A report on Volcano

Bromo volcano in Indonesia. This country has more than 130 active volcanoes, one of which is a supervolcano, making Indonesia the country with the most active volcanoes in the world.
Cordillera de Apaneca volcanic range in El Salvador. The country is home to 170 volcanoes, 23 which are active, including two calderas, one being a supervolcano. El Salvador has earned the epithets endearment La Tierra de Soberbios Volcanes, (The Land of Magnificent Volcanoes).
Sabancaya volcano erupting, Peru in 2017
Cleveland Volcano in the Aleutian Islands of Alaska photographed from the International Space Station, May 2006
An eruption of Mount Pinatubo on June 12, 1991, three days before its climactic eruption
Fountain of lava erupting from a volcanic cone in Hawaii, 1983
Aerial view of the Barren Island, Andaman Islands, India, during an eruption in 1995. It is the only active volcano in South Asia.
Map showing the divergent plate boundaries (oceanic spreading ridges) and recent sub-aerial volcanoes (mostly at convergent boundaries)
Lakagigar fissure vent in Iceland, the source of the major world climate alteration of 1783–84, has a chain of volcanic cones along its length.
Skjaldbreiður, a shield volcano whose name means "broad shield"
Izalco volcano, the youngest volcano in El Salvador. Izalco erupted almost continuously from 1770 (when it formed) to 1958, earning it the nickname of "Lighthouse of the Pacific".
Cross-section through a stratovolcano (vertical scale is exaggerated):
Satellite images of the 15 January 2022 eruption of Hunga Tonga-Hunga Haʻapai
Pāhoehoe lava flow on Hawaii. The picture shows overflows of a main lava channel.
The Stromboli stratovolcano off the coast of Sicily has erupted continuously for thousands of years, giving rise to its nickname "Lighthouse of the Mediterranean"
Columnar-jointed basalt lava erupted from a volcano, South Penghu Marine National Park in Taiwan
Light-microscope image of tuff as seen in thin section (long dimension is several mm): The curved shapes of altered glass shards (ash fragments) are well preserved, although the glass is partly altered. The shapes were formed around bubbles of expanding, water-rich gas.
Fresco with Mount Vesuvius behind Bacchus and Agathodaemon, as seen in Pompeii's House of the Centenary
Narcondam Island, India, is classified as a dormant volcano by the Geological Survey of India
Fourpeaked volcano, Alaska, in September 2006 after being thought extinct for over 10,000 years
Mount Rinjani eruption in 1994, in Lombok, Indonesia
Shiprock in New Mexico, US
Capulin Volcano National Monument in New Mexico, US
Koryaksky volcano towering over Petropavlovsk-Kamchatsky on Kamchatka Peninsula, Far Eastern Russia
Schematic of volcano injection of aerosols and gases
Solar radiation graph 1958–2008, showing how the radiation is reduced after major volcanic eruptions
Sulfur dioxide concentration over the Sierra Negra Volcano, Galapagos Islands, during an eruption in October 2005
Comparison of major United States supereruptions (VEI 7 and 8) with major historical volcanic eruptions in the 19th and 20th century. From left to right: Yellowstone 2.1 Ma, Yellowstone 1.3 Ma, Long Valley 6.26 Ma, Yellowstone 0.64 Ma . 19th century eruptions: Tambora 1815, Krakatoa 1883. 20th century eruptions: Novarupta 1912, St. Helens 1980, Pinatubo 1991.
The Tvashtar volcano erupts a plume 330 km (205 mi) above the surface of Jupiter's moon Io.
Olympus Mons (Latin, "Mount Olympus"), located on the planet Mars, is the tallest known mountain in the Solar System.

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.

- Volcano
Bromo volcano in Indonesia. This country has more than 130 active volcanoes, one of which is a supervolcano, making Indonesia the country with the most active volcanoes in the world.

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Overall
Mount Mazama's eruption timeline, an example of caldera formation

Caldera

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Large cauldron-like hollow that forms shortly after the emptying of a magma chamber in a volcanic eruption.

