What is a supervolcano exactly?
I think the name says it all, but officially, scientists define it as a volcano capable of an eruption thousands of times greater than any ordinary volcanic explosion.
These supervolcanoes burst when a growing pressure of molten rock, or magma, rises up from the Earth’s mantle.
When the crust can’t contain the buildup anymore — boom.
The Yellowstone Super Volcano, as it is currently known, is believed to be of common source with the Columbia River Basalt eruptions which formed the Columbia R. Gorge. It was located beneath the Southern Oregon border region at that time, feeding a plume of hot and molten rock that produced “caldera” (giant volcanic crater) eruptions – the biggest kind of volcanic eruption on Earth. This same plume, beginning about 2 million years ago, is now located underneath Yellowstone producing the Yellowstone Super Volcano.
They are currently closely monitoring Yellowstone because of the intensifying geothermal activity and swarms of earthquakes in the area.
This simulation from First Science shows the immediate effects of a Supervolcano explosion. (Youtube/ FirstScience.tv)