Scientists often detect a series of small earthquakes just before a volcanic eruption and a new study published in the Journal of Volcanology and Geothermal Research has shown that these tremors can happen in such a rapid succession – that they create sound vibrations that rise in pitch until the volcano erupts.

 

The study authors came to their conclusion by looking at the March 2009 eruption of Alaska’s Redoubt Volcano, which was preceded by a series of significantly higher frequencies, referred to as a harmonic tremor.

“The frequency of this tremor is unusually high for a volcano, and it’s not easily explained by many of the accepted theories,” said co-author Alicia Hotovec-Ellis, a University of Washington doctoral student in Earth and space sciences.

Some volcanoes emit sound as liquid-hot magma rises through thin cracks in the Earth’s crust, generating resonant frequencies. However, the study researchers said harmonic tremors occur as magma is forced into the center of the mountain.