query: where are volcanoes located in relation to a subduction zone

pos: Volcanic arc plate and introduces it to the mantle. Here the mantle melts and forms magma at depth under the overriding plate. The magma ascends to form an arc of volcanoes parallel to the subduction zone. These should not be confused with hotspot volcanic chains, where volcanoes often form one after another in the middle of a tectonic plate, as the plate moves over the hotspot, and so the volcanoes progress in age from one end of the chain to the other. The Hawaiian Islands form a typical hotspot chain; the older islands (tens of millions of years old) to the northwest

pos: Volcanic arc plate and introduces it to the mantle. Here the mantle melts and forms magma at depth under the overriding plate. The magma ascends to form an arc of volcanoes parallel to the subduction zone. These should not be confused with hotspot volcanic chains, where volcanoes often form one after another in the middle of a tectonic plate, as the plate moves over the hotspot, and so the volcanoes progress in age from one end of the chain to the other. The Hawaiian Islands form a typical hotspot chain; the older islands (tens of millions of years old) to the northwest

neg: Ring of Fire Bali, Flores, and Timor. Bolivia hosts numerous active and extinct volcanoes across its territory. The active volcanoes are located in western Bolivia where they make up the Cordillera Occidental, the western limit of the Altiplano plateau. Many of the active volcanoes are international mountains shared with Chile. All Cenozoic volcanoes of Bolivia are part of the Central Volcanic Zone (CVZ) of the Andean Volcanic Belt that results due to processes involved in the subduction of the Nazca Plate under the South American Plate. The Central Volcanic Zone is a major upper Cenozoic volcanic province. Apart from Andean volcanoes, the geology

neg: Cascadia subduction zone volcanoes above the subduction zone include: Cascadia subduction zone The Cascadia subduction zone (also referred to as the Cascadia fault) is a convergent plate boundary that stretches from northern Vancouver Island in Canada to Northern California in the United States. It is a very long, sloping subduction zone where the Explorer, Juan de Fuca, and Gorda plates move to the east and slide below the much larger mostly continental North American Plate. The zone varies in width and lies offshore of British Columbia, Washington, Oregon, and Northern California. The Explorer, Juan de Fuca, and Gorda plates are some of the

neg: Farallon Negro (volcano) volcanism persists to the present day. Farallon Negro is located in the border zone between the flat subduction zone and the zone of steeper subduction farther north that has generated the Central Volcanic Zone. A number of volcanoes in this transitional zone are found on northwest trending lineaments; this includes Cerro Negro de Chorillos, Farallon Negro, Galan and Cerro Tuzgle. The Tucuman fault zone is located in the area. The basement in the Farallon Negro area of the Sierras Pampeanas are schists and gneisses of deep water origin with an intruded batholith of Ordovician-Silurian age. This plutonic activity coincided with

neg: Continental arc to the asthenosphere, where pressures and temperatures are much higher than the surface of earth. Under such conditions, the downgoing plate releases volatiles such as HO and CO, which cause partial melting of the above asthenosphere. This process can create relatively buoyant magma, which subsequently forms a series of volcanoes at the surface along the subduction zone. There are some researchers who argue that refertilization of arc lithospheric mantle may also be an important process associated with arc magmatism. Because the subduction zone (which is also the plate boundary) is generally an arc-shape, geologists named those volcanoes "volcanic arcs". A

neg: Cascade Volcanoes the subduction zone. At issue are the current estimates of plate configuration and rate of subduction, but based on the chemistry of these volcanoes, they are also subduction related and therefore part of the Cascade Volcanic Arc. The Cascade Volcanic Arc appears to be segmented; the central portion of the arc is the most active and the northern end least active. Lavas representing the earliest stage in the development of the Cascade Volcanic Arc mostly crop out south of the North Cascades proper, where uplift of the Cascade Range has been less, and a thicker blanket of Cascade Arc volcanic

neg: Volcanic belt often creates an orogenic zone with many volcanoes and earthquakes. In a sense, subduction zones are the opposite of divergent boundaries, areas where material rises up from the mantle and plates are moving apart. An example of a subduction-zone related volcanic belt is the Okhotsk-Chukotka Volcanic Belt in northeastern Eurasia, which is one of the largest subduction-zone related volcanic provinces in the world, stretching some 3200 km and comprising about 2 million km of volcanic and plutonic material. Volcanic belts may also be formed by hotspots, which is a location on the Earth's surface that has experienced active volcanism for

neg: Cerro Panizos by the subduction of the Nazca plate beneath the South America plate; magmas formed from the subduction process trigger the melting of the crust. The large calderas are located east of the main volcanic arc of the Central Volcanic Zone, Panizos being east of the main arc. Volcanism in the area is heavily dominated by calderic silicic volcanics with volumes of contrasting to less than andesites. The volcano is part of the so-called "Tin belt", a territory in the Andes where large tin mineral deposits are found in granitic and extrusive rocks, formed from sulfidation reactions involving the numerous volcanoes

neg: Mount Meager massif in the Cascade Arc, including rhyolites, dacites, andesites and basaltic andesites. Such rock types are produced by subduction zone volcanism indicating volcanism at Silverthrone and is probably related to subduction. If these two volcanoes are true Cascade Arc volcanoes, the massif is not the northernmost volcano of the Garibaldi Belt or the Cascade Arc. Volcanism in the Cascade Volcanic Arc is caused by subduction of the Juan de Fuca Plate under the North American Plate at the . This is a long fault zone lying off the from Northern California to southwestern British Columbia. The plates move at a relative

neg: Caroline Plate active subduction zone as indicated by the lack of active volcanoes. The Caroline-Pacific boundary is a complex, evolving system partly and potentially developing into a subduction zone. The south-east boundary, along the Manus Trench, is a convergent boundary, but in the absence of active volcanoes and earthquakes, is not a subduction zone at present. The Caroline Plate moves at velocities very close to those of the Pacific Plate and its age of formation and current status as an independent plate are uncertain. There is a very slow rate of spreading between the Caroline and Philippine plates but the Caroline Plate

neg: Viedma (volcano) of which are separated from the Austral Volcanic Zone and each other by gaps where no volcanic activity occurs. Unlike the Austral Volcanic Zone, volcanism in these other zones is controlled by the subduction of the Nazca Plate beneath the South American Plate. The Austral Volcanic Zone was identified as such in 1976, but some volcanoes were identified and localized later. Owing to their similar composition the three northerly volcanoes Lautaro, Viedma and Aguilera are grouped as the "northern Austral Volcanic Zone". Volcanism in the Austral Volcanic Zone is not well known before the Holocene; it is likely that a

neg: Mount Garibaldi the Cascade volcanoes, Mount Garibaldi has its origins in the Cascadia subduction zone—a long convergent plate boundary that stretches from mid-Vancouver Island to Northern California. The subduction zone separates the Juan de Fuca, Explorer, Gorda and North American Plates. Here, the oceanic crust of the Pacific Ocean sinks beneath North America at a rate of per year. Hot magma upwelling above the descending oceanic plate creates volcanoes, and each individual volcano erupts for a few million years. The subduction zone has existed for at least 37 million years, and has created a line of volcanoes called the Cascade Volcanic Arc

