What Lies Beneath
A moderate sized (magnitude 4.8) earthquake shook Yellowstone National Park yesterday. This is notable partly because Yellowstone has a history as a supervolcano. It only blows every 700,000 years or so - last time about 700,000 years ago (OK, OK, it was only 640 kyrs ago) - but when it does, it's a spectacular, continent annihilating event with global consequences. There seems to be a big pool of magma collecting down below:
Late last year a new study into the enormous super volcano found the underground magma chamber to be 2.5 times larger than previously thought — a cavern spanning some 90km by 30km and capable of holding 300 billion cubic kilometres of molten rock.
Students of geometry might be impressed by the thought that a pool of areal extent less than 2700 km^2 could house "300 billion cubic kilometers of molten rock." Let's make the plausible guess that they really meant 300 billion cubic meters, or a more reasonable 300 cubic kilometers - it's still quite a bit.