The Kawah Ijen volcano in East Java Indonesia has erupted, and strangely, electric-blue lava was seen flowing out of it. The flow appears luminescent. It looks the best at night. Photographers from the National Geographic have taken some amazing pictures of the eruption and flow.

This blue glow, unusual for a volcano, isn’t of course lava, which is always red in color. However, texturally or physically, the flow isn’t really that different from the sort of lava that emerges from most volcanoes. It’s actually a tweak of chemistry. Lava temperature can range from 1,292°F to 2,192°F, and this ridiculously high thermal radiation is what makes it some variant of red or orange.

In Kawah Ijen’s case, pockets of sulfur are spewing out the volcanic crevices along with the molten rock. The high temperature of the lava burns these pockets of sulfur, in turn creating the electric-blue awesomeness. When gas comes in contact with air temperatures that exceed 360C, it gives off a blue light. Pockets of sulphuric gases are contained within the lava, which are released when it reaches the surface.

It is the sulfur that is giving the flow its spectacular blue color.

Kawah Ijen is the biggest “acidic volcanic crater lake” in the world. Kawah Ijen is actually a collection of volcanoes. It has a cauldron shaped caldera that spans 22 kilometers. The highest peak of Kawah Ijen is the volcano Gunung Merapi, which translates to “mountain of fire”.

There are seven active volcanoes in Java, the highest being Mount Semeru (3,676 m). In fact, the island of Java is almost entirely of volcanic origin. The most active volcano in Java and also in Indonesia is Mount Merapi (2,930 m).

There are some spectacular volcanoes throughout the planet and our solar system. However the most spectacular ones are probably on Io, a moon of Jupiter that produce eruption columns that reach heights of 500 kilometers or 310 miles.