neg: Nevado de Longaví strong northsouth gradient among volcanoes of the Southern Volcanic Zone. The northernmost volcanoes are the highest and lie on thicker crust which causes their magmas to have a stronger crustal contribution. The output of the northernmost volcanoes is dominated by andesitic and more evolved magmas and they have the highest quantity of incompatible elements in their magmas. Southern volcanoes are lower, tend to erupt mafic magmas and are located west of the continental divide. Volcanism in areas of subduction is caused by the release of slab fluids from the subducting slab into the abovelying asthenospheric mantle. The injection of such

neg: Cascade Volcanoes County, Washington. The Cascade Volcanoes were formed by the subduction of the Juan de Fuca, Explorer and the Gorda Plate (remnants of the much larger Farallon Plate) under the North American Plate along the Cascadia subduction zone. This is a long fault, running off the coast of the Pacific Northwest from northern California to Vancouver Island, British Columbia. The plates move at a relative rate of over 0.4 inches (10 mm) per year at a somewhat oblique angle to the subduction zone. Because of the very large fault area, the Cascadia subduction zone can produce very large earthquakes, magnitude 9.0

neg: Cascade Volcanoes highest Cascade volcanoes: Cascade Volcanoes The Cascade Volcanoes (also known as the Cascade Volcanic Arc or the Cascade Arc) are a number of volcanoes in a volcanic arc in western North America, extending from southwestern British Columbia through Washington and Oregon to Northern California, a distance of well over . The arc has formed due to subduction along the Cascadia subduction zone. Although taking its name from the Cascade Range, this term is a geologic grouping rather than a geographic one, and the Cascade Volcanoes extend north into the Coast Mountains, past the Fraser River which is the northward limit

neg: Silverthrone Caldera subduction related. The Cascadia subduction zone is a long convergent plate boundary that separates the Juan de Fuca, Explorer, Gorda and North American Plates. Here, the oceanic crust of the Pacific Ocean sinks beneath North America at a rate of per year. Hot magma upwelling above the descending oceanic plate creates volcanoes, each of which erupts for a few million years. It is estimated that the subduction zone has existed for at least 37 million years; in that time it has created a line of volcanoes, called the Cascade Volcanic Arc, that stretches over along the subduction zone from Northern

neg: Cerro Panizos Cerro Panizos Panizos is a Late Miocene era caldera in the Santa Cruz department of Bolivia and the Jujuy Province of Argentina. It is part of the Altiplano-Puna volcanic complex of the Central Volcanic Zone in the Andes. 50 volcanoes active in recent times are found in the Central Volcanic Zone, and several major caldera complexes are situated in the area. The caldera is located in a logistically difficult area of the Andes. Panizos and the majority of these volcanoes are formed by the subduction of the oceanic Nazca Plate under the continental South American continental lithosphere. The caldera is

neg: Lascar (volcano) Volcanic Zone of which Lascar is a member of is the largest, covering parts of Peru, Bolivia, Argentina and Chile. The Central Volcanic Zone is located between two areas where subduction is shallower and volcanic activity is absent. In the Central Volcanic Zone, volcanism has been active for 120 million years, although it has undergone eastward migration during this time. Water released from the subducting plate triggers the formation of basaltic magmas that are then injected into the crust. About 122 volcanoes with Holocene eruptions exist in the Andean Volcanic Belt, including Ojos del Salado which with a height of

neg: Cascade Volcanoes Cascade Volcanoes The Cascade Volcanoes (also known as the Cascade Volcanic Arc or the Cascade Arc) are a number of volcanoes in a volcanic arc in western North America, extending from southwestern British Columbia through Washington and Oregon to Northern California, a distance of well over . The arc has formed due to subduction along the Cascadia subduction zone. Although taking its name from the Cascade Range, this term is a geologic grouping rather than a geographic one, and the Cascade Volcanoes extend north into the Coast Mountains, past the Fraser River which is the northward limit of the Cascade

neg: Subduction used to study them. Not surprisingly, the shallowest portions of subduction zones are known best. Subduction zones are strongly asymmetric for the first several hundred kilometers of their descent. They start to go down at oceanic trenches. Their descents are marked by inclined zones of earthquakes that dip away from the trench beneath the volcanoes and extend down to the 660-kilometer discontinuity. Subduction zones are defined by the inclined array of earthquakes known as the Wadati–Benioff zone after the two scientists who first identified this distinctive aspect. Subduction zone earthquakes occur at greater depths (up to 600 km) than elsewhere

neg: Mount Pelée found adrift from the island, unconscious. The event marked the only major volcanic disaster in the history of France and its overseas territories. Mount Pelée is the result of a typical subduction zone. The subduction formed the Lesser Antilles island arc, a curved chain of volcanoes approximately in length, between Puerto Rico and Venezuela, where the Caribbean Plate meets Atlantic oceanic crust belonging to the South American Plate. Other volcanoes in the island arc are also known for their volcanic activity, including Saint Vincent's La Soufrière, Guadeloupe's La Grande Soufriere volcano, Montserrat's Soufrière Hills, and the submarine volcano Kick 'em

neg: Volcanology of Venus with tectonic plates. In this type of volcano, the oceanic crust of one plate is sliding underneath the other in a subduction zone, together with an inflow of seawater, producing a gummier lava that restricts the exit of the gases, and for that reason, composite volcanoes tend to erupt more violently. On Venus, where there are no tectonic plates or seawater, volcanoes are mostly of the shield type . Nevertheless, the morphology of volcanoes on Venus is different: on Earth, shield volcanoes can be a few tens of kilometres wide and up to high in the case of Mauna Kea,

neg: Incapillo The Nazca plate subducts beneath the South America plate at a speed of per year in the area of the Central Volcanic Zone. The subduction results in volcanism along the occidental Cordillera east of the trench formed by the subduction. Incapillo is one of at least six different ignimbrite or caldera volcanoes that are part of the Central Volcanic Zone, in Chile, Bolivia and Argentina. The Central Volcanic Zone is one of four different volcanic arcs in the Andes. About west of Incapillo lies the Maricunga Belt, where volcanism started 27mya and involved phases of ignimbritic and stratovolcanic activity, including

neg: Jotabeche extreme southern end of the Central Volcanic Zone (CVZ) of the Andes. The Central Volcanic Zone is one of the four volcanic zones of the Andean Volcanic Belt. In this belt, ongoing subduction of the Antarctica plate, Nazca plate and its precursor the Farallon plate are responsible for ongoing volcanic activity, including such volcanoes as Villarica and Nevado del Ruiz. The Central Volcanic Zone sub-belt itself contains about 44 volcanic centres and over five major Quaternary caldera and ignimbrite complexes. The so-called Abancay deflection separates the CVZ in the north from the Peruvian flat subduction segment where no volcanic activity

neg: Lascar (volcano) is the highest volcano in the world. Many of these volcanoes are covered by snow and ice. A number of supervolcanoes exist in the Central Volcanic Zone, they are part of the Altiplano-Puna volcanic complex. The volcanism of Lascar relates to the subduction of the Nazca Plate beneath the South America Plate. The Central Andes contain many hundreds of volcanoes, extending over the countries of Argentina, Bolivia, Chile and Peru. In this remote territory, where eruptions are poorly recorded, many volcanoes are higher than . They are constructed on a crust that is between thick. Volcanic centres include calderas and

