OVSICORI-UNA reported that at 2030 on 23 June tremor increased at Turrialba and continued to fluctuate through the next day. At 0544 on 24 June a short-lived (less than three minutes) emission of ash and gas rose no higher than 200 m above the crater. A small gas-and-ash plume rose from the crater at 0650. Wind directions shifted from NW to SW. Tremor disappeared at 0740 but then reappeared at 0850 and continued. Neighborhoods in San José reported ashfall and a sulfur odor. From 2005 on 24 June through 1500 on 25 June there were 14 episodes of increased tremor amplitude, accompanied by gas-and-ash emissions that rose no more than 200 m. Rocks were occasionally ejected from the crater. A few more periods of increased tremor and ash-and-gas emissions were recorded later that evening and the morning of 26 June. Several neighborhoods in San José and Heredia reported ashfall and a sulfur odor. Between 0604 and 1930 on 26 June the seismic network recorded almost continuous, variable-amplitude volcanic tremor, with frequent spikes in amplitude associated with passive gas-and-ash emissions. At around 1930 tremor amplitude decreased and ash emissions ceased. Local areas continued to report ashfall. Tremor again increased on 28 June at 2159, though the height of the associated ash emissions was not distinguishable.

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)