If you’ve been to the Indonesian island of Java recently, you’ve likely been treated to a stunning view: electric blue rivers streaming out from underneath the Kawah Ijen volcano. It looks like lava, but it’s actually molten sulfur.
“I’ve never seen this much sulfur flowing at a volcano,” U.S. Geological Survey research geologist Cynthia Werner said.
Although seeing this much sulfur is a bit rare, it is common to see blue flames around volcanoes. Sulfur has a pretty low melting point at 239 degrees Fahrenheit. Kawah Ijen has the largest blue flame area, though.