neg: Puerto Rico Trench obliquely at the trench while to the southeast, the South American Plate is being more directly subducted along the Lesser Antilles subduction zone. This subduction zone explains the presence of active volcanoes over the southeastern part of the Caribbean Sea. Volcanic activity is frequent along the island arc southeast from Puerto Rico to the coast of South America. Puerto Rico, the United States Virgin Islands, British Virgin Islands, and the Dominican Republic do not have active volcanoes; however, they are at risk from earthquakes and tsunamis. The Puerto Rico Trench is capable of producing earthquakes greater than magnitude 8.0. Knowledge

neg: Caribbean Plate a subduction zone, the Lesser Antilles subduction zone, where oceanic crust of the South American Plate is being subducted under the Caribbean Plate. Subduction forms the volcanic islands of the Lesser Antilles Volcanic Arc from the Virgin Islands in the north to the islands off the coast of Venezuela in the south. This boundary contains seventeen active volcanoes, most notably Soufriere Hills on Montserrat; Mount Pelée on Martinique; La Grande Soufrière on Guadeloupe; Soufrière Saint Vincent on Saint Vincent; and the submarine volcano Kick 'em Jenny which lies about 10 km north of Grenada. Large historical earthquakes in 1839 and

neg: Llullaillaco Zone is associated with the subduction of the Juan Fernandez Ridge, and the Patagonian volcanic gap between the Southern and the Austral Volcanic Zone is associated with the Chile Triple Junction. About 178 volcanoes are found in the Andes, 60 of which have been active in historical times. In addition, large calderas and monogenetic volcanoes exist in the Andes. Llullaillaco is part of the Central Volcanic Zone. At least 44 volcanic centres with historical activity and 18 large caldera-forming volcanoes have been identified in the Central Volcanic Zone. Volcanism in the Central Volcanic Zone mostly occurs on the Altiplano and

neg: Kermadec-Tonga subduction zone Kermadec-Tonga subduction zone The Kermadec-Tonga subduction zone is a convergent plate boundary that stretches from the North Island of New Zealand northward. The formation of the Kermadec and Tonga Plates started about 4–5 million years ago. Today, the eastern boundary of the Tonga Plate is one of the fastest subduction zones, with a rate up to 24 cm/yr. The trench formed between the Kermadec-Tonga and Pacific Plates is also home to the second deepest trench in the world, at about 10,800 m, as well as the longest chain of submerged volcanoes. The Kermadec-Tonga subduction zone is a convergent plate boundary

neg: Sollipulli separated by gaps where there is no volcanic activity and the subduction of the Pacific Ocean crust is shallower than in the volcanically active areas. About 60 volcanoes have erupted in historical time in the Andes, and 118 additional volcanic systems show evidence of Holocene eruptions. There are 60 volcanoes in the Southern Volcanic Zone; among these are Cerro Azul and Cerro Hudson, which experienced large eruptions in 1932 and 1991 that resulted in the emission of substantial volumes of ash. The volcanoes Llaima and Villarrica have been regularly active during recent history. Sollipulli is a stratovolcano, which has one

neg: Lastarria 2013. It is considered the 45th most dangerous volcano in Chile. Lastarria Lastarria is a volcano that lies on the border between Chile and Argentina. It is part of the Central Volcanic Zone, one of the four segments of the volcanic arc of the Andes. Several volcanoes are located in this chain of volcanoes, which is formed by subduction of the Nazca Plate beneath the South American Plate. Lastarria is formed by two volcanic edifices and one subsidiary lava flow field. There is no recorded eruptive activity, but the volcano displays vigorous fumarolic activity. It is located on top of

neg: Lastarria Lastarria Lastarria is a volcano that lies on the border between Chile and Argentina. It is part of the Central Volcanic Zone, one of the four segments of the volcanic arc of the Andes. Several volcanoes are located in this chain of volcanoes, which is formed by subduction of the Nazca Plate beneath the South American Plate. Lastarria is formed by two volcanic edifices and one subsidiary lava flow field. There is no recorded eruptive activity, but the volcano displays vigorous fumarolic activity. It is located on top of older volcanic rocks and features both andesite and dacite. Lastarria has

neg: Death Valley National Park continent was pushed against the oceanic plate under the Pacific Ocean, creating a subduction zone. A subduction zone is a type of contact between different crustal plates where heavier crust slides below lighter crust. Erupting volcanoes and uplifting mountains were created as a result, and the coastline was pushed to the west. The Sierran Arc started to form to the northwest from heat and pressure generated from subduction, and compressive forces caused thrust faults to develop. A long period of uplift and erosion was concurrent with and followed the above events, creating a major unconformity, which is a large gap

neg: Lesser Antilles Volcanic Arc Lesser Antilles Volcanic Arc The Lesser Antilles Volcanic Arc is a volcanic arc that forms the eastern boundary of the Caribbean Plate. It is part of a subduction zone, also known as the Lesser Antilles subduction zone, where the oceanic crust of the South American Plate is being subducted under the Caribbean Plate. This subduction process formed a number of volcanic islands, from the Virgin Islands in the north to the islands off the coast of Venezuela in the south. The Lesser Antilles Volcanic Arc includes nineteen 'active' volcanoes., notably Soufriere Hills on Montserrat; Mount Pelée on Martinique; La Grande

neg: Geography of British Columbia about 1300 years ago. The volcanoes are grouped into four volcanic belts with different tectonic settings. The Garibaldi Volcanic Belt is a north-south range of volcanoes in southwestern British Columbia. It is the northern extension of the Cascade Volcanic Arc in the United States and contains the most explosive young volcanoes in Canada. It was formed by subduction of the Juan de Fuca Plate at the Cascadia subduction zone. Eruption styles within the belt range from effusive to explosive, with compositions from basalt to rhyolite. The most recent major catastrophic eruption was the 2350 BP eruption of the Mount Meager

neg: Mount Price (British Columbia) in the Quaternary period. Clinker Peak, a breached volcanic crater on its western flank, was formed during a period of volcanic activity about 10,000 years ago. Oxidation of Price's volcanic rocks has given the mountain a red colour. Like other volcanoes in the Garibaldi Volcanic Belt, Mount Price formed as a result of subduction zone volcanism. As the Juan de Fuca Plate subducts under the North American Plate at the Cascadia subduction zone, it forms volcanoes and volcanic eruptions. Unlike most subduction zones worldwide, there is no deep oceanic trench present along the continental margin in Cascadia. There is also

neg: Nevado del Ruiz of the 204 Holocene-age volcanoes in South America. The Andean Volcanic Belt is produced by the eastward subduction of the oceanic Nazca Plate beneath the South American continental plate. As is the case for many subduction-zone volcanoes, Nevado del Ruiz can generate explosive Plinian eruptions with associated pyroclastic flows that can melt snow and glaciers near the summit, producing large and sometimes devastating lahars (mud and debris flows). Like many other Andean volcanoes, Nevado del Ruiz is a stratovolcano: a voluminous, roughly conical volcano consisting of many strata of hardened lava and tephra including volcanic ash. Its lavas are andesitic–dacitic

