Yellowstone Caldera in the context of "Supervolcano"

A supervolcano is a volcano that has had an eruption with a volcanic explosivity index (VEI) of 8, the largest recorded value on the index. This means the volume of deposits for such an eruption is greater than 1,000 cubic kilometers (240 cubic miles).

Supervolcanoes occur when magma in the mantle rises into the crust but is unable to break through it. Pressure builds in a large and growing magma pool until the crust is unable to contain the pressure and ruptures. This can occur at hotspots (for example, Yellowstone Caldera) or at subduction zones (for example, Toba).

The Yellowstone hotspot is a volcanic hotspot in the United States responsible for large scale volcanism in Idaho, Montana, Nevada, Oregon, and Wyoming, formed as the North American tectonic plate moved over it. It formed the eastern Snake River Plain through a succession of caldera-forming eruptions. The resulting calderas include the Island Park Caldera, Henry's Fork Caldera, and the Bruneau-Jarbidge caldera. The hotspot currently lies under the Yellowstone Caldera. The hotspot's most recent caldera-forming supereruption, known as the Lava Creek Eruption, took place 640,000 years ago and created the Lava Creek Tuff, and the most recent Yellowstone Caldera. The Yellowstone hotspot is one of a few volcanic hotspots underlying the North American tectonic plate; another example is the Anahim hotspot.

Mammoth Hot Springs is a large complex of hot springs on a hill of travertine in Yellowstone National Park adjacent to Fort Yellowstone and the Mammoth Hot Springs Historic District. It was created over thousands of years as hot water from the spring cooled and deposited calcium carbonate (over two tons flow into Mammoth each day in a solution). Because of the huge amount of geothermal vents, travertine flourishes. Although these springs lie outside the caldera boundary, their energy has been attributed to the same magmatic system that fuels other Yellowstone geothermal areas.

The hot water that feeds Mammoth comes from Norris Geyser Basin after traveling underground via a fault line that runs through limestone and roughly parallel to the Norris-to-Mammoth road. The limestone from rock formations along the fault is the source of the calcium carbonate. Shallow circulation along this corridor allows Norris's superheated water to slightly cool before surfacing at Mammoth, generally at about 170 °F (80 °C). Algae living in the warm pools have tinted the travertine shades of brown, orange, red, and green.