Why The Hell Is Kilauea's Eruption Now Making Blue Fire?


Robin Andrews

Science & Policy Writer

Now you're just showing off, Kilauea. USGS via Facebook

From explosively-generated ash plumes at Kilauea’s summit to the utterly spectacular lava fountaining taking places on its flanks via one of its dozens of fissures, this corner of Hawaii’s Big Island is putting on quite the show.

Something almost magical is also afoot. Spotted in some of the footage provided by the United States Geological Survey (USGS), and clearly shown in a newly released photograph, blue flames are now shooting out of the ground around the Leilani Estates subdivision.


It’s not literally magic, of course, but this glorious quirk of chemistry has got everyone understandably excited. As Earther opined so magnificently, it looks a lot like "bioluminescent waves lapping against the shores of hell."

So what’s the deal? You might guess that the lava itself is burning, but that’s not what’s happening here. It’s in fact down to the escape and ignition of methane gas, which burns with a characteristic blue flame.


As you’ve probably realized, lava is pretty damn hot; in fact, the gas-rich, fluid glorious gloop that’s emerging from these fissures is clearly hot enough to cause almost anything it encounters to combust, and that includes plenty of vegetation.

If you look closely at the shot, however, you can see the blue flames not appearing from all over the place, but only from within the cracks in the road. The nearby trees and plants and grass at the surface, parts of which are also burning, aren’t burning blue, but instead showing a rubbish orange-yellow flame.


This is because the combustion of these surface materials are getting far more oxygen, and are a bit closer to complete combustion. Under ideal conditions, this doesn’t produce methane gas. When lava smothers vegetation, however, oxygen isn’t able to get to it. This triggers incomplete combustion, or perhaps a slower process named pyrolysis, which leads to the production of methane gas.


This methane gas is still trapped, however, which is why it’s finding its way out through cracks in the ground. When ignited by the lava’s heat, either direct or ambient, it ignites and produces this stunning, electric blue flame.

This isn’t the only way you can get an ethereal blue flame when lava’s involved, mind you. In fact, a savvy member of the public brings up the topic of sulfur to the USGS under the photograph – the natural burning of which has been made somewhat famous by Kawah Ijen, a complex volcano on the Indonesian island of Java.

Although Kilauea may be tooting out plenty of sulfur dioxide gas as of late, it’s nothing compared to this beastie halfway across the world. This volcano emits a profuse smorgasbord of sulfuric gases; it also deposits plenty of condensed or solidified sulfur across its distinctly alien landscape.


When the heat of the lava ignites this sulfur, it also burns with that beautiful blue flame. Although not as visible in the day, at night this is truly one of the greatest natural wonders in the world. The USGS, in response to the aforementioned curious commentator, explains that in the lower East Rift Zone (ERZ) of Kilauea, there aren’t any native sulfur deposits, so what you’re seeing there is all methane.

Saying that, they also note that there are some at Kilauea's summit, and they were observed to burn blue back in 2008 during a chance encounter. Back then, a minor explosion propelled a hot rock across the crater, which landed on a sulfur deposit, formed by years of condensed-out gas emissions.

"This occurred at night,” the USGS recounts, “and a [Hawaiian Volcano Observatory] scientist who was observing the activity noted blue flames emanating from the area of the sulfur deposit, as the hot rocks from the explosion caused the sulfur to combust!”

Goddamn, Kilauea. Now you’re just showing off.


Update: the USGS just posted a superb explainer on the phenomenon. In it, they add that, at Kilauea, "the lava temperature is high enough to accelerate chemical breakdown of biomass as it heats or distills the organic compounds - [such as] natural gas - from the buried grass, shrubs, ferns, roots, and other vegetation.

"A similar process—pyrolysis—cooks wood in large, very hot ovens to make charcoal and another fuel byproduct called 'producer gas.'"



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