The sides of Kawa Ijen, a volcano in Indonesia, are wreathed in blue flame.
This is the crater lake at the top of Kawa Ijen, a rather innocuous volcano in East Java, Indonesia:
The yellow patches at the bottom of this picture are natural sulphur deposits – also known as brimstone. It is a valuable material. The billowing vent at the top of the volcano carries enough sulphur to support a mining operation. Pipes collect the gases, condense the sulphur, and then spit it out in molten chunks. Once those chunks cool, people collect them and carry them down from the slopes in baskets. It’s hot, hard, dangerous, and absurdly underpaid work.
The sulphur in Kawa Ijen leads to one of its most distinctive and haunting features: the blue lava. It’s not actually lava, of course, but flames from burning sulphur. The heat underground is sufficient to ignite the sulphur. It burns with a bright blue exceptionally hot flame up to five metres high, cascading down the sides of the volcano and resembling nothing so much as electric-blue lava streams.
This volcanic phenomenon is visible only at night. Kawa Ijen is not the only place in the world with blue lava: it also occurs around Dallol in Ethiopia, which I wrote about in July of last year (extreme heat).
There are a few other places around the world where flames spring from the ground. A couple of decades ago I hiked up Mount Chimaera in Turkey to see Yanartaş. There, methane gases escape the rocks and fuel natural flames coming out of the ground. I remember being told that the flames will sometimes go out on their own, so tour guides will surreptitiously reignite them with cigarette lighters.
And then there’s the Darvaza crater, a 70 metre wide hole in the ground in Turkmenistan that has been burning since Soviet scientists set it alight in 1970.
It is known, appropriately enough, as the Gates of Hell.