Thursday, January 14, 2010

Snowball earth and other ice ages

I've blogged on this before but Snowballearth.org is still the best site for all your Snowball Earth needs although it looks like it needs a bit of an update.
Their Questions section includes:

What caused the snowball earths?
Possibly by a lowering of atmospheric greenhouse gases to near-present levels through tectonically-mediated rock weathering, when the Sun was considerably dimmer than present.

Well, that's the short answer - here's the longer answer.

The Wikipedia article on Snowball Earth is also a really nice summary of the topic and covers the evidence for the theory, the various different controversies and, most relevant to us, a discussion of how life itself might have survived, and the implications for evolution.

We know more about what causes regular ice-ages but even then it seems that the relative contribution of different factors is much debated.

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