The Yellowstone Caldera is the volcanic caldera in Yellowstone National Park in the United States. It is located in the northwest corner of Wyoming, measuring about 55 kilometers (34 mi) by 72 kilometers (45 mi). The caldera was discovered based on geological field work conducted by Bob Christiansen of the United States Geological Survey in the 1960s and 1970s. After a BBC television science program coined the term supervolcano in 2000, it has often been referred to as the "Yellowstone supervolcano."

Volcanism

Yellowstone, like the Hawaii hotspot, is believed to lie on top of one of the planet's few dozen hotspots where light, hot, molten mantle rock rises towards the surface. The Yellowstone hotspot has a long history. Over the past 17 million years or so, successive eruptions have flooded lava over wide stretches of Washington, Oregon, California, Nevada, and Idaho, forming a string of comparatively flat calderas linked like beads, as the North American plate moves across the stationary hotspot. The oldest identified caldera remnant is straddling the border near McDermitt, Nevada-Oregon. The caldera's apparent motion to the east-northeast forms the Snake River Plain. However, what is actually happening is the result of the North American plate moving west-southwest over the stationary hotspot deep underneath.

Yellowstone sits on top of three overlapping calderas. (USGS)

The volcanic eruptions, as well as the continuing geothermal activity, are a result of a large chamber of magma located below the caldera's surface. The magma in this chamber contains gases that are kept dissolved only by the immense pressure that the magma is under. If the pressure is released to a sufficient degree by some geological shift, then some of the gases bubble out and cause the magma to expand. This can cause a runaway reaction. If the expansion results in further relief of pressure, for example, by blowing crust material off the top of the chamber, the result is a very large gas explosion.

Volcanic hazard

A full-scale eruption of the Yellowstone caldera could result in millions of deaths. The last full-scale eruption, the so-called Lava Creek eruption, ejected approximately 240 cubic miles of rock and dust into the sky.

Geologists are closely monitoring the rise and fall of the Yellowstone Plateau, which averages +/- 0.6 inches (about 1.5 cm) yearly, as an indication of changes in magma chamber pressure.^[3][4] The upward movement of the Yellowstone caldera floor ? almost 3 inches (7 centimeters) per year for the past three years ? is more than three times greater than ever observed since such measurements began in 1923.^[5] From mid-Summer 2004 through mid-Summer 2008, the land surface within the caldera has moved upwards, as much as 8 inches at the White Lake GPS station ^[6]. The U.S. Geological Survey, University of Utah and National Park Service scientists with the Yellowstone Volcano Observatory "see no evidence that another such cataclysmic eruption will occur at Yellowstone in the foreseeable future. Recurrence intervals of these events are neither regular nor predictable."^[7].

Hydrothermal explosion hazard

Studies and analysis may indicate that the greater hazard comes from hydrothermal activity which occurs independently of volcanic activity. Over 20 large craters have been produced in the past 14,000 years since the glaciers retreated from Yellowstone, resulting in such features as Mary Bay, Turbid Lake and Indian Pond.

Lisa Morgan, a USGS researcher, explored this threat in a 2003 report, and in a recent talk postulated that an earthquake may have displaced more than of water in Yellowstone Lake, creating huge waves that essentially unsealed a capped geothermal system leading into the hydrothermal explosion that formed Mary Bay.^[8][9]

Further research shows that earthquakes from great distances do reach and have effects upon the activities at Yellowstone, such as the 1992 7.3 magnitude Landers earthquake in California?s Mojave Desert that triggered a swarm of quakes from more than away and the Denali fault earthquake away in Alaska that altered the activity of many geysers and hot springs for several months afterwards.^[10]

The head of the Yellowstone Volcano Observatory, Jake Lowenstern, has proposed major upgrades and extended monitoring since the U.S. Geological Survey classified Yellowstone as a ?high-threat? system.^[11]

Origin

Path of the Yellowstone hot spot over the past 15 million years

See also

• Supervolcano, a two-part docudrama about a hypothetical eruption of the Yellowstone caldera
• When Yellowstone Erupts, a documentary about the hypothetical after-effects of the Yellowstone caldera eruption, and warning signs that scientists are looking for.
• Long Valley Caldera, Valles Caldera, La Garita Caldera, and Bruneau-Jarbidge - examples of other calderas close to but not related to Yellowstone.
• End Day, an apocalyptic docu-drama with five scenarios, the fourth being the eruption of the Yellowstone supervolcano.

Further reading

• Breining, Greg, Super Volcano: The Ticking Time Bomb beneath Yellowstone National Park (St. Paul, MN: Voyageur Press, 2007). A popularized scientific look at the Yellowstone area's geological past and potential future. ISBN 978-0-7603-2925-2
• Vazquez, J.A., and Reid, M.R., 2002, Time scales of magma storage and differentiation of voluminous rhyolites at Yellowstone caldera, Wyoming: Contributions to Mineralogy & Petrology, v. 144, p. 274-285
• Iceland hotspot and Iceland plume describes aspects of volcanic processes
• Sutherland, Wayne, and Sutherland, Judy, Yellowstone Farewell (SPUR RIDGE, 2003). A novel looking at an eruption in the Yellowstone Caldera written by a practicing Wyoming geologist. Contains a wealth of technical details on the geology of western Wyoming.

References

External links

• Geology report about the Yellowstone hotspot
• Yellowstone Volcano Observatory
  • YVO FAQ relating to ''Supervolcano''
• USGS Fact Sheet on Yellowstone's future
• Supervolcano documentary from BBC

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