phreatic eruption


phreatic eruption
ALASKA VOLCANO OBSERVATORY GLOSSARY
An explosive volcanic eruption caused when water and heated volcanic rocks interact to produce a violent expulsion of steam and pulverized rocks. Magma is not involved.
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GLOSSARY OF VOLCANIC TERMS
A steam eruption, commonly associated with water, mud, and other earth materials, that is caused when groundwater, heated by a magma, flashes (and explosively expands) into steam (Harris, 2000, p. 1301). Phreatic eruptions expel no juvenile (magmatic) material, and are commonly the precursor to magmatic eruptive activity.
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USGS PHOTO GLOSSARY OF VOLCANIC TERMS
Phreatic eruptions are steam-driven explosions that occur when water beneath the ground or on the surface is heated by magma, lava, hot rocks, or new volcanic deposits (for example, tephra and pyroclastic-flow deposits). The intense heat of such material (as high as 1,170° C for basaltic lava) may cause water to boil and flash to steam, thereby generating an explosion of steam, water, ash, blocks, and bombs.
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Photograph by D.A. Swanson on 4 April 1980
Phreatic eruption at the summit of Mount St. Helens, Washington. Hundreds of these steam-driven explosive eruptions occurred as magma steadily rose into the cone and boiled groundwater. These phreatic eruptions preceded the volcano's plinian eruption on 18 May 1980.

Glossary of volcanic terms. - University of Wisconsin Oshkosh. . 2001.

Look at other dictionaries:

  • Phreatic eruption — A Phreatic eruption, also called an ultravulcanian eruption, occurs when rising magma makes contact with ground or surface water. The extreme temperature of the magma (anywhere from 600 °C to 1,170 °C (1110–2140 °F)) causes near instantaneous… …   Wikipedia

  • phreatic eruption — /friætɪk əˈrʌpʃən/ (say freeatik uh rupshuhn) noun a volcanic eruption, as the Mount St Helens eruption, in which rising magma makes contact with ground or surface water causing it to immediately vaporise resulting in an eruption of steam, ash,… …   Australian English dictionary

  • Phreatic — The term phreatic is used in Earth sciences to refer to matters relating to ground water below the static water table (the word originates from the Greek phrear , phreat meaning well or spring ). The term phreatic surface is where the hydrostatic …   Wikipedia

  • phreatic — [frɪ atɪk] adjective Geology relating to or denoting underground water in the zone below the water table. Compare with vadose. ↘(of a volcanic eruption) caused by the heating and expansion of groundwater. Origin C19: from Gk phrear, phreat a well …   English new terms dictionary

  • phreatic — adj. Geol. 1 (of water) situated underground in the zone of saturation; ground water. 2 (of a volcanic eruption or explosion) caused by the heating and expansion of underground water. Etymology: Gk phrear phreatos well …   Useful english dictionary

  • Phreatomagmatic eruption — Phreatomagmatic eruptions are defined as juvenile forming eruptions as a result of interaction between water and magma. They are different from magmatic and phreatic eruptions. The products of phreatomagmatic eruptions contain juvenile clasts,… …   Wikipedia

  • 1888 Eruption of Mount Bandai — The 1888 Eruption of Mount Bandai was a major volcanic eruption which occurred during the Meiji period of the Empire of Japan. The eruption occurred on 1888 07 15, and pyroclastic flows buried villages on the northern foot of the mountain, and… …   Wikipedia

  • 1980 eruption of Mount St. Helens — Photograph of the eruption column, May 18, 1980 Volcano Mount St. Helens …   Wikipedia

  • Minoan eruption — Satellite image of Thera, November 21, 2000 Volcano Thera Date 2nd millennium BCE Type …   Wikipedia

  • Types of volcanic eruptions — In this article types of eruption will be used to refer to the mechanism causing the eruption. The style of eruption will be used to describe subcategories of eruption, which have the same eruptive mechanism. For example strombolian and vulcanian …   Wikipedia