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Maybe you've seen pictures of glowing blue lava flows and dismissed them as Photoshop trickery. Healthy skepticism is good, but there really is a volcano in Indonesia where a unique fluke of chemistry creates an eerie blue glow.

Hosted by: Olivia Gordon
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Olivia: While scrolling through social media, you might have seen some pictures of bright blue lava flows and raised a skeptical eyebrow And hey! Good for you doubting stuff on the internet because Photoshop is a thing. But those photos are real.

Even though the molten rock isn't what's blue. It's actually combusting gases that make the glowing blue flames. A volcanic crater on the island of Java in Indonesia called Kawah Ijen is the best place to see this phenomenon at night. Plus, the crater also has a deadly vivid turquoise lake which is full of acid.

The chemistry of the volcano causes both of these brilliant colors, but in two different ways. Lots of volcanoes spit up gaseous sulfur compounds. Like the Dallol Volcano in Ethiopia, so blue flames aren't unique to this crater.

But Kawah Ijen happens to have spectacular amounts of sulfur, enough to support a huge mine. The miners are after the bright yellow chunks of solidified sulfur rock. But its sulfur forms a yellow solid, why do the sulfuric gases seeping up from the ground burn blue?

It all has to do with the chemistry of combustion. When a fuel like a sulfur compound mixes with oxygen and high enough temperatures, a combustion reaction happens. Heat gets released and new chemicals are formed, like sulfur dioxide, and the visible part of the fire is the flames which are caused by a bunch of atoms spewing out light energy.

Basically, the energy from the combustion reaction boosts the electrons in the fuel atoms to a more energetic state. When the electrons fall back to their original state, they release all that extra energy as a photon of light. The wavelengths of those photons determine what the flame's color is. And in the case of sulfur compounds catching fire, it's an eerie blue glow.

During the day, Kawah Ijen's lava looks pretty much like the orangey-red lava of any active volcano. All the sulfuric gases are still burning, but the bright sunlight washes the color out. But at night, sightseers flock to see all of the glowing blue flames on the rivers of molten rock. If that wasn't enough to make Kawah Ijen one of the world's weirdest places, then there's also that turquoise acid lake.

Volcanoes tend to bring all sorts of chemicals from the Earth's interior up to the surface. And in Kawah Ijen's case, there are plenty of things besides sulfur like chlorine and a bunch of metals. In the crater lake water, the sulfur dioxide gas made by the combustion reaction dissolves and forms sulfuric acid. And the chlorine compounds mean that there's hydrochloric acid in there too. The pH of that crater lake is, no joke, below 0.5. Which is really really acidic, like stronger than the acid in your car battery.

Needless to say: don't go swimming in that death lake, no matter how cool it looks. Even just measuring the pH of the water can be a really dangerous job. Acid that strong can dissolve metals no problem, and dissolved metals do something that organic carbon containing chemicals usually don't: they turn bright colors. The color you get and whether you get a color it all has to do with the chemistry and geometry of the metal ions floating inside the solution.

Many kinds of metal ions absorb certain wavelengths of visible light, and your eyes perceive color based on the wavelengths of light that are reflected off an object, so when a metal ion absorbs one color of visible light, you'll usually see a complementary color to the one that's absorbed, the hue that's across from it on the color wheel. If a compound absorbs light outside of the visible spectrum, all of the visible light gets reflected and the solution looks white or clear.

That's why organic chemistry might as well be called "six hundred colorless compounds and how to draw them." Inorganic chemistry is where all the colors are, so, the mixture of dissolved metals in Kawah Ijen's lake is what makes the water look vividly turquoise. If the volcano were to erupt, there's a chance that the lakebed could rupture and send that acidic "death water" cascading down the mountain to do serious harm. And because Java is so densely populated, volcanologists keep a very very close eye on any volcanic activity in the area.

So Kawah Ijen owes its incredible colors to sulfur compounds. Whether they're burning or dissolved in the lake with some metals. Those two different kinds of chemistry make this weird place a beautiful and deadly destination.

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