Mariana Islands, an oceanic island arc

Cascade Volcanic Arc, a continental volcanic arc

A volcanic arc is a chain of volcanic islands or mountains formed by plate tectonics as an oceanic tectonic plate subducts under another tectonic plate and produces magma. There are two types of volcanic arcs: oceanic arcs (commonly called island arcs, a type of archipelago) and continental arcs. In the former, oceanic crust subducts beneath other oceanic crust on an adjacent plate, while in the latter case the oceanic crust subducts beneath continental crust. 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. Image File history File links Download high-resolution version (809x1000, 70 KB) Mariana Islands Maps from http://www. ... Image File history File links Download high-resolution version (809x1000, 70 KB) Mariana Islands Maps from http://www. ... Download high resolution version (502x739, 29 KB) Cascadia subduction zone. ... Download high resolution version (502x739, 29 KB) Cascadia subduction zone. ... For other uses, see Volcano (disambiguation). ... Lyskamm, 4 527 m, Pennine Alps A mountain is a landform that extends above the surrounding terrain in a limited area. ... The tectonic plates of the world were mapped in the second half of the 20th century. ... The tectonic plates of the world were mapped in the second half of the 20th century. ... The Juan de Fuca plate sinks below the North America plate at the Cascadia subduction zone. ... Magma is molten rock located beneath the surface of the Earth (or any other terrestrial planet), and which often collects in a magma chamber. ... The Mergui Archipelago An archipelago is a landform which consists of a chain or cluster of islands. ... Age of oceanic crust Oceanic crust is the part of Earths lithosphere which underlies the ocean basins. ... The continental crust is the layer of granitic, sedimentary and metamorphic rocks which form the continents and the areas of shallow seabed close to their shores, known as continental shelves. ...

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 example of an arc with both sets of characteristics is the Aleutian Arc in the North Pacific, which consists of the Aleutian Islands and their extension the Aleutian Range on the Alaska Peninsula. The Mariana Islands (also the Marianas; up to the early 20th century sometimes called Ladrone Islands, from Spanish Islas de los Ladrones meaning Islands of Thieves) are an archipelago made up by the summits of 15 volcanic mountains in the north-western Pacific Ocean, in about 12 to 21 N... Location of the Lesser Antilles (green) in relation to the rest of the Caribbean Islands of the Lesser Antilles The Lesser Antilles, also known as the Caribbees,[1] are part of the Antilles, which together with the Bahamas and Greater Antilles form the West Indies. ... This article or section does not adequately cite its references or sources. ... World map showing North America A satellite composite image of North America. ... Planes view of the Andes, Peru. ... South America South America is a continent crossed by the equator, with most of its area in the Southern Hemisphere. ... Aleutians seen from space The Aleutian Islands (possibly from Chukchi aliat, island) are a chain of more than 300 small volcanic islands forming an island arc in the Northern Pacific Ocean, occupying an area of 6,821 sq mi (17,666 km²) and extending about 1,200 mi (1,900... The Aleutian Range is the mountain range of the Alaska Peninsula in southeast Alaska. ... Volcanoes on the Alaska Peninsula The Alaska Peninsula is a peninsula extending about 800 km (500 miles) to the southwest from the mainland of Alaska and ending in the Aleutian Islands. ...

Petrology

In the subduction zone, loss of volatiles 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. Calc-alkaline, or calc-alkalic series rocks, are igneous rocks which share a trend of alkali and calcium enrichment. ... Magma is molten rock located beneath the surface of the Earth (or any other terrestrial planet), and which often collects in a magma chamber. ...

