The Kawah Ijen volcano in Indonesia is a sulfur mine by day and a surreal alien landscape in the night. The infernal mountain spews out electric-blue lava in the night time and it’s an absolutely mind-blowing sight.
Photographer Olivier Grunewald first learned about the mountain in 2008. He collaborated with Régis Etienne to photograph and film the incredible natural wonder in extremely dangerous conditions. The results of their work can be seen in a 52-minute documentary called Kawah Ijen, The Mystery of the Blue Flames.
The crater has an active vent that’s a source of elemental sulfur. Despite the treacherous conditions, locals have been mining sulfur from the vent for over 40 years. They reportedly mine 14 tons of pure sulfur a day for the Indonesian food and chemical industry.
The molten sulfur appears bright red during the day, but gives off an eerie blue light in the night. The blue flames are a byproduct of the sulphuric gas. When the gas is ignited, it produces a blue flame that can reach temperatures of up to 1,112 °F (600 °C).