Scientists keep watch on Turrialba volcano after ash rain

This was the Turrialba crater at noon Wednesday as seen from a remote camera

The Turrialba volcano continues to perk along and dump acidic gases on the surrounding farmland.

Scientists still are trying to figure out why the restless mountain put forth gas and ash last week. They have been hampered by the weather.

Mid-afternoon Friday residents of the community of La Central near the volcano began to report the fall of ash and a strong sulfur odor. They also reported rumbling between 5 and 6 p.m.

A quick check of instruments at the Observatorio Vulcanológico y Sismológico de Costa Rica failed to show any earthquakes or explosions, the observatory reported.

Saturday scientists from the observatory, which is part of Universidad Nacional in Heredia, traveled to the communities close to the volcano. La Central is just two kilometers, about 1.25 miles, from the volcano peak.

They said they found much less ash than they were expecting, and rains had washed much away.

The volcano has been under intense scrutiny for a year because of eruptions Jan. 4 and 5, 2010, when it opened up a new crater. Scientists have installed a video monitor trained on the peak. Saturday scientists found the expected plume of gases, mostly water, carbon dioxide, sulfur dioxide and hydrogen sulfide, among others.

The Turrialba volcano as seen from near Parque La Sabana Monday morning. Gases are headed northwest. Photo: Observatorio Vulcanológico y Sismológico de Costa Rica/María Martínez Cruz

ientists noted that the gases are toxic and that some, like carbon dioxide, are heavier than air so they accumulate in depressions and other low spots when there is little wind. That is why they recommend that the public avoid the area.

Farming, mostly dairy, still goes on in the shadow of the volcano even though the gases have turned much of the vegetation yellow.

Scientists speculate in a report released Tuesday that strong winds and heavy rains earlier last week caused small landslides within the new volcano crater and that is why ash was transported out of the volcano into the surrounding area. A lot of the gas and volcanic material drifts north and west of the crater, mostly into Parque Nacional Braulio Carrillo.

The volcano’s twin, Volcán Irazú, also continues to put out acidic gases but to a lesser degree. Scientists plan to visit the Turrialba crater to see if they can detect sidewalls that may have collapsed, causing the emission of ash.

A major eruption and a rain of ash on the metro area would be a major problem. That is what happened in 1963 when Irazú blew its top.

The cleanup continued for two years.

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