OVSICORI-UNA reported that during 18-22 October continuous passive ash emissions rose from Turrialba as high as 1 km above the vent and drifted NE and W. The activity was accompanied by stable, low-to-moderate amplitude tremor with a few brief intervals of rest. Ash fell in Siquirres (30 ENE), Guacimo (23 km NNE), Guapiles (21 km N), and Moravia (27 km W). During 23-25 October emissions were discontinuous and ash content was low; plumes drifted NW and W. Ashfall was reported in San José (36 km WSW), Tibás (35 km WSW), Guadalupe (32 km WSW), Curridabat (32 km WSW), Tres Ríos (27 km SW), Moravia, San Pedro (32 km WSW), and various areas of the Valle Central.

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)