Volcanic arc - wikipedia Volcanic arc Not to be confused with Volcanic belt. Volcanic arc formation along a subducting plate A volcanic arc is a chain of volcanoes formed above a subducting plate, positioned in an arc shape as seen from above. Offshore volcanoes form islands, resulting in a volcanic island arc. Generally, volcanic arcs result from the subduction of an oceanic tectonic plate under another tectonic plate, and often parallel an oceanic trench. The oceanic plate is saturated with water, and volatiles such as water drastically lower the melting point of the mantle. As the oceanic plate is subducted, it is subjected to greater and greater pressures with increasing depth. This pressure squeezes water out of the 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 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 : oceanic arcs form when oceanic crust subducts beneath other oceanic crust on an adjacent plate, creating a volcanic island arc. ( Not all island arcs are volcanic island arcs. ) continental arcs form when oceanic crust subducts beneath continental crust on an adjacent plate, creating an arc - shaped mountain belt. ( Not all mountain belts form in this way. ) 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. ( The term `` volcanic arc '' is often confused with the term `` island arc ''. The former is a series of volcanoes, but not necessarily offshore. The latter is a series of islands, not necessarily composed solely of volcanoes. ) Volcanoes are present in almost any mountain belt, but this does not make it a volcanic 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. Contents 1 Petrology 2 Examples 2.1 Continental arcs 2.2 Island arcs 2.3 Ancient island arcs 3 See also 4 References Petrology 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 be extruded through the lithosphere of the overriding plate. This loss of water is due to the destabilization of the mineral chlorite at approximately 40 -- 60 km depth. This is the reason for island arc volcanism at consistent distances from the subducting slab : because the temperature - pressure conditions for flux - melting volcanism due to chlorite destabilization will always occur at the same depth, the distance from the trench to the arc volcanoes is determined only by the dip angle of the subducting slab. On the subducting side of the island arc is a deep and narrow oceanic trench, which is the trace at the Earth 's surface of the boundary between the downgoing and overriding plates. This trench is created by the gravitational pull of the relatively dense subducting plate pulling the leading edge of the plate downward. Multiple earthquakes occur along this subduction boundary with the seismic hypocenters located at increasing depth under the island arc : these quakes define the Wadati -- Benioff zones. The volcanic arc forms when the subducting plate reaches a depth of about 100 km. Ocean basins that are being reduced by subduction are called ' remnant oceans ' as they will slowly be shrunken out of existence and crushed in the subsequent orogenic collision. This process has happened over and over in the geologic history of the Earth. In the rock record, volcanic arcs can be seen as the volcanic rocks themselves, but because volcanic rock is easily weathered and eroded, it is more typical that they are seen as plutonic rocks, the rocks that formed underneath the arc ( e.g. the Sierra Nevada batholith ), or in the sedimentary record as lithic sandstones. Cascade Volcanic Arc, a continental volcanic arc The Aleutian Arc, with both oceanic and continental parts. Examples Two classic examples of oceanic island arcs are the Mariana Islands in the western Pacific Ocean and the Lesser Antilles in the western Atlantic Ocean. The Cascade Volcanic Arc in western North America and the Andes along the western edge of South America are examples of continental volcanic arcs. The best examples of volcanic arcs with both sets of characteristics are in the North Pacific, with the Aleutian Arc consisting of the Aleutian Islands and their extension the Aleutian Range on the Alaska Peninsula, and the Kuril - Kamchatka Arc comprising the Kuril Islands and southern Kamchatka Peninsula. Continental arcs Cascade Volcanic Arc Alaska Peninsula and Aleutian Range Kamchatka Andes North Volcanic Zone Central Volcanic Zone South Volcanic Zone Austral Volcanic Zone Central America Volcanic Arc Island arcs Aleutian Islands Kuril Islands Northeastern Japan Arc Japanese Archipelago including the Ryukyu Islands Izu - Bonin - Mariana Arc : Izu Islands Bonin Islands Mariana Islands Luzon Volcanic Arc Philippines Tonga and Kermadec Islands Andaman and Nicobar Islands Mentawai Islands Sunda Arc Lesser Sunda Islands Tanimbar and Kai Islands Solomon Islands South Aegean Volcanic Arc Egean, or Hellenic arc Lesser Antilles, including the Leeward Antilles Scotia Arc : South Sandwich Islands Mascarene Islands Ancient island arcs Insular Islands Intermontane Islands Sakhalin Island Arc See also Back - arc basin High island Island arc Subduction zone metamorphism Volcanic field References Jump up ^ `` Volcanic arc definition from the Dictionary of Geology ''. Retrieved 2014 - 11 - 01. Jump up ^ Grove, T.L., N. Chatterjee, S.W. Parman, and E. Médard ( 2006 ), The Influence of H O on Mantle Wedge Melting, Earth and Planetary Science Letters, 249, 74 -- 89. Jump up ^ Grove, T.L., C.B. Till, N. Chatterjee, and E. Médard ( submitted 2008 ), Transport of H2O in subduction zones and its role in the formation and location of arc volcanoes, Nature. Subduction Zone Volcanism Tectonics and Volcanoes of Japan USGS : Island - Arc, Oceanic, and Continental Volcanoes Types of basalts Basalts by tectonic setting Flood basalt Mid-ocean ridge basalt Ocean island basalt Volcanic arc basalt Basalts by