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Report on Poas (Costa Rica) — 9 August-15 August 2023


Poas

Smithsonian Institution / US Geological Survey
Weekly Volcanic Activity Report, 9 August-15 August 2023
Managing Editor: Sally Sennert.

Please cite this report as:

Global Volcanism Program, 2023. Report on Poas (Costa Rica) (Sennert, S, ed.). Weekly Volcanic Activity Report, 9 August-15 August 2023. Smithsonian Institution and US Geological Survey.

Weekly Report (9 August-15 August 2023)

Poas

Costa Rica

10.2°N, 84.233°W; summit elev. 2697 m

All times are local (unless otherwise noted)


OVSICORI-UNA reported that fumarolic degassing and lake convection at Poás were visible during 9-15 August. A small phreatic eruption at the center of the lake ejected material 5 m above the lake at 0842 on 11 August.

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)