Southern Volcanic Zone

Southern Volcanic Zone
Name	Southern Volcanic Zone
Location	Chile, Argentina
Type	Volcanic arc
Last eruption	Various (historical and Holocene activity)

Southern Volcanic Zone is a major volcanic arc in the Andes that runs along central and southern Chile and adjacent Argentina, forming part of the Pacific Ring of Fire. The arc hosts numerous stratovolcanoes, volcanic fields, and geothermal systems that are integral to studies of subduction, magmatism, and hazards in the Southern Cone. Scientists from institutions such as the Smithsonian Institution, Servicio Nacional de Geología y Minería (SERNAGEOMIN), United States Geological Survey, Universidad de Chile, and Universidad Nacional de La Plata collaborate to monitor and research the region.

Geography and extent

The arc extends roughly from the vicinity of the Llaima Volcano area near the Chilean Bío Bío Region southward to the Maule Region and into Patagonia near the Aysén Region, traversing provinces and regions of Chile and Argentina. It lies landward of the trench formed by the subduction of the Nazca Plate beneath the South American Plate and overlaps geographically with zones influenced by the Patagonian Ice Sheet and the South Atlantic Ocean climate systems. Major nearby geographic features include the Andes, the coastal ranges of Chile, the Lake District (Chile) basins such as Llanquihue Lake, and trans-Andean crossings like the Paso Puyehue corridor.

Tectonic setting and geodynamics

The arc is generated by convergent plate interactions where the Nazca Plate subducts beneath the South American Plate at rates varying along strike, interacting with features such as the Juan Fernández Ridge and the Chile Rise. This subduction regime produces mantle wedge melting, slab dehydration, and crustal assimilation processes akin to those documented at arcs like the Aleutian Arc, Cascades, and the Japanese Archipelago. Regional structures including the Liquine-Ofqui Fault Zone, the Andean Fault System, and crustal blocks studied by researchers at institutions like Geological Survey of Argentina control magma ascent and volcanic localization. Geodynamic models from groups at Caltech and ETH Zurich are applied to interpret slab geometry, back-arc extension, and magmatic plumbing.

Volcanic centers and stratovolcanoes

The arc comprises notable volcanic centers and stratovolcanoes such as Villarrica, Lanin, Osorno, Tupungatito, Calbuco, and Puyehue-Cordón Caulle, as well as calderas like Sierra Nevada, Chilean Southern Volcanic Complex, and volcanic fields including the Puyehue and Chillán complexes. Each edifice is a focus for studies by teams from University of Cambridge, University of California, Berkeley, and Universidad Austral de Chile investigating eruption styles, edifice stability, and glacial interactions. Volcanoes in the zone have produced lava flows, pyroclastic density currents, lahars, and phreatomagmatic deposits comparable to eruptions at Mount St. Helens, Mount Pinatubo, and Mount Ruapehu.

Eruption history and hazards

Eruptive records encompass Holocene activity and historical eruptions documented by agencies including SERNAGEOMIN and the Global Volcanism Program. Significant events include the 1960s–21st-century eruptions at centers like Chaitén and the 2011 Puyehue-Cordón Caulle eruption, which generated regional ash clouds affecting aviation authorities such as International Civil Aviation Organization and produced transnational impacts felt in Argentina, Uruguay, and New Zealand flight routes. Hazards encompass ash fall, pyroclastic flows, ballistic projectiles, lahars exacerbated by glacial and snowmelt from interactions with the Patagonian Icefields, and volcanic gas emissions with implications for public health agencies like World Health Organization and national emergency services. Hazard mapping and evacuation planning involve coordination with local governments such as the Gobierno Regional de Los Ríos and international partners including United Nations Office for Disaster Risk Reduction.

Petrology and geochemistry

Rocks range from basaltic andesite to dacite and rhyolite, with compositions reflecting processes of slab-derived fluid input, mantle melting, and crustal contamination analogous to suites described in the Andean Central Volcanic Zone and the Mexican Volcanic Belt. Geochemical studies conducted by groups at University of Tokyo, Pontificia Universidad Católica de Chile, and University of Oxford use major and trace element analyses, radiogenic isotopes (Sr-Nd-Pb), and volatile contents to trace source components and melting regimes. Petrological evidence documents crystal fractionation, magma mixing, and volatile exsolution that control eruption explosivity, comparable to mechanisms inferred for Eyjafjallajökull and Krakatoa.

Seismicity and monitoring

Seismicity associated with the arc includes volcano-tectonic earthquakes, long-period events, and tremor recorded by networks operated by SERNAGEOMIN, Observatorio Volcanológico de los Andes del Sur (OVDAS), and international collaborations with Incorporated Research Institutions for Seismology (IRIS). Monitoring integrates seismic arrays, GPS and InSAR deformation studies by research teams at Jet Propulsion Laboratory, gas flux measurements, thermal remote sensing from satellites such as Landsat and Sentinel, and field geodetic campaigns led by Universidad de Concepción. Early warning practices draw on protocols used by USGS volcano observatories and regional civil defense agencies.

Climate and environmental impacts

Volcanic emissions influence regional climates through injection of ash and sulfur-bearing gases into the troposphere and stratosphere, affecting radiative balance in patterns comparable to documented effects from Mount Pinatubo and El Chichón. Ash deposition alters soil properties and lake chemistry in basins like Llanquihue Lake and impacts ecosystems studied by ecologists from Universidad de Magallanes and conservation bodies such as World Wildlife Fund. Glacial retreat in the Andes, monitored by teams at British Antarctic Survey and Instituto Antártico Chileno (INACH), changes lahar dynamics and hydrology, linking volcanic hazards with climate change-driven shifts observed across the Southern Hemisphere.

Category:Volcanic arcs