Report on Poas (Costa Rica) — 13 February-19 February 2019
Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
13 February-19 February 2019
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2019. Report on Poas (Costa Rica). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 13 February-19 February 2019. 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 since 8 February almost continuous emissions of gas has been recorded at Poás, with plumes rising as high as 1 km and drifting mainly SW. During 13-14 February the emissions contained ash; gas-and-ash plumes drifted SW, impacting areas downwind including Naranjo, Zarcero, and Grecia (16 km SW). Gas-and-ash emissions rose from the crater on 15 February, and gas emissions were recorded on 18 February.
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.