Fumaroles are vents from which volcanic gas escapes into the atmosphere.

Fumaroles are vents from which volcanic gas escapes into the atmosphere. 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. They may persist for decades or centuries if they are above a persistent heat source (active Magma chamber) or disappear within weeks to months if they occur atop a fresh volcanic deposit that quickly cools.

The teperatures rise from 70 C - 100 C or more. In some cases they are hidden in the ground (like in Stephanos-Crater on Nisyros) and you can break into them. The gases are dangerous and a gas-mask is often needed. They are always a sign of active volcanism.

Photo:
On the dark and stormy night of September 12, 2013 at Hverir, a geothermally active area along the volcanic landscape in northeastern Iceland geomagnetic storms produced the auroral display in the starry night sky while ghostly towers of steam and gas venting from fumaroles danced against the eerie greenish light.

Photo via APOD
Image Credit & Copyright: Stéphane Vetter (Nuits sacrées)
http://www.nuitsacrees.fr/

How does a fumarole really looks?
Watch: https://www.youtube.com/watch?v=kuvwttCMB-A 

Know more:
http://pubs.usgs.gov/gip/volc/geysers.html

#naturalphenomena   #fumarole   #aurora