OVSICORI-UNA reported that an explosion at Turrialba at 1140 on 16 May generated gas-and-ash emissions, though the height of the plume was not determined due to fog. Wind models suggested that the ash plume rose 3 km above the crater and drifted WNW towards Valle Central. Officials on farms 2.5 km WNW reported abundant ashfall. Sustained tremor with significant and highly-variable amplitude continued to be recorded. On 17 May gas-and-steam emissions, intermittently but frequently containing ash, were recorded by the webcam. Throughout the day volcanic tremor amplitude decreased substantially, though numerous earthquakes continued to be recorded. Ash emissions gradually ended. At 1800 the seismic network began recording a large number of very-long-period earthquake, and at around 2200 volcanic tremor with significant amplitude was detected. Seismicity remained high the next morning.

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)