Old Faithful Geyser

Yellowstone is a thermal "hot spot" in the earth. In fact, most of the western part of the
Park sits in an ancient caldera of a volcano. About 600,000 years ago, the volcano erupted
creating the landscape that is Yellowstone today. Yellowstone is filled with geysers,
relief valves, as it were, from the earth's inner heat. Old Faithful goes off more or less predictably
every 90 minutes. It is one of the most popular sights of the Park. Indeed, Yellowstone was
America's first National Park and was intended to preserve these amazing - and fragile -
natural features. See more geysers in the area around Old Faithful.