neg: Andagua volcanic field Peruvian flat-slab subduction area, where no recent volcanism is present. The volcanic field is located in the Western Cordillera, on thick crust. The main volcanic arc is located here, with a Wadati-Benioff zone deep. The arc is now long. A number of fault systems and orogenic events occurred in the area during the Cretaceous-Paleogene. Volcanic activity resulting in the formation of calderas in the Miocene and ores from hydrothermal activity. The volcanoes are constructed on Jurassic Yura Group sandstones and Pleistocene alluvium. The number of individual centres observed varies, roughly 121 lava domes and 46 pyroclastic cones, one of which,

neg: Mountain formation plate tectonics in the 1960s geosyncline theory was used to explain much mountain-building. There are four main types of mountains: volcanic, fold,residual, and block. A more detailed classification useful on a local scale predates plate tectonics and adds to these categories. Movements of tectonic plates create volcanoes along the plate boundaries, which erupt and form mountains. A "volcanic arc system" is a series of volcanoes that form near a subduction zone where the crust of a sinking oceanic plate melts and drags water down with the subducting crust. Most volcanoes occur in a band encircling the Pacific Ocean (the Pacific

neg: Hotspot (geology) of a major controversy in Earth science. Estimates for the number of hotspots postulated to be fed by mantle plumes have ranged from about 20 to several thousands, over the years, with most geologists considering a few tens to exist. Hawaii, Réunion, Yellowstone, Galápagos, and Iceland are some of the most active volcanic regions to which the hypothesis is applied. Most hotspot volcanoes are basaltic (e.g., Hawaii, Tahiti). As a result, they are less explosive than subduction zone volcanoes, in which water is trapped under the overriding plate. Where hotspots occur in continental regions, basaltic magma rises through the continental

neg: Tacora reach the surface. Subduction of the Nazca Plate beneath the South America Plate is responsible for the volcanism of the Andes. This volcanism does not occur along the entire strike of the Andes, but in three selected volcanic belts, the Northern Volcanic Zone, the Central Volcanic Zone and the Southern Volcanic Zone. A fourth volcanic zone, the Austral Volcanic Zone, lies south of the Southern Volcanic Zone. These volcanically active belts are separated by gaps where recent volcanism is absent and the subducting plate descends in a much shallower angle. Volcanoes of the Peruvian Central Volcanic Zone generally occur within

neg: Island arc Island arc Island arcs are long chains of active volcanoes with intense seismic activity found along convergent tectonic plate boundaries (such as the Ring of Fire). Most island arcs originate on oceanic crust and have resulted from the descent of the lithosphere into the mantle along the subduction zone. They are the principal way by which continental growth is achieved. Island arcs can either be active or inactive based on their seismicity and presence of volcanoes. Active arcs are ridges of recent volcanoes with an associated deep seismic zone. They also possess a distinct curved form, a chain of active

neg: Solimana (volcano) ; it has slowed down since the Oligocene. This subduction process is responsible for the formation of the Andes mountains in the region. Together with Sara Sara and Coropuna, Solimana is located on the northwestern end of the Central Volcanic Zone; no volcanism occurs farther north where the Nazca Plate subducts at a shallower angle than beneath the Central Volcanic Zone. Of these volcanoes, Solimana is considered to be the oldest and Coropuna the youngest. Solimana together with Ampato and Coropuna form the Cordillera Ampato. The basement dates back to the Precambrian-Paleozoic and is buried beneath several pre-Oligocene formations. The

neg: Slow earthquake determine where exactly the focus is located. Both methods find that LFEs are indeed triggered at the plate contact. The Cascadia subduction zone spans from northern California to about halfway up Vancouver Island and is where the Juan de Fuca, Explorer, and Gorda plates are overridden by North America. In the Cascadia subduction zone, LFEs are predominantly observed at the plate interface down-dip of the seismogenic zone. In the southern section of the subduction zone from latitudes 40°N to 41.8°N low frequency earthquakes occur at depths between 28–47 kilometers, whereas farther north near Vancouver Island the range contracts to approximately

neg: Pica gap Pica gap Pica gap is a segment in the Central Volcanic Zone of Chile where volcanic activity is absent. It is named after the Altos de Pica region. This segment is long and extends between the volcanoes Isluga in the north and Irruputuncu in the south. Volcanoes in the gap are old, Miocene to Pliocene in age and are heavily eroded. Examples include , Cerro Cariquima and Cerro Tatjachura. At the latitude of the Pica gap, an underwater rise known as the Iquique rise is subducted in the Peru-Chile Trench. It is unclear if the subduction of this rise is

neg: Island arc leading edge of the plate. Multiple earthquakes occur along this subduction boundary with the seismic hypocenters located at increasing depth under the island arc: these quakes define the Benioff zone. Island arcs can be formed in intra-oceanic settings, or from the fragments of continental crust that have migrated away from an adjacent continental land mass or at subduction-related volcanoes active at the margins of continents. Below are some of the generalized features present in most island arcs. Fore-arc: This region comprises the trench, the accretionary prism, and the fore-arc basin. A bump from the trench in the oceanward side of

neg: Aleutian subduction zone rocks, with trace amounts of Paleozoic rocks intruded by Mesozoic batholiths. Most of the Aleutian Islands are composed of sedimentary rocks from granitic and metamorphic rocks from Oligocene-Miocene. There are Quaternary volcanoes on the north of the Aleutian Islands structural axis, which is composed of andesite mostly, mixed with olivine basalt to rhyolite. The eastern Aleutian volcanoes have more silicic magma while the western Aleutian arcs lack the sial magma. The Aleutian Trench formation is associated with the subduction of the Pacific Plate beneath the North American plate. The horizontally-curved shape of the trench is due to the change in

neg: Nevado de Longaví Chile and Argentina that lie within the Southern Volcanic Zone. Among the largest volcanic eruptions in this area were the 1932 Quizapu and the 1991 Cerro Hudson eruptions. Nevado de Longaví is usually put into the "Transitional Southern Volcanic Zone", one of the four segments which the Southern Volcanic Zone is subdivided into; they are characterized by different thicknesses of the crust that the volcanoes are constructed on and by differences in the volcanic rocks. Farther east lie the Tatara-San Pedro and Laguna del Maule volcanoes. Volcanism in the Southern Volcanic Zone is caused by the subduction of the Nazca

neg: Volcanic arc arc. Often there are isolated, but impressively huge volcanoes in a mountain belt. For instance, Vesuvius and the Etna volcanoes in Italy are part of separate but different kinds of mountainous volcanic ensembles. The active front of a volcanic arc is the belt where volcanism develops at a given time. Active fronts may move over time (millions of years), changing their distance from the oceanic trench as well as their width. In the subduction zone, loss of water from the subducted slab induces partial melting of the overriding mantle and generates low-density, calc-alkaline magma that buoyantly rises to intrude and

