Photographs of Upper Geyser Basin, Yellowstone National Park

Like most springs on Geyser Hill, Pump Geyser is filled by boiling alkaline water, and is one of the most active features in the area; although its eruptions are relatively small they are almost continuous. The water constantly simmers and splashes, rising to heights of a few feet, and sustaining an area of delicate deposited sinter formations. The vent itself is semi-circular and quite colorful, viewable from both sides as the boardwalk trail loops part of the way around the spring. Eruptions are accompanied by a dull thumping noise, on account of which the geyser was named, early in the 20th century.

Back to map of the Upper Geyser Basin

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