Snowball Earth

The extreme climate changes of the past million years, characterized by successive ice ages, are minor compared to the even greater extremes of 60 million years ago, when even the tropics were frozen in ice. Evidence of the massive climate reversals is held in layers of ancient rock and glacial debr...

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Bibliographic Details
Published in:Scientific American 2000-01, Vol.282 (1), p.68-75
Main Authors: Hoffmann, Paul F., Schrag, Daniel P.
Format: Magazinearticle
Language:English
Subjects:
Atmosphere
Biology
Carbon dioxide
Carbon isotopes
Carbonates
Climate
Climate change
Earth
Evidence
Evolution
Geological time
Glacial landforms
Glaciers
Greenhouse effect
Ice
Ice ages
Neoproterozoic era
Oceans
Radiation
Rocks
Scientists
Sea level
Snowball Earth hypothesis
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Summary:The extreme climate changes of the past million years, characterized by successive ice ages, are minor compared to the even greater extremes of 60 million years ago, when even the tropics were frozen in ice. Evidence of the massive climate reversals is held in layers of ancient rock and glacial debris, deposited there when the continents were relatively centered around the equator. Scientists have begun to analyze cliff geology and the arrangement of layers of carbon-containing rock and indications of the rapid accumulation of carbon. The snowball earth theory proposed four stages of rapid climate change: the prologue in which the breakup of landmasses pushes more land areas closer to oceanic moisture; the onset of a runaway freeze which kills all life except some remaining around volcanic hotsprings; the thawing instigated by volcanic activity and the release of atmospheric carbon dioxide; and the hothouse aftermath, in which greenhouse conditions are intensified.
ISSN:0036-8733
1946-7087
DOI:10.1038/scientificamerican0100-68