The magma is generated within the deep mantle wedge of the overriding plate. A subducting plate carries with it a lot of sediment, altered basalt, and hydrated peridotite, all of which are rich in water. As the plate gets deeper and deeper, the water is released and migrates upwards. The water causes the melting point of the upper mantle rock (that is wedged between the two plates) to drop and thus magma is formed. It is this magma derived from the asthenosphere and enriched in water and other constituents from the subducting plate (and also probably contaminated by melted material from the overlying crust) that erupts in an arc volcano. Sediment is any particulate matter that can be transported by fluid flow and which eventually is deposited as a layer of solid particles on the bed or bottom of a body of water or other liquid. ... Basalt Basalt (IPA: ) is a common gray to black volcanic rock. ... Peridotite xenolith from San Carlos, southwestern United States. ... Impact of a drop of water creating circular capillary waves. ... Earth cutaway from core to exosphere. ... Earth cutaway from core to exosphere. ... Earth cutaway from core to exosphere. ...

The type of igneous rock most characteristic of volcanic arcs is andesite, but a range of rock types from basalt to rhyolite is commonly present in the volcanoes. These rock types make up the calc-alkaline series. The presence of the calc-alkaline series is used as a tool to identify parts of the continental crust formed in volcanic arcs, long after the arcs themselves have vanished. Volcanic rock on North America Plutonic rock on North America Igneous rocks are formed when rock (magma) cools and solidifies, with or without crystallization, either below the surface as intrusive (plutonic) rocks or on the surface as extrusive (volcanic) rocks. ... A sample of andesite (dark groundmass) with amygdaloidal vesicules filled with zeolite. ... Basalt Basalt (IPA: ) is a common gray to black volcanic rock. ... Rhyolite This page is about a volcanic rock. ... Calc-alkaline, or calc-alkalic series rocks, are igneous rocks which share a trend of alkali and calcium enrichment. ...

Geomorphology

The resulting chain of volcanoes has the shape of an arc parallel to the convergent plate boundary and convex toward the subducting plate. This is a consequence of the geometry of the spherical plate crumpling along a line on a spherical surface.

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 oceanic trenches are hemispheric-scale long but narrow topographic depressions of the sea floor. ... An earthquake is the result from the sudden release of stored energy in the Earths crust that creates seismic waves. ... Seismology (from the Greek seismos = earthquake and logos = word) is the scientific study of earthquakes and the movement of waves through the Earth. ... The hypocenter or hypocentre (literally: below the center from the Greek υπόκεντρον), also known as the focus. ... Subduction zones mark sites of convective downwelling of the Earths lithosphere. ...

Oceans 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. // Orogeny (Greek for mountain generating) is the process of mountain building, and may be studied as a tectonic structural event, as a geographical event and a chronological event, in that orogenic events cause distinctive structural phenomena and related tectonic activity, affect certain regions of rocks and crust and happen within...

The Aleutian Arc, with both oceanic and continental parts.

Image File history File links Size of this preview: 640 × 456 pixelsFull resolution (640 × 456 pixel, file size: 226 KB, MIME type: image/jpeg) Map of Alaska volcanoes, Okmok Cardera, Alaska Volcanoes of the Alaska Peninsula and Aleutian Islands. ... Image File history File links Size of this preview: 640 × 456 pixelsFull resolution (640 × 456 pixel, file size: 226 KB, MIME type: image/jpeg) Map of Alaska volcanoes, Okmok Cardera, Alaska Volcanoes of the Alaska Peninsula and Aleutian Islands. ...

Examples

Continental arcs

• Cascade Volcanic Arc
• Alaska Peninsula and Aleutian Range
• Kamchatka
• Andes

This article or section does not adequately cite its references or sources. ... Volcanoes on the Alaska Peninsula The Alaska Peninsula is a peninsula extending about 800 km (500 miles) to the southwest from the mainland of Alaska and ending in the Aleutian Islands. ... The Aleutian Range is the mountain range of the Alaska Peninsula in southeast Alaska. ... Kamchatka Oblast, an oblast in Russia. ... Planes view of the Andes, Peru. ...

