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.
Northern Volcanic Zone 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 the
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 significant sources of hazards. It has been estimated that crustal thickness beneath this region varies from around 40 to perhaps more than . whose responsibility is to monitor
Ecuador's numerous active
volcanoes in the Andean Volcanic Belt (which is part of the
Ring of Fire) and the
Galápagos Islands.
Central Volcanic Zone The Central Volcanic Zone (CVZ) is a volcanic arc in western South America and 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 devoid 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 . Within this zone, there are 44 major and 18 minor volcanic centers that are considered to be active.
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 . The arc has formed due to the 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 is 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. From north to south the Southern Volcanic Zone is divided into four segments according to the characteristics of the
continental crust, volcanoes and
volcanic rocks: • Northern SVZ (NSVZ; 33°S–34°30′S) • Transitional SVZ (TSVZ; 34°30′S–37°S) • Central SVZ (CSVZ; 37°S–41.5°S) • Southern SVZ (SSVZ: 41.5°S–46°S) In Central Southern Volcanic Zone and Southern Southern Volcanic Zone, magma ascent occur primarily by the
Liquiñe-Ofqui Fault. The
Principal Cordillera of Andes (east Santiago)
rose in late Cenozoic and became extensively glaciated about one million years ago. This meant lavas from NSVZ volcanoes begun to be channeled along a network of glacial valleys ever since. The
Maipo caldera exploded about 450 thousand years ago, leaving behind copious amounts of ash and
ignimbrite rock that can be observed today both in Chile and Argentina. A reduction in the convergence rate of the
Nazca and the
South American plate from per year to The southern part of the SVZ retained vigorous activity only in the west, especially around the
Liquiñe-Ofqui Fault Zone, Several volcanoes of the SVZ are being monitored by the
Southern Andean Volcano Observatory (OVDAS) based in
Temuco. The volcanoes monitored have varied over time, but some, like
Villarrica and
Llaima, are monitored constantly. In recent years, there have been major eruptions at
Chaitén (2008–2010),
Cordón Caulle (2011) and
Calbuco (2015).
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. Volcanism in the Austral Volcanic Zone is less vigorous than in the Southern Volcanic Zone. Recorded eruptions are rare due to the area being unexplored well into the 19th century; the cloudy weather of its western coast might also have prevented sightings of eruptions. The Austral Volcanic Zone hosts both glaciated stratovolcanoes as well as
subglacial volcanoes under the
Southern Patagonian Ice Field. ==Volcanic gaps==