The lava glows blue high on the slopes of Java’s Kawah Ijen volcano, much like the rare sights also seen in Ethiopia. At first glance, it looks like lava flowing down the mountain. But the otherworldly glow is not what it seems.
The phenomenon, known as blue fire, isn’t produced by lava at all. It comes from burning sulphur gases that escape from cracks in the volcano. As the hot gases, reaching temperatures of up to 600°C (about 1,100°F), meet oxygen in the air, they ignite and burn with an electric blue flame.
The illusion of blue lava
Though the actual lava at Kawah Ijen glows with the usual red-orange color seen at most volcanoes, the flames of burning sulfur give the illusion of glowing blue lava. The result is a dazzling display that is only visible at night.
How breathtaking is the morning view of Erta Ale, the fiery, living volcano in Ethiopia’s #Afar region. A natural wonder where earth speaks in flame and light.#Ethiopia 🇪🇹#ErtaAle pic.twitter.com/Lvk7owWpO7
— Behiwot Tilahun🇪🇹 በህይወት ጥላሁን🇪🇹 (@BehiwotTilahun) May 27, 2025
Locals call it Api Biru, which means “blue fire.” The gases burn continuously, but the flames are almost invisible in daylight. The mountain transforms as night falls, revealing the full glow of this rare natural event.
The photographer who helped bring global attention
Photographer Olivier Grunewald helped bring this spectacle to global attention. His famous images of Kawah Ijen show glowing rivers of what appears to be blue lava flowing through the dark. These photos, taken under challenging and dangerous conditions, sparked worldwide interest in the remote volcano.
The science behind the glow is simple but fascinating. When sulphur gases burn, the heat excites particles inside the gas. These particles quickly release energy in the form of light. In the case of sulfur, that light appears as a deep blue or violet hue.
This light show doesn’t happen everywhere. While Grunewald has also photographed blue flames at the Dallol volcano in Ethiopia’s Danakil Depression, Kawah Ijen remains the most striking and consistent site. Its high sulfur content and strong gas emissions make it the only known place where the blue fire burns steadily.
A once-in-a-lifetime view for visitors
Travelers, scientists, and photographers continue to visit Kawah Ijen to see the rare glow firsthand. Though it involves hiking steep paths in the dark and braving the strong smell of sulfur, many say the view is worth it.
The glowing blue fire of Kawah Ijen stands as one of nature’s rarest shows. It’s not the lava that draws people in, but the flames that dance silently across the mountain, lighting up the night with a color not often seen in the nature.
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