A mesmerizing video of electric-blue flames emerging from Indonesia's Kawah Ijen volcano has amazed social media users. The unique phenomenon, captured by photographer Olivier Grunewald, is the result of the combustion of sulfuric gases, producing a dazzling blue glow.

Originally filmed a few years ago, the footage has recently gone viral on social media. Olivier Grunewald released the video as part of a documentary in collaboration with Geneva's Society for Volcanology, reported NDTV. The captivating scenes showcase streams of striking blue flames rapidly emanating from the volcano.

 Blue Fire at Ijen Crater. Kawah Ijen is an active volcano.

Extremely high quantities of sulfuric gases emerge at high pressures and temperatures (sometimes more than 600°C) along with the lava.

When sulfur from within the volcano breaches the surface, it can reach temperatures… pic.twitter.com/ELzzKYXtqL


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Why is the Ijen lava blue?

According to IFL Science, the Ijen volcano is similar to any other, but the blue lava phenomenon is caused by an abundance of sulfur pockets in the rock. The chemical is released from cracks in volcanic rocks at high pressure and temperature when the rock burns and turns sulfur dioxide, a noxious gas, after coming into contact with the air. It also creates a striking blue flame.

"This blue glow - unusual for a volcano - isn't, of course, lava, as unfortunately can be read on many websites," Grunewald, from France, told National Geographic. "It is due to the combustion of sulfuric gases in contact with air at temperatures above 360 degrees Celsius," he further said.

These flames can be up to 16 feet (or five meters). The blue gas and rock have a market. Smithsonian Magazine said that miners living around the volcano extract the sulfuric rock - formed after the blue flames have gone out - for use in the food and chemical industries.

They carry rock-filled baskets by hand down the mountain and sell them, though the price is not very good. These rocks sell for about 680 Indonesian rupiahs per kilogram - the equivalent of about six cents. Grunewald estimates that these nighttime miners can mine and carry between 80 to 100 kg over 12 hours of work - about $5 to $6.

Kawah Ijen volcano: All you need to know

The vast volcanic complex is situated within a crater formed when a volcano erupts and collapses, often creating a large lake. The Ijen complex comprises around 22 eruption points, mostly around the rim of the caldera, as per IFL Science. The lake formed by the volcanic eruption is the largest acid lake in the world and has a pH value of zero. Swimming in the lake has been warned against by experts, stating it could be life-threatening.