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Turrialba calmer, but helium emissions create a stir 3 February 2010

Posted by admin in activity reports, Costa Rica, Turrialba.
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Turrialba, which erupted on a small scale at the beginning of January, has returned to a state of ‘passive degassing’ similar to that which pertained before the eruption, according to reports from Costa Rica. However, Ovsicori experts have warned that although activity has declined low intensity earthquakes continue, the volcano remains active and people should not be complacent. The Comisión Nacional de Emergencias (CNE) has revised the alert levels currently applied to the area surrounding the volcano, with Yellow Alert now applying to a 2 km radius zone around the volcano and Green Alert to areas beyond that limit (CNE news release: Alerta Verde y Alerta Amarilla ante Actividad Volcánica).

Levels of gas emission from Turrialba have fallen since the eruption but this volcano is a persistent and unpleasant degasser, and this aspect of its activity continues. In particular, the appearance of large amounts of helium in Turrialba’s emissions has been attracting the attention of the experts. There’s nothing official about this yet from Ovsicori, but the Costa Rican newspaper La Nación reports that ‘the volcanologists could not believe what was happening’ when Jorge Andres Díaz, a physicist and gas measurement specialist working for the Comisión Nacional de Emergencias reported that measurements taken on 19 January 2010 indicated there was 30 ppm (parts per million) of helium in Turrialba’s emissions:

For the volcanologists of the National Seismological Network and Ovsicori, that figure was much too ‘high’, because normally helium at the volcano fluctuates between 2 and 8 ppm. ‘That would be way too much’, says Raúl Mora, volcanologist at the [National Seismological] Network.

The volcanologists and Díaz apparently got into a discussion lasting several hours about this at the CNE headquarters yesterday, according to La Nación.

However, the presence of high proportions of helium in gas emissions from Turrialba was noted back in April 2008, when it was interpreted as being the result of magma build-up within the volcano. Measurements taken in March 2008, also by Díaz, indicated helium levels of 80 ppm. At that time, Ovsicori reported the normal level of helium for Turrialba as 25 ppm, which would make a possible level of 30 ppm now a bit less of a leap (an earlier report in the Tico Times has Díaz reporting levels of 20 ppm). In any case, the presence of elevated helium levels in Turrialba’s emissions is an indicator that fresh magma is being intruded into the volcanic system.

(Useful information about the significance of magmatic helium can be found in ‘Helium discharge at Mammoth Mountain Fumarole’, from the USGS’s Long Valley Volcano Observatory.)

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

News
Helium also rising from Costa Rica’s Turrialba volcanoTico Times, 21 January 2010
Medición de helio generó intenso debateLa Nación, 31 January 2010
El Turrialba lanza menos gases pero siguen los sismosLa Nación, 30 January 2010
CNE outlines risk areas around Turrialba volcano as gas still spewsTico Times, 1 February 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
Turrialba webcam – Ovsicori’s webcam at Turrialba’s summit
Monitoreo Volcanico (Red Sismológica Nacional) – volcano monitoring updates from the Costa Rican national seismological network

The Volcanism Blog