Great Oxidation Event (Great Oxidation, Great Oxygenation Ev

Great Oxygenation Event:

-The first of these hypotheses, called tectonic trigger, explains that the accumulation of oxygen in the atmosphere had to wait for a series of tectonic shifts in the "anatomy" of the Earth took place.

The "delay" of the Great Oxygenation Event

-Another hypothesis is defended that the atmospheric methane abundant at the time due to the dominance of anaerobic organisms, was also an important molecular oxygen trap, because it is rapidly oxidized to carbon dioxide in the presence of ultraviolet radiation.

From the moment in which the first photosynthetic organisms oxygenic began to produce oxygen (makes about 2,800 Millions years) to the time when there was the Great Oxygenation Event (due to a rapid increase in atmospheric oxygen), there was a delay of about 300 - 350 million years. Although the exact causes of the timing difference are unknown, there are several hypotheses to try to explain:

-A recent theory (2006) is the bistability, which seeks to explain the 300 million years of delay by a mathematical model of the atmosphere, which recognizes that the protection against ultraviolet radiation decreases the rate of oxidation of methane once oxygen levels are sufficient to form an ozone layer.

-Another factor that may explain the delay in the oxygen enrichment of the atmosphere may have been due to photosynthetic production of molecular hydrogen which would be stored first in the atmosphere (oxygen prevents filling) before slowly lost in space.

Paleoarcaica, where you can see the greenish color of the oceans (rich in dissolved Fe) and the red-anaranada of the atmosphere (rich in carbon dioxide and methane) aura.

Another important result was the subsequent climate changes. The generation of methane (CH4) levels was due in large part to anaerobic organisms, which suffered population declines due to increasing atmospheric molecular oxygen. Furthermore, methane, compared to molecular oxygen and ultraviolet radiation, are rapidly oxidized, generating carbon dioxide (CO2). This change of CH4 to CO2 in the atmosphere considerably reduce the overall temperature, since the potential greenhouse methane is several times greater than that of carbon dioxide. This drastic drop in temperature would trigger Huronian glaciation, which occurred makes 2,400 - 2,100 Millions years approximately.

However, this dramatic transformation also offered a new opportunity for biological diversity and enormous changes in the nature of the chemical interactions between rocks, sand, clays and other geological substrates, and the atmosphere, oceans and other waters surface. Despite the natural recycling of organic matter, life energy had remained limited to the wide availability of oxygen. This advance in the evolution of metabolism greatly increased the supply of energy for living organisms, producing a comprehensive environmental impact.

Beginning of the Great Oxygenation Event:

The first photosynthetic organisms that existed performed the anoxygenic photosynthesis, in which no oxygen is clear (as do today the green sulfur bacteria or purple bacteria). But when the first organisms capable of perform oxygenic photosynthesis (such as cyanobacteria, which produce stromatolites) makes about 2,800 Millions years emerged, it began to produce molecular oxygen (O2) in large quantities, which was slowly invading the atmosphere and oceans. The issuance of such excess oxygen to the environment caused an ecological crisis for biodiversity of the time, so oxygen was toxic to the dominant anaerobic microorganisms at the time.

While this was happening, the oxygen was consumed in producing various chemical reactions taking place in the oceans, then it reacted mainly generated with iron and minerals such as magnetite (Fe3O4) and hematite (Fe2O3), which precipitated and They deposited in ocean funds and inland water. Water, which until then had been green color due to Fe dissolved in it, began to lose this Fe, which led him to take his current bluish. The proof of this phenomenon is found in ancient rocks that contain massive banded iron formations or BIF from the oxidation of iron in the ocean and now constitute the major iron deposits exploited commercially

Great Oxygenation Event (Great Oxidation or simply GOE, in English) was a major environmental change that occurred probably during the sidereal period, in the early Paleoproterozoic Era (about 2400 Millions years ago), and It resulted in the deposition of a large amount of oxidized iron, which until then had been dissolved in ocean waters. Given the importance of oxygen in this environmental change, this event is also often called oxygen crisis, revolution oxygen or catastrophe oxygen.