Large cauldron-like hollow that forms shortly after the emptying of a magma chamber in a volcanic eruption.

Mount Mazama's eruption timeline, an example of caldera formation
Animation of analogue experiment showing the origin of the volcanic caldera in box filled with flour.
Landsat image of Lake Toba, on the island of Sumatra, Indonesia (100 km/62 mi long and 30 km/19 mi wide, one of the world's largest calderas). A resurgent dome formed the island of Samosir.
Caldera formation under water.
Valle Caldera, New Mexico
Satellite photograph of the summit caldera on Fernandina Island in the Galápagos archipelago.
Oblique aerial photo of Nemrut Caldera, Van Lake, Eastern Turkey
Sollipulli Caldera, located in central Chile near the border with Argentina, filled with ice. The volcano is in the southern Andes Mountains within Chile's Parque Nacional Villarica.

A collapse is triggered by the emptying of the magma chamber beneath the volcano, sometimes as the result of a large explosive volcanic eruption (see Tambora in 1815), but also during effusive eruptions on the flanks of a volcano (see Piton de la Fournaise in 2007) or in a connected fissure system (see Bárðarbunga in 2014–2015).

10 m lava fountain in Hawaii, United States

Lava

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Molten or partially molten rock that has been expelled from the interior of a terrestrial planet (such as Earth) or a moon onto its surface.

Molten or partially molten rock that has been expelled from the interior of a terrestrial planet (such as Earth) or a moon onto its surface.

10 m lava fountain in Hawaii, United States
Lava flow during a rift eruption at Krafla, Iceland in 1984
Pāhoehoe and ʻaʻā lava flows side by side in Hawaii, September 2007
Toes of a pāhoehoe advance across a road in Kalapana on the east rift zone of Kīlauea Volcano in Hawaii, United States
Columnar jointing in Giant's Causeway in Northern Ireland
Lava entering the sea to expand the big island of Hawaii, Hawaii Volcanoes National Park
Lava enters the Pacific at the Big Island of Hawaii
Glowing aā flow front advancing over pāhoehoe on the coastal plain of Kilauea in Hawaii, United States
Pāhoehoe lava from Kīlauea volcano, Hawaii, United States
Block lava at Fantastic Lava Beds near Cinder Cone in Lassen Volcanic National Park
Pillow lava on the ocean floor near Hawaii
Arenal Volcano, Costa Rica, is a stratovolcano.
A forested lava dome in the midst of the Valle Grande, the largest meadow in the Valles Caldera National Preserve, New Mexico, United States
Shiprock, New Mexico, United States: a volcanic neck in the distance, with a radiating dike on its south side
450 m-high lava fountain at Kilauea
Lava can easily destroy entire towns. This picture shows one of over 100 houses destroyed by the lava flow in Kalapana, Hawaii, United States, in 1990.

Lava may be erupted at a volcano or through a fracture in the crust, on land or underwater, usually at temperatures from 800 to 1200 C. The volcanic rock resulting from subsequent cooling is also often called lava.

Lava flow on Hawaii. Lava is the extrusive equivalent of magma.

Magma

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Molten or semi-molten natural material from which all igneous rocks are formed.

Molten or semi-molten natural material from which all igneous rocks are formed.

Lava flow on Hawaii. Lava is the extrusive equivalent of magma.
Phase diagram for the diopside-anorthite system
Schematic diagrams showing the principles behind fractional crystallisation in a magma. While cooling, the magma evolves in composition because different minerals crystallize from the melt. 1: olivine crystallizes; 2: olivine and pyroxene crystallize; 3: pyroxene and plagioclase crystallize; 4: plagioclase crystallizes. At the bottom of the magma reservoir, a cumulate rock forms.
A single silica tetrahedron
Two silica tetrahedra joined by a bridging oxygen ion (tinted pink)

Following its ascent through the crust, magma may feed a volcano and be extruded as lava, or it may solidify underground to form an intrusion, such as a dike, a sill, a laccolith, a pluton, or a batholith.

