How Blue Lava Works

Electric Blue "Lava" from Volcanoes Is Sulfur

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This "blue lava" from the Kawah Ijen volcano is really burning sulfur. Stocktrek Images, Getty Images

Indonesia's Kawah Ijen volcano has gained internet fame for Paris-based photographer Olivier Grunewald's photographs of its stunning electric blue lava. However, the blue glow doesn't actually come from lava and the phenomenon isn't restricted to that volcano. Here's a look at the chemical composition of the blue stuff and where you can go to see it.

What Is Blue Lava?

The lava that flows from the Kawah Ijen volcano on the island of Java is the usual glowing red color of molten rock flowing from any volcano.

The flowing electric blue color arises from the combustion of sulfur-rich gases. Hot, pressurized gases push through cracks in the volcano wall, burning as they come into contact with air. As they burn, sulfur condenses into a liquid, which flows downward. It's still burning, so it looks like blue lava. Because the gases are pressurized, the blue flames shoot up to 5 meters in the air. Because sulfur has a relatively low melting point of  239°F (115°C), it can flow for some distance before solidifying into the familiar yellow form of the element. Although the phenomenon occurs all the time, the blue flames are most visible at night. If you view the volcano during the day, it wouldn't appear unusual.

Unusual Colors of Sulfur

Sulfur is an interesting non-metal that displays different colors, depending on its state of matter. Sulfur burns with a blue flame. The solid is yellow. Liquid sulfur is blood red (resembling lava).

Because of its low melting point and availability, you can burn sulfur in a flame and see this for yourself. When it cools, elemental sulfur forms a polymer or plastic or monoclinic crystals (depending on conditions), that spontaneously change into rhombic crystals.

    Where To View Blue Lava

    The Kawah Ijen volcano releases unusually high levels of sulfuric gases, so it's probably the best place to view the phenomenon. It is a 2-hour hike to the rim of the volcano, followed by a 45-minute hike down to the caldera. If you travel to Indonesia to see it, you should bring a gas mask to protect yourself from the fumes, which may be harmful to your health. Workers who collect and sell the sulfur typically do not wear protection, so you can leave your mask for them when you leave.

    Although the Kawah volcano is most readily accessible, other volcanoes in the Ijen may also produce the effect. Although it is less spectacular at other volcanoes in the world, if you view the base of any eruption at night, you may see the blue fire.

    Another volcanic location known for the blue fire is Yellowstone National Park. Forest fires have been known to melt and burn sulfur, causing it to flow as burning blue "rivers" in the park. Traces of these flows appear as black lines.

    Molten sulfur may be found around many volcanic fumaroles. If the temperature is high enough, the sulfur will burn. Although most fumaroles aren't open to the public during the night (for fairly obvious safety reasons), if you live in a volcanic region, it might be worth watching and waiting for sunset to see if there is blue fire or blue "lava".

    Fun Project To Try

    If you don't have sulfur but want to make a glowing blue eruption, grab some tonic water, Mentos candies, and a black light and make a glowing Mentos volcano.

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    Helmenstine, Anne Marie, Ph.D. "How Blue Lava Works." ThoughtCo, Sep. 24, 2015, thoughtco.com/how-blue-lava-works-607589. Helmenstine, Anne Marie, Ph.D. (2015, September 24). How Blue Lava Works. Retrieved from https://www.thoughtco.com/how-blue-lava-works-607589 Helmenstine, Anne Marie, Ph.D. "How Blue Lava Works." ThoughtCo. https://www.thoughtco.com/how-blue-lava-works-607589 (accessed November 23, 2017).