Disclaimer: I'm no Danish teaching expert, I just happen to be an Icelander who was forced to learn Danish as my second language - and although I always got very good grades in Danish, I was never good in Danish: can't speak it, can't understand a Dane - I can maybe read it a little bit...
University of Utah geology and geophysics professor Fan-Chi Lin said the blob-shaped lower magma reservoir in Earth's lower crust is located 12 to 28 miles (20-45 km) under Yellowstone, with a volume of 11,500 cubic miles (46,000 cubic km), or 11.2 times the volume of Arizona's Grand Canyon.
Of these only three percent are geysers. The rest are steaming pools, hissing fumaroles, bubbling mud pots or warm seeps. Most of Yellowstone's geysers are small, and sputter and splash, barely reaching ten feet in height. Only six grand geysers, those which erupt 100 feet or higher on a predictable daily basis, exist. Old Faithful, the most famous of these, erupts once approximately every 45 to 90 minutes. Beneath the thermal basins lie the mechanisms which control these features.