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A caldera is a large cauldron-like hollow that forms shortly after the emptying of a magma chamber in a volcano eruption. An eruption that ejects large volumes of magma over a short period of time can cause significant detriment to the structural integrity of such a chamber, greatly diminishing its capacity to support its own roof, and any substrate or rock resting above. The ground surface then collapses into the emptied or partially emptied magma chamber, leaving a large depression at the surface. Although sometimes described as a crater, the feature is actually a type of sinkhole, as it is formed through subsidence and collapse rather than an explosion or impact. Compared to the thousands of volcanic eruptions that occur over the course of a century, the formation of a caldera is a rare event, occurring only a few times within a given window of 100 years. Only seven caldera-forming collapses are known to have occurred between 1911 and 2016. More recently, a caldera collapse occurred at Kīlauea, Hawaii in 2018.
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.
Rangitoto Island is a volcanic island in the Hauraki Gulf near Auckland, New Zealand. The 5.5 km (3.4 mi) wide island is a symmetrical shield volcano cone capped by central scoria cones, reaching a height of 260 m (850 ft). Rangitoto is the youngest and largest of the approximately 50 volcanoes of the Auckland volcanic field, having erupted in two phases about 1450 CE and 1500 CE and covering an area of 2,311 ha. It is separated from the mainland of Auckland's North Shore by the Rangitoto Channel. Since World War II, it has been linked by a causeway to the much older, non-volcanic Motutapu Island.
Volcanic cones are among the simplest volcanic landforms. They are built by ejecta from a volcanic vent, piling up around the vent in the shape of a cone with a central crater. Volcanic cones are of different types, depending upon the nature and size of the fragments ejected during the eruption. Types of volcanic cones include stratocones, spatter cones, tuff cones, and cinder cones.
A shield volcano is a type of volcano named for its low profile, resembling a shield lying on the ground. It is formed by the eruption of highly fluid lava, which travels farther and forms thinner flows than the more viscous lava erupted from a stratovolcano. Repeated eruptions result in the steady accumulation of broad sheets of lava, building up the shield volcano's distinctive form.
Parícutin is a cinder cone volcano located in the Mexican state of Michoacán, near the city of Uruapan and about 322 kilometers (200 mi) west of Mexico City. The volcano surged suddenly from the cornfield of local farmer Dionisio Pulido in 1943, attracting both popular and scientific attention.
The Cumbre Vieja is an active volcanic ridge on the island of La Palma in the Canary Islands, Spain. The spine of Cumbre Vieja trends in an approximate north–south direction, comprising the southern half of La Palma, with both summit ridge and flanks pockmarked by dozens of craters and cones. The latest eruption began on 19 September 2021 in a forested area of Las Manchas locality known as Cabeza de Vaca. Voluminous lava flows quickly reached populated areas downslope, fanning out across settlements and banana plantations, destroying thousands of buildings and ultimately pouring over steep cliffs into the ocean to enlarge the island at several locations. The volcano went quiet on 13 December 2021, and on 25 December 2021, the local government declared the eruption to be over.
The Auckland volcanic field is an area of monogenetic volcanoes covered by much of the metropolitan area of Auckland, New Zealand's largest city, located in the North Island. The approximately 53 volcanoes in the field have produced a diverse array of maars, tuff rings, scoria cones, and lava flows. With the exception of Rangitoto, no volcano has erupted more than once, but the other eruptions lasted for various periods ranging from a few weeks to several years. Rangitoto erupted several times and recently twice; in an eruption that occurred about 600 years ago, followed by a second eruption approximately 50 years later. The field is fuelled entirely by basaltic magma, unlike the explosive subduction-driven volcanism in the central North Island, such as at Mount Ruapehu and Lake Taupō.
A volcanic field or crater row is an area of Earth's crust that is prone to localized volcanic activity. The type and number of volcanoes required to be called a "field" is not well-defined. Volcanic fields usually consist of clusters of up to 100 volcanoes such as cinder cones. Lava flows may also occur. They may occur as a monogenetic volcanic field or a polygenetic volcanic field.
An active volcano is a volcano that has erupted during the Holocene, is currently erupting, or has the potential to erupt in the future. A volcano that is not currently erupting but could erupt in the future is known as a dormant volcano. Volcanoes that will not erupt again are known as extinct volcanoes.
El Jorullo is a cinder cone volcano in Michoacán, central Mexico, on the southwest slope of the central plateau, 33 miles southeast of Uruapan in an area known as the Michoacán-Guanajuato volcanic field. It is about 6 miles (9.7 km) east-northeast of La Huacana. Its current elevation is 4,360 ft (1,329 m). El Jorullo has four smaller cinder cones which have grown from its flanks. The vents of El Jorullo are aligned in a northeast to southwest direction. Lava from these vents cover nine square km around the volcano. Later eruptions produced lavas that had higher silica contents making them thicker than the earlier basalts and basaltic andesite lavas. El Jorullo's crater is about 1,300 by 1,640 feet wide and 490 feet (150 m) deep.
