The volcano last erupted approximately 174,000 years ago, creating what is now known as the West Thumb of Yellowstone Lake, the NPS said on its website.

The volcano last erupted approximately 174,000 years ago, creating what is now known as the West Thumb of Yellowstone Lake, the NPS said on its website.

U. research • Seismologists found a massive chamber of lava and rock 12 to 28 miles below the park, much larger than the one closer to surface. Yellowstone's underground plumbing is becoming ...