Yellowstone Caldera

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Yellowstone Caldera
Image:Yellowstone River in Hayden Valley.jpg The northeastern part of Yellowstone Caldera, with the Yellowstone River flowing through Hayden Valley and the caldera rim in the distance
Elevation	10,308 feet (3,142 m) at Mount Sheridan
Location	Wyoming, U.S.
Range	Rocky Mountains
Coordinates	44°24′N, 110°42′W
Topo map	USGS Yellowstone National Park
Type	Caldera
Age of rock	70,000 – 2.1 million years
Last eruption	640,000 years ago
Easiest route	hike/auto/bus

The Yellowstone Caldera is a 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."

Contents 1 Volcanism 1.1 Volcanic hazard 2 Origin 3 See also 4 Further reading 5 References 6 External links

[edit] Volcanism

Yellowstone, like the Hawaiian Islands, is believed to lie on top of one of the planet's few dozen hot spots where light, hot, molten mantle rock rises towards the surface. The Yellowstone hot spot 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 hot spot. The oldest identified caldera remnant is straddling the border near McDermitt, Nevada-Oregon. The calderas' 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 hot spot deep underneath.

Currently, volcanic activity is exhibited only via numerous geothermal vents scattered throughout the region, including the famous Old Faithful Geyser, but within the past two million years, it has undergone three extremely large explosive eruptions, up to 2,500 times the size of the 1980 Mount St. Helens eruption. The three eruptions happened 2.1 million years ago, 1.3 million years ago, and the most recent such eruption produced the Lava Creek Tuff 640,000 years ago and spread a layer of volcanic ash over most of the North American continent. Smaller steam explosions occur every 20,000 years or so; an explosion 13,000 years ago left a 5 kilometer diameter crater at Mary Bay on the edge of Yellowstone Lake (located in the center of the caldera). Additionally, non-explosive eruptions of lava flows have occurred in and near the caldera since the last major eruption; the most recent of these was about 70,000 years ago. Craters of the Moon National Monument in Idaho is the result of volcanic activity between 11,000 and 2,000 years ago.

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.

[edit] Volcanic hazard

A full-scale eruption of the Yellowstone caldera could result in millions of deaths locally and catastrophic climatic effects globally, but there is little indication that such an eruption is imminent^[1]. However, the system is not yet completely understood, and the study of Yellowstone is ongoing. Geologists are closely monitoring the rise and fall of the Yellowstone Plateau, which averages +/- 1.5 cm yearly, as an indication of changes in magma chamber pressure.^[2][3] Major eruptions of the Yellowstone hotspot appear to occur roughly every 700,000 years. The Lava Creek Tuff eruption 630,000 years ago was the last major eruption.

[edit] Origin

The source of the Yellowstone Hot Spot is not without controversy. Some geoscientists theorize that the Yellowstone Hot Spot is the effect of an interaction between local conditions in the lithosphere and upper mantle convection^[4][5]. Others prefer a deep mantle origin (mantle plume)^[6]. No theory is close to airtight. Part of the controversy is due to the rather sudden appearance of the hot spot in the geologic record. Additionally, the Columbia Basalt flows appear at the same approximate point in time, causing speculation about their origin^[7].

[edit] 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, Valle Grande, 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.

[edit] 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.
• 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.

[edit] References

[edit] 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 BBCde:Yellowstone (Vulkan)

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