Semi Centennial Geyser
Semi-Centennial Geyser erupts at 198 degrees Fahrenheit alongside the Grand Loop Road in Yellowstone National Park, just 34 meters from pavement at 7,540 feet elevation with dilute chemistry showing minimal dissolved solids.
The geyser occupies thermal ground in Yellowstone's Roaring Mountain area where fumaroles and acidic springs alter volcanic bedrock to white and yellow clay. At 7,540 feet on the park's northern plateau, the site receives 28 inches of precipitation and 138 inches of snowfall annually. Lodgepole pine forest surrounds the thermal features, with dead standing timber marking areas of increased thermal activity. The Gallatin Range extends westward from this roadside location on the main park circuit.
Visit May through October when the Grand Loop Road operates fully. Winter access requires snowcoach or ski touring. The roadside location permits viewing without hiking, though boardwalks and established paths protect thermal ground. Average annual temperature of 35 degrees means cold weather soaking is impractical; this functions as a viewing feature. Indian Creek Campground lies 11 kilometers north.
The name commemorates the park's 50th anniversary in 1922, when thermal activity intensified at this previously quiet location. The feature demonstrates Yellowstone's dynamic hydrothermal system, with documented chemistry showing pH 6.0 and low mineral content. The geyser continues as a roadside thermal feature under National Park Service monitoring.
The water at Semi Centennial Geyser is slightly acidic (pH 6.0).
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Overview Located about eight miles (13 km) south of Mammoth Hot Springs on the road to Norris, Indian Creek Campground—elevation 7,300 feet (2225 m)—sits near the base of the Gallatin Mountains and offers breathtaking views of Electric Peak. The area offers easy access to fishing and hiking. The campground is away from the main road and provides a quieter, more primitive, experience than many other locations. For reservations at the campgrounds managed by Yellowstone National Park Lodges (Fi...
Semi Centennial Geyser sits at 7,540 feet above sea level, way above the mile-high mark. You may not feel the altitude strongly, but hot water still dehydrates you faster at elevation. UV is about 30% stronger than at sea level, so bring sunscreen and drink more water than you normally would.
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Semi Centennial Geyser is road-accessible, so you can bring more gear. The water is dangerously hot — bring water shoes and test pools carefully. Cold air temperatures make a changing robe or warm layers essential.
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