neg: Geology of the Pacific Northwest locked in the minerals of solid rock to escape. The water vapor rises into the pliable mantle above the subducting plate, causing some of the mantle to melt. This newly formed magma rises toward the Earth's surface to erupt, forming a chain of volcanoes (the Cascade Volcanic Arc) above the subduction zone. A close-up look at the Cascades reveals a more complicated picture than a simple subduction zone. Not far off the coast of the North Pacific lies a spreading ridge; a divergent plate boundary made up of a series of breaks in the oceanic crust where new ocean crust

neg: Plate Boundary Observatory (light-activated radar), and geochronology. The GPS stations are categorized into clusters. The transform cluster is near the San Andreas Fault in California; the subduction cluster is in the Cascadia subduction zone (northern California, Oregon, Washington, and southern British Columbia); the extension cluster is in the Basin and Range region; the volcanic cluster is in the Yellowstone caldera, the Long Valley caldera, and the Cascade volcanoes; the backbone cluster is at 100–200 km intervals across the United States to provide complete spatial coverage. Data from the PBO is transmitted to UNAVCO to the data center where it is collected, archived and

neg: Geology of the United States chain of volcanoes (the Cascade Range) above the subduction zone. A close-up look at the Cascades reveals a more complicated picture than the simple subduction zone shown in the image on theleft. Not far off the coast of the North Pacific lies a spreading ridge; a divergent plate boundary made up of a series of breaks in the oceanic crust where new ocean crust is created. On one side of the spreading ridge new Pacific Plate crust is made, then moves away from the ridge. On the other side of the spreading ridge the Juan de Fuca Plate and Gorda

neg: Licancabur of melts. Not all volcanism in Chile is relative to subduction of the Nazca Plate; the Chile Ridge exhibits submarine volcanism, and volcanism in the Austral Volcanic Zone is triggered by the Antarctic Plate subducting beneath the South American Plate. One hundred ninety-eight South American volcanoes are on the Global Volcanism Program's Holocene volcano list. Licancabur is part of the Central Volcanic Zone at the western edge of the Altiplano. Among the region's active volcanoes are Putana (erupted at the end of the 19th century), Llullaillaco (1868) and Lascar (1993). Other stratovolcanoes are Tacora, Nevados de Payachata, Isluga, Tata Sabaya,

neg: Troodos Ophiolite calc-alkaline chemistries. In the early 1980s the term supra-subduction zone was coined to infer the formation of lavas above a subducting lithospheric slab, with no specification of where in relation to the subducting slab they form. From subsequent studies of other ophiolites it has been found that these generally have a similar geochemical signature, and so it is inferred that most are supra-subduction zone related. In the Troodos ophiolite it was observed from the variation in magma types, which can be seen to go from evolved to less evolved mafic rocks in localised cross cutting field relationships implying the presence

neg: Fueguino by glacial loading effects. The subduction of the Nazca Plate and Antarctic Plate beneath the South America Plate is responsible for the formation of the Andean Volcanic Belt. This volcanic belt is subdivided into the Northern Volcanic Zone, the Central Volcanic Zone, the Southern Volcanic Zone and the Austral Volcanic Zone. The Austral Volcanic Zone features six Quaternary volcanoes and is long. It is separated from the Southern Volcanic Zone by the Patagonian volcanic gap, where arc volcanism ceased 12 million years ago. South of where the Chile Rise intersects the Peru-Chile Trench, the trench disappears as it is increasingly

neg: Cerro Guacha Cerro Guacha Cerro Guacha is a Miocene caldera in southwestern Bolivia's Sur Lípez Province. Part of the volcanic system of the Andes, it is considered to be part of the Central Volcanic Zone (CVZ), one of the three volcanic arcs of the Andes, and its associated Altiplano-Puna volcanic complex (APVC). A number of volcanic calderas occur within the latter. Cerro Guacha and the other volcanoes of that region are formed from the subduction of the Nazca plate beneath the South America plate. Above the subduction zone, the crust is chemically modified and generates large volumes of melts that form the

neg: Geology of the Western Carpathians block. Main earthquakes in the ALCAPA were located in the subduction arc of the Hellenides and Calabrids. Deep focus earthquakes are known only from the zone of Vrancea, where the subduction is still active. No deep focused earthquakes related to subduction were recorded in the Western Carpathians. A period of significant continental collision and shortening of the crust affected the area in the Miocene. Later, primarily extensional and strike-slip movement in the Neogene generated new or reactivated older faults. There are five principal earthquake zones located in the area of the Western Carpathians: the Pezinok-Pernek zone, which is a continuation

neg: Cascade Volcanoes Range proper. Some of the major cities along the length of the arc include Portland, Seattle, and Vancouver, and the population in the region exceeds 10 million. All could be potentially affected by volcanic activity and great subduction-zone earthquakes along the arc. Because the population of the Pacific Northwest is rapidly increasing, the Cascade volcanoes are some of the most dangerous, due to their eruptive history and potential for future eruptions, and because they are underlain by weak, hydrothermally altered volcanic rocks that are susceptible to failure. Consequently, Mount Rainier is one of the Decade Volcanoes identified by the International

neg: Volcanic arc are smaller and more lush than the recently created (400,000 years ago) Hawaii island itself, which is more rocky. Hotspot volcanoes are also known as "intra-plate" volcanoes, and the islands they create are known as Volcanic Ocean Islands. Volcanic arcs do not generally exhibit such a simple age-pattern. There are two types of volcanic arcs: In some situations, a single subduction zone may show both aspects along its length, as part of a plate subducts beneath a continent and part beneath adjacent oceanic crust. Volcanoes are present in almost any mountain belt, but this does not make it a volcanic

neg: Volcanology of Chile Volcanology of Chile Volcanology of Chile studies a continuous volcanic process that has a strong influence on Chilean landscape, geology, economy and society. Volcanism constantly renews the Chilean landscape with lava flows, lava plateaus, lava domes, cinder cones, stratovolcanoes, shield volcanoes, submarine volcanoes, calderas, diatremes, and maars. However volcanism in Chile as well as in other parts of the world is also associated with several natural hazards such as lahars, earthquakes, pyroclastic flows, toxic gases and ash. Continental Chile has a high concentration of active volcanoes due to its location along the Peru–Chile Trench, a subduction zone where the Nazca

neg: Sunda Arc can be identified. The India and Australian Plates are subducting beneath the Sunda and Burma plates along the Sunda Arc. The tectonic deformation along this subduction zone in the Java Trench (also known as the Sunda Trench) caused the 2004 Indian Ocean earthquake of 26 December, 2004. The Sunda Arc is home to some of the world's most dangerous and explosive volcanoes. The 1815 eruption of Mount Tambora on Sumbawa and the 1257 eruption of Mount Samalas on Lombok were among the largest in the last two millennia, ranking 7 on the VEI scale. The Sunda Arc subduction zone was

neg: Geography of British Columbia volcanoes. Several eruptions are known to have occurred within this region in the past 400 years and contains Canada's largest volcanoes. It formed as a result of faulting, cracking, rifting and the interaction between the Pacific and the North American plates. The Chilcotin Group in southern British Columbia is thought to have formed as a result of back-arc extension behind the Cascadia subduction zone. The Wells Gray-Clearwater volcanic field in southeastern British Columbia consists of numerous small, basaltic volcanoes and extensive lava flows. Many individual volcanoes in the field have been active for the last 3 million years during which

