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A short history of nearly everythingThere is a serious problem in all this in that the geological evidence indicates ice everywhere, including around the equator, while the biological evidence suggests just as firmly that there must have been open water somewhere. For one thing, cyanobacteria survived the experience, and they photosynthesize. For that they needed sunlight, but as you will know if you have ever tried to peer through it, ice quickly becomes opaque and after only a few yards would pass on no light at all. Two possibilities have been suggested. One is that a little ocean water did remain exposed (perhaps because of some kind of localized warming at a hot spot); the other is that maybe the ice formed in such a way that it remained translucent-a condition that does sometimes happen in nature. If Earth did freeze over, then there is the very difficult question of how it ever got warm again. An icy planet should reflect so much heat that it would stay frozen forever. It appears that rescue may have come from our molten interior. Once again, we may be indebted to tectonics for allowing us to be here ...» | Код для вставки книги в блог HTML
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