Elevation: 9,203 ft.
The Henry's Fork Caldera in Idaho is a caldera located an area known as Island Park west of Yellowstone National Park. The caldera was formed by one of the World's supervolcanos in an eruption of more than 280 cubic kilometers 1.3 million years BP, and is the source of the Mesa Falls Tuff.
The Henry's Fork Caldera is nested inside of the Island Park Caldera and the calderas share a rim on the western side. The earlier Island Park Caldera is much larger and more oval and extends well into Yellowstone Park.
Of the many calderas formed by the Yellowstone hotspot, including the later Yellowstone Caldera, the Henry's Fork Caldera is the only one that is currently clearly visible. It is one of a succession of supervolcanoes and calderas that formed the Snake River Plain.