neg: Solomon Sea Plate be a transform fault marking the boundary with the adjoining Woodlark Plate. The northern subduction zone is located where the Solomon Plate is diving below the South Bismarck Plate to the northwest and the Pacific Plate to the northeast. The northwest part of the subduction zone is called the New Britain Subduction Zone. New Britain in Papua New Guinea is the volcanic island formed from this collision and resulting volcanism. The southwestern subduction zone is where the Solomon Pate is diving below the Indo-Australian Plate. Solomon Sea Plate The Solomon Sea Plate is a minor tectonic plate to the northwest

neg: Guadeloupe crust of the Atlantic Plate under the Caribbean Plate in the Lesser Antilles subduction zone. This process is ongoing and is responsible for volcanic and earthquake activity in the region. There is an active volcano in Guadeloupe called "La Soufrière," located in the South of Basse-Terre. La Soufrière is actually a part of a volcanic complex that is composed of the Carmichael volcanoes, the Nez Cassé, the Echelle, the Cistern and the Madeleine. It is one of the nine active volcanoes of the Lesser Antilles. Its last eruption was in 1976. This eruption led to the evacuation of the southern

neg: Slow earthquake with high pore fluid pressures. The presence of water at the subduction interface and its relation to the generation of LFEs is not fully understood, but hydrolytic weakening of the rock contact is likely important. Where megathrust earthquakes (M>8) have been repeatedly observed in the shallow sections (<25 km depth) of the Cascadia subduction zone, low frequency earthquakes have recently been discovered to occur at greater depths, down-dip of the seismogenic zone. The first indicator of low frequency earthquakes in Cascadia was discovered in 1999 when an aseismic event took place at the subduction interface wherein the overriding North American

neg: Mentolat no recent volcanic activity has occurred. These gaps are not static; the gap separating the Austral and the Southern Volcanic Zones has been moving northward for the past 15-20 million years. The Southern Volcanic Zone itself is subdivided into additional volcanic zones, the Northern, Transitional, Central and Southern Southern Volcanic Zone. More volcanoes in the neighbourhood of Mentolat include Melimoyu and Cay to the north, Maca and Cerro Hudson to the south, as well as several monogenetic volcanoes. South of Hudson, the Chile Rise subducts in the trench. Volcanic activity is absent in the long area, as its subduction disrupts

neg: Río Murta (volcano) of the gap generated by the fast subduction of the older and colder Nazca Plate beneath the South America Plate and Austral Volcanic Zone volcanism south of the gap formed by the slow subduction of the younger and warmer Antarctic Plate. In between these two subduction processes, a slab window opened up and allowed the rise of alkali basalt magmas. Río Murta rocks are basalts with a low content of potassium. They contain phenocrysts of clinopyroxene, olivine and plagioclase. The chemical composition is unlike that of other regional basaltic volcanoes, and reflects the influence of oceanic asthenosphere. The basement in

neg: Lihir Island Lihir Island Lihir Island (a.k.a. Niolam Island) is the largest island in the Lihir group of islands, 22 km long and 14.5 km wide, in Papua New Guinea's New Ireland Province. It consists of a complex of several overlapping basaltic stratovolcanoes rising 700 m above sea level. While the volcanoes are not currently active, geothermal activity is still present. The island is in what was the forearc basin associated with the subduction of the Pacific Plate beneath the North Bismarck Plate. Subduction stopped about 10 million years ago with the collision of the Ontong Java plateau with the subduction zone.

neg: Mount Cleveland (Alaska) vicinity of the volcano, and volcanic ash released from eruptions can damage sensitive electronic equipment and sensors. Mount Cleveland is located from the western end of the Aleutian Arc, a long volcanic chain extending off the coast of Alaska. Containing over 75 volcanoes, this volcanic arc occurs above the subduction zone where the Pacific Plate plunges under the North American plate. As the plate moves deeper into the earth, the increasing pressure results in the loss of volatiles, certain elements and compounds with low boiling points, from various hydrous minerals. One of these compounds is water; its addition to the

neg: Goat Rocks boundaries, which can probably be explained by its slow rate of subduction. According to the United States Geological Survey, the Nazca and North American plates converge at a rate of to each year, just half of their convergence rate as recently as 7 million years ago. The Cascade Volcanoes in Washington are restricted to four belts; Goat Rocks forms one segment of the north–south trending Mount Adams belt that also incorporates Tumac Mountain, Adams, and the King Mountain Fissure Zone. Of the four Cascade arcs, this belt contains the second most volcanoes, and its volcanoes are predominantly made of calc-alkalic

neg: Yucamane Yucamane Yucamane, Yucamani or Yucumane is an andesitic stratovolcano in the Tacna Region of southern Peru. It is part of the Peruvian segment of the Central Volcanic Zone, one of the three volcanic belts of the Andes generated by the subduction of the Nazca plate beneath the South America plate. Peru's active volcanoes Ubinas, Sabancaya and El Misti are also part of the Central Volcanic Zone. Yucamane, together with the volcanoes Yucamane Chico and Calientes farther north, forms a Pleistocene volcanic group. Yucamane is constructed mainly by lava flows with subordinate pyroclastic deposits, and it has a well preserved summit

neg: Coast Mountains volcanoes form part of the Northern Cordilleran Volcanic Province, the most volcanically active area in Canada. The first event began 130 million years ago when a group of active volcanic islands approached a pre-existing continental margin and coastline of North America. These volcanic islands, known as the Insular Islands by geoscientists, were formed on a pre-existing tectonic plate called the Insular Plate by subduction of the former Farallon Plate to the west during the early Paleozoic era. This subduction zone records another subduction zone to the east under an ancient ocean basin between the Insular Islands and the former continental

neg: Tacora Tacora Tacora is a stratovolcano located in the Andes of the Arica y Parinacota Region of Chile. Bordering Peru, it is the northernmost volcano of Chile. It is part of the Central Volcanic Zone in Chile, one of the four volcanic belts of the Andes. The Central Volcanic Zone has several of the highest volcanoes in the world. Tacora itself is a stratovolcano with a caldera and a crater. The youngest radiometric age is 50,000 years ago and it is heavily eroded by glacial activity. Volcanism in the Central Volcanic Zone results from the subduction of the Nazca Plate beneath

neg: Sierra Nevada (U.S.) arc collided with the west coast of North America and raised a chain of volcanoes, in an event called the Nevadan orogeny. Nearly all subaerial Sierran Arc volcanoes have since disappeared; their remains were redeposited during the Great Valley Sequence and the subsequent Cenozoic filling of the Great Valley, which is the source of much of the sedimentary rock in California. In the Cretaceous, a subduction zone formed at the edge of the continent. This means that an oceanic plate started to dive beneath the North American plate. Magma formed through the subduction of the ancient Farallon Plate rose in

neg: Yucamane is concentrated in three belts (Northern Volcanic Zone, Central Volcanic Zone and Southern Volcanic Zone) where the angle of subduction is steep enough. Volcanism in the region has been active since the Jurassic, with remnants of the oldest volcanic arc recognizable in the Peruvian Coastal Cordillera. During the Miocene epoch, volcanic activity occurred along the entire length of Peru; Pliocene-Pleistocene activity on the other hand is confined to southern Peru as part of the Central Volcanic Zone, with volcanic centres concentrated in the Western Cordillera. Volcanoes in Peru were first catalogued in 1962 and 1966, with a major compilation being

