snowball earth roopa kamesh matt beversdorf kathy groome
Post on 20-Dec-2015
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Snowball EarthRoopa Kamesh
Matt Beversdorf
Kathy Groome
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Theory of Snowball Earth• Continents and oceans were covered in ice approximately 600 million years ago.
• Earth was in a deep freeze, chemical cycles were halted; carbon dioxide accumulated in the atmosphere causing an extreme greenhouse effect.
• Believed to have caused the explosion of life forms seen in Cambrian fossils
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Snowball Earth occurred during the Neoproterozoic
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Existing Evidence• Glacial Deposits and Carbonate Caps• Paleomagnetic Studies• Banded Iron Formations• Manganese Deposits• Isotope Analysis• Plate Tectonics, Carbon Dioxide Emissions • Ice Albedo Feedback• Proterozoic Biostratigraphy: Persistence and the Explosion of Life • Extremophiles
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Glacial Deposits and Carbonate Caps
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Paleomagnetic Studies
From Understanding Earth, Press and Seiver, W.H. Freeman and Co.
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Banded Iron Formations
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Isotope Analysis
Carbon isotopes (Stanley, Steven, M., 1999)
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Isotope Examples
Source: A.H. Knoll. 2000. Learning to tell Neoproterozoic Time
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Albedo Effect
Once the continents were glaciated to 30 degrees latitude, there was a runaway albedo effect.
Albedo refers to the reflective ability of a material. You can see the difference in how each material reflects sunlight in the table above.
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Extremophiles
Extremophiles provide evidence that life could have persisted under snowball Earth conditions.
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Problems with the Snowball Earth Theory
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The Explosion of Life: Just a Coincidence?
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Arguments Against
• Organisms need sunlight and/or oxygen to survive (e.g. algae)
• Freeze thaw structures – no glacial deposits on a completely frozen planet
• Sea-level change – evidence for lowering of sea level
• Inconsistency of isotope results: Kennedy
• Carbon dioxide emissions - what about methane?
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Alternative Theories
• Earth’s Obliquity: Increased Axial Tilt
• Slushball Earth: A variation of snowball earth where the planet did not entirely freeze. This theory is based more on climate models for the Neoproterozoic.
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What do you think???