For the first time ever, scientists have indisputably recorded the sounds of thunder generated by the lightning inside a plume of volcanic ash—a feat previously thought to be difficult, if not impossible, thanks to the ear-splitting grumbling of the volcanic eruption itself. Alaska’s Bogoslof volcano, which juts its head above the Bering Sea halfway down the Aleutian Island chain, has long been monitored by scientists.
Between December 2016 and August 2017, their instruments captured sounds from several eruptions (including the 28 May 2017 one pictured above). And for two of those events, the eruptions of 8 March and 10 June, the recordings chronicled rumblings that occurred well after the actual eruption had ceased, but while lightning still flashed within the ash cloud above, the researchers report today in Geophysical Research Letters.
The timing and volume of the rumblings—which arrived at the instruments about 3 minutes after other sensors noted that lightning bolts had flashed forth in the ash plume—as well as the direction from which they arrived, strongly indicate they were indeed thunder, the researchers say. Such rumblings could one day offer a new way for researchers to monitor eruptions and their plumes.