Kawah Ijen is one of several volcanoes located within the 20 km wide Ijen Caldera in East Java, Indonesia. The caldera of Kawah Ijen harbors a kilometer-wide, turquoise colored, acidic crater lake that leaks sulphurous gases constantly. At night the hot gases burn to emit an eerie blue glow that is unique to Kawah Ijen. The gases emerge from the cracks in the volcano at high pressure and temperature, up to 600°C, and when they come in contact with the air, they ignite, sending flames up to 16 feet high. Some of the gases condense into liquid sulfur, and continues to burn as it flows down the slopes giving the feeling of blue lava flowing.

Kawah Ijen’s sulphuric gases are also mined for sulphur. The volcanic gases are trapped by the local miners and channeled through a network of ceramic pipes, resulting in condensation of molten sulfur. The sulfur, which is deep red in color when molten, pours slowly from the ends of these pipes and pools on the ground, turning bright yellow as it cools. The miners break the cooled material into large pieces and carry it away in baskets to a nearby refinery. A worker can earn up to $13 dollars a day in this way.

The workers work in extremely hazardous condition with insufficient protection. Most of them suffers from numerous respiratory problems due to breathing toxic fumes day in and out. At times they work at night under to escape the heat of the sun, and to earn extra income.

These pictures were captured by photographer Olivier Grunewald, who lost two lenses and a camera to sulphuric corrosion while trying to capture the mysterious pictures.

Sources: National Geographic / Photovolcanica / Boston Globe / Wikipedia