The Yellowstone Caldera & Plate Tectonics

  Yellowstone is one of the most fascinating geological features on Earth!  It is the largest volcanic caldera on the planet.  A caldera is a cauldron-like feature created by a collapsed supervolcano.  The caldera sits astride a geologic hotspot; an area of the earth's crust where hot, lightweight molten rock rises near the surface.  This phenomenon is responsible for "Old Faithful", other geothermal vents (geysers), and for other features like hot, bubbling mud pans.
     Yellowstone is actually comprised of three overlapping calderas. Plate tectonics accounts for its enormous size.  Over a long period of time, volcanic activity created the first caldera.  The hotspot remained in place as the plate with its caldera moved west.  The hotspot erupted again and eventually formed another caldera which, in turn, moved west with the plate.  The process continues today.  The area is monitored constantly because the threat of another supervolcanic event is ever-present.  Yellowstone experiences 1000-2000 measurable earthquakes every year.