Four-time World Press Photo winner Olivier Grunewald recerntly traveled to East Java, Indonesia to capture these surreal nighttime images of the sulfur mine in the crater of the Kawah Ijen volcano. The photos, spotted on Smithsonian mag, were snapped during shooting of a new documentary Grunewald is releasing with Régis Etienne, the president of Geneva’s Society for Volcanology. Taken without the aid of digital filters, the photos showcase the volcano’s luminescent blue glow–a result of the combustion of sulfuric gases in contact with air at temperatures above 360°C.
“The vision of these flames at night is strange and extraordinary,” Grunewald says. “After several nights in the crater, we felt really living on another planet.”