neg: Pacific Ranges rapid rates of uplift over the past 4 million years, which has led to relatively high rates of erosion. The Garibaldi Volcanic Belt is within the Pacific Ranges, which is a volcanic belt formed by the subduction of the Juan de Fuca Plate (a remnant of the much larger Farallon Plate) under the North American Plate along the Cascadia subduction zone. The belt is the northern extension of the Cascade Volcanic Arc in the United States (which includes the volcanoes Mount St. Helens and Mount Baker) and contains the most explosive young volcanoes in Canada. The eruption styles in the

neg: La Pacana La Pacana La Pacana is a Miocene age caldera in northern Chile's Antofagasta Region. Part of the Central Volcanic Zone of the Andes, it is part of the Altiplano-Puna volcanic complex, a major caldera and silicic ignimbrite volcanic field. This volcanic field is located in remote regions at the Zapaleri tripoint between Chile, Bolivia and Argentina. La Pacana along with other regional volcanoes was formed by the subduction of the Nazca Plate beneath the South American Plate in the Peru-Chile Trench. La Pacana is situated in a basement formed by various Paleozoic formations and Tertiary ignimbrites and volcanoes. Several major

neg: Taapaca they interact with the mantle wedge above the downgoing plate. This subduction does not result in volcanic activity everywhere; in places where the process is shallower ("flat slab" subduction) there is no recent volcanism. Volcanism has been ongoing in the Andes since about 185 million years ago, with an increase about 27 million years ago when the Farallon Plate broke up. In 1994, the Andes were considered to contain about 178 volcanoes with Holocene activity, of which 60 were further assumed to have been active during historical time. Taapaca is part of the Central Volcanic Zone of the Andes, which

neg: Tocomar Tocomar Tocomar is a Pleistocene volcano in the Jujuy Province, Argentina. Located in the Argentine segment of the Andean Volcanic Belt, it is part of the Central Volcanic Zone of the Andes which is one of four distinct volcanic belts in South America. The Central Volcanic Zone consists of about 44 active volcanoes and large calderas of the Altiplano-Puna volcanic complex. Its volcanism is caused by the subduction of the Nazca Plate beneath the South America Plate in the Peru-Chile Trench, but at Tocomar volcanism is further influenced by a large fault zone, the Calama-Olacapato-El Toro fault, which runs diagonally

neg: Mount Merapi subduction zone, where the Indo-Australian Plate is subducting under the Sunda Plate. It is one of at least 129 active volcanoes in Indonesia, part of the volcano is located in the Southeastern part of the Pacific Ring of Fire–a section of fault lines stretching from the Western Hemisphere through Japan and South East Asia. Stratigraphic analysis reveals that eruptions in the Merapi area began about 400,000 years ago, and from then until about 10,000 years ago, eruptions were typically effusive, and the out flowing lava emitted was basaltic. Since then, eruptions have become more explosive, with viscous andesitic lavas often

neg: Subduction arcs. Volcanoes that exist along arcs tend to produce dangerous eruptions because they are rich in water (from the slab and sediments) and tend to be extremely explosive. Krakatoa, Nevado del Ruiz, and Mount Vesuvius are all examples of arc volcanoes. Arcs are also known to be associated with precious metals such as gold, silver and copper believed to be carried by water and concentrated in and around their host volcanoes in rock called "ore". Although the process of subduction as it occurs today is fairly well understood, its origin remains a matter of discussion and continuing study. Subduction initiation

neg: Los Angeles metropolitan area carbon (C) and water vapor (H2O). About 30% is sulfur (S). The sulfur mixes with the water vapor to form sulfuric acid which is notorious for eating away at almost anything from plants to rocks. For the 99% percent of plutons that didn't make it to the surface they cooled to form granite monoliths under these volcanoes. When subduction activities ceased about 55 million years ago, these volcanoes were subject to erosion due to their steep slopes. Because granite is classified as a hard igneous rock, it is the only remnant of the volcanic chain from this subduction zone. These

neg: Taupo Volcanic Zone of the South Island, although here the subduction is in the opposite direction. Solander Island is an extinct volcano associated with this subduction zone, and the only one that protudes above the sea. Recent scientific work indicates that the Earth's crust below the Taupo Volcanic Zone may be as little as 16 kilometres thick. A film of magma 50 kilometres (30 mi) wide and 160 kilometres (100 mi) long lies 10 kilometres under the surface. The geological record indicates that some of the volcanoes in the area erupt infrequently but have large, violent and destructive eruptions when they do. There

neg: Mentolat volcanoes in the region and its magmas appear to originate from parental melts that contain more water and volatiles than the parental melts of the magmas of other volcanoes. The Nazca Plate at the Peru-Chile Trench subducts beneath the South America Plate at an average rate of . This subduction occurs at an angle and has generated the Liquiñe-Ofqui fault zone which runs along the volcanic arc. Where the Chile Rise intersects the trench the Nazca Plate ends and the Antarctic Plate begins. This plate also subducts farther south beneath the South America Plate but at a lower pace of

neg: Nevado Sajama side of the volcano originates the Sajama River which flows due south and increasingly turns southeast before joining the Lauca River. The other rivers draining Sajama and its ice cap also eventually join the Lauca River and end in the Salar de Coipasa. Nevado Sajama is part of the Central Volcanic Zone of the Andes, where volcanism is triggered by the subduction of the Nazca Plate beneath the South America Plate. Changes in the subduction regime took place during the Oligocene and directed an increase of volcanic activity in the region. Volcanoes in the region have ages ranging from Pleistocene

neg: Volcanology of Canada massif where Garibaldi Belt lavas rest on uplifted and deeply eroded remnants of Pemberton Belt subvolcanic intrusions and combines to form a single belt. A few isolated volcanoes northwest of the Mount Meager massif, such as Silverthrone Caldera and Franklin Glacier Complex, are also grouped as part of the Garibaldi Volcanic Belt. However, their tectonic origins are largely unexplained and are a matter of going research. When the Farallon Plate ruptured to create the Nootka Fault between five and seven million years ago, there were some apparent changes along the Cascadia subduction zone. At issue is the current plate configuration

neg: Cascade Range rock to escape. The water vapor rises into the pliable mantle above the subducting plate, causing some of the mantle to melt. This newly formed magma rises toward the Earth's surface to erupt, forming a chain of volcanoes (the Cascade Volcanic Arc) above the subduction zone. Soil conditions for farming are generally good, especially downwind of volcanoes. This is largely because volcanic rocks are often rich in potassium bearing minerals such as orthoclase and decay easily. Volcanic debris, especially lahars, also have a leveling effect and the storage of water in the form of snow and ice is also important.

