Ever heard of a blue lava volcano? The island nation of Indonesia, dominated by active volcanoes, has an eerily beautiful volcano of blue fire. Most volcanoes are found in Java, which itself was formed because of volcanic eruptions. The 13th largest island in the world, Java also houses the mysterious Kawah Ijen volcano—the one that spews blue lava. 

Blue lava is not really blue, instead, it is the blue fire or sulfur fire that results from the sulphur being released as it burns. It burns as an electric-blue flame due to sulphur that has the illusory appearance of lava.  Sulfur burns as it comes into contact with hot air (combusts at temperatures above 360 °C (680 °F), the resulting flames are energetic and blue. For lava to be blue it would need to be at least 6,000 °C (10,830 °F) which is far hotter than anything naturally possible on the Earth's surface.

It is situated within the crater is the world's largest known acidic crater lake. Its bluish-green colour comes from a high concentration of dissolved metals. The gases from the volcano react with the water resulting in a low pH of 0.5. As soon as the gases cool down, they leave sulphur deposits around the lake as residue.