20.1: Introduction
- Page ID
- 22758
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The “Snowball Earth” glaciations were a series of ice ages during the Neoproterozoic era of geologic time, mainly confined to the Cryogenian period, but perhaps also into the Ediacaran period, too. These ice ages were thought to have been so profound that perhaps the entire surface of the planet froze over, all the way from the poles to the equator. In a 1992 paper, Caltech geophysicist Joe Kirschvink quipped that from a vantage point in outer space, the planet would have looked like a giant snowball. The evocative name stuck, and there has been an avalanche of scientific studies investigating the Snowball Earth glaciations ever since.
Depending on how you count, there were two episodes of Snowball Earth glaciation during the Neoproterozoic, or perhaps three.
They are called the Sturtian (about 720 to 660 Ma) and the Marinoan (about 645 to 640 Ma), with the Gaskiers (or Ediacaran, at about 580 Ma) being the possible third event in the sequence. There’s pretty good evidence that the Sturtian and Marinoan ice ages were true “Snowballs,” with glaciers flowing at sea level at the equator, but the Gaskiers event seems to have not been as extensive.
Did I Get It? - Quiz
When were the "Snowball Earth" glaciations?
a. During the Paleoproterozoic era of geologic time
b. During the Neoproterozoic era of geologic time
c. During the Mesoproterozoic era of geologic time
d. During the Mesozoic era of geologic time
- Answer
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b. During the Neoproterozoic era of geologic time
How many episodes of Snowball Earth glaciation happened?
a. 1, perhaps 2 (depending on what counts)
b. About 10, perhaps 12 (depending on what counts)
c. 3, perhaps 4 (depending on what counts)
d. 2, perhaps 3 (depending on what counts)
- Answer
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d. 2, perhaps 3 (depending on what counts)