Roaring Mountain is a large, acidic thermal area (solfatara) that contains many steam vents (fumaroles). In the late 1800s and early 1900s, the number, size, and power of the fumaroles was much greater than today.

Fumaroles (Steam Vents)

Fumaroles or steam vents, are the hottest hydrothermal features in the park. The limited amount of water flashes into steam before reaching the surface. The result is a loud hissing of steam and gases.

Norris Geyser Basin

Norris Geyser Basin is one of the hottest and most acidic of Yellowstone's hydrothermal areas.

It is outside of the most recent Yellowstone caldera, but inside the first and largest caldera. It sits on the intersection of three major faults and is a very active earthquake area.

Even small earthquakes can trigger changes in hydrothermal behavior. This sudden activity is known as a "thermal disturbance" and can last a few days, or more than a week. Gradually, most features return to "normal."

Norris has the greatest water chemistry diversity among Yellowstone's hydrothermal areas. The water chemistry changes as the water levels of underground hot water reservoirs fluctuates.

Although Norris is known for its acid features, it also has alkaline hot springs and geysers.

Accessibility

Large parking pullout. Exhibit is wheelchair-accessible.