OVSICORI-UNA reported that members of the media and local communities observed a gas-and-steam plume from Turrialba that rose to an altitude greater than 5.3 km (17,400 ft) a.s.l. on 5 December. Fieldwork confirmed an unusual output of gas from several fumaroles along the S outer wall. Areas burned by acute acidification have extended in the last month. Pastures turned yellowish near the upper areas, and native and exotic tree species were impacted as well as birch tree patches along most drainages. Within the W crater, temperatures of fumaroles reached 280 degrees Celsius and native sulfur was present.

Geological Summary. Turrialba, the easternmost of Costa Rica's Holocene volcanoes, is a large vegetated basaltic-to-dacitic stratovolcano located across a broad saddle NE of Irazú volcano overlooking the city of Cartago. The massive edifice covers an area of 500 km2. Three well-defined craters occur at the upper SW end of a broad 800 x 2200 m summit depression that is breached to the NE. Most activity originated from the summit vent complex, but two pyroclastic cones are located on the SW flank. Five major explosive eruptions have occurred during the past 3500 years. A series of explosive eruptions during the 19th century were sometimes accompanied by pyroclastic flows. Fumarolic activity continues at the central and SW summit craters.

Source: Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad Nacional (OVSICORI-UNA)