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Costa Rica: eruption at Turrialba 6 January 2010

Posted by admin in activity reports, Costa Rica, eruptions, Turrialba.
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There have been signs of increased activity at Turrialba volcano in Costa Rica for some time – a rise in gas emissions, temperature increases around the crater, new cracks in the summit area – and now comes news that there has been a small eruption, the first at Turrialba since 1866. The Costa Rican geological service Ovsicori have issued a bulletin on the eruption (PDF), which reports as follows:

On 5 January 2010 at 14:48 local time an inhabitant of the La Central area located to the south-west of Turrialba volcano reported hearing a strong eruption of Turrialba, much later people living near the volcano reported ashfall. Also, officials of the Parque Nacional Volcán Irazú reported the presence of ash in vehicles parked in the car park inside the national park. Additionally, residents of Turrialba, Tres Ríos and owners of properties on the slopes of Turrialba volcano reported ashfall.

From mid-December 2009 until 4 January 2010, LP-type earthquakes (low frequency) had been predominantly registered, with a significant decrease of volcanic tremor. On 4 January 2010 there was a significant increase in volcanic tremor, both in duration of registration and in the amplitude of the signal. Coinciding with the increase in the recording of tremor there was a significant decrease in LP-type earthquakes. In the early hours of Wednesday 6 January an OVSICORI-UNA team will go to the area to make observations and collect data and information to carry out relevant studies.

A green (preventative) alert was issued by the authorities for the area around Turrialba, and about 20 people were evacuated from the volcano’s slopes.

The volcanic deposits reported as falling in villages to the south-west of Turrialba up to 3 km from the crater were described by Ovsicori as ‘white powder’. Eliécer Duarte of Ovsicori told La Nación that ‘this is not ash. Ash is black, glassy, sharp, and causes much damage’. Duarte said that the material produced by this eruption could represent ‘a stage preceding the eruption of juvenile material’, indicating that the volcano ‘now has the capacity to erupt much heavier material into the atmosphere’. The suggestion is that the material erupted so far is pulverized old rock rather than fresh magmatic material. However, local inhabitants have insisted that the material is ‘black and sandy. A Red Cross official in one affected village has reported sulphurous smells and ashfall, and says that there are ‘black spots’ on the plastic sheeting covering crops in local plantations. The National Emergencies Commission (CNE), meanwhile, describes Turrialba’s activity in a press release as ‘a minor ash eruption with a little acid rain’.

Overall, the Costa Rican authorities seem to be regarding this event as a minor eruption, but a possible precursor of larger-scale activity to come.

For all our coverage of Turrialba: Turrialba « The Volcanism Blog.

News
Ovsicori confirma erupción de sedimento blanco del TurrialbaLa Nación, 5 January 2010
Alerta en Costa Rica por erupción de ceniza en el volcán Turrialba – EFE, 5 January 2010
Vecinos insisten en que cayó ceniza en poblados de Oreamuno y CartagoLa Nación, 5 January 2010
Tras 145 años, despierta el volcán TurrialbaEl Informador, 5 January 2010
Costa Rican volcano erupts after long silence – Reuters, 5 January 2010
Families evacuate Turrialba area as volcano acts upTico Times, 5 January 2010

Information
Global Volcanism Program: Turrialba – summary information for Turrialba (1405-07=)
Observatorio Vulcanológico y Sismológico de Costa Rica – Ovsicori website
Volcán Turrialba – information from Ovsicori
Monitoreo Volcanico (Red Sismológica Nacional) – volcano monitoring updates from the Costa Rican national seismological network

The Volcanism Blog