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

Types of volcanic eruptions

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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
Diagram showing the scale of VEI correlation with total ejecta volume
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) [[:File:Hawaiian Eruption-numbers.svg|Click for larger version]].
Ropey pahoehoe lava from Kilauea, Hawaii
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) [[:File:Strombolian Eruption-numbers.svg|Click for larger version]].
An example of the lava arcs formed during Strombolian activity. This image is of Stromboli itself.
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) [[:File:Vulcanian Eruption-numbers.svg|Click for larger version.]]
Tavurvur in Papua New Guinea erupting
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) [[:File:Pelean Eruption-numbers.svg|Click for larger version]].
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) [[:File:Plinian Eruption-numbers.svg|Click for larger version]].
21 April 1990 eruptive column from Redoubt Volcano, as viewed to the west from the Kenai Peninsula
Lahar flows from the 1985 eruption of Nevado del Ruiz, which totally destroyed Armero in Colombia
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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) [[:File:Surtseyan Eruption-numbers.svg|Click for larger version]].
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) [[:File:Submarine Eruption-numbers.svg|Click to enlarge]].
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) [[:File:Subglacial Eruption-numbers.svg|Click for larger version]].
Herðubreið, a tuya in Iceland
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)
Pyroclastic flows at Mayon Volcano, Philippines, 1984
The lava spine that developed after the 1902 eruption of Mount Pelée
Mount Lamington following the devastating 1951 eruption
Surtsey, erupting 13 days after breaching the water. A tuff ring surrounds the vent.
The fissure formed by the 1886 eruption of Mount Tarawera, an example of a fracture zone eruption

Several types of volcanic eruptions—during which lava, tephra (ash, lapilli, volcanic bombs and volcanic blocks), and assorted gases are expelled from a volcanic vent or fissure—have been distinguished by volcanologists.

Pyroclastic flows sweep down the flanks of Mayon Volcano, Philippines, in 1984

Pyroclastic flow

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Pyroclastic flows sweep down the flanks of Mayon Volcano, Philippines, in 1984
Pyroclastic rocks from the Bishop tuff; uncompressed with pumice (on left), compressed with fiamme (on right)
Building remnant in Francisco Leon destroyed by pyroclastic surges and flows during eruption of El Chichon volcano in Mexico in 1982. Reinforcement rods in the concrete were bent in the direction of the flow.
A scientist examines pumice blocks at the edge of a pyroclastic flow deposit from Mount St. Helens
The casts of some victims in the so-called "Garden of the Fugitives", Pompeii

A pyroclastic flow (also known as a pyroclastic density current or a pyroclastic cloud) is a fast-moving current of hot gas and volcanic matter (collectively known as tephra) that flows along the ground away from a volcano at average speeds of 100 km/h but is capable of reaching speeds up to 700 km/h.

Diagram showing a cross section through the Earth's lithosphere (in yellow) with magma rising from the mantle (in red). Lower diagram illustrates a hotspot track caused by the lithosphere's movement.

Hotspot (geology)

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Diagram showing a cross section through the Earth's lithosphere (in yellow) with magma rising from the mantle (in red). Lower diagram illustrates a hotspot track caused by the lithosphere's movement.
Schematic diagram showing the physical processes inside the Earth that lead to the generation of magma. Partial melting begins above the fusion point.
Over millions of years, the Pacific Plate has moved over the Hawaii hotspot, creating a trail of underwater mountains that stretches across the Pacific
Kilauea is the most active shield volcano in the world. The volcano erupted nonstop from 1983 to 2018 and it is part of the Hawaiian–Emperor seamount chain.
Mauna Loa is a large shield volcano. Its last eruption was in 1984 and it is part of the Hawaiian–Emperor seamount chain.
Bowie Seamount is a dormant submarine volcano and it is part of the Kodiak-Bowie Seamount chain.
Axial Seamount is the youngest seamount of the Cobb–Eickelberg Seamount chain. Its last eruption was on 6 April 2011.
Mauna Kea is the tallest volcano in the Hawaiian–Emperor seamount chain. It is dormant and it has cinder cones growing on the volcano.
Hualalai is a massive shield volcano in the Hawaiian–Emperor seamount chain. Its last eruption was in 1801.
An example of mantle plume locations suggested by one recent group. Figure from Foulger (2010).
Distribution of hotspots in the list to the left, with the numbers corresponding to those in the list. The Afar hotspot (29) is misplaced.
Over millions of years, the Pacific Plate has moved over the Bowie hotspot, creating the Kodiak-Bowie Seamount chain in the Gulf of Alaska

