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.
The last large eruption at Yellowstone was 640,000 years ago, and ejected around 1,000 cubic kilometres (240 cubic miles) of volcanic material. This cataclysm created the Yellowstone caldera. To get an idea of the scale of this, the largest eruption in recorded history, Mount Tambora in 1815, erupted about a sixth of that. Magma reservoirs are thought to occur beneath most volcanoes, and play a crucial role in the dynamics of eruptions.