Island Park resides within a large volcanic caldera system that includes two of the three calderas that make up the Yellowstone Supervolcano structure.
As illustrated below the Island Park Caldera is the 1st Yellowstone Caldera, which is the worlds largest caldera. This caldera is 58 miles by 48 miles in size. When it erupted 2.1 million years ago it emitted 2,500 times more volcanic ash than Mt. St. Helens did in 1980.
Within the 1st caldera resides the 2nd caldera, the Henry’s Fork Caldera. This caldera was formed 1.3 million years ago.