neg: Anahim hotspot The more abundant lava domes and volcanic cones are much smaller in size (less than one kilometre in volume). These comprise two extensive volcanic fields in the vicinity of the Itcha Range. Although many Anahim volcanoes are surrounded by Chilcotin Group basalt flows, the exact nature of their relationship is unknown. It is unlikely that the Anahim volcanoes ever were a source area for the Chilcotin basalts as they have distinct transitional geochemistries. The Chilcotin Group is interpreted to be related to back-arc extension behind the Cascadia subduction zone. Each volcano type produced by the Anahim hotspot has its own

neg: Oceanic trench for example the Marianas, and this allows buoyant serpentinite to rise to the seafloor where they form serpentinite mud volcanoes. Chemosynthetic communities are also found on non-accretionary margins such as the Marianas, where they thrive on vents associated with serpentinite mud volcanoes. Trenches seem positionally stable over time, but scientists believe that some trenches—particularly those associated with subduction zones where two oceanic plates converge—move backward into the subducting plate. This is called trench rollback or hinge retreat (also hinge rollback) and is one explanation for the existence of back-arc basins. Slab rollback occurs during the subduction of two tectonic plates,

neg: Savu streams run dry and local inhabitants must depend on wells for their water supplies. The Savu Islands are situated in a tectonic subduction zone, where the Indo-Australian Plate is moving northward, sliding under the Eurasian Plate. The islands lie on a ridge that was created by volcanic eruptions caused by the plate movement. Sediments carried into the Earth's crust heat up and rise in plumes of magma, which cool and solidify to form igneous rock. The Sumba Ridge is no longer volcanically active, but active volcanoes are on the island of Flores, to the north. The compression of the two

neg: Geological history of Borneo Geological history of Borneo The base of rocks that underlie Borneo, an island in Southeast Asia, was formed by the arc-continent collisions, continent–continent collisions and subduction–accretion due to convergence between the Asian, India–Australia, and Philippine Sea-Pacific plates over the last 400 million years. The active geological processes of Borneo are mild as all of the volcanoes are extinct. The geological forces shaping SE Asia today are from three plate boundaries: the collisional zone in Sulawesi southeast of Borneo, the Java-Sumatra subduction boundary and the India-Eurasia continental collision. The SE Asia region is made up of fragments of crust that drifted

neg: Seamount to the surface. Volcanoes formed near or above subducting zones are created because the subducting tectonic plate adds volatiles to the overriding plate that lowers its melting point. Which of these two process involved in the formation of a seamount has a profound effect on its eruptive materials. Lava flows from mid-ocean ridge and plate boundary seamounts are mostly basaltic (both tholeiitic and alkalic), whereas flows from subducting ridge volcanoes are mostly calc-alkaline lavas. Compared to mid-ocean ridge seamounts, subduction zone seamounts generally have more sodium, alkali, and volatile abundances, and less magnesium, resulting in more explosive, viscous eruptions. All

neg: Taapaca mining activity employed a significant number of the people in Putre. Taapaca Taapaca is a Holocene volcanic complex in northern Chile's Arica y Parinacota Region. Located in the Chilean Andes, it is part of the Central Volcanic Zone of the Andean Volcanic Belt, one of four distinct volcanic chains in South America. The town of Putre lies at the southwestern foot of the volcano. Like other volcanoes of the Central Volcanic Zone, Taapaca formed from the subduction of the Nazca Plate beneath the South America Plate. It lies on the western margin of the Altiplano high plateau, on top of

neg: Taapaca Taapaca Taapaca is a Holocene volcanic complex in northern Chile's Arica y Parinacota Region. Located in the Chilean Andes, it is part of the Central Volcanic Zone of the Andean Volcanic Belt, one of four distinct volcanic chains in South America. The town of Putre lies at the southwestern foot of the volcano. Like other volcanoes of the Central Volcanic Zone, Taapaca formed from the subduction of the Nazca Plate beneath the South America Plate. It lies on the western margin of the Altiplano high plateau, on top of older volcanic and sedimentary units. Taapaca has mainly erupted dacite, in

neg: Stratovolcano the top surface, it pools in a magma chamber within the crust below the stratovolcano. There, the relatively low pressure allows water and other volatiles (mainly CO, SO, Cl, and HO) dissolved in the magma to escape from solution, as occurs when a bottle of carbonated water is opened, releasing CO. Once a critical volume of magma and gas accumulates, the plug (solidified blockage) of the volcanic vent is broken, leading to a sudden explosive eruption. In recorded history, explosive eruptions at subduction zone (convergent-boundary) volcanoes have posed the greatest hazard to civilizations. Subduction-zone stratovolcanoes, such as Mount St. Helens,

neg: Volcanic belt that pairs of opposite hot spots may result from the impact of a large meteor. Geologists have identified some 40-50 such hotspots around the globe, with Hawaii, Réunion, Yellowstone, Galápagos, and Iceland overlying the most currently active. An example of a hotspot volcanic belt is the Anahim Volcanic Belt in British Columbia, Canada, which was formed as a result of the North American Plate sliding westward over the Anahim hotspot. Most hotspot volcanoes are basaltic because they erupt through oceanic lithosphere (e.g., Hawaii, Tahiti). As a result, they are less explosive than subduction zone volcanoes, which have high water contents.

neg: El Toro volcanic field El Toro volcanic field El Toro volcanic field is part of the Central Volcanic Zone of the Andes in the northern Puna of Argentina. Three of the cones in the volcanic field are located southwest of the town of El Toro and the fourth is found north. Part of a field of monogenetic volcanoes associated with subduction of the Nazca plate beneath the South America plate, it is constructed from three main cones and an additional lava flow. The field formed between six and two million years ago. El Toro belongs to a formation of monogenetic volcanism, which in this

neg: Cerro Macá the summit area. Pyroclastic cones with associated lava flows are found on its southwestern flank but also on the other slopes of the volcano, as far down as sea level and in the Bahia Aysen. The volcano is part of the southernmost Southern Volcanic Zone of Chile, where volcanism is caused by the subduction of the Nazca Plate. Other volcanoes in the area are Melimoyu, Mentolat, Cay and Cerro Hudson. Macá specifically is formed by basalt and basaltic andesite. 1,440 ± 40 calibrated radiocarbon years ago a moderate explosive eruption deposited the MAC1 tephra, which reaches thicknesses of east of

neg: Mount Meager massif about the volcanoes north of the massif, such as the Silverthrone and , experts disagree about their nature. Some scientists regard the Silverthrone Caldera as the northernmost volcano of the Garibaldi Volcanic Belt, while others contend that the geology of the massif more closely matches that of the GVB. It is also unclear whether the Milbanke Sound Cones are part of the Garibaldi Belt or formed by different tectonic processes. However, there is evidence the Silverthrone and complexes are related to activity at the Cascadia subduction zone. Geologically these two volcanoes contain the same rock types as those found elsewhere

neg: San Jose, Camarines Sur axis of a trench marks, the position of a subduction zone where old oceanic lithospheric plates begin their descent into the earth's interior. In 1987, a study was conducted which reveals that the Bicol Region particularly the location of San Jose is a part prone to earthquakes of intensify 5 from the above-cited source zones. Based on the frequency of volcanic eruptions that occurred in the region, there are three prominent volcanoes which are considered to be active, namely: Mt. Mayon, Mt. Bulusan, and Mt. Iriga (Asog). The latter is the nearest to the Municipality of San Jose. Mount Iriga