A supervolcano is a volcano that erupts more than 240 cubic miles of lava and has the capability to destroy up to a billion lives. This is not a volcano that will disrupt the lives of people in surrounding cities, but a volcano that will disrupt the lives of people on multiple continents. This is not a volcano that will interrupt travel with a large ash cloud, this is a volcano that will make day-to-day life so difficult a vacation is not even an option. Most importantly, this is not a hypothetical volcano out in the middle of the ocean somewhere; this is a very real volcano underneath Yellowstone National Park.
The Yellowstone supervolcano is the largest known on the planet, and the magma chamber spans underneath the entire 37 by 25 mile park. Pressure from this chamber is released through earthquakes, smaller volcanoes, and geysers to keep the magma levels in check, but if there is not enough ventilation a massive eruption can occur.
First, a series of large earthquakes would break out around the Yellowstone area. One earthquake would finally shift the ground enough to create a vent from the magma chamber to the surface and would unleash all the pressure that had been building for hundreds of thousands of years. Magma would explode into the atmosphere with a force equal to 1000 Hiroshima atomic bombs every second. Within minutes, thousands in the surrounding area would be dead from the falling ash and the lava would destroy everything within miles of the eruption. The ash would coat most of the United States killing crops and livestock, almost instantly obliterating the entire nation’s food source.
After the destruction from the initial explosion, the ash cloud would coat the sky and block out the sun all over the world. Temperatures would drop a drastic 20 degrees or more globally and the earth would be cast in the equivalent of a nuclear winter for decades. Any rain that fell would be black with the poison and acid flung into the atmosphere and man would be pushed to the edge of extinction.