OVSICORI-UNA reported that during 23-31 July activity at Turrialba was characterized by sporadic, passive gas-and-ash emissions detected almost daily. The plumes rose no higher than 300 m above the vent rim, and drifted NW, W, and SW. Ashfall was reported in several neighborhoods in the Valle Central, including Coronado, Tibás (35 km WSW), Goicoechea (28 km WSW), and Moravia (31 km WSW) on 24 July, and in Tres Ríos (27 km SW) on 31 July. A sulfur odor was occasionally reported.

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)