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Snowball Earth

Snowball Earth . History of Glaciation. Main Periods of Glaciation. Huronian glaciations 2.5-2.2 billion years ago Late Proterozoic glaciations 900-545 million years ago Late Ordivician glaciations 446-440 million years ago Permo-carboniferous glaciations 310-270 million years ago

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Snowball Earth

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  1. Snowball Earth History of Glaciation

  2. Main Periods of Glaciation Huronian glaciations 2.5-2.2 billion years ago Late Proterozoic glaciations 900-545 million years ago Late Ordivician glaciations 446-440 million years ago Permo-carboniferous glaciations 310-270 million years ago Pleistocene glaciations 1.8 million – 10,000 years ago

  3. Huronian Glaciations How do we get glaciers in a methane-rich atmosphere? - rise of O2 atmosphere 2.3 bya - elimination of methane in atmosphere - decreased greeenhouse gases - Earth enters deep-freeze Evidence?

  4. Huronian Glaciations: Evidence Kump, Kasting, and Crane (2004)

  5. Huronian Glaciations: Recovery CO2 outgassing

  6. Snowball EarthLate Proterozoic Glaciation Glaciation on 6 of 7 continents - Antarctica: maybe was glaciated but too much ice today to tell Evidence: tillites, glacial striations, dropstones Continental reconstructions show land was centered around equator

  7. Carbonate cap above glacial dropstones in Namibia http://www-eps.harvard.edu/people/faculty/hoffman/snowball_paper.html

  8. Bagganjarga tillite and striated bedrock in Norway

  9. How did Earth Cool? Less solar luminosity – about 6% less than today Removal of CO2 from atmosphere continents at equator – silicate weathering even as Earth cools

  10. http://www-eps.harvard.edu/people/faculty/hoffman/snowball_paper.htmlhttp://www-eps.harvard.edu/people/faculty/hoffman/snowball_paper.html

  11. How did Earth Cool? Polar ice sheets form at poles and grow increased albedo decreased surface temperatures

  12. http://www-eps.harvard.edu/people/faculty/hoffman/snowball_paper.htmlhttp://www-eps.harvard.edu/people/faculty/hoffman/snowball_paper.html

  13. How did Earth warm? Earth completely frozen Silicate weathering ceases CO2 outgassing continues Ice starts melting decreased albedo increased suface temperatures

  14. Times, temps, and rates Glaciers freezing from 30 degrees to equator - decades Surface temperature = -40 or -50 degrees C CO2 buildup during Snowball Earth - 10 million years Entire disappearance of glaciers after CO2 buildup - thousands of years CO2 rich atmosphere, low albedo - surface temperature = 50 or 60 degrees C Silicate weathering increases, climate system restored

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