snowball earth


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snowball earth,

hypothesized condition in which the earth was covered completely by ice during several periods in the Proterozoic. The hypothesis was originally developed to explain evidence of the contribution of glaciation to the formation of siltstone whose layered structure and paleomagnetic composition indicated that its sediments were most likely deposited at sea level in the tropics. In the most extreme form of the hypothesis, glaciation that reached within 30° of the equator (a subtropical latitude) resulted in the reflection of so much sunlight that the earth cooled sufficiently to allow ice sheets to reach the equator, where temperatures were similar to those of present-day Antarctica; the ice sheets completely covered the earth for tens of millions of years. Many proponents of the theory support a slushball earth hypothesis in which glaciation reaches into the tropics but is not complete. The snowball earth hypothesis is controversial. Many critics have questioned if a snowball earth condition would be reversible, and if early life could have survived such extreme conditions. The long-term accumulation of very high levels of carbon dioxide in the atmosphere from volcanic eruptions is generally proposed as the cause of the ice sheets' retreat, and it has been suggested that specialized environments, such as hydrothermal ventshydrothermal vent,
crack along a rift or ridge in the deep ocean floor that spews out water heated to high temperatures by the magma under the earth's crust. Some vents are in areas of seafloor spreading, and in some locations water temperatures above 350°C; (660°F;) have
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, could have enabled life to survive. Despite these disagreements, there is evidence for glaciation several times during the Proterozoic; the Marinoan (650 to 635 million years ago) and Sturtian (750 to 700 million years ago) glaciations are generally considered to be the times when snowball or slushball earth conditions most likely existed.
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Yet, half a dozen ice ages chilled Earth during that time, two of them severe enough to turn the planet into a Snowball Earth with ice covering much of the surface.
Extreme volcanic outpourings resulting in so-called large igneous provinces could be responsible for these Snowball Earth global glaciations.
OUTLANDISH: Researchers have come to accept the outlandish notion that, a few times in its 4.6-billion-year history, the planet froze over and became a "Snowball Earth."
From the roaring hurricane winds of Katrina to the frozen oceans of Snowball Earth, "18 Miles" gives readers a long overdue look at the very air we breathe and how human activity is affecting it.
ON THIS DAY LAST YEAR: A global ice age known as 'Snowball Earth' triggered the development of complex life 650 million years ago, new evidence suggested.
It includes hazy worlds like the Archean; it includes icy worlds like the 'snowball Earth' intervals; it includes anoxic worlds with exclusively microbial ecosystems; it includes worlds with complex and intelligent life; and it includes worlds that we haven't even seen yet." That's helpful for scientists, she added, who need several models for what life on other worlds might look like.
Despite its simplicity, FOAM has been used in dozens of research publications on paleoclimate, snowball Earth, vegetation feedbacks, and atmospheric teleconnections (www.mcs.anl.gov/research/projects/foam/publications.html).
A BIRMINGHAM scientist is part of a team which has cracked one of the oldest riddles in world history - how "snowball Earth" ended 635 million years ago.
Prof Fairchild explained: "The idea of a deep-frozen world, 'snowball Earth', has captured the imagination since first proposed in the 1990s.
This writer would have liked also to have seen a distinction between the Biosphere, lawless" and Gaia, around for the last 10 millennia or so and likely to fall prey to the Anthopocene age as it did during the long era of "Snowball earth".
An additional way for a terrestrial planet to achieve high amounts of heating would be to cover in a very thick ice shell, similar to an extreme "snowball Earth." and it was also found that some planets could move into a safer orbit about 10 to 100 times faster than previously expected.
Snowball Earth morphed into hothouse Earth and back again, with an assist from the steady march of plate tectonics across the surface of the globe.