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...)
Selected article -
In December 2021, an eruption began on Hunga Tonga–Hunga Haʻapai, a submarine volcano in the Tongan archipelago in the southern Pacific Ocean. The eruption reached a very large and powerful climax nearly four weeks later, on 15 January 2022. Hunga Tonga–Hunga Haʻapai is 65 kilometres (40 mi) north of Tongatapu, the country's main island, and is part of the highly active Tonga–Kermadec Islands volcanic arc, a subduction zone extending from New Zealand to Fiji. On the Volcanic Explosivity Index scale, the eruption was rated at least a VEI-5. Described by scientists as a "magma hammer", the volcano at its height produced a series of four underwater thrusts, displaced 10 cubic kilometres (2.4 cu mi) of rock, ash and sediment, and generated the largest atmospheric explosion recorded by modern instrumentation.
The eruption caused tsunamis in Tonga, Fiji, American Samoa, Vanuatu, New Zealand, Japan, the United States, the Russian Far East, Chile and Peru. At least four people were killed, some were injured, and some remain possibly missing in Tonga from tsunami waves up to 20 m (66 ft) high. Tsunami waves with run-up heights up to 45 m (148 ft) struck the uninhabited island of Tofua. Two people drowned in Peru when 2 m (6 ft 7 in) waves struck the coast, while another died of indirect causes in Fiji. It was the largest volcanic eruption since the 1991 eruption of Mount Pinatubo. NASA determined that the eruption was "hundreds of times more powerful" than the atomic bomb dropped on Hiroshima. The eruption was the largest explosion recorded in the atmosphere by modern instrumentation, far larger than any 20th-century volcanic event or nuclear bomb test. It is thought that in recent centuries, only the Krakatoa eruption of 1883 rivalled the atmospheric disturbance produced. (Full article...)
Did you know
- ... that the Cameroon line of volcanoes is 1,000 kilometres (620 mi) long, and includes Mount Oku, the second highest mountain in Cameroon?
- ... that there was intense volcanic activity in Uruguay during the Cretaceous period about 130 million years ago?
- ... that seismologist Fusakichi Omori (pictured) of the Imperial University of Tokyo, who mapped the effects of the 1906 San Francisco earthquake, later designed and donated the equipment to found the Hawaiian Volcano Observatory?
- ... that Heart Peaks in northern British Columbia, Canada, is the third largest volcano in the Northern Cordilleran Volcanic Province?
- ... that Green Seamount, an underwater volcano, could have taken up to 260,000 years to reach its present height?
- ... that both the Pole Creek Wilderness and North Fork Owyhee Wilderness have some of the largest concentrations of sheer-walled volcanic rhyolite and basalt canyons in the western United States?
- ... that volcanologist Harry Glicken was saved from the 1980 eruption of Mount St. Helens due to a scheduling conflict, only to die in the eruption of Mount Unzen in 1991?
- ...that the eruption of Pu'u 'O'o added 544 acres (2.2 km²) of land to the island of Hawaii?
General images
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Lava-flooded craters and large expanses of smooth volcanic plains on Mercury (from List of extraterrestrial volcanoes) -
Eruption of mud at Dashgil mud volcano in Gobustan, Azerbaijan (from Volcanism) -
Colima Volcano eruption column, December 2016 (from Decade Volcanoes) -
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Diagrammatic representation of a plume on Enceladus (from Volcanism) -
Diagram of a Strombolian eruption. (key: 1. Ash plume 2. Lapilli 3. Volcanic ash rain 4. Lava fountain 5. Volcanic bomb 6. Lava flow 7. Layers of lava and ash 8. Stratum 9. Dike 10. Magma conduit 11. Magma chamber 12. Sill) Click for larger version. (from Types of volcanic eruptions) -
The final eruptions in the creation of Banks Peninsula in New Zealand occurred about 9 million years ago. (from Timeline of volcanism on Earth) -
NASA, Global Dimming - El Chichon, VEI 5; Pinatubo, VEI 6. (from Timeline of volcanism on Earth) -
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Some features of volcanism found in Earth's crust (from Volcanism) -
Diagram of a Plinian eruption. (key: 1. Ash plume 2. Magma conduit 3. Volcanic ash rain 4. Layers of lava and ash 5. Stratum 6. Magma chamber) Click for larger version. (from Types of volcanic eruptions) -
Mount Lamington following the devastating 1951 eruption (from Types of volcanic eruptions) -
A major eruption of Gran Canaria took place around 14 million years ago. (from Timeline of volcanism on Earth) -
Distribution of selected hotspots. The numbers in the figure are related to the listed hotspots on Hotspot (geology). (from Timeline of volcanism on Earth) -
Diagram of a phreatic eruption. (key: 1. Water vapor cloud 2. Magma conduit 3. Layers of lava and ash 4. Stratum 5. Water table 6. Explosion 7. Magma chamber) (from Types of volcanic eruptions) -
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Sarychev Peak: the sulphur dioxide cloud generated by the eruption on June 12, 2009 (in Dobson units). (from Timeline of volcanism on Earth) -
Some of the eruptive structures formed during volcanic activity (counterclockwise): a Plinian eruption column, Hawaiian pahoehoe flows, and a lava arc from a Strombolian eruption (from Types of volcanic eruptions) -
Sulfur dioxide emissions by volcanoes. Mount Pinatubo: 20 million tons of sulfur dioxide. (from Timeline of volcanism on Earth) -
2016 eruption of Mount Sinabung (from Types of volcanic eruptions) -
