Brilliantly colored sulfur and other minerals precipitate around high-temperature fumaroles in the summit crater of Poás volcano. Fumarolic temperatures approaching 600 degrees Centigrade were recorded in 1988, several times higher than the melting point of sulfur. The ejection of pyroclastic material consisting of scoriaceous sulfur resembling basaltic scoria as well as the emission of small sulfur lava flows has been documented during several historical eruptions at Poás.

Photo by Jorge Barquero (Universidad Nacional Costa Rica).

Poás