Villarrica (volcano)

Active volcano in southern Chile
Villarrica, with its lava of basaltic andesitic composition, is one of a small number worldwide known to have an active (but in this case intermittent) lava lake within its crater. The volcano usually generates strombolian eruptions with ejection of incandescent pyroclasts and lava flows. Rainfall plus melted snow and glacier ice can cause massive lahars (mud and debris flows), such as during the eruptions of 1964 and 1971. Villarrica is one of 9 volcanoes currently monitored by the Deep Earth Carbon Degassing Project. The project is collecting data on the carbon dioxide and sulphur dioxide emission rates from subaerial volcanoes.

Villarica stands just east of the Chilean Central Valley as the westernmost of an alignment of three large stratovolcanoes. The alignment is attributed to the existence of an old fracture in the crust, the North West South East trending Mocha Villarrica Fault Zone,

Villarrica covers an area of 400 km2 and has an estimated volume of 250 km3. It contains volcanic caves and about 26 scoria cones. The constant degassing at the lava lake turns the otherwise quite effusive lava more viscous, heightening its explosive potential. Two large ignimbrite layers are visible; the Licán Ignimbrite and the more recent Pucón Ignimbrite.

The upper part of Villarrica is permanently covered by snow and has some 40 km2 of glaciers, the largest of which is the Pichillancahue Turbio Glacier situated on its southeastern flank. Ash from the eruptions can increase the ablation of snow and ice by absorption of solar radiation. Some ash coverings are thicker than 5 cm and insulate the glacier, decreasing ablation instead of enhancing it. Between 1961 and 2003, Villarrica lost 25% of its glaciated surface and the glaciers shrank at an average rate of 0.4 km2 each year.

Villarrica is popular for climbing with guided hikes to the crater from the town of Pucón, but these may be suspended due to cloud or volcanic activity. Helicopter over flights have been available since 2007. In the winter (July–September) a ski resort operates on the northern slopes. The youngest person to reach the summit recognized by the Chilean government was Christopher Heussner of Texas at the age of 9 in 1999.

Villarrica is one of Chile's most active volcanoes; eruptions have been recorded since the conquest of Chile and the founding of the city of Villarrica in 1552. This city was originally founded near the site of present day Pucón. Villarrica volcano had frequent strombolian eruptions in the second half of the 16th century. The 1562 eruption in particular deposited thin ash layers as far as 200 km away from the volcano. However mining activity declined over time.

The volcano resumed eruptive activity on March 8, 1963. On March 12 a flank vent some 250 metres below the summit begun to pour lava that ended up making a 1000 m long and 150 meter broad lava flow. At some point, the inhabitants of Coñaripe decided to return to their houses in search of shelter from the heavy rainfall. The hamlet of Chaillupén was also destroyed by the lahar meaning 30 houses were destroyed, however, there were no deaths. Such views reflect the belief that nature was "allied with the Indians".

On 29 October 1971, at 3:00 am, there were several explosions in the crater and a column of white and then black smoke appeared.

On February 7, 2015, Villarrica triggered a yellow alert at both Servicio Nacional de Geología y Minería and Onemi. Minor explosions and low emissions of ashes were visible. Ten days later, another eruption occurred. The National Service of Geology and Mining (Sernageomin) declared a yellow alert after volcanic and seismic activity increased again, while the National Emergency Office of the Interior Ministry (ONEMI) kept the yellow alert. At approximately 03:01 AM on March 3, 2015, it erupted, raising the alert to red up to 10 kilometers around. The eruption exceeded the height of the volcano, causing a loud explosion that woke the neighbors, and forcing the evacuation of 3,385 people in nearby communities. The Southern Andean Volcano Observatory (OVDAS) indicated that a new imminent eruption would continue until 12:29 of March 19, 2015. As of July 2015, the eruption was continuing. Volcanic gas emissions from this volcano are measured by a Multi Component Gas Analyzer System, which detects pre eruptive degassing of rising magmas, improving prediction of volcanic activity. Analysis of seismicity prior to the eruption show that there was no seismicity that could be reliably related to the upcoming eruption. However, a series of small earthquakes with hypocenters about 9 km beneath Villarrica volcano that occurred 45 days after the eruption are thought to have been caused by the cooling of the eruption's feeder dykes.