Yellowstone, it turns out, is a supervolcano. It sits on top of an enormous hot spot, a reservoir of molten rock which begins at least 200 kilometres down in the Earth and rises to near the surface, forming what is known as a superplume. The heat from the hot spot is what powers all of Yellowstone's vents, geysers, hot springs and popping mud pots. Beneath the surface is a magma chamber that is about 72 kilometres across - roughly the same dimensions as the park - and about 13 kilometres thick at its thickest point. Imagine a pile of TNT about the size of an English county and reaching 13 kilometres into the sky, to about the height of the highest cirrus clouds, and you have some idea of what visitors to Yellowstone are shuffling around on top of. The pressure that such a pool of exerts on the crust above has lifted Yellowstone and its surrounding territory about half a kilometre higher than they would otherwise be. If it blew, the cataclysm is pretty well beyond imagining. According to Professor Bill McGuire of University College London, 'you wouldn't be able to get within a thousand kilometres of it' while it was erupting. The consequences that followed would be even worse. (From A Short History of Nearly Everything , page 199)
I read this just after it came out, in 2003. I had read Bryson's travel books before and enjoyed his sense of humour. This book appealed to my interest in science and my belief that theologians who do not understand basic science, have no calling to be doing theology in todays world. There is no excuse when there are books like this one readily available. I suppose there's little chance of any significant change when so many Christians are scared of a proof that their treasured beliefs about God are wrong.
The section about Yellowstone is thrilling. The whole story, as Bryson tells it, of cosmology and geology, puts us firmly in our place. We may be at home in the universe but we are extremely lucky to be here. We are led to reflect that our existence is conditional. This is why I prefer to think of God as artist rather than designer.
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