Book contents
9 - The cryosphere in the past
from Part III - The cryosphere past and future
Published online by Cambridge University Press: 05 June 2012
Summary
Introduction
The Earth has undergone enormous changes in its snow and ice cover during geological time. There have been at least six major Ice Ages, as well as periods when there has probably been no ice, like the Cretaceous. Ice ages are periods when significant portions of the Earth’s surface are covered by glaciers and extensive sheets of ice; there is no strict quantitative definition. The major ice ages were the Huronian/Makganyene glaciations in the Neoarchean–Paleoproterozoc (~2,700 to 2,200 million years ago, Ma), the Sturtian, Marinoan, and Ediacaran glaciations of the Neoproterozoic (~730–700 Ma, 665–635 Ma, and 635–542 Ma), the late Ordovician glaciation (460 Ma), the late Devonian glaciation (360 Ma), the Permo-Carboniferous glaciation (320–250 Ma) and the late Cenozoic glaciation (beginning ~40 Ma). Glaciations appear to account for ~28 percent of Paleozoic time.
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- Information
- The Global CryospherePast, Present and Future, pp. 299 - 317Publisher: Cambridge University PressPrint publication year: 2011