis of cyanobacteria's common name, blu ...
produced oxygen gas, but oxygen did not begin to accumulate in the atmosphere until later in the Archean.
See also
* * * *References
External links
Mesoarchean (chronostratigraphy scale)
*03 Geological eras Precambrian geochronology {{Geochronology-stub