Report on Turrialba (Costa Rica) — 6 July-12 July 2016
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 6 July-12 July 2016
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2016. Report on Turrialba (Costa Rica). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 6 July-12 July 2016. Smithsonian Institution and US Geological Survey.
10.025°N, 83.767°W; summit elev. 3340 m
All times are local (unless otherwise noted)
OVSICORI-UNA reported that strong tremor at Turrialba started at 0658 on 7 July. An accompanying explosion produced an ash plume that rose 1 km above the crater and likely drifted WNW and WSW. Weather conditions mostly prevented views of the crater, although at 1551 a large amount of water-vapor-and-gas emissions with minor amounts of ash were observed. Ashfall was recorded in areas downwind including in neighborhoods of San José (Coronado, La Uruca, Tibás, Rancho Redondo, Guadalupe, Sabanilla, Moravia, Ipís, Sabanilla, La Guácima of Alajuela, and San Rafael de Alajuela), Heredia (38 km W), and Turrubares. Almost continuous tremor was detected through the next day; a period of increased tremor amplitude was detected during 1030-1230. Emissions of gas, water vapor, and large amounts of ash were visible with the webcam. Ash fell in many of the same areas as the day before. Tremor levels dropped at 2030, though increased again at 0030 on 9 July. Ash emissions rose no higher than 500 m above the crater around 0900 on 9 July. Ash emissions to 300 m above the crater and elevated tremor levels continued throughout the day. Ashfall was reported in Ipís de Guadalupe and San Rafael de Heredia. Tremor significantly declined at 0115 on 10 July. Views of the crater at 0600 showed emissions of water vapor and gas with minor amounts of ash. Tremor again increased on 11 July, at 0930, and a possible ash emission occurred between 1000 and 1030, although weather conditions prevented confirmation.
Geologic Background. 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.