National Geographic - Supervolcano - New Documentary HD 2018
A supervolcano is a large volcano that has had an eruption of magnitude 8, which is the largest value on the Volcanic Explosivity Index (VEI). This means the volume of deposits for that eruption is greater than 1,000 cubic kilometers (240 cubic miles).[1] A supervolcanic eruption may be a single short-term event, or a massive outpouring of lava lasting up to millions of years.
Supervolcanoes occur when magma in the mantle rises into the crust but is unable to break through it and pressure builds in a large and growing magma pool until the crust is unable to contain the pressure. This can occur at hotspots (for example, Yellowstone Caldera) or at subduction zones (for example, Toba). Another setting for the eruption of very large amounts of volcanic material is in large igneous provinces, which can cover huge areas with lava and volcanic ash, causing long-lasting climate change (such as the triggering of a small ice age), which can threaten species with extinction. The Oruanui eruption of New Zealand's Taupo Volcano (about 26,500 years ago)[2] was the world's most recent super eruption at a VEI-8 eruption.