Snowball Earth

Depiction of Earth when it was completely frozen.


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The Cryogenian Period: The Equator Under Ice Last Updated on 2010-12-18 00:00:00 About 0.73 Ga, Earth underwent severe glaciations that eliminated much of life. The Cryogenian (Greek; ice + birth) period was initiated by several conditions. [1] The breakup of the supercontinent Rodinia exposed organic matter to anaerobic respiration, creating an atmosphere in which the major greenhouse gas was methane (CH4). Atmospheric CH4, in contrast with CO2, reacts with O2 and is not buffered by a massive ocean reservoir; therefore, atmospheric CH4 levels decreased rapidly once continental movements diminished and less organic matter was exposed. As CH4 declined, Earth cooled. Cooler temperatures inhibited biological production of CH4, accelerating the cooling. Ice appeared on the land masses near the equator, increasing the reflectance of solar energy (a phenomenon called albedo) and decreasing the solar energy retained at Earth’s surface. Temperatures sank until even... More »