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The Huronian glaciation (or Makganyene glaciation) was a glaciation that extended from 2400 million years ago to 2100 million years ago, during the Siderian and Rhyacian periods of the Paleoproterozoic era. The Huronian glaciation followed after the Great Oxygenation Event (GOE), a time when increased atmospheric oxygen decreased atmospheric methane. The oxygen combined with the methane to form carbon dioxide and water, which do not retain heat as well as methane does.
It is the oldest and longest ice age, occurring at a time when in biological sense, only simple, unicellular life existed on Earth. This ice age lead to a mass-extinction on earth.
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Before the Huronian Ice Age, most organisms were anaerobic. However, one bacteria evolved to be able to perform photosynthesis, known as cyanobacteria. These bacteria were able to reproduce at exponential rates, due to no competition for their energy, as well as a limitless supply of energy, the sun. Since these organisms performed photosynthesis, they produced oxygen as a waste product, which was expelled into the air. Most of this oxygen was disposed of through the oxidization of iron and decomposition of life forms. However, as the population of the cyanobacteria continued to grow, more oxygen was produced than the environment could handle. This led to a mass extinction, as oxygen was toxic to most life forms, which were anaerobic at the time. This led to oxygen "polluting" the atmosphere, as the atmosphere consisted mostly of methane. The methane bonded with the oxygen to form carbon dioxide and water, forming a different, thinner atmosphere. Earth began to slowly lose heat due to the thinner atmosphere, which began the Huronian Ice Age.
- Kopp, Robert (14 June 2005). "The Paleoproterozoic snowball Earth: A climate disaster triggered by the evolution of oxygenic photosynthesis" (PDF). PNAS. Retrieved 8 August 2016 – via PNAS.
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