No filters were used in these photos of Kawah Ijen, a volcano on the Indonesian isle of Java.

The glow radiating from the volcano in this photo comes from the combustion of sulfuric gases emitting from the volcano itself.

“This blue glow—unusual for a volcano—isn’t, of course, lava, as unfortunately can be read on many websites.”

Some of the gases condense into liquid sulfur, “which continues to burn as it flows down the slopes,” said Grunewald, “giving the feeling of lava flowing.” – Oliver Grunewald told National Geographic in an email about Kawah Ijen, a volcano on the island of Java.The glow is actually the light from the combustion of sulfuric gases, Grunewald explained

Sulfur under high pressure & temperature (up to 1,112F) emits from cracks in the volcano and combusts ignites when it meets the air.  The flames from this sulfur combustion can reach up to 15 feet high.

Learn more about this Volcano-Sulfur-Blue-Fire Phenomenon:

Stunning Electric-Blue Flames Erupt From Volcanoes