Global Volcanism Program | Image GVP-09133
Poás erupted intermittently from June 1987 to June 1990, producing ash-bearing plumes such as this one seen on March 6, 1989. Geyser-like phreatic explosions had resumed at Poás from June 1987 until at least October 1988, punctuated by large explosions on April 9, 1988. The crater lake completely disappeared by April 1989, and during May ash plumes reached heights of 1.5-2 km above the crater. Sulfur-rich fumarolic activity constructed sulfur cones, lakes of molten sulfur, and sulfur flows up to 30 m long.
Photo by Gerardo Soto, 1989 (Instituto Costarricense de Electricidad, published in Alvarado, 1989).