Portal:Volcanoes
The Volcanoes portal
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. The process that forms volcanoes is called volcanism.
On Earth, volcanoes are most often found where tectonic plates are diverging or converging, and because most of Earth's plate boundaries are underwater, most volcanoes are found underwater. For example, a mid-ocean 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, such as in the East African Rift, the Wells Gray-Clearwater volcanic field, and the Rio Grande rift in North America. Volcanism away from plate boundaries has been postulated to arise from upwelling diapirs from the core–mantle boundary, 3,000 kilometers (1,900 mi) deep within Earth. This results in hotspot volcanism, of which the Hawaiian hotspot is an example. Volcanoes are usually not created where two tectonic plates slide past one another.
Large eruptions can affect atmospheric temperature as ash and droplets of sulfuric acid obscure the Sun and cool Earth's troposphere. Historically, large volcanic eruptions have been followed by volcanic winters which have caused catastrophic famines.
Other planets besides Earth have volcanoes. For example, volcanoes are very numerous on Venus. In 2009, a paper was published suggesting a new definition for the word 'volcano' that includes processes such as cryovolcanism. It suggested that a volcano be defined as 'an opening on a planet or moon's surface from which magma, as defined for that body, and/or magmatic gas is erupted.'
This article mainly covers volcanoes on Earth. See § Volcanoes on other celestial bodies and cryovolcano for more information. (Full article...)
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Mount Tambora, or Tomboro, is an active stratovolcano in West Nusa Tenggara, Indonesia. Located on Sumbawa in the Lesser Sunda Islands, it was formed by the active subduction zones beneath it. Before 1815, its elevation reached more than 4,300 metres (14,100 feet) high, making it one of the tallest peaks in the Indonesian archipelago.
Tambora violently erupted in a series of eruptions beginning 5 April 1815, culminating in the largest eruption in recorded human history and the largest of the Holocene (10,000 years ago to present). The magma chamber under Tambora had been drained by previous eruptions and underwent several centuries of dormancy as it refilled. Volcanic activity reached a peak that year, culminating in an explosive eruption. The explosion was heard on Sumatra island, more than 2,600 kilometres (1,600 miles) away and possibly over 3350 km (2060 miles) away in Thailand and Laos. Heavy volcanic ash rains were observed as far away as Borneo, Sulawesi, Java, and Maluku islands, and the maximum elevation of Tambora was reduced from about 4,300 to 2,850 metres (14,110 to 9,350 feet). Although estimates vary, the death toll was at least 71,000 people. The eruption contributed to global climate anomalies in the following years, while 1816 became known as the "year without a summer" because of the impact on North American and European weather. In the Northern Hemisphere, crops failed and livestock died, resulting in the worst famine of the century. (Full article...)
Did you know
- ...that Regal Mountain (pictured), an eroded stratovolcano in the Wrangell Mountains, is the third-highest thirteener (a peak between 13,000 and 14,000 feet in elevation) in Alaska?
- ...that Canadian scientist Bill Mathews was a pioneer in the study of subglacial eruptions and volcano-ice interactions in North America?
- ...that thermal vent ecosystems have been discovered in the Aegean Sea, in the caldera of Kolumbo underwater volcano?
- ...that Hawaii's Chain of Craters Road has been blocked repeatedly by lava flows from Kīlauea volcano since it was built in 1928?
- ...that Halemaʻumaʻu Crater in Hawaiʻi Volcanoes National Park erupted explosively on March 19, 2008 for the first time since 1924?
- ... that Bowie Seamount on the British Columbia Coast of Canada is one of the most biologically rich submarine volcanoes on Earth and was an active volcanic island throughout the Last Glacial Period?
- ... that the Lava River Cave in Newberry National Volcanic Monument is the longest known uncollapsed lava tube in Oregon, U.S.?
- ... that the early pre-Columbian site of Xochitecatl in Mexico was abandoned for centuries after the Popocatépetl volcano erupted around 150 AD?
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Selected biography -
George Julius Poulett Scrope FRS (10 March 1797 – 19 January 1876) was an English geologist and political economist as well as a Member of Parliament and magistrate for Stroud in Gloucestershire.
While an undergraduate at Cambridge, through the influence of Edward Clarke and Adam Sedgwick he became interested in mineralogy and geology. During the winter of 1816–1817 he was at Naples, and was so keenly interested in Vesuvius that he renewed his studies of the volcano in 1818; and in the following year visited Etna and the Lipari Islands. In 1821 he married the daughter and heiress of William Scrope of Castle Combe, Wiltshire, and assumed her name; and he entered the House of Commons of the United Kingdom in 1833 as MP for Stroud, retaining his seat until 1868.
Meanwhile he began to study the volcanic regions of central France in 1821, and visited the Eifel district in 1823. In 1825 he published Considerations on Volcanos, leading to the establishment of a new theory of the Earth, and in the following year was elected FRS. This earlier work was subsequently amplified and issued under the title of Volcanos (1862); an authoritative text-book of which a second edition was published ten years later. In 1827 he issued his classic Memoir on the Geology of Central France, including the Volcanic formations of Auvergne, the Velay and the Vivarais, a quarto volume illustrated by maps and plates. The substance of this was reproduced in a revised and somewhat more popular form in The Geology and Extinct Volcanos of Central France (1858). These books were the first widely published descriptions of the Chaîne des Puys, a chain of over 70 small volcanoes in the Massif Central. (Full article...)
Selected picture
Aerial view of Mount Kilimanjaro, the highest peak in Africa and the fourth highest of the Seven Summits. The volcano consists of three distinctive volcanic cones; of which the Kibo cone, pictured, is highest.
Selected quote
"Do we need to bring a sleeping bag, or will the volcano keep us warm at night?"
— Documentary producer at Mount Etna, 2000.
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Featured 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) • Kamaʻehuakanaloa 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.
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