The sources that emit lava from the craters of the summit of a volcano can be preceded by “musical” signals that allow us to predict the progressive rise of the magma inside the conduit up to a day before the start of the eruption, revealed the National Institute of Geophysics and Volcanology (INGV) of Italy .
An investigation into the activity of the Etna volcano (southern Italy) has revealed that the lava source emitted on February 20, 2021 by the Italian volcano was preceded by an intense infrasound band acoustic signal coming from the southeast crater by more than 24 hours. before the rash began, which was characterized by a progressive increase in frequency.
This type of sound is a low-frequency acoustic signal, not audible to humans, whose recordings through special microphones are increasingly used by volcano observatories for monitoring, according to the study, in which universities also participate. from Catania (Sicily, southern Italy), from Canterbury (New Zealand) and from Boise (United States).
“In fact, volcanoes behave like huge musical instruments and generate acoustic signals both during eruptive activities and during simple degassing, and that is why volcanic ducts resonate like organ pipes whose notes depend mainly on the length of the channel” , explains the INGV in a statement.
Etna volcano sounded like an organ pipe
In the case of the Etna eruption, “due to the deep explosions, the duct of the southeast crater sounded like an organ pipe,” he details.
The modeling of the infrasound signal, integrated with the results of a topographic survey with drones, has made it possible to accurately reconstruct the dimensions of the resonant part of the duct.
And this made it possible to evaluate the progressive rise of the magma inside it, from about 170 meters deep to about 80 meters during the 24 hours prior to the lava source.
Due to the nuisances that lava flows can cause, such as the problems in air traffic caused by the cloud of ash from volcanoes, “careful monitoring is essential to identify precursor signs of eruptions that are linked to the rise of the magma”.
Infrasound is increasingly applied as a tool to investigate the dynamics of magma in active volcanoes, especially open volcanoes, as is the case with Etna, which are still prodigious sources of infrasound, according to the INGV.