The caldera was formed by an eruption 1.3 million years ago of the Yellowstone hotspot.

The eruption distributed at least 280 cubic kilometers of ash known as the Mesa Falls Tuff, covering a region including all of Wyoming and most of Colorado, Nebraska, and Kansas.

[1] Although much smaller than the Island Park Caldera, the Henry's Fork Caldera is still sizeable at 18 miles (29 km) long and 23 miles (37 km) wide and its curved rim is plainly visible from many locations in the Island Park area.

The Henry's Fork caldera is in an area called Island Park, known for its beautiful forests, large springs, clear streams, waterfalls, lakes, ponds, marshes, wildlife, and fishing.

Snowmobiling, fishing, and Nordic skiing, and wildlife viewing are popular activities in the area.