The Andean Volcanic Belt is a major volcanic belt along the Andean cordillera in Colombia, Bolivia, Peru, Ecuador, Chile and Argentina. It formed as a result of subduction of the Nazca Plate and Antarctic Plate underneath the South American Plate. The belt is subdivided into four main volcanic zones that are separed from each other by volcanic gaps. The volcanoes of the belt are diverse in terms of activity style, products and morphology. While some differences can be explained by which volcanic zone a volcano belongs to, there significant differences inside volcanic zones and even between neighboring volcanoes. Despite being a type location for calc-alkalic and subduction volcanism, the Andean Volcanic Belt has a large range of volcano-tectonic settings, such as rift systems and extrensional zones, transpressional faults, subduction of mid-ocean ridges and seamount chains apart from a large range on crustal thicknesses and magma ascent paths, and different amount of crustal assimilations.

Nevado del Ruiz in Colombia is the northernmost member of the Andean Volcanic Belt.^[1] South of latitude 45° S in the Austral Volcanic Zone volcanic activity decreases being the southernmost known volcano Fueguino in Tierra del Fuego archipelago.

Contents 1 Volcanic zones 1.1 Northern Volcanic Zone 1.2 Central Volcanic Zone 1.3 Southern Volcanic Zone 1.4 Austral Volcanic Zone 2 Volcanic gaps 2.1 Peruvian gap 3 Back-arc volcanism 4 Geothermal activity 5 See also 6 References 7 External links

[edit] Volcanic zones

[edit] Northern Volcanic Zone

The Northern Volcanic Zone (NVZ) is a volcanic arc in northwestern South America and one of the four volcanic zones of the Andes. The Northern Volcanic Zone extends from Colombia to Ecuador and include all volcanoes on the continental mainland of these countries. The volcanic arc has formed due to subduction of the Nazca Plate under western South America.

[edit] Central Volcanic Zone

The Central Volcanic Zone (CVZ) is a volcanic arc in western South America. It is one of the four volcanic zones of the Andes. The Central Volcanic Zone extends from Peru to Chile and forms the western boundary of the Altiplano plateau. The volcanic arc has formed due to subduction of the Nazca Plate under western South America along the Peru-Chile Trench. To the south the CVZ is limited by the Pampean flat-slab segment or Norte Chico flat-slab segment, a region absent of volcanism due to a lower subduction angle caused by the subduction of Juan Fernández Ridge.

The CVZ is characterized by a continental crust that reaches a thickness of approximately 70 km.^[2] Within this zone there are 44 major and 18 minor volcanic centers that are considered to be active.^[2] This volcanic zone also contains not less than six potentially active large silicic volcanic systems, which include those of the Altiplano-Puna Volcanic Complex, as are Cerro Panizos, Pastos Grandes, Cerro Guacha and La Pacana. Other silicic systems are Los Frailes ignimbrite plateau in Bolivia, and the caldera complexes of Incapillo and Cerro Galán in Argentina.^[2][3][4]

[edit] Southern Volcanic Zone

The South Volcanic Zone (SVZ) extends roughly from Central Chile's Andes at the latitude of Santiago, at ca. 33°S, to Cerro Arenales in Aysén Region at ca. 46°S, a distance of well over 870 mi (1,400 km). The arc has formed due to subduction of the Nazca Plate under the South American Plate along the Peru-Chile Trench. The northern boundary of the SVZ is marked by the flat-slab subduction of the Juan Fernández Ridge, which us believed to have produced a volcanic gap called the Pampean flat-slab segment in the Norte Chico region since the late Miocene. The southern end of the SVZ is marked by the Chile Triple Junction where the Chile Rise subducts under South America at the Taitao Peninsula giving origin to the Patagonian Volcanic Gap. Further south lies the Austral Volcanic Zone.

During the Pliocene the SVZ south of 38°S consisted in broad volcanic arc. The broad of the area with volcanic activity 1 to 2 million years ago between 39°S-42°S was up to 300 km broad if including back-arc volcanism.^[5] A reduction in the convergence rate of Nazca and the South American Plate from 9 cm per year to 7.9 cm^[5] per year 2-3 million years ago contributed to a narrowing of the southern SVZ that occurred possibly 1.6 million years ago.^[6] The southern part of the SVZ retained vigorous activity only in the west specially around the Liquiñe-Ofqui Fault Zone,^[6] while eastern volcanoes like Tronador and Cerro Pantoja became extinct.

Eight volcanoes of the SVZ (Chaiten, Cordón Caulle, Lonquimay, Llaima, Villarrica, Mocho-Choshuenco, Osorno and Calbuco) are being monitored by the Southern Andean Volcano Observatory (OVDAS) based in Temuco. In recent years, there have been major eruptions at Llaima (most recently in 2008-9), and Chaitén (2008–2010).

