Andean Volcanic Belt

The Andean Volcanic Belt is a central volcanic belt along the South American coast within the Andes mountain system in Argentina, Bolivia, Chile, Colombia, Ecuador, and Peru. It is formed due to the Nazca and Antarctic tectonic plate subduction underneath the South American Plate.

The belt is subdivided into four main volcanic zones that are separated from each other by volcanic gaps. As a result, the volcanoes of the belt are diverse in terms of activity style, products and morphology.

The Romeral stratovolcano 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. The southernmost volcano is Fueguino in the Tierra del Fuego archipelago.

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

Volcanic gaps interpose the different volcanic zones. These gaps lack volcanic activity despite lying at the proper distance from an oceanic trench. The Andes has three significant volcanic gaps:

• Peruvian flat slab segment (3 °S - 15 °S)

• Pampean flat slab segment (27 °S - 33 °S)

• Patagonian Volcanic Gap (46 °S - 49 °S)

_{Map showing zones of the Andean Volcanic Belt}

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 Zone. The volcanic arc has formed due to the subduction of the Nazca Plate underneath western South America.

Some volcanoes of the Northern Volcanic Zone, such as Galeras and Nevado del Ruiz, lie in densely populated highland areas and are significant sources of hazards.

It has been estimated that crustal thickness beneath this region varies from around 40 km (25 mi) to perhaps more than 55 km (34 mi). Sangay is the southernmost volcano within the Northern Volcanic Zone.

Central Volcanic Zone

The Central Volcanic Zone (CVZ) extends from Peru to Chile and forms the western boundary of the Altiplano plateau. The volcanic arc has developed due to the subduction of the Nazca Plate under western South America along the Peru-Chile Trench.

To the south, the CVZ is limited by the Pampean (or Norte Chico) flat slab segment, a region devoid of volcanism due to a lower subduction angle caused by the subduction of the Juan Fernández Ridge.

The CVZ is characterized by a continental crust that reaches a thickness of approximately 70 km (43 mi). Within this zone, 44 major and 18 minor volcanic centers are active.

This volcanic zone also contains not less than six potentially active large silicic volcanic systems, which include those of the Altiplano-Puna Volcanic Complex: Cerro Panizos, Pastos Grandes, Cerro Guacha and La Pacana.

Other silicic systems are the Los Frailes ignimbrite plateau in Bolivia and the caldera complexes of Incapillo and Cerro Galán in Argentina.

Southern Volcanic Zone

The South Volcanic Zone (SVZ) extends roughly from Central Chile's Andes mountains at Santiago to Cerro Arenales in the Aysén Region, well over 870 mi (1,400 km). 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.

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 the Tierra del Fuego archipelago, well over 600 mi (1,000 km).

The arc has formed due to the 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 glaciated stratovolcanoes and subglacial volcanoes under the Southern Patagonian Ice Field.

_{Map depicting the volcanic arcs that form the Ring of Fire}

Pacific Ring of Fire

The Pacific Ring of Fire (also known as the Circum-Pacific belt) is an area in the Pacific Ocean basin where many earthquakes and volcanic eruptions occur. The Ring of Fire directly results from plate tectonics: the movement and collisions of lithospheric plates.

In a large 40,000 km (25,000 mi) horseshoe shape, the Ring of Fire is associated with a nearly continuous series of oceanic trenches, volcanic arcs, volcanic belts and plate movements. It consists of more than 450 volcanoes (over 75% of the world's active and dormant volcanoes).

Approximately 90% of the world's and 80% of the world's largest earthquakes occur along the Ring of Fire. In addition, all but three of the world's 25 most significant volcanic eruptions of the last 11,700 years emerged from the Ring of Fire volcanoes.

In Central America, the Cocos Plate is being subducted beneath the Caribbean Plate, resulting in the Central America Volcanic Arc. Likewise, portions of the Pacific Plate and the small Juan de Fuca Plate are subducted beneath the North American Plate.

Along the west coast of South America, the Ring of Fire's eastern section results from the Nazca Plate and the Cocos Plate being subducted beneath the westward-moving South American Plate.

_{Map depicting the oceanic trenches that form the Pacific Ring of Fire}