Henry's Fork Caldera

Henry's Fork Caldera is a volcanic crater in Fremont County in eastern Idaho. It measures about 37 kilometers (23 miles) wide and 29 kilometers (18 miles) long, forming a circular depression within the larger Island Park Caldera.

This caldera formed about 1.3 million years ago from a massive volcanic eruption. The explosion scattered enormous amounts of ash across Wyoming, Colorado, Nebraska, and Kansas.

Scientists and geologists frequently visit this location to study volcanic processes and monitor the ongoing activity of the Yellowstone hotspot system.

The caldera is accessible by car, and visitors can enjoy outdoor activities like Nordic skiing, fishing, and snowmobiling depending on the season. The best time to visit is summer and early fall when roads are generally open and accessible.

The Henry's Fork of Snake River flows through the center of this caldera, creating a remarkable natural feature. While multiple calderas formed in this region from the Yellowstone hotspot system, this one stands out by showing visible geological structures today.

Location: Fremont County

Elevation above the sea: 2,805 m

GPS coordinates: 44.33000,-111.33000

Latest update: January 1, 2026 10:02