Report on Poas (Costa Rica) — 31 May-6 June 2017
Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
31 May-6 June 2017
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2017. Report on Poas (Costa Rica). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 31 May-6 June 2017. 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 tremor amplitude at Poás fluctuated from low to medium levels during 30-31 May, often associated with the vigor of emissions of water vapor, magmatic gases, and material from vents. An event at 1200 on 2 June generated a plume consisting of water vapor, gases, and minor amounts of ash that rose 600 m above the crater. Another event recorded at 1353 could not be confirmed visually due to weather conditions. An event at 0858 on 6 June generated a plume that rose 1 km.
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.