Island arcs

• Aleutian Islands
• Kuril Islands
• Japan and Ryukyu Islands
• Izu Islands and Bonin Islands
• Philippines
• Mariana Islands
• Tonga and Kermadec Islands
• Ogasawara Islands
• Crete and Dodecanese
• Andaman and Nicobar Islands
• Mentawai Islands
• Sunda Arc
• Lesser Sunda Islands
• Tanimbar and Kai Islands
• Solomon Islands
• Lesser Antilles, including the Leeward Antilles
• South Sandwich Islands

Aleutians seen from space The Aleutian Islands (possibly from Chukchi aliat, island) are a chain of more than 300 small volcanic islands forming an island arc in the Northern Pacific Ocean, occupying an area of 6,821 sq mi (17,666 km²) and extending about 1,200 mi (1,900... Location of Kuril Islands in the Western Pacific. ... Location of Ryukyu Islands. ... Location Map of Islands The Izu Islands (伊豆諸島) are a group of volcanic islands stretching south and east from the Izu Peninsula of Honshu, Japan. ... The Ogasawara Islands (小笠原諸島) are an Japan. ... The Mariana Islands (also the Marianas; up to the early 20th century sometimes called Ladrone Islands, from Spanish Islas de los Ladrones meaning Islands of Thieves) are an archipelago made up by the summits of 15 volcanic mountains in the north-western Pacific Ocean, in about 12 to 21 N... The Kermadec Islands are an island arc in the Pacific Ocean. ... A map of the Ogasawara Islands south of Japan The Ogasawara Islands (小笠原諸島) are an archipelago of over 30 subtropical islands some 1,000 km directly south of central Tokyo, Japan. ... For the famous World War II battle, see: Battle of Crete For other uses, see Crete (disambiguation). ... The Dodecanese (Greek: Δωδεκάνησα, Dodekánisa, meaning twelve islands; see also List of traditional Greek place names) are a group of Greek islands in the Aegean Sea, off the southwest coast of Turkey. ... This article or section may be confusing for some readers, and should be edited to be clearer or more simplified. ... Map of Nicobar Islands The Nicobar Islands are an island chain in the eastern Indian Ocean, and are part of India. ... The Mentawai Islands are a chain of islands off the west coast of Sumatra in Indonesia. ... Categories: Geology stubs | Plate tectonics ... Map of Lesser Sunda Islands The Nusa Tenggara, or Lesser Sunda Islands, are a group of islands in the middle-south part of the Malay Archipelago. ... The Tanimbar Islands, also called Timor Laut, are a group of about 30 islands in the Maluku province of Indonesia. ... The Kai Islands (also Kei Islands) of Indonesia are in the south-eastern part of the Maluku Islands, in Maluku province. ... Location of the Lesser Antilles (green) in relation to the rest of the Caribbean Islands of the Lesser Antilles The Lesser Antilles, also known as the Caribbees,[1] are part of the Antilles, which together with the Bahamas and Greater Antilles form the West Indies. ... The Leeward Antilles are a chain of islands in the Caribbean – specifically, the southerly islands of the Lesser Antilles (and, in turn, the West Indies) along the southeastern fringe of the Caribbean Sea, just north of the Venezuelan coast of the South American mainland. ... South Georgia and the South Sandwich Islands is an overseas territory of the United Kingdom, also claimed by Argentina. ...

Ancient Island arcs

• Insular Islands
• Intermontane Islands

The Insular Islands were a giant chain of active volcanic islands somewhere in the Pacific Ocean during the Cretaceous time that rode on top a microplate called the Insular Plate, beginning around 130 million years ago. ... The Intermontane Islands where a volcanic chain in the Pacific Ocean during the Jurassic period. ...

See also

• Back-arc basin
• Volcanic belt

Back-arc basins (or retro-arc basins) are geologic features, submarine basins associated with island arcs and subduction zones. ... A volcanic belt is a district of volcanoes, located in a certain area. ...

References

• Subduction Zone Volcanism
• Tectonics and Volcanoes of Japan
• USGS: Island-Arc, Oceanic, and Continental Volcanoes