Report on Poas (Costa Rica) — 15 December-21 December 2010
Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
15 December-21 December 2010
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2010. Report on Poas (Costa Rica). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 15 December-21 December 2010. Smithsonian Institution and US Geological Survey.
10.2°N, 84.233°W; summit elev. 2697 m
All times are local (unless otherwise noted)
OVSICORI-UNA reported that during November several phreatic eruptions from the central part of Laguna Caliente, a summit lake of Poás, ejected material that fell back into the lake, occasionally producing small waves. Dark-colored gas plumes rose a few meters to several tens of meters above the lake surface. The temperature of the lava dome was 630 degrees Celsius at accessible areas. Fumarolic plumes from the dome rose 1 km and drifted W and SW. Some foliage on the SW flank, about 3.5 km from the crater, showed signs of damage from gases.
Geological Summary. The broad vegetated edifice of Poás, one of the most active volcanoes of Costa Rica, contains three craters along a N-S line. The frequently visited multi-hued summit crater lakes of the basaltic-to-dacitic volcano are easily accessible by vehicle from the nearby capital city of San José. A N-S-trending fissure cutting the complex stratovolcano extends to the lower N flank, where it has produced the Congo stratovolcano and several lake-filled maars. The southernmost of the two summit crater lakes, Botos, last erupted about 7,500 years ago. The more prominent geothermally heated northern lake, Laguna Caliente, is one of the world's most acidic natural lakes, with a pH of near zero. It has been the site of frequent phreatic and phreatomagmatic eruptions since an eruption was reported in 1828. Eruptions often include geyser-like ejections of crater-lake water.
Source: Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad Nacional (OVSICORI-UNA)