Yellowstone National Park is a great place to visit if you're ever in Wyoming, Montana, or Idaho!
I have been to Yellowstone a few times.  Very interesting geology there.  Have you ever heard of the super-caldera there?
Yellowstone Caldera
The Yellowstone Caldera is a volcanic caldera and supervolcano in Yellowstone National Park in the Western United States, sometimes referred to as the Yellowstone Supervolcano. The caldera and most of the park are located in the northwest corner of Wyoming. The major features of the caldera measure about 34 by 45 miles (55 by 72 km). 
The caldera formed during the last of three supereruptions over the past 2.1 million years: the Huckleberry Ridge eruption 2.1 million years ago (which created the Island Park Caldera and the
Greater Yellowstone Ecosystem
The Greater Yellowstone Ecosystem (GYE) is one of the last remaining large, nearly intact ecosystems in the northern temperate zone of the Earth. It is located within the northern Rocky Mountains, in areas of northwestern Wyoming, southwestern Montana, and eastern Idaho, and is about 18 million acres. Yellowstone National Park and the Yellowstone Caldera 'hotspot' are within it.
Conflict over ecological and resource management has been controversial, and the area is a flagship site among conservation groups that promote ecosystem management.