The charges travel fast, at up to around 200 metres per second,” he explained in a 2014 article for The Conversation. “It’s like switching on a battery, generating electrical charges that can flow out of the stressed rocks into and through unstressed rocks. “Prior to earthquakes, huge volumes of rock - hundreds of thousands of cubic kilometers of rocks in the Earth’s crust - are being stressed and the stresses are causing shifting of the grain, the mineral grains relative (to) each other,” he added in an interview via video call. Rock is an insulator that, when mechanically stressed, becomes a semiconductor, he said. Antonio Liraįriedemann Freund, Derr’s collaborator and an adjunct professor at San Jose University and a former researcher at NASA Ames Research Center, has come up with one theory for earthquake lights.įreund explained that when certain defects or impurities in crystals in rocks are put under mechanical stress - such as during the build-up of tectonic stresses before or during a major earthquake - they instantly break apart and generate electricity. Moreover, earthquake lights were more likely to occur on or near rift valleys, places where - at some point in the past - Earth’s crust had been pulled apart, creating an elongated lowland region that lies between two higher blocks of land.Įarthquake lights spotted in Guayaquil, Ecuador, shine white. However, the 2014 study found that the vast majority of earthquakes linked to luminous phenomena occurred within tectonic plates, rather than at their boundaries. In most cases, the phenomenon was observed shortly before or during the seismic event, and it was visible up 600 kilometers (372.8 miles) from the quake epicenter.Įarthquakes, particularly powerful ones, are most likely to occur along or in the vicinity of the areas where tectonic plates meet. The researchers found that some 80% of the EQL occurrences studied were observed for earthquakes with magnitudes greater than 5.0. They shared their work in a 2014 paper published in the journal Seismological Research Letters. To better understand earthquake lights, Derr and his colleagues gathered information on 65 American and European earthquakes associated with trustworthy reports of earthquake lights dating back to 1600. They may also look like small flames flickering or creeping along or near the ground or larger flames emerging from the ground.Ī video taken in China shortly before the 2008 Sichuan earthquake shows luminous clouds floating in the sky. Other times they resemble glowing spheres floating midair. Sometimes, the lights may appear similar to ordinary lightning, or they may be like a luminous band in the atmosphere akin to polar aurora. “If you saw them nobody would believe what you saw.”Įarthquake lights can take several different forms, according to a chapter on the phenomenon coauthored by Derr and published in the 2019 edition of the Encyclopedia of Solid Earth Geophysics. “Forty years ago, it was impossible,” he said. Juan Antonio Lira Cacho, a physics professor at Universidad Nacional Mayor de San Marcos in Peru and the Pontifical Catholic University of Peru, who has studied the phenomenon, said cell phone video and the widespread use of security cameras has made studying earthquake lights easier. He said the recent video from Morocco shared online looked like the earthquake lights caught on security cameras during a 2007 quake in Pisco, Peru. “Seeing EQL depends on darkness and other favorability factors,” he explained in an email. He has coauthored several scientific papers on earthquake lights, or EQL. These outbursts of bright, dancing light in different colors have long puzzled scientists, and there’s still no consensus on what causes them, but they are “definitely real,” said John Derr, a retired geophysicist who used to work at the US Geological Survey. Reports of “earthquake lights,” like the ones seen in videos captured before Friday’s 6.8-magnitude earthquake in Morocco, go back centuries to ancient Greece.
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