San José, Costa Rica, since 1956

Scientists Study Causes Of Turrialba Volcano Activity

After weeks of studying the unusually active Turrialba Volcano, on the Caribbean slope, scientists say that its spectacular increase in gas emissions was most likely caused by tectonic shifts in the region. The volcano, which last erupted in 1866, is unlikely to repeat that performance now, scientists say – though they can’t rule it out just yet.

Mario Fernández, of the National Seismological Network (RSN), told the daily La Nación that although onlookers and experts often interpret increased gas emissions as a sign that an eruption may be imminent, small quakes, rather than magma movement within the volcano, can also produce this effect.

However, “we can’t rule out that there is magma on the rise in Turrialba Volcano and that an eruption will occur,” he said.

Costa Rica experienced 424 quakes (most of them too small to be felt) in April, 58 more than in March. Many of these took place close to the volcano, according to Fernández.

The active volcano, which last erupted from 1864-1866, began releasing increased amounts of sulfuric gases and water vapor March 31, when tourists reported the activity to authorities. Specialists who visited the site quickly concluded there was no reason for alarm and an eruption was not imminent, but the National Emergency Commission (CNE) decided to restrict entrance to the volcano’s crater, a popular tourism destination, to 100 people at a time.

CNE spokeswoman Rebeca Madrigal told The Tico Times this week that the 100-person restriction is still in effect.

The commission is also working on preventive measures including weekly visits to the area to monitor the volcano; installing communications equipment at the volcano so the commission can stay in contact with park guards; and establishing community and national park evacuation routes, along with possible temporary shelter locations in case of emergency, according to an e-mail from Madrigal.

Observers have reported plumes of gases reaching 40-100 meters high.


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