OVSICORI-UNA reported that small, frequent phreatic eruptions at Poás continued during 6-13 February. Data from the monitoring network indicated that 50-600 phreatic explosive events per day were occurring, but only a few events ejected material more than 100 m. At 0107 on 6 February an eruptive event generated a column that rose at least 300 m above the crater. At 1221 on 8 February an event generated a column of steam-and-ash that rose 200 m above the crater, and a gas-and-steam column that rose over 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.

Source: Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad Nacional (OVSICORI-UNA)