form and flow Columnar basalt Pillow basalt Aa lava Pahoehoe lava Basalts by chemistry Tholeiitic basalt Calc - alkaline basalt Alkali basalt Trachybasalt Hawaiite Mugearite Picrite Important minerals Olivine Pyroxene Plagioclase Amphibole Magnetite Ilmenite Quartz Cristobalite Trydimite Physical oceanography Waves Airy wave theory Ballantine scale Benjamin -- Feir instability Boussinesq approximation Breaking wave Clapotis Cnoidal wave Cross sea Dispersion Edge wave Equatorial waves Fetch Gravity wave Green 's law Infragravity wave Internal wave Iribarren number Kelvin wave Kinematic wave Longshore drift Luke 's variational principle Mild - slope equation Radiation stress Rogue wave Rossby wave Rossby - gravity waves Sea state Seiche Significant wave height Soliton Stokes boundary layer Stokes drift Stokes wave Swell Trochoidal wave Tsunami megatsunami Undertow Ursell number Wave action Wave base Wave height Wave power Wave radar Wave setup Wave shoaling Wave turbulence Wave -- current interaction Waves and shallow water one - dimensional Saint - Venant equations shallow water equations Wind wave model Circulation Atmospheric circulation Baroclinity Boundary current Coriolis force Coriolis -- Stokes force Craik -- Leibovich vortex force Downwelling Eddy Ekman layer Ekman spiral Ekman transport El Niño -- Southern Oscillation General circulation model Geostrophic current Global Ocean Data Analysis Project Gulf Stream Halothermal circulation Humboldt Current Hydrothermal circulation Langmuir circulation Longshore drift Loop Current Modular Ocean Model Ocean dynamics Ocean gyre Princeton Ocean Model Rip current Subsurface currents Sverdrup balance Thermohaline circulation shutdown Upwelling Whirlpool World Ocean Circulation Experiment Tides Amphidromic point Earth tide Head of tide Internal tide Lunitidal interval Perigean spring tide Rip tide Rule of twelfths Slack water Tidal bore Tidal force Tidal power Tidal race Tidal range Tidal resonance Tide gauge Tideline Landforms Abyssal fan Abyssal plain Atoll Bathymetric chart Coastal geography Cold seep Continental margin Continental rise Continental shelf Contourite Guyot Hydrography Oceanic basin Oceanic plateau Oceanic trench Passive margin Seabed Seamount Submarine canyon Submarine volcano Plate tectonics Convergent boundary Divergent boundary Fracture zone Hydrothermal vent Marine geology Mid-ocean ridge Mohorovičić discontinuity Vine -- Matthews -- Morley hypothesis Oceanic crust Outer trench swell Ridge push Seafloor spreading Slab pull Slab suction Slab window Subduction Transform fault Volcanic arc Ocean zones Benthic Deep ocean water Deep sea Littoral Mesopelagic Oceanic Pelagic Photic Surf Swash Sea level Deep - ocean Assessment and Reporting of Tsunamis Future sea level Global Sea Level Observing System North West Shelf Operational Oceanographic System Sea - level curve Sea level rise World Geodetic System Acoustics Deep scattering layer Hydroacoustics Ocean acoustic tomography Sofar bomb SOFAR channel Underwater acoustics Satellites Jason - 1 Jason - 2 ( Ocean Surface Topography Mission ) Jason - 3 Related Argo Benthic lander Color of water DSV Alvin Marginal sea Marine energy Marine pollution Mooring National Oceanographic Data Center Ocean Ocean exploration Ocean observations Ocean reanalysis Ocean surface topography Ocean thermal energy conversion Oceanography Pelagic sediment Sea surface microlayer Sea surface temperature Seawater Science On a Sphere Thermocline Underwater glider Water column World Ocean Atlas Category Commons Coastal geography Landforms Anchialine pool Archipelago Atoll Avulsion Ayre Barrier island Bay Baymouth bar Bight Bodden Brackish marsh Cape Channel Cliff Coast Coastal plain Coastal waterfall Continental margin Continental shelf Coral reef Cove Dune cliff - top Estuary Firth Fjard Fjord Freshwater marsh Fundus Gat Geo Gulf Gut Headland Inlet Intertidal wetland Island Islet Isthmus Lagoon Machair Marine terrace Mega delta Mouth bar Mudflat Natural arch Peninsula Reef Regressive delta Ria River delta Salt marsh Shoal Shore Skerry Sound Spit Stack Strait Strand plain Submarine canyon Tidal island Tidal marsh Tide pool Tied island Tombolo Windwatt Beaches Beach cusps Beach evolution Coastal morphodynamics Beach ridge Beachrock Pocket beach Raised beach Recession Shell beach Shingle beach Storm beach Wash margin Processes Blowhole Cliffed coast Coastal biogeomorphology Coastal erosion Concordant coastline Current Cuspate foreland Discordant coastline Emergent coastline Feeder bluff Fetch Flat coast Graded shoreline Headlands and bays Ingression coast Large - scale coastal behaviour Longshore drift Marine regression Marine transgression Raised shoreline Rip current Rocky shore Sea cave Sea foam Shoal Steep coast Submergent coastline Surf break Surf zone Surge channel Swash Undertow Volcanic arc Wave - cut platform Wave shoaling Wind wave Wrack zone Management Accretion Coastal management Integrated coastal zone management Submersion Related Bulkhead line Grain size boulder clay cobble granule pebble sand shingle silt Intertidal zone Littoral zone Physical oceanography Region of freshwater influence Category Commons Retrieved from `` https://en.wikipedia.org/w/index.php?title=Volcanic_arc&oldid=806007599 '' Categories : Volcanic arcs Archipelagoes Plate tectonics Coastal and oceanic landforms Talk Contents About Wikipedia Català Eesti Español Esperanto Euskara فارسی Français हिन्दी Bahasa Indonesia Italiano עברית Nederlands 日本 語 Norsk Norsk nynorsk Português Română Српски / srpski Türkçe Українська Tiếng Việt 中文 Edit links This page was last edited on 19 October 2017, at 01 : 49. 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Question: where are volcanoes located in relation to a subduction zone
Answer: parallel to the subduction zone