What are these strange lights and why they appear before earthquake?

It has been nearly a week since the devastating 6.8 earthquake shook Morocco to its core killing more than 2,900 people and leaving more than 3,000 others injured, as rescuers are continuing to search from the rubble to find any hope of life stuck beneath the heaps of debris. 

The powerful earthquake struck southwest of Marrakech last Friday with a French expert issuing warnings about the aftershocks, despite the country not being in the "most active seismological region". 

Several CCTV videos have surfaced on social media from Morocco since the earthquake showing a light emanating from the horizon just before the shaking. Experts have termed these luminous phenomena real however, they are still scratching their heads for what causes them in the first place. 

According to reports, these lights have historical roots. 

John Derr, a retired geophysicist who worked at the US Geological Survey told CNN that these different colours of lights are definitely real.

"Seeing EQL depends on darkness and other favorability factors,” Derr, who worked on these earthquake lights explained.

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."

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 video and security cameras have made studying earthquake lights easier.

Different forms of earthquake lights

There are several types of lights as mentioned by a paper coauthored by Derr and published in the 2019 edition of the Encyclopedia of Solid Earth Geophysics.

the lights appear as normal lighting or sometimes it may look like a band same as a polar aurora. They may also look as floating in midair. One of the kind also includes a flame-like emanation from the ground.

To make sense of this, Derr and his colleagues collected all the concerned information from earthquake lights as old as the year 1600. 

Their work was published in 2014 in a paper in the journal Seismological Research Letters.

Their findings revealed that some 80% of the earthquake lights were found in earthquakes of over 5.0 magnitudes. According to the findings, the occurrence was witnessed shortly before or during the earthquake, visible up 600 kilometres (372.8 miles) from the epicentre.

Most of the time, earthquakes take place in the nearby convergence areas of tectonic plates. However, the study found that in most of cases, luminous phenomena occurred within tectonic plates, rather than at their boundaries.

According to reports, these lights are most likely to be visible near rift valleys, places where Earth’s crust had been forced apart.

What may be the causes of earthquake lights? 

A theory was put forth by Friedemann Freund, Derr’s collaborator, an adjunct professor at San Jose University and a former Nasa researcher.

Freund told CNN that when certain defects or impurities in crystals in rocks are put under mechanical stress — such as during activity between tectonic plates — they instantly break apart and generate electricity.

He noted that rock is an insulator that, when mechanically stressