Portal:Volcanoes
The Volcanoes portalCleveland Volcano in the Aleutian Islands of Alaska photographed from the International Space Station, May 2006 A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. Earth's volcanoes occur because its crust is broken into 17 major, rigid tectonic plates that float on a hotter, softer layer in its mantle. Therefore, on Earth, volcanoes are generally found where tectonic plates are diverging or converging, and most are found underwater. For example, a mid-oceanic ridge, such as the Mid-Atlantic Ridge, has volcanoes caused by divergent tectonic plates whereas the Pacific Ring of Fire has volcanoes caused by convergent tectonic plates. Volcanoes can also form where there is stretching and thinning of the crust's plates, e.g., in the East African Rift and the Wells Gray-Clearwater volcanic field and Rio Grande Rift in North America. This type of volcanism falls under the umbrella of "plate hypothesis" volcanism. Volcanism away from plate boundaries has also been explained as mantle plumes. These so-called "hotspots", for example Hawaii, are postulated to arise from upwelling diapirs with magma from the core–mantle boundary, 3,000 km deep in the Earth. Volcanoes are usually not created where two tectonic plates slide past one another. Erupting volcanoes can pose many hazards, not only in the immediate vicinity of the eruption. One such hazard is that volcanic ash can be a threat to aircraft, in particular those with jet engines where ash particles can be melted by the high operating temperature; the melted particles then adhere to the turbine blades and alter their shape, disrupting the operation of the turbine. Large eruptions can affect temperature as ash and droplets of sulfuric acid obscure the sun and cool the Earth's lower atmosphere (or troposphere); however, they also absorb heat radiated from the Earth, thereby warming the upper atmosphere (or stratosphere). Historically, volcanic winters have caused catastrophic famines. Selected article
Amchitka is a volcanic, tectonically unstable island in the Rat Islands group of the Aleutian Islands in southwest Alaska. It is about 68 kilometres (42 mi)* long, and varies from 3 to 6 km (2–3.75 mi) in width.It has a maritime climate, with many storms, and mostly overcast skies. The island was populated for more than 2,500 years by the Aleut people, but has had no permanent population since 1832. It was included in the Alaska Purchase of 1867, and has since been part of the United States. During World War II, it was used as an airfield by US forces in the Battle of the Aleutian Islands. Amchitka was selected by the United States Atomic Energy Commission to be the site for underground detonations of nuclear weapons. Three such tests were carried out: Long Shot, an 80 kiloton blast in 1965; Milrow, a 1 megaton blast in 1969; and Cannikin in 1971 — at "under 5 megatons", the largest underground test ever conducted by the United States. The tests were highly controversial, with environmental groups fearing that the Cannikin explosion, in particular, would cause severe earthquakes and tsunamis. Amchitka is no longer used for nuclear testing, although it is monitored for the leakage of radioactive materials. Amchitka has a maritime climate, often foggy and windswept, with cloud cover 98 percent of the time.
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David Alexander Johnston (December 18, 1949 – May 18, 1980) was a volcanologist with the United States Geological Survey (USGS); he was killed by the 1980 eruption of the Mount St. Helens volcano in Washington. He was killed while manning an observation post about 6 miles (10 km) from the volcano on the morning of May 18, 1980. He was the first to report the eruption, transmitting the famous message "Vancouver! Vancouver! This is it!" before being swept away by the lateral blast created by the collapse of the mountain's north flank. Ham radio operator Jerry Martin observed the lateral blast overtaking Johnston's camp. Though Johnston's remains have never been found, remnants of his USGS trailer were found by state highway workers in 1993.
Johnston was the only geologist with the USGS to correctly predict the nature of the eruption. The official USGS prediction was that the volcano would experience a conventional vertical column eruption, while Johnston (who had been doing extensive research on the volcano and the geologic forces at play within and around it) had proposed that the blast would be lateral and originate from the bulge which he had observed developing on the side of the mountain. Did you know
Volcanoes topicsCore topics: Volcano • Volcanology • Igneous petrology • Lava • Magma • Decade Volcanoes • List of volcanoes • Plate tectonics • Hotspot Types of volcanoes: Fissure vent • Shield volcano • Lava dome • Cinder cone • Stratovolcano • Supervolcano • Submarine volcano • Subglacial volcano • Mud volcano Types of eruptions: (Overview) • Strombolian • Vulcanian • Peléan • Hawaiian • Surtseyan • Plinian • Submarine • Subglacial • Phreatic Related portalsSelected imageEyjafjallajökull is one of the smaller glaciers of Iceland. It is situated to the north of Skógar and to the west of the bigger glacier Mýrdalsjökull. The ice cap of the glacier covers a volcano which has erupted rather frequently since the Ice Age. The volcano's disruptive 2010 eruption was the first since 1823. Selected quote
Project collaboration
The project collaboration is a drive to improve our coverage of an important volcano-related topic. Once the article has been improved significantly, a new collaboration is chosen. Please improve the article any way you can. WikiProjectsCategoriesWhat you can do
Featured work and other approved contentFeatured articles: 1980 eruption of Mount St. Helens • 2007–2008 Nazko earthquakes • Amchitka • Armero tragedy • Craters of the Moon National Monument and Preserve • Cerro Azul (Chile volcano) • David A. Johnston • Enceladus (moon) • Geology of the Lassen volcanic area • Io (moon) • Loihi Seamount • Mauna Kea • Mauna Loa • Metacomet Ridge • Mono-Inyo Craters • Mount Cayley volcanic field • Mount St. Helens • Mount Tambora • Nevado del Ruiz • Surtsey • The Volcano (British Columbia) • Triton (moon) • Upper and Lower Table Rock • Volcanism on Io • Volcano (South Park) • Yellowstone National Park Featured lists: List of volcanoes in Indonesia • List of volcanoes in the Hawaiian – Emperor seamount chain • List of largest volcanic eruptions Featured pictures: There are currently 43 volcano-related Featured pictures. A full gallery can be seen here. Good articles: Abyssal plain • Amak Volcano • Anahim hotspot • Axial Seamount • Ben Nevis • Bowie Seamount • Crater Lake • Davidson Seamount • Ferdinandea • Gareloi Volcano • Geyser • Glacier Peak • Hawaii hotspot • Hualālai • Kohala (mountain) • Lake Toba • Minoan eruption • Mount Adams (Washington) • Mount Bailey • Mount Baker • Mount Cleveland (Alaska) • Mount Edziza volcanic complex • Mount Garibaldi • Mount Hood • Mount Kenya • Mount Rainier • Mount Redoubt • Mount Tehama • Mount Thielsen • Mount Vesuvius • Peter I Island • Roxy Ann Peak • Rùm • Sakurajima • Sangay • Silverthrone Caldera • Staffa • Types of volcanic eruptions • Volcanic ash • Weh Island • Wells Gray-Clearwater volcanic field • Yamsay Mountain Valued pictures: A gallery of volcano-related valued pictures can be seen here. Associated Wikimedia |