OVSICORI-UNA reported that after three days of continuous ash emissions at Turrialba activity decreased during the morning of 8 December. Weak and sporadic emissions rising no higher than 200 m above the vent were observed in the afternoon. Events at 0919 and 0934 on 9 December produced ash plumes that rose 500 m and drifted NW. Weak and sporadic ash emissions the rest of the day rose no higher than 500 m. Passive ash emissions on 12 December did not exceed 500 m and drifted NW.

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)