Along with the abundant wildlife and beautiful scenery in Yellowstone another one of its most spectacular sights is its hydrothermal features. Yellowstone has the greatest concentration of geysers in the world, and also has beautiful hot springs and fumaroles. This concentration of hydrothermal features is caused by the combination of abundant groundwater and surface water, the high permeability of the bedrock underground, and the hot spot that lies below Yellowstone.
The hot spot in the mantle below the park is exactly what its name implies: a heat source in a specific area within the earth's mantle. This hot spot is somewhat of a mystery to scientists because they don't know exactly what creates it nor why it is in that specific location. Nonetheless, it exists and heats the bedrock, causing it to melt and create magma chambers. The magma is the source that fed the Yellowstone volcano to catastrophically erupt half a million years ago. The explosion was so vast that today, deposits of Yellowstone ash that are several meters thick cover parts of Death Valley, California. You might ask, "Where is the volcano now?" Well, the eruption completely emptied its magma chamber and collapsed in on itself to form a crater, called a caldera. Yellowstone's geothermal features are located within this giant caldera.
Here is an illustration that shows two theories of where the hot spot could be located in the earth’s mantle below Yellowstone. The right side of the drawing shows the theory that the hot spot is shallow in the mantle, while the left side shows the hot spot to be much deeper.
In fact, Yellowstone is still an active “super volcano.” The magma's movement underground and faults (that stretch and extend earth's crust) within and around the park cause hundreds of minor earthquakes to occur every month. For example, U.S. Geological Survey recorded 263 earthquakes in Yellowstone during January of 2008. However, large earthquakes have occurred recently. In 1959 an earthquake measuring magnitude 7.5 cuased a huge rock just west of the park boundary to start a giant landslide, which killed 28 campers and dammed up the river to create Earthquake Lake (pictured above).
The illustration below shows the location of Yellowstone inside the caldera, the faults surrounding the park that cause crustal extension and earthquakes, and the hot spot below.
This video explains the theory surrounding the hot spot underneath Yellowstone and the potential for this super volcano to erupt again.
