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Earth's atmosphere at this stage was somewhat comparable to today's atmosphere of Titan. [19] The Archean atmosphere is thought to have almost completely lacked free oxygen; oxygen levels were less than 0.001% of their present atmospheric level, [20] [21] with some analyses suggesting they were as low as 0.00001% of modern levels. [22]
ɑːr ˈ k iː ə n / EE-oh-ar-KEE-ən; also spelled Eoarchaean) is the first era of the Archean Eon of the geologic record. It spans 431 million years, from the end of the Hadean Eon 4031 Mya to the start of the Paleoarchean Era 3600 Mya. Some estimates place the beginnings of life on Earth in this era, while others [2] place it earlier.
It was created around 3.26 Ga when a large asteroid, about 37 to 58 kilometres (23–36 mi) wide, collided with the Earth. [6] The Buck Reef chert and the Josefsdal chert, two rock formations in the Barberton Greenstone Belt, both contain microbial mats with fossilized bacteria from the Paleoarchean era. [ 4 ]
Earth of the early Archean may have had a different tectonic style. It is widely believed that the early Earth was dominated by vertical tectonic processes, such as stagnant lid, [19] [20] heat-pipe, [21] or sagduction, [22] [23] [24] which eventually transitioned to plate tectonics during the planet's mid-stage evolution. However, an ...
The first eon in Earth's history, the Hadean, begins with the Earth's formation and is followed by the Archean eon at 3.8 Ga. [2]: 145 The oldest rocks found on Earth date to about 4.0 Ga, and the oldest detrital zircon crystals in rocks to about 4.4 Ga, [34] [35] [36] soon after the formation of the Earth's crust and the Earth
Early Earth also known as proto-earth is loosely defined as encompassing Earth in its first one billion years, or gigayear (Ga, 10 9 y), [1] from its initial formation in the young Solar System at about 4.55 Ga to some time in the Archean eon in approximately 3.5 Ga. [2] On the geologic time scale, this comprises all of the Hadean eon, starting ...
A paleoatmosphere (or palaeoatmosphere) is an atmosphere, particularly that of Earth, at some unspecified time in the geological past.. When regarding geological history of Earth, the paleoatmosphere can be chronologically divided into the Hadean first atmosphere, which resembled the compositions of the solar nebula; the Archean second atmosphere (also known as the prebiotic atmosphere), which ...
Lopian orogeny – Archean orogeny – Formation of two different types of terrain compatible with plate tectonic concepts. One is a belt of high-grade gneisses formed in a regime of strong mobility, while the other is a region of granitoid intrusions and greenstone belts surrounded by the remnants of a Saamian substratum, (2.9–2.6 Ga)