Blue lava oozes from the Kawah Ijen volcano of East Java. The flowing molten rock gets its vibrant appearance through the combustion of sulfur gas, which burns blue, as it seeps out from volcanic cracks at high temperatures and reacts with oxygen in the air. The rest of this article is behind a paywall. Please sign in or subscribe to access the full content.

Sulfur is often abundant in volcanic settings, but it’s thought that Ijen is the only volcano in the world that regularly burns blue thanks to its unusually large sulfur deposits and the intense heat of its hydrothermal system, which can reach more than 600°C (1,112°F)

If you look closely (image below), you’ll notice the physical lava itself is not totally blue. Instead, the color comes from an intense but soft blue flame emanat

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