[edit] Austral Volcanic Zone

The Austral Volcanic Zone (AVZ) is a volcanic arc in the Andes of southwestern South America. It is one of the four volcanic zones of the Andes. The AVZ extends south of the Patagonian Volcanic Gap to Tierra del Fuego archipelago, a distance of well over 600 mi (1,000 km). The arc has formed due to subduction of the Antarctic Plate under the South American Plate. Eruption products consist chiefly of alkaline basalt and basanite.^[7]

[edit] Volcanic gaps

The different volcanic zones are intercalated by volcanic gaps, zones that despite lying at the right distance from an oceanic trench lack volcanic activity.^[8] The Andes has three major volcanic gaps the Peruvian flat-slab segment (3 °S—15 °S), the Pampean flat-slab segment (27 °S—33 °S) and the Patagonian Volcanic Gap (46 °S). The first one separates the Northern from the Central Volcanic Zone, the second the Central from the Southern and the last separates the Southern from the Austral Volcanic Zone. The Peruvian and Pampean gaps coincide with "flat slab" (low angle) subduction areas and therefore the lack of volcanism is believed to be caused by the shallow dip of the subducting Nazca Plate in these places. The shallow dip has in turn been explained by the subduction of the Nazca Ridge and the Juan Fernández Ridge for the Peruvian and Pampean gaps respectively. Since the Nazca and Juan Fernández Ridge are created by volcanic activity in Pacific hotspots (Easter and Juan Fernández) it can be said that volcanic activity in the Pacific is responsible for the suppression of volcanism in parts of the Andes.

The Patagonian gap is different in nature it is caused not by the subduction of an aseismic ridge but by the subduction of the Chile Rise, the boundary ridge between the Nazca and the Antarctic Plate.

[edit] Peruvian gap

Between the latitudes of 3 °S—15 °S in Peru the last volcanic activity occurred 2.7 million years ago in Cordillera Blanca.^[9] The lack of volcanism in central and northern Peru is widely attributed to a side effect of the flat-slab (low angle) subducion of the Nazca Plate occurring there. While the subduction of the Nazca Ridge has often been credited for causing this flat-slab and hence the lack of volcanism many researchers find the gap to wide to be explained by this alone.

One hypothesis claims that the flat-slab is caused by the ongoing subduction of an oceanic plateau. This hypothethical plateau named Inca Plateau would be a mirror image of the Marquesas Plateau in the South Pacific.^[9]

[edit] Back-arc volcanism

Please help improve this article by expanding it. Further information might be found on the talk page. (May 2010)

Back-arc volcanism is a significant phenomenon in Argentine Patagonia and Mendoza Province. Flat-slab subduction along the Peru-Chile Trench during the Miocene has been pointed out as being responsible for back-arc volcanism in Mendoza and Neuquén Province during the Quaternary.^[10]

[edit] Geothermal activity

The Andean Volcanic Belt represents a large geothermal province, with numerous hot springs, solfataras and geysers associated to its volcanoes. The geothermal exploration in the Andes was pioneered in Chile in the 1960s,^[11] although the site of El Tatio was invistigated already in the 1920s. Compared to neighboring Central America the Anden region is poorly explored and exploited for geothermal resources.

[edit] See also

• List of volcanoes in Argentina
• List of volcanoes in Bolivia
• List of volcanoes in Chile
• List of volcanoes in Colombia
• List of volcanoes in Ecuador
• List of volcanoes in Peru

[edit] References

• Massimo D'Orazio, Samuele Agostinia, Francesco Mazzarinib, Fabrizio Innocentia, Piero Manettic, Miguel J. Hallerd and Alfredo Lahsen (2000) The Pali Aike Volcanic Field, Patagonia: slab-window magmatism near the tip of South America, Tectonophysics, volume 321, Issue 4, 30 June 2000, Pages 407-427
• Pali Aike National Park (2008) [1]
• UNESCO (1998) Submittal for inscription: Pali Aike and Fell Cave sites [2]
• Active Andean volcanism: its geologic and tectonic setting

[edit] External links

• B and 11B behaviour in the Northern Volcanic Zone of the Andes. Insights on the devolatilization of the slab and related magma genesis processes.
• Central Volcanic Zone
• OVDAS website

v • d • e Andean volcanoes Northern Volcanic Zone (6° N–3° S) Nevado del Ruiz · Nevado del Huila · Galeras · Cayambe · Reventador · Pichincha · Antisana · Illiniza · Cotopaxi · Quilotoa · Tungurahua · Sangay Central Volcanic Zone (15°–27° S) Coropuna · Sabancaya · Chachani · El Misti · Ubinas · Huaynaputina · Parinacota · Pastos Grandes · Sairecabur · Pacana · Licancabur · Lascar · Llullaillaco · Galán · San Francisco · Ojos del Salado Southern Volcanic Zone (33°–46° S) Tupungato · Tupungatito · Maipo · Descabezado Grande · Cerro Azul · Nevado de Longaví · Nevados de Chillán · Antuco  · Copahue · Callaqui · Lonquimay · Llaima · Sollipulli · Villarrica · Quetrupillán · Lanín · Mocho-Choshuenco · Carrán-Los Venados  · Puyehue-Cordón Caulle · Osorno · Calbuco · Hornopirén · Michinmahuida · Chaitén · Corcovado · Cay · Macá · Hudson Austral Volcanic Zone (49°–55° S) Lautaro · Viedma · Aguilera · Reclus · Pali-Aike · Burney · Fueguino Note: volcanoes are ordered by latitude from north to south

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