Travellers flock to the Indonesian island of Java to see the magnificent Kawah Ijen volcano – but what they don’t expect to find is the stunning turquoise-hued caldera lake at the volcano’s summit. To add to the drama, bright, citrine-coloured stones and billows of white gasses surround the 1km-wide aquamarine lake in a spectacular show.
One element is responsible for the entire, striking scene: sulphur. The magma chamber below the volcano pours sulphuric gases into the lake. Combined with a high concentration of dissolved metals, the gases turn the water a brilliant shade of blue. They also render the Ijen crater-lake the world’s largest highly acidic lake with a pH of 0.5.
That same chamber blasts a continuous stream of sulphuric gas from lakeside fumaroles that swirl around the lake. When the gas condenses and falls to the ground, it dyes the lake’s surrounding stones a shocking shade of electric yellow.
“Hydrogen chloride released from Ijen volcano mixed with the lake and turned it into an acidic monstrosity that it is today,” writes Quora user Vinay Sisodia. “What makes this place even more stunning, especially at night, is shots of sulphuric gases that combust into glints of bright blue upon contact with air.”