Poás volcano, in Alajuela province, spewed a column of water, sediment and steam of 66 to 98 feet long. The eruption occurred on Sunday morning and took place in the active crater of the volcano, covered by an ultra-acid lake.
Such eruptions are normal and occur when the under-water pressure at the Poás lake comes out and ejects sediments, according to volcanologist Eliecer Duarte, from the Volcanological and Seismological Observatory of Costa Rica (OVSICORI).
The explosion poses no risk to the surroundings, just a strong smell of sulfur was noticeable.
Since 28 May, fumaroles from the lake bottom have become more frequent, and also the lake surface changed from green to gray, due to abundant sulfur.