The Red Sismológica Nacional at the Universidad de Costa Rica said that its scientists were watching the mountain since Wednesday when a 200-meter column of sulfur gas escaped from the volcano crater.
About 3 p.m. Thursday the volcano emitted fine ash, gases and vapor at a point where a new aperture in the crater formed. There was another 200-meter (about 660-foot) column, but this time the composition was ash, the Red Sismológica said. Four of its geologists, Raúl Mora, Carlos Ramírez, Gino González y Yemerith Alpízar, were at the summit of the volcano, and the crater was being observed by a thermal imaging camera mounted nearby.
Rangers at the Parque Nacional Volcán Turrialba closed the facility and asked tourists to leave after the 3 p.m. incident. The Comisión Nacional de Prevención de Riesgos y Atención de Emergencias said that the scientists were treating the event as a superficial eruption similar to ones that have taken place in the recent past. The last major eruption was in January 2010 when a large plume of ash came out of the southwest crater.
The emission Thursday was from the central crater as well as the southwest one. There are three craters in all.
Some low-level earth movements also were reported. The commission said there were no reports of odors or other activity that might hurt humans. However, the mountain has been putting out acid vapor since 2010, and the local vegetation has been affected. That also has taken place on the mountain’s sister volcano, Irazú. Both are east of San José. The emergency commission officials will be meeting with scientists today to consider what might be the future of the mountain.
The temperature of the central crater earlier Thursday was 550 degrees C (more than 1,000 degrees F), said the Red Sismológica. Later the thermal cameras recorded temperatures of 137 (about 280 F) and 187 degrees C (about 370 F) at the crater, said the Red Sismológica.
The national park and volcano are northeast of the city of Turrialba. At 3,340 meters (about 10,958 feet), Turrialba is the second tallest volcano in the country. There have been two big eruptions there, one in 1864 and one in 1868. There has been visible activity there since 2001.
Officials closed the park in July 2009 for the protection of visitors and only reopened it last July.