Island Park Caldera

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 2,500 km3 occurred 2.1 Ma and produced 2,500 times as much ash as the 1980 Mount St. Helens eruption. Island Park Caldera has the smaller and younger Henry's Fork Caldera nested inside it.
The caldera clearly visible today is the later Henry's Fork Caldera, which is the source of the Mesa Falls Tuff. It was formed 1.3 Ma in an eruption of more than 280 km3 . The two nested calderas share the same rim on their western sides, but the older Island Park Caldera is much larger and more oval and extends well into Yellowstone National Park. The Island Park Caldera is sometimes referred to as the First Phase Yellowstone Caldera or the Huckleberry Ridge Caldera.

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