Volcanoes, already rather frightening, are now believed to emit a sound not unlike a scream before they erupt, according to a new study.
A new analysis of a 2009 eruption of Alaska’s Redoubt Volcano revealed a swarm of smaller tremors that rose in frequency and pitch just before the volcano’s release. As the quakes become smaller and more numerous, they coalesce into a kind of “scream,” that ceases right before the final eruption.
While the source of the tremors isn’t exactly known, the University of Washington’s Alicia Hotovec-Ellis, who conducted the study, believes that the harmonic tremors are the result of magma being forced through a narrow conduit deep in the mountain. “Because there’s less time between each earthquake, there’s not enough time to build up enough pressure for a bigger one,” she said. “After the frequency glides up to a ridiculously high frequency, it pauses and then it explodes.”
The study of the scream, which has also been documented at Arenal Volcano in Costa Rica and Soufrière Hills volcano in the Caribbean, should help scientists better model a volcano’s pressurization patterns, allowing for better understanding of the eruption cycle.
You can hear audio of the volcano’s siren song right here.