Volcanic lightning is something that seems utterly magical when you think about it for the briefest of moments: Sparks, leaping about an eruption column full of fire and fury, illuminating its glassy contours and swirling plumes.
Although its formation mechanisms are still somewhat debated, at least we’ve been able to capture it on camera. Volcanic thunder, on the other hand, has escaped our technological traps – until now. A stunning new paper published in Geophysical Research Letters has revealed that the sound of such hellish thunder has been recorded for the very first time in human history.
It seems initially curious that such a phenomenon hadn’t been recorded until now, but remember that volcanic eruptions are extremely loud. Those that tend to feature volcanic lightning are explosive, producing tall, sustained eruption columns of superheated gas, ash, and lava flecks – so the sound of thunder is generally drowned out by the violence already in play.
In order to put this dramatic quest to an end, the team looked closer at Bogoslof volcano, one of around 50 volcanic islets in Alaska’s Aleutian Island chain. A relatively young volcano currently emerging from the sea, its sporadic eruptions mean that, in recent history, it’s both risen and fallen beneath the waves. Some have termed it a “Jack-in-the-Box” volcano, rather marvelously.
Bogoslof's eruptions often trigger the emergence of sustained eruption columns, perfect for volcanic lightning. Even if the eruption isn't seen at first, thunderstorms are rare in the Aleutian Islands, so when a global network of detectors pick up a lightning strike in the region, it’s almost certainly a sign of an eruption.
The Alaska Volcano Observatory (AVO) – which led the latest study – point out in their paper that even when the eruptions themselves died down, the columns remained, still triggering lightning bolts.
In both March and June of 2017, during two eruptive sessions, the team listened in on infrasound and sonic recording equipment some 60 kilometers (37 miles) from the volcano itself. Finally, during the quieter, dying moments of those eruptions, they managed to isolate clear sounds of volcanic thunder. In some instances, the ashy thunderclaps were so loud that they’d likely be heard over the pandemonium of the eruption itself.
On these sped-up recordings, volcanic thunder can be heard as clicks and pops, while the eruption itself makes lower-pitched grumbling noises.