In geology, hotspots (or hot spots) are volcanic locales thought to be fed by underlying mantle that is anomalously hot compared with the surrounding mantle.

Rhyolitic lava dome of Chaitén Volcano during its 2008–2010 eruption

Lava dome

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Rhyolitic lava dome of Chaitén Volcano during its 2008–2010 eruption
One of the Inyo Craters, an example of a rhyolite dome
Nea Kameni seen from Thera, Santorini
Lava domes in the crater of Mount St. Helens
The bulging cryptodome of Mt. St. Helens on April 27, 1980
Soufrière Hills lava spine before the 1997 eruption
Chao dacite coulée flow-domes (left center), northern Chile, viewed from Landsat 8

In volcanology, a lava dome is a circular mound-shaped protrusion resulting from the slow extrusion of viscous lava from a volcano.

Volcanic eruptions of lava are major sources of igneous rocks. (Mayon volcano in the Philippines, erupting in 2009)

Igneous rock

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One of the three main rock types, the others being sedimentary and metamorphic.

One of the three main rock types, the others being sedimentary and metamorphic.

Volcanic eruptions of lava are major sources of igneous rocks. (Mayon volcano in the Philippines, erupting in 2009)
Natural columns of igneous rock separated from each other by columnar joints, in Madeira
Formation of igneous rock
Basic types of intrusions:
Extrusive igneous rock is made from lava released by volcanoes
Sample of basalt (an extrusive igneous rock), found in Massachusetts
Close-up of granite (an intrusive igneous rock) exposed in Chennai, India
Gabbro specimen showing phaneritic texture, from Rock Creek Canyon, eastern Sierra Nevada, California
Basic classification scheme for igneous rocks based on their mineral composition. If the approximate volume fractions of minerals in the rock are known, the rock name and silica content can be read off the diagram. This is not an exact method, because the classification of igneous rocks also depends on other components, yet in most cases it is a good first guess.
Total alkali versus silica classification scheme (TAS) as proposed in Le Maitre's 2002 Igneous Rocks – A classification and glossary of terms Blue area is roughly where alkaline rocks plot; yellow area is where subalkaline rocks plot.
AFM ternary diagram showing the relative proportions of Na2O + K2O (A for Alkali earth metals), FeO + Fe2O3 (F), and MgO (M) with arrows showing the path of chemical variation in tholeiitic and calc-alkaline series magmas
Schematic diagrams showing the principles behind fractional crystallisation in a magma. While cooling, the magma evolves in composition because different minerals crystallize from the melt. 1: olivine crystallizes; 2: olivine and pyroxene crystallize; 3: pyroxene and plagioclase crystallize; 4: plagioclase crystallizes. At the bottom of the magma reservoir, a cumulate rock forms.
Kanaga volcano in the Aleutian Islands with a 1906 lava flow in the foreground
A "skylight" hole, about {{cvt|6|m}} across, in a solidified lava crust reveals molten lava below (flowing towards the top right) in an eruption of Kīlauea in Hawaii
Devils Tower, an eroded laccolith in the Black Hills of Wyoming
A cascade of molten lava flowing into Aloi Crater during the 1969-1971 Mauna Ulu eruption of Kilauea volcano
Columnar jointing in the Alcantara Gorge, Sicily
A laccolith of granite (light-coloured) that was intruded into older sedimentary rocks (dark-coloured) at Cuernos del Paine, Torres del Paine National Park, Chile
An igneous intrusion cut by a pegmatite dike, which in turn is cut by a dolerite dike

Eruptions of volcanoes into air are termed subaerial, whereas those occurring underneath the ocean are termed submarine.