In volcanology, a Strombolian eruption is a type of volcanic eruption with relatively mild blasts, typically having a Volcanic Explosivity Index of 1 or 2. Strombolian eruptions consist of ejection of incandescent cinders, lapilli, and volcanic bombs, to altitudes of tens to a few hundreds of metres. The eruptions are small to medium in volume, with sporadic violence. This type of eruption is named for the Italian volcano Stromboli.
A complex volcano, also called a compound volcano or a volcanic complex, is a mixed landform consisting of related volcanic centers and their associated lava flows and pyroclastic rock. They may form due to changes in eruptive habit or in the location of the principal vent area on a particular volcano. Stratovolcanoes can also form a large caldera that gets filled in by a lava dome, or else multiple small cinder cones, lava domes and craters may develop on the caldera's rim.
Teneguía is a monogenetic cinder cone – a volcanic vent which has been active once and has had further seismic activity. It is situated on the island of La Palma, one of the Canary Islands, and is located at the southern end of the sub-aerial section of the Cumbre Vieja volcano, of which Teneguía is just one of several vents.
A cinder cone is a steep conical hill of loose pyroclastic fragments, such as volcanic clinkers, volcanic ash, or scoria that has been built around a volcanic vent. The pyroclastic fragments are formed by explosive eruptions or lava fountains from a single, typically cylindrical, vent. As the gas-charged lava is blown violently into the air, it breaks into small fragments that solidify and fall as either cinders, clinkers, or scoria around the vent to form a cone that often is symmetrical; with slopes between 30 and 40°; and a nearly circular ground plan. Most cinder cones have a bowl-shaped crater at the summit.
A polygenetic volcanic field is a group of polygenetic volcanoes, each of which erupts repeatedly, in contrast with monogenetic volcanoes, each of which erupts only once. Polygenetic volcanic fields generally occur where there is a high-level magma chamber. These volcanic fields may show lithological discontinuities due to major changes in magma chemistry, volcanotectonic events, or long erosional intervals, and may last over 10 million years.
The volcanism of New Zealand has been responsible for many of the country's geographical features, especially in the North Island and the country's outlying islands.
The 2011–2012 El Hierro eruption occurred just off the island of El Hierro, the smallest and farthest south and west of the Canary Islands, in the Atlantic Ocean off the coast of Africa. The island is also the youngest in the volcanic chain. The October 2011 – March 2012 eruption was underwater, with a fissure of vents located approximately 2 kilometres to the south of the fishing village of La Restinga on the southern coast of the island. Increased seismicity in June 2012 to the north-west of the vent did not result in another phase of eruptive activity. Until the 2021 La Palma eruption, which started on 19 September 2021, this was the last volcanic eruption in Spain.
Michoacán–Guanajuato volcanic field is located in the Michoacán and Guanajuato states of central Mexico. It is a volcanic field that takes the form of a large cinder cone field, with numerous shield volcanoes and maars. Pico de Tancítaro is the highest peak.
An eruption at the Cumbre Vieja volcanic ridge, comprising the southern half of the Spanish island of La Palma in the Canary Islands, took place between 19 September and 13 December 2021. It was the first volcanic eruption on the island since the eruption of Teneguía in 1971. At 85 days, it is the longest known and the most damaging volcanic eruption on La Palma since records began. The total damage caused by the volcano amounts up to 843 million euros.
References
- 1 2 Michelfelder, Gary S.; Horkley, Lawrence K.; Reinier, Clayton; Hudson, Sarah (2021). "A preliminary assessment of olivine phenocrysts from the monogenetic basalt of the McCartys Flow, Zuni-Bandera Volcanic Field, New Mexico" (PDF). New Mexico Geological Society Field Conference Series. 72: 141–152. Retrieved 24 August 2021.
- ↑ Walker, George P. L. (2000). "Basaltic volcanoes and volcanic systems". In Sigurdsson, Haraldur (ed.). Encyclopedia of Volcanoes.
- ↑ McGee, Lucy E.; Smith, Ian E. M.; Millet, Marc-Alban; Handley, Heather K.; Lindsay, Jan M. (October 2013). "Asthenospheric Control of Melting Processes in a Monogenetic Basaltic System: a Case Study of the Auckland Volcanic Field, New Zealand". Journal of Petrology. 54 (10): 2125–2153. doi: 10.1093/petrology/egt043 .
- ↑ Bischoff, Alan; Nicol, Andrew; Cole, Jim; Gravley, Darren (2019-10-25). "Stratigraphy of Architectural Elements of a Buried Monogenetic Volcanic System". Open Geosciences. 11 (1): 581–616. Bibcode:2019OGeo...11...48B. doi: 10.1515/geo-2019-0048 .
- ↑ Burns, F.; Cole, M.; Vaccaro, W.; Alonso Cótchico, M.; Melián, G.; Asensio-Ramos, M.; Padron, E.; Hernandez Perez, P.A.; Perez, N.M. (2017). Monitoring diffuse degassing in monogentic volcanic field during a quiescent period: the case of Cumbre Vieja (La Palma,Canary Islands, Spain). American Geophysical Union, Fall Meeting 2017. Bibcode:2017AGUFM.V23C0495B . Retrieved 5 October 2023.
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