Author: Carolyn Gramling / Source: Science News
Ecuador’s Cotopaxi volcano has a deep and distinct voice. Between late 2015 and early 2016, Cotopaxi repeated an unusual pattern of low-frequency sounds that researchers now say is linked to the unique geometry of the interior of its crater.
Identifying the distinct “voiceprint” of various volcanoes could help scientists better anticipate changes within the craters, including those that foretell an eruption.Ecuadoran scientists installed a network of specialized microphones on the volcano’s flanks that can record very low frequency sounds, or infrasound. Two weeks after the volcano’s August 2015 eruption, the network recorded the unusual sound pattern — a strong, clear oscillation that tapers off through time. The sound curve resembles a screw, or “tornillo” in Spanish, scientists report online June 13 in Geophysical Research Letters.
Cotopaxi repeated this tornillo pattern 37 times between September 2015 and April 2016. Each time, the signal lasted through a dozen or more oscillations, resonating much like a musical instrument, before dying away. “[Cotopaxi] rang like a bell for more than a minute,” says geophysicist Jeffrey Johnson at Boise State University in Idaho, who led the study.
On February 13, 2016, Cotopaxi uttered a strong, clear sound that resonated at low frequencies around 0.2 hertz. The amplitude of the oscillating sound died away after about 90 seconds, forming a pattern called a “tornillo” for the Spanish word for “screw.”
Although Cotopaxi’s actual sounds are inaudible to humans, researchers re-created the tornillo pattern using oscillations in white noise at the same amplitudes as the original tornillo signal; the pattern here has…
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