Graph summarizing the eruptions of Kïlauea during the past 200 years. The Pu‘u ‘Ö‘ö- Kupaianaha eruption has continued into the 21st century. Information is sketchy for eruptions before 1823, when the first missionaries arrived on the Island of Hawai‘i. The total duration of eruptive activity in a given year, shown by the length of the vertical bar, may be for a single eruption or a combination of several separate eruptions.

Kīlauea

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Active shield volcano in the Hawaiian Islands.

Active shield volcano in the Hawaiian Islands.

Graph summarizing the eruptions of Kïlauea during the past 200 years. The Pu‘u ‘Ö‘ö- Kupaianaha eruption has continued into the 21st century. Information is sketchy for eruptions before 1823, when the first missionaries arrived on the Island of Hawai‘i. The total duration of eruptive activity in a given year, shown by the length of the vertical bar, may be for a single eruption or a combination of several separate eruptions.
Rainbow and volcanic ash with sulfur dioxide emissions from Halemaʻumaʻu
Painting of the 1891 eruption
The Mauna Ulu eruption of 1969 generated a 300 m-high lava fountain
Puʻu ʻŌʻō at dusk, June 1983
Lava from a fissure slowly advanced to the northeast on Hoʻokupu Street in Leilani Estates subdivision (May 5, 2018)
Kilauea Volcano Fissure 8 captured on May 3rd, 2019
Two views of Halemaʻumaʻu from roughly the same vantage point. At left is the view from 2008, with a distinct gas plume from the Overlook vent, the location of what would become a long-lived lava lake. At right is a view of Halemaʻumaʻu after the eruptive events of 2018, showing the collapsed crater.
View of the eruption from outside the summit caldera, on December 20, 2020
Ōhia (Metrosideros polymorpha) growing on a barren lava field dating from 1986, formerly the village of Kalapana, Hawaii. The myrtle in this picture, taken in 2009, may have since been covered over—fresh flows in 2010 partially re-covered the area.
The 'amakihi (Chlorodrepanis virens) is one of the many birds that live on the volcano's flanks.
A view from Kīlauea's eastern rift zone captured during a USGS expedition.
View from the edge of Kilauea Iki: across the caldera, Halemaʻumaʻu is emitting fume on the left side of the caldera, while Mauna Loa towers above in the background

Historically, it is the most active of the five volcanoes that together form Hawaii island.

Mauna Loa, a shield volcano in Hawaii

Shield volcano

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Mauna Loa, a shield volcano in Hawaii
An Ancient Greek warrior's shield–its circular shape and gently sloping surface, with a central raised area, is a shape shared by many shield volcanoes
Skjaldbreiður is a shield volcano in Iceland, whose name means broad shield in Icelandic.
Scaled image showing Olympus Mons, top, and the Hawaiian island chain, bottom. Martian volcanoes are far larger than those found on Earth.
{{okina}}A{{okina}}a advances over solidified pāhoehoe on Kīlauea, Hawai{{okina}}i
A pāhoehoe lava fountain on Kīlauea erupts
A lava lake in the caldera of Erta Ale, an active shield volcano in Ethiopia
Pāhoehoe flows enter the Pacific Ocean on Hawai{{okina}}i island
Puʻu ʻŌʻō, a parasitic cinder cone on Kīlauea, lava fountaining at dusk in June 1983, near the start of its eruptive cycle
Nāhuku, a famous lava tube on Hawai{{okina}}i island, now a tourist attraction in the Hawaiʻi Volcanoes National Park

A shield volcano is a type of volcano named for its low profile, resembling a warrior's shield lying on the ground.