OVSICORI-UNA reported that an area of incandescence on the NW inner wall of Turrialba’s West Crater had been periodically visible at least since mid-November, and was visible during 26-27 December, suggesting that fumarolic temperatures exceeded 300 degrees Celsius. At 0644 on 28 December a one-minute-long eruption produced an ash emission that rose 50 m above the crater rim and drifted W. Another small eruption that produced ash emissions was recorded at 1105 by the seismicity and infrasound networks. The event was heard by authorities in the Parque Nacional Volcán Turrialba.

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)