Old Faithful in Yellowstone

Old Faithful is one of the most famous geysers in the world. It is located in Yellowstone National Park, mostly in Wyoming, where underground heat from ancient volcanic activity warms water deep below the surface. Pressure builds until the water flashes into steam and bursts upward through the geyser's narrow plumbing system.

Old Faithful earned its name because its eruptions are fairly predictable compared with many other geysers. It does not erupt exactly on a clock, but park rangers can estimate the next eruption by observing the length and strength of the previous one. Most eruptions send a tall column of hot water and steam into the air, creating one of Yellowstone's most memorable sights.

The geyser is part of the Upper Geyser Basin, an area filled with hot springs, steam vents, mudpots, and other geothermal features. These places are beautiful, but they are also dangerous. The water can be extremely hot, and the crust around thermal areas can be thin. Visitors protect themselves and the park by staying on boardwalks and marked trails.

Yellowstone became the first national park in the United States in 1872, helping launch the idea that extraordinary natural places should be protected for everyone. Old Faithful quickly became one of the park's best-known landmarks because visitors could gather nearby and have a good chance of seeing an eruption.

Long before Yellowstone became a national park, Indigenous peoples knew the region's geysers, hot springs, wildlife, and travel routes. Today, Yellowstone's geothermal features are studied by scientists, protected by park staff, and visited by people from around the world.