Science is Fun Fridays!

"Blue lava" erupting from the Kawah Ijen volcano in Indonesia - this is due to combustible sulfuric gases coming into contact with hot air.

This volcano has extremely high quantities of sulfuric gases.  Exposed to oxygen and ignited by the lava, the gases readily burn.  This effect is only visible at night.

Lava/sulfur flow.  

This acid lake in the crater is colored turquoise because of the acidity and dissolved metal content. We can also see the "solfatara," the white plume where sulfur-rich gases escape through a vent.

After the sulfur gas cools it combines with the lava to form a solidified rock, which miners brave the conditions to obtain and sell to the refinery.  Prolonged exposure can lead to throat and lung irritation, difficulty breathing, and a propensity for lung disease.

Smithsonian

Geology