A major fumarole is active on the summit of the volcano, its plume reaching heights of . It is strong enough that it can be seen on the ground from over away. The vent of the fumarole lies in the summit lava domes, more specifically in a high and wide collapse scar in the southeasternmost lava dome of the compound summit lava dome. Other volcanoes in the area with fumarolic activity include San Pedro and Putana.