Ancient Greece, where scientific inquiry laid its foundations, is also where the earliest reports of “earthquake lights” can be traced. These mesmerizing bursts of colorful light during seismic events have baffled scientists for centuries. Although the cause remains elusive, experts unanimously agree that these phenomena are undeniably real.
Dr. John Derr, a retired geophysicist who previously worked at the US Geological Survey, has coauthored numerous scientific papers on earthquake lights (EQL). He emphasized that witnessing EQL depends on factors like darkness and other favorable conditions.
The recent video capturing EQL during a 6.8-magnitude earthquake in Morocco, which circulated widely online, bore a striking resemblance to EQL captured on security cameras during a 2007 quake in Pisco, Peru. Thanks to the prevalence of cell phones and security cameras, studying these elusive lights has become more feasible in recent years.
Juan Antonio Lira Cacho, a physics professor at Peru’s Universidad Nacional Mayor de San Marcos and the Pontifical Catholic University of Peru, noted that four decades ago, studying EQL was virtually impossible. “If you saw them, nobody would believe what you saw,” he remarked.
EQL, as detailed in a chapter coauthored by Derr and published in the 2019 Encyclopedia of Solid Earth Geophysics, can manifest in various forms. Sometimes, they resemble ordinary lightning, while at other times, they appear as luminous bands in the atmosphere akin to polar auroras. They can also take the form of floating glowing spheres, flickering flames, or even larger flames emerging from the ground.
To gain a better understanding of EQL, Derr and his colleagues collected information on 65 American and European earthquakes associated with trustworthy EQL reports dating back to 1600. Their findings, shared in a 2014 paper in the journal Seismological Research Letters, revealed that around 80% of EQL occurrences were observed in earthquakes with magnitudes greater than 5.0. Often, these phenomena were seen shortly before or during the seismic event, visible from distances of up to 600 kilometers (372.8 miles) from the earthquake epicenter.
Interestingly, while powerful earthquakes are typically expected to occur at tectonic plate boundaries, the study found that the majority of EQL-linked earthquakes occurred within tectonic plates, rather than at their edges. Moreover, EQL were more likely to occur in or near rift valleys, regions where Earth’s crust had previously pulled apart, creating elongated lowland areas between higher land blocks.
One theory proposed by Dr. Friedemann Freund, Derr’s collaborator and an adjunct professor at San Jose University with a background at NASA Ames Research Center, suggests that certain defects or impurities in crystals within rocks generate electricity when subjected to mechanical stress, such as that preceding a major earthquake. Rock, usually an insulator, becomes a semiconductor when mechanically stressed, creating electrical charges that can rapidly flow through rocks. Freund’s theory offers a potential avenue for understanding EQL, but consensus among seismologists on the precise mechanism behind these lights remains elusive.
While the mystery of earthquake lights persists, scientists like Freund hold onto the hope that one day these phenomena, or the electric charge responsible for them, could be used in combination with other factors to forecast impending major earthquakes, potentially saving lives and mitigating damage.
