Summary: The Neoproterozoic Era

The Neoproterozoic Era extends from 1000 million years ago to 542 million years ago. During the Neoproterozoic, the earth is believed to have been covered from pole to pole by glacial ice. These events are believed to have occurred twice during this era and are the most severe glaciations known to have happened on Earth. This phenomenon is often referred to as Snowball Earth. The first Snowball episode began around 715 million years ago and the second Snowball event is believed to have begun 630 million years ago. There are several theories that explain how these events occurred. Some of these theories include a rapid decrease in greenhouse gases due to uplift and weathering, the release of aerosols into the atmosphere and a decrease in solar output. Once the ice reaches a certain latitude, it continues to spread and increases the likelihood that glacial ice will cover the equator.

There is evidence that suggests that along with rising carbon dioxide levels, volcanic dust may have been a large contributing factor in the deglaciation of Snowball Earth. Evidence supporting ice covered continents and oceans has been provided by deposits such as iron-manganese in glacial sediments. This indicates that the ocean was lacking oxygen and that there were probably glacial formations (Hoffman & Li, 2009). Simulations have shown that for atmospheric carbon dioxide to have been fully responsible for the termination of snowball Earth, the levels would have to have been about 550 times the present levels (Pierrehumbert, 2004). It is highly unlikely that the level of carbon