Geophysicists recorded the rumble of volcanic thunder as they watched a series of violent eruptions on an island in the North Pacific Ocean in 2017.
The rolling thunder was accompanied by lightning in streams of ash that rose from the Bogoslov volcano in the Aleutian Islands. The roar was registered by microphones on another island - at a distance of 64 km.
The sound of volcanic thunder has never been recorded before, as it is very difficult to separate it from the explosions and rumbles that accompany volcanic eruptions. In audio recordings, the sounds of thunder sound like pops and clicks against the background of the low rumble of the eruption.
“People who were present at the eruptions certainly saw and heard this before, but for the first time we accurately recorded and identified this sound,” says Matt Haney, a seismologist at the Alaska Volcanic Observatory in Anchorage, USA.
Volcano Bogoslov exploded more than 60 times between December 2016 and August 2017, providing researchers with the perfect opportunity to record explosions on the neighboring island of Umnak. In March and June, microphones detected the distinct sounds of volcanic thunder, which arrived at Umnak three minutes after a global network of lightning detectors detected flashes in Theologian's ash plume.
“If people watched the eruption in person, they would hear thunder,” Haney says. Thunder follows lightning, which is created in the jet when tiny particles of ash and ice collide with each other and become electrically charged in the process.