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  • The boiling point of water increases with pressure. Therefore, water deep in the earth can be much hotter than boiling water near the surface. If the pressure that confines this deep water is reduced quickly, as may occur if there is a change in the underground plumbing system, large volumes of water may suddenly flash into steam, causing a violent hydrothermal explosion.

    Colonel Philetus W. Norris In 1881, Colonel Philetus W. Norris, Yellowstone’s second superintendent, witnessed a hydrothermal explosion at Excelsior Geyser in the Midway Geyser Basin. Afterwards, Norris described the changes: “The pool was considerably enlarged, its immediate borders swept entirely clear of all movable rock, enough of which had been hurled or forced back to form a ridge from knee to breast high at a distance of from 20 to 50 feet (6-15 m) from the ragged edge of the yawning chasm.”

    Before and after photos of Excelsior Geyser

    A series of such explosions were repeated in the early 1890s, which likely damaged the feature's plumbing system. Excelsior, once one of the largest geysers in the world, is now a large, boiling hot spring.

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    This work is supported by

    National Science Foundation    Yellowstone Park Foundation

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