Turrialba volcano erupts, Costa Rica


Costa Rica's Turrialba volcano experienced a relatively large eruption starting 05:10 UTC on October 30, 2014 (23:10 local time on October 29). The eruption lasted about 25 minutes and ended with a large explosion. The volcano rumbled back to life in 2010 after 144 years of sleep.

According to the National Seismological Network (RSN), this was Turrialba’s largest eruption in 150 years which managed to merge two of the volcano's craters.

It was characterized by a small phreatic eruption and ash emission which was carried to the west-southwest. The fumarole reached several hundred meters, Carlos Ramírez, a volcanologist at the crater, told The Tico Times. Ramírez said that the eruption involved ash, rocks and possibly magma.

National Emergency Commission (CNE) officials declared a Yellow Alert in the volcano area and the Turrialba Volcano National Park is closed to visitors until further notice.

Ash was reported in San Gerardo de Irazú, San Ramón de Tres Ríos, Coronado, Moravia, Curridabat, Desamparados, Aserrí, Escazú, Santa Ana, Belén, Guácima de Alajuela, Río Segundo de Alajuela, San Pedro Montes de Oca, Guadalupe, San José and in some areas of Heredia. Image credit: OVSICORI-UNA

Members of the Red Cross were the first to reach the scene in the early morning hours of Thursday (local time) distributing masks to visibly shaken residents. Costa Rica’s emergency response officials have prepared an evacuation plan, should the order for evacuation be given.

Image credit CNE.

Gas, vapor and ash spewing remained constant on Thursday morning. A second explosion was observed at 14:29 UTC (08:29 local time) today.

Volcanological and Seismological Observatory of Costa Rica (OVSICORI-UNA) volcanologists climbed the volcano's summit yesterday morning and observed very elevated temperatures.

An increase in the SO2 emission was also observed and was measured at 2 000 tonnes per day. This represents an increase to September's average of 1 300 tonnes of SO2 per day and is the highest emission recorded this year.

Turrialba's last major eruption was in 1866, but in January 2001, the volcano experienced increased activity, displaying strong fumaroles at the central craters. The volcanic activities have increased since 2005.

In January 2010, the volcano erupted, and two villages, La Central and El Retiro, were evacuated. OVSICORI-UNA reported that a phreatic eruption from Turrialba that began on January 5 was preceded by a day of increased seismicity and about 30 minutes of almost constant tremor. Two events detected about 15 minutes apart were followed by reports of ashfall as far away as 30 km. Field observations on January 6 revealed that two small vents had opened and joined together on the SE inner wall of the SW crater. 

Similar activity was reported throughout 2010 and the next notable episode happened during June/July 2011 with the Turrialba spewing out greater emission of gases with sound that appeared similar to a jet engine.

Another wave of eruptions started on January 12, 2012. OVSICORI-UNA reported that on January 11 local people around Turrialba heard several instances of rumbling. On January 12 an eruption occurred from a fissure on the SE flank of the main crater, in an area called La Quemada. An ash plume rose 500 m above the crater and drifted NNW, rising to an altitude of 4 km (13,000 ft) a.s.l. Later that day residents reported: a dark plume from La Quemada and a white vapor plume that rose from the fumarolic vent formed in the main crater on January 5, 2010.

According to a news article, the Turriabla National Park closed on January 12 and the CNE raised the Alert Level from Green to Yellow in the communities of La Central (34 km SW), Santa Cruz (7 km SE), and around the perimeter of the crater. Towns of Jiménez (21 km N), Oreamuno (45 km SW), Alvarado (38 km SW), and Cartago (25 km SW) remained at Alert Level Green.

An OVSICORI-UNA pilot observed an ash plume that rose to altitudes of 4.3-6.1 km (14,000-20,000 ft) a.s.l. on January 18, 2012.

The same agency reported that an eruption from Turrialba's West Crater on May 21, 2013 was preceded by seismic activity characterized by more than 150 volcanic earthquakes per day since April 18, 2013. Increased gas emissions were detected on May 20, 2013 producing a sky-blue plume visible from nearby areas. Hybrid earthquakes also increased and became numerous at 04:52 on May 21. Continuous harmonic tremor followed and then increased at 07:20. Eruptions from West Crater occurred at 08:30 and after 11:00 from two vents which opened in January 2010 (Boca 2010, on the W wall) and January 2012 (Boca 2012, on the E wall). The eruptions generated ash plumes that rose more than 500 m; ashfall was reported in the area of Picada (N), and in San José (35 km WSW) and Heredia (38 km W) of Ipís de Guadalupe, Goicoechea (28 km WSW), la Fazio, Zetillal (43 km W), San Isidro-San Pedro de Coronado, and San Luis de Santo Domingo (28 km W). At around 12:00 ash emissions ceased and seismicity decreased.

The volcano also showed an increased activity in July 2013. Low-frequency signals indicating fluid movement grew from an average of less than 200 events per day to over 600 events on July 14, reaching a peak of activity with over 1 000 events on July 15. Low-frequency tremor was detected during July 18 – 19, 2013. 

An increase in seismic activity was later observed in September 2014.

A swarm of earthquakes started mid-October 2014, with largest being M2.8 at 02:35 UTC on October 17, 2014.

Geologic summary

Turrialba, the easternmost of Costa Rica's Holocene volcanoes, is a large vegetated basaltic-to-dacitic stratovolcano located across a broad saddle NE of Irazú volcano overlooking the city of Cartago. The massive 3340-m-high Turrialba is exceeded in height only by Irazú, covers an area of 500 sq km, and is one of Costa Rica's most voluminous volcanoes. Three well-defined craters occur at the upper SW end of a broad 800 x 2200 m summit depression that is breached to the NE.

Most activity originated from the summit vent complex, but two pyroclastic cones are located on the SW flank. Five major explosive eruptions have occurred during the past 3500 years. A series of explosive eruptions during the 19th century were sometimes accompanied by pyroclastic flows. Fumarolic activity continues at the central and SW summit craters.

Featured image: Turrialba eruption on October 29, 2014. Image credit OVSICORI-UNA

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