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Electric-blue molten streams run down the side of an Indonesian volcano , periodically bursting into blue flames that shroud the black night in otherworldly colors. This unique volcano, Kawah Ijen on the eastern edge of Java, erupts molten sulfur and presents tourists with a nighttime show.
Olivier Grunewald, a renowned nature photographer, has documented Kawah Ijen and provided an opportunity to study the behaviors of one of the most unique volcanoes in the world. Below, I'll examine the details surrounding the sulfuric gas combustion, what produces significant amounts of sulfur in this volcano, and more.
Electric blue sulfur flows from Kawah Ijen (Credit: Olivier Grunewald)
Unfortunately, many websites have claimed that this electric blue liquid is lava, when in fact it is condensed sulfur coming from high temperatures and pressures beneath the Kawah Ijen volcano.
Why Does Kawah Ijen Burn Blue?
You may remember from chemistry class that sulfur is flammable and when burned produces a neon blue flame. This is essentially the same reaction that occurs at Kawah Ijen but with different environmental factors that I'll address below. The combustion of sulfur produces sulfur dioxide and sulfur trioxide in the following chemical reactions. The sulfur acts to replace wood or hydrocarbons in type of combustion.
S(s) + O2(g) ——> SO2(g)
2S(s) + 3O2(g) ——> 2SO3(g)
You may also note that sulfur combustion is not ideal for the environment surrounding us as it provides additional sulfur dioxide and sulfur trioxide to produce sulfurous and sulfuric acid in the form of acid rain.
SO2(g) + H2O(g) ——> H2SO3(g) [sulfurous acid]
SO3(g) + H2O(g) ——> H2SO4(g) [sulfuric acid]
When the sulfur breaches the surface of the volcano it can be up to 1,112°F (600°C) and very highly pressured. The high pressures and lack of oxygen within the volcano prevents significant combustion. However, when the sulfur emerges from the volcano, it is immediately surrounded by a highly oxygenated environment, along with abruptly lower temperatures and pressures. This causes the sulfur to immediately ignite and send flames tens of feet into the air.
Meanwhile, there is a fraction of sulfur that condensates when it cools below the sulfur boiling temperature of 832.4°F. This then flows down the side of Kawah Ijen to produce what appears to be electric blue lava.
Origin of Kawah Ijen & Source Of Sulfur
Kawah Ijen is part of a volcano complex on East Java, Indonesia. This grouping of stratovolcanoes lie within the 20km wide Ijen caldera formed 50,000 years ago from many explosive eruptions. Since then, small eruptions have created stratovolcanoes including Kawah Ijen within the larger Ijen caldera. This caldera complex is underlain by Miocene limestone
There is a permanent solfatara that produces native sulfur and multiple fumaroles that allow volcanic gas to escape to the atmosphere along fissures in the volcano. Within the Ijen crater there is the world's largest highly acidic lake with a pH<0.5. For reference, that's somewhere between the gastric acid within your stomach and battery acid. This acidic lake was produced by the reaction of hydrogen chloride gas with water to form hydrochloric acid.
Sulfur Mining From Kawah Ijen
If you ever visit Kawah Ijen you'll notice numerous miners walking with loaded baskets of sulfur deposits down the volcano. Each trip a miner will walk up the volcano, break apart the sulfur deposits and walk down the volcano with 200 pounds of sulfur to the nearby refinery. These miners are exploiting sulfur deposits that were formed during the cooling of sulfur rich gasses as they are emitted around the lake.
To speed up this process of sulfur mineralization, miners have installed a number of pipes to vent the sulfur and cool it quickly to form liquid sulfur, which then forms sulfur mats. This allows the miners easier access to sulfur deposits and provides a constant rejuvenation of supply. Miners make less than 25 U.S. cents per pound according to Grunewald and often times carry 200-pound baskets 1 to 2 times a day.
"Our families worry when we come here. They say working here can shorten your life," says Haltom, a 34-year-old sulfur miner of 12 years.
