While actual lava's color is typically red-orange due to its temperature, true blue lava would need to reach exceedingly high temperatures – temperatures far beyond what naturally occurs on Earth's surface. Specifically, truly-blue lava would require a temperature of at least 6,000 °C (10,830 °F), according to Planck's Law.
Therefore, what is often referred to as "blue lava" is not actually lava exhibiting blue color due to its heat. It's an optical effect.
The Reality of "Blue Lava"
The "blue lava" seen in places like Kawah Ijen volcano in Indonesia isn't actually blue because of extreme heat. The blue glow is caused by the combustion of sulfuric gases. Kawah Ijen releases high-pressure, high-temperature gases through vents. These gases, rich in sulfur, react with oxygen in the air, creating a bright blue flame. This phenomenon isn't related to the temperature of the actual molten rock but rather to the chemical reactions of the gases.
In summary, naturally occurring lava never achieves a temperature high enough to glow blue due to its heat. The term "blue lava" is usually a misnomer describing the blue flames from burning sulfur gases, not molten rock itself.
