The Island Park Caldera, in the U.S. states of Idaho and Wyoming, is one of the world's largest calderas, with approximate dimensions of 80 by 65 km. Its ashfall is the source of the Huckleberry Ridge Tuff that is found from southern California to the Mississippi River near St. Louis. This super-eruption of approximately occurred 2.1 Ma (million years ago) and produced 2,500 times as much ash as the 1980 eruption of Mount St. Helens. Island Park Caldera has the smaller and younger Henry's Fork Caldera nested inside it.