Yellowstone Geology

Yellowstone National Park’s unique landscape has been created and continues to change by numerous geological forces—from the activity of the Yellowstone volcanoes to earthquakes, glaciers and erosion. Resting on one of the largest active volcanoes in the world, Yellowstone National Park is a dynamic landscape including geysers, fumaroles, mud pots and hot springs. Three major volcanic eruptions have occurred in Yellowstone, the most recent occurring about 640,000 years ago. This eruption created the Yellowstone caldera, which measures approximately 30 by 45 miles.

Today, the hot magma near the surface fuels the hot springs, causes geysers to spew water, expels hot gasses from fumaroles, and allows mud pots to bubble. You’ll also find many volcanic rocks scattered throughout the landscape as evidence of this tumultuous past.