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Snowball Earth

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Wade Hampton III

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Snowball Earth

PostThu Feb 16, 2017 11:44 pm

What is Snowball Earth?

Planet Earth covered by ice from pole to pole for long periods in the geological past.

snowball_earth.jpg (49.84 KiB) Viewed 47 times

Snowball earth describes the coldest global climate imaginable - a planet covered by
glacial ice from pole to pole. The global mean temperature would 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 fraction of radiation reflected is termed albedo (a) and it ranges widely
from ~0.1 for liquid water, ~0.3 for bare land, ~0.45-0.65 for bare ice depending on the
bubble content, to ~0.9 for fresh snow.] The average equatorial temperature would be
about -20°C (-10°F), roughly similar to 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 (direct
change from solid to vapor) to areas of condensation. Given sufficient time, glacial
ice would thicken and flow in the opposite direction. Glacial flowage results in
sedimentary deposits (glacial erratics, tills, moraines, eskers, ice-rafted debris,
etc.) that fingerprint the glacial activity long after the ice has disappeared.

720 Million Years Ago
Rodinia.jpg (84.75 KiB) Viewed 47 times

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