Report on Poas (Costa Rica) — 3 May-9 May 2017
Smithsonian Institution / US Geological Survey
Weekly Volcanic Activity Report, 3 May-9 May 2017
Managing Editor: Sally Sennert.
Please cite this report as:
Global Volcanism Program, 2017. Report on Poas (Costa Rica) (Sennert, S, ed.). Weekly Volcanic Activity Report, 3 May-9 May 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 an eruption at Poás was detected at 1724 on 6 May though poor visibility prevented visual confirmation of the event. During 6-7 May volcano-tectonic and long-period earthquakes were detected, as well as moderate-amplitude tremor.
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.