Patagonian Volcanic Gap

The Andean Volcanic Belt is a major volcanic belt along the Andean cordillera in Argentina, Bolivia, Chile, Colombia, Ecuador and Peru. 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 separated 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 are significant differences within 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 extensional 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.

Romeral in Colombia is the northernmost active member of the Andean Volcanic Belt. South of latitude 49° S within the Austral Volcanic Zone volcanic activity decreases with the southernmost volcano Fueguino in Tierra del Fuego archipelago.

The Andean Volcanic Belt is segmented into four main areas of active volcanism; the Northern, Central, Southern and Austral volcanic zones, each of which is a separate continental volcanic arc.

The Northern Volcanic Zone (NVZ) extends from Colombia to Ecuador and includes all volcanoes on the continental mainland of these countries. Of the volcanoes in this zone, 55 are located in Ecuador, while 19 are in Colombia. In Ecuador, the volcanoes are located in the Cordillera Occidental and Cordillera Real while in Colombia they are located in the Western and Central Ranges. The Pliocene Iza-Paipa volcanic complex in Boyacá, in the Eastern Ranges is the northernmost manifestation of the Northern Andean Volcanic Belt. The volcanic arc has formed due to subduction of the Nazca Plate underneath western South America. Some volcanoes of the Northern Volcanic Zone, such as Galeras and Nevado del Ruiz that lie in densely populated highland areas, are major sources of hazards. It has been estimated that crustal thickness beneath this region varies from around 40 to perhaps more than 55 kilometres (34 mi).Sangay is the southernmost volcano of the Northern Volcanic Zone.

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