Diagram of a Surtseyan eruption. (key: 1. Water vapor cloud 2. Compressed ash 3. Crater 4. Water 5. Layers of lava and ash 6. Stratum 7. Magma conduit 8. Magma chamber 9. Dike) Click for larger version. (from Types of volcanic eruptions) -
A diagram of a Subglacial eruption. (key: 1. Water vapor cloud 2. Crater lake 3. Ice 4. Layers of lava and ash 5. Stratum 6. Pillow lava 7. Magma conduit 8. Magma chamber 9. Dike) Click for larger version. (from Types of volcanic eruptions) -
Diagram of Peléan eruption. (key: 1. Ash plume 2. Volcanic ash rain 3. Lava dome 4. Volcanic bomb 5. Pyroclastic flow 6. Layers of lava and ash 7. Stratum 8. Magma conduit 9. Magma chamber 10. Dike) Click for larger version. (from Types of volcanic eruptions) -
Lahar flows from the 1985 eruption of Nevado del Ruiz, which totally destroyed Armero in Colombia (from Types of volcanic eruptions) -
Cross section diagram of Earth showing some settings for volcanism on the planet (from Volcanism) -
MLO transmission ratio - Solar radiation reduction due to volcanic eruptions (from Timeline of volcanism on Earth) -
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The lava spine that developed after the 1902 eruption of Mount Pelée (from Types of volcanic eruptions) -
The high initial temperatures of silicate lavas mean that they emit visible light before cooling. (from Volcanism) -
Diagram of a Submarine eruption. (key: 1. Water vapor cloud 2. Water 3. Stratum 4. Lava flow 5. Magma conduit 6. Magma chamber 7. Dike 8. Pillow lava) Click to enlarge. (from Types of volcanic eruptions) -
Location of Mount Pinatubo, showing area over which ash from the 1991 eruption fell. (from Timeline of volcanism on Earth) -
Satellite animation of the initial ash plume and shockwave of the 2022 Hunga Tonga–Hunga Ha’apai eruption and tsunami. The massive explosive eruption was hundreds of times more powerful than the atomic bomb dropped on Hiroshima. (from Volcanism) -
Diagram of a Vulcanian eruption. (key: 1. Ash plume 2. Lapilli 3. Lava fountain 4. Volcanic ash rain 5. Volcanic bomb 6. Lava flow 7. Layers of lava and ash 8. Stratum 9. Sill 10. Magma conduit 11. Magma chamber 12. Dike) Click for larger version. (from Types of volcanic eruptions) -
Phreatic explosion captured at the Main Crater of Taal Volcano in January 2020, from an installed IP camera of the Philippine Institute of Volcanology and Seismology (PHIVOLCS) monitoring the volcano. (from Decade Volcanoes) -
Diagram of a Hawaiian eruption. (key: 1. Ash plume 2. Lava fountain 3. Crater 4. Lava lake 5. Fumaroles 6. Lava flow 7. Layers of lava and ash 8. Stratum 9. Sill 10. Magma conduit 11. Magma chamber 12. Dike) Click for larger version. (from Types of volcanic eruptions) -
TOMS sulfur dioxide from the June 15, 1991 eruption of Mount Pinatubo. (from Timeline of volcanism on Earth) -
VEI and ejecta volume correlation (from Timeline of volcanism on Earth) -
21 April 1990 eruptive column from Redoubt Volcano, as viewed to the west from the Kenai Peninsula (from Types of volcanic eruptions) -
Diagram showing the scale of VEI correlation with total ejecta volume (from Types of volcanic eruptions)
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Olympus Mons (Latin, "Mount Olympus"), located on the planet Mars, is the tallest known mountain in the Solar System. (from Volcanism) -
An example of the lava arcs formed during Strombolian activity. This image is of Stromboli itself. (from Types of volcanic eruptions) -
Satellite measurements of ash and aerosol emissions from Mount Pinatubo. (from Timeline of volcanism on Earth) -
A gentle, or effusive, volcanic eruption, in which liquid material (lava) gently flows from a vent, in this case in south-eastern Hawai’i island (from Volcanism)
Selected biography -
Harry Glicken (March 7, 1958 – June 3, 1991) was an American volcanologist. He researched Mount St. Helens in the United States before and after its 1980 eruption, and was very distraught about the death of volcanologist David A. Johnston, who was Glicken's mentor and supervisor in Spring 1980 at Mount St. Helens. Glicken was initially assigned to the USGS observation post in the weeks leading up to the eruption but was called away the night before the eruption.
In 1991, while conducting avalanche research on Mount Unzen in Japan, Glicken and fellow volcanologists Katia and Maurice Krafft were killed by a pyroclastic flow. His remains were found four days later and were cremated in accordance with his parents' request. Glicken and Johnston remain the only American volcanologists known to have died in volcanic eruptions.
Despite a long-term interest in working for the United States Geological Survey, Glicken never received a permanent post there because there was a hiring freeze for federal agencies when he graduated with his PhD. While conducting research from sponsorships granted by the National Science Foundation and other organizations, Glicken accrued expertise in the field of volcanic debris avalanches. He also wrote several major publications on the topic, including his doctoral dissertation based on his research at Mount St. Helens titled "Rockslide-debris Avalanche of May 18, 1980, Mount St. Helens Volcano, Washington" that initiated widespread interest in the phenomenon. (Full article...)
Selected picture
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View of the summit fissure created by the explosive 1886 eruption of Mount Tarawera in New Zealand. Deteriorating scoria cliffs surround the rift.
Selected quote
"Is this volcano active?"
— Tourist on Mount Etna, after being reprimanded for camping out at the base of a dangerous volcanic vent, 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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