Yellowstone Volcano Observatory

U.S. Geological Survey
Open-File Report 2007-1071
Version 1.1

Preliminary Assessment of Volcanic and Hydrothermal Hazards in Yellowstone National Park and Vicinity

By Robert L. Christiansen, Jacob B. Lowenstern, Robert B. Smith, Henry Heasler, Lisa A. Morgan, Manuel Nathenson, Larry G. Mastin, L.J. Patrick Muffler, and Joel E. Robinson


photo of slide
Porkchop Geyser, in the Norris Geyser Basin, formed by a hydrothermal explosion in September 1989 (Fournier and others, 1991). Blocks of silica sinter thrown from the geyser's throat form a berm around the new crater. The silica will likely continue to dry out and disaggregate over time, subduing evidence of the explosive activity. Photo by Jim Peaco, 2003 (NPS stock photo) (from figure 19).

Possible future violent events in the active hydrothermal, magmatic, and tectonic system of Yellowstone National Park pose potential hazards to park visitors and infrastructure. Most of the national park and vicinity are sparsely populated, but significant numbers of people as well as park resources could nevertheless be at risk from these hazards. Depending on the nature and magnitude of a particular hazardous event and the particular time and season when it might occur, 70,000 to more than 100,000 persons could be affected; the most violent events could affect a broader region or even continent-wide areas. This assessment of such hazards is presented both as a guide for future activities of the Yellowstone Volcano Observatory (YVO) and to aid appropriate response planning by the National Park Service and surrounding agencies and communities. Although the assessment is presented here in some technical detail, this summary is intended to be understandable to non-scientists. The principal conclusions also will be made available in other forms, more accessible to general readers.

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For questions about the content of this report, contact Robert Christiansen (

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