Information AboutPhreatic Eruption |
| CATEGORIES ABOUT PHREATIC ERUPTION | |
| volcanic eruption types | |
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Phreatic eruptions, also called '''ultravulcanian eruptions''', occur when rising Magma makes contact with Ground or surface water. The extreme temperature of the magma (anywhere from 600°C to 1,170°C (1112° - 2138° F)) causes near-instantaneous evaporation to Steam resulting in an explosion of steam, water, ash, rock, and Volcanic Bomb s. At Mount St. Helens hundreds of steam explosions preceded a 1980 Plinian eruption of the Volcano . A less intense geothermal event may result in a Mud Volcano . In 1949, Thomas Jaggar described this kind of activity as '''steam-blast eruptions'''. Phreatic eruptions typically include steam and rock fragments; the inclusion of lava is unusual. The temperature of the fragments can range from cold to Incandescent . If molten material is included, the term phreato-magmatic may be used. These eruptions occasionally create broad, low-relief Crater s called Maar . Phreatic explosions can be accompanied by Carbon Dioxide or Hydrogen Sulfide gas emissions. The former can Asphyxiate at sufficient concentration; the latter is a broad spectrum poison. A 1979 phreatic eruption on the island of Java killed 149 people, most of whom were overcome by poisonous gases. It is believed the 1883 eruption of Krakatoa - which obliterated most of the volcanic island and created the loudest sound in recorded human history - was a phreatic event. Kilauea , in Hawaii , has a long record of phreatic explosions; a 1924 phreatic eruption hurled rocks estimated at eight tons up to a distance of one kilometer. Additional examples are the 1963-65 eruption of Surtsey , and the 1965 eruption of Taal Volcano . RELATED SITE USGS Photo Glossary Entry for "Phreatic Eruption" |
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