A fumarole (Latinfumus, smoke) is an opening in a planet's crust, often in the neighborhood of volcanoes, which emits steam and gases such as carbon dioxide, sulfur dioxide, hydrogen chloride, and hydrogen sulfide. The steam is created when superheated water turns to steam as its pressure drops when it emerges from the ground. The name solfatara, from the Italiansolfo, sulfur (via the Sicilian dialect), is given to fumaroles that emit sulfurous gases.
Fumaroles may occur along tiny cracks or long fissures, in chaotic clusters or fields, and on the surfaces of lava flows and thick deposits of pyroclastic flows. A fumarole field is an area of thermal springs and gas vents where magma or hot igneous rocks at shallow depth are releasing gases or interacting with groundwater. From the perspective of groundwater, fumaroles could be described as a hot spring that boils off all its water before the water reaches the surface.
Fumaroles may persist for decades or centuries if they are above a persistent heat source, or disappear within weeks to months if they occur atop a fresh volcanic deposit that quickly cools. The Valley of Ten Thousand Smokes, for example, was formed during the 1912 eruption of Novarupta in Alaska. Initially, there were thousands of fumaroles in the cooling ash from the eruption, but over time most of them have become extinct.
This area is characterized by intense volcanic activity and the sulphur springs field, not geysers as sometimes it can be read, is full of mud lakes and steam pools with boiling mud. Industrial logging has been attempted in the end of the 80s, but is uneconomic. There are still several holes, the best known emits pressurized steam, visible in the morning up to 50 meters high. This is not a geyser, but a well in the artificial geothermal field. The major mud lakes are located at 4850 m.