Global Volcanism Program | Image GVP-09294
Fumarolic plumes at Poás volcano are sometimes tinted yellow by the high-temperature combustion of sulfur. Pyroclastic scoriaceous sulfur fragments have been ejected during some explosive eruptions. Acidic gas plumes from Poás have damaged vegetation in the national park and surrounding areas, causing widespread devastation to coffee and other plantation crops. An explosion on April 9, 1988 dropped acidic sulfur-rich mud on visitors, cars, and plants near the tourist overlook.
Photo by Jorge Barquero (Universidad Nacional Costa Rica).