The Times When the Earth Froze Over

Hey guys, in ironic celebration of the start of Summer, we are going to cover the few periods of Earth’s vast geologic history where we had an Ice Age so strong, it froze the world over.

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There are few times that the Earth completely or nearly froze over. The first was the Huronian glaciation which started 2.4 billion years ago and lasted 300 million years. It was by far the largest Ice Age in Earth’s history.  This glaciation followed an event called the Great Oxygenation Event which was the rapid change of Earth’s atmospheric composition following the introduction of Aerobic life.

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Previously the atmosphere had large concentrations of Methane, a notorious greenhouse gas that traps heat. When oxygen started to enter the atmosphere in large amounts, it started to react with the methane to produce carbon dioxide and water which doesn’t hold heat in as well. This rapid change caused a glaciation beyond Biblical proportions. Photosynthesis nearly stopped and a mass extinction followed wiping out a great deal of the genetic diversity of the planet.

Much later in the Proterozoic Eon (2500 mya to 541 mya) there were a series of mass Glaciation periods which covered the entire surface of the world.

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All of these occurrences shared one this – massive glaciation. However, there are various reasons operating independently as well as in conjunction with each other to produce such anomalies. All need to have a cooling mechanism that self-reinforces such that the climate of the entire planet shifts to be much cooler.

The various mechanisms to cause a Snowball Earth are as follows: reduction in GHG concentration, eruption of a super volcano, decreases in solar output, change in orbit or tilt, continental orientation, and elephantine positive feedback loops.

Continental Orientation is one of the major causes of Snowball Earths. If there is a tropical distribution of continents, then less heat is absorbed because there is less water. Also, rains lead to weathering processes which suck in CO2 from the atmosphere over oceans.

Zipper Rifts, where a supercontinent breaks up, can also cause massive climactic shifts through continental subsidence.

In any case, Snowball Earths while looking beautiful, caused mass exinctions that dramatically decreased the biodiversity of the planet.


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