Evolution Message Board - Msg: 26976998

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Politics : Evolution

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To: Jacques Chitte who wrote (10087)	11/21/2010 3:55:04 PM
From: Jacques Chitte	Read Replies (1) of 69300

Someone made mention of the Snowball Earth events, which are believed to have occurred about 2 billion and 650 million years ago. These two events underline a Gaia effect that did not rely on participation by living things. What started the freezes is open to unlimited conjecture. Once frozen shut, the Earth should have been stuck in a cold state - with its surface white, it would have shed sunlight and become colder than an Antarctic night. Geochemistry broke both snowball eras. Vulcanism was not affected by the freezeover. It took ten, twenty million years for volcanic plumes to inject enough carbon dioxide into the air to raise temperatures to the point where even a snowball would begin to thaw under sunlight. Since the thaw brought Earth's albedo down, the thaw was a runaway event, leading to high temperatures (imagine oceanic surface temps above fifty degrees!), intense erosion by weather and acid rain, and (mechanism not clear, but what a cool outcome) huge step-function increases in the complexity and sheer consequence of planetary life.

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