Earth was covered by ice  for long periods in the geological past. Snowball earth describes the coldest global climate imaginable – a planet covered by glacial ice . The global mean temperature reaches be about -50°C (-74°F) because most of the Sun’s (Solar) radiation would be reflected back to space by the icy surface. The average equatorial temperature would be about -20°C (-10°F), roughly similar to the temperature of present Antarctica. Without the moderating effect of the oceans, temperature fluctuations associated with the day-night and seasonal cycles would be greatly enhanced. Because of its solid surface, the climate on a snowball earth would have much in common with present Mars. Despite the cold and dry climate, the atmosphere would still transport some water vapor from areas of sublimation to areas of condensation. Given sufficient time, glacial ice would thicken and flow in the opposite direction. Glacial flowage results in sedimentary deposits such  as glacial erratics, tills, moraines, eskers, ice-rafted debris, etc.

The term “Snowball Earth” was coined by Joseph Kirschvink, a professor of geobiology at the California Institute of Technology, in a short paper published in 1992 within a lengthy volume concerning the biology of the Proterozoic eon.The major contributions from this work were:

(1) the recognition that the presence of banded iron formations is consistent with such a glacial episode and

(2) the introduction of a mechanism with which to escape from an ice-covered Earth — the accumulation of CO2 from volcanic outgassing leading to an ultra-greenhouse effect.

Different  Snowball Earths Occurred

Neoproterozoic

Paleoproterozoic

Karoo Ice Age

Current Work

Stephen Warren, a professor from the University of Washington in Seattle, will lead a small team of U.S. researchers to Antarctica for the 2009-10 and 2010-11 summer field seasons to add more data in support of the Snowball Earth hypothesis. A project funded by the National Science Foundation, the project will study different ice types found in Antarctica that may have existed during the previous Snowball Earth events, specifically to learn more about their albedo, or reflectivity, information important in understanding the processes involved in the exteme glaciation. The team will spend time on the sea ice in McMurdo Sound and in Garwood Valley in the McMurdo Dry Valleys the first season. The second season will be spent in the Transantarctic Mountains.

Sources

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