As Wikipedia defines it, “A fumarole (Latin, fumus, “smoke”) is an opening in a planet’s crust which emits steam and gases such as carbon dioxide, sulfur dioxide, hydrogen chloride, and hydrogen sulfide. The steam forms when superheated water boils as its pressure drops when it emerges from the ground.”
Our friend AnnMarie Ichiki recently posted this photo of Aso. Apparently, a new fumarole has formed. - William