Scientists Spy on Mount Etna With Fiber Optic Cables

Towering 11,000 toes above 1,000,000 people, Mount Etna is without doubt one of the most thoroughly-monitored volcanoes on Earth. A whole bunch of sensors dot its flanks, and for good motive: It’s Europe’s most energetic volcano, periodically spewing lava and big plumes of particles that floor planes and customarily make life depressing for these residing in its shadow.

However now scientists have been spying on Etna with an unlikely new surveillance machine: fiber optic cables, like those that convey you the web. Writing final week within the journal Nature Communications, researchers described how they used a way referred to as distributed acoustic sensing, or DAS, to choose up seismic indicators that typical sensors missed. This might assist enhance the early warning system that folks within the surrounding components of Italy depend on. Hundreds of thousands extra world wide are additionally on the mercy of energetic volcanoes, which create chaos whether or not they’re massive or small.

DAS is shaking up (sorry) science in an enormous manner. When the web was rising within the Nineties, telecoms ended up laying down extra fiber optic cable than they wanted, for the reason that materials itself was low-cost in comparison with the labor required to bury it. That further cable stays unused, or “darkish,” and scientists can lease it out to run DAS experiments. Engineers use it to observe land deformation, geophysicists use it to review earthquakes, and biologists are even utilizing underwater cables to choose up the vibrations of whale calls. 

Fiber optics work by transporting indicators from level A to level B as pulses of sunshine. But when the cable is disturbed by, say, an earthquake, a tiny quantity of that mild will get bounced again to the supply. To measure this, scientists use an “interrogator,” which fires a laser by means of the fibers and analyzes what comes again. As a result of researchers know the pace of sunshine, they’ll decide disturbances at numerous lengths alongside the cable: One thing occurring 60 toes away will bounce again mild that takes barely longer to get to the interrogator than one thing occurring at 50 toes. 

These measurements are delicate. For instance, within the spring of 2020, in the course of the early days of Covid-19 lockdowns, scientists at Pennsylvania State College used their campus’ buried darkish fiber optics to look at as pedestrian and car motion waned and picked up once more. They might even inform the supply of the aboveground disturbance by the frequency of its vibration: a human footstep is between 1 and 5 hertz, whereas automobile site visitors is 40 to 50 hertz.

This new analysis facilities on the identical thought, solely these scientists did it on an energetic volcano. As a result of telecoms by no means bothered to put fiber optics on Mount Etna, the researchers dug a three-quarter-mile-long ditch lower than a foot deep and buried their very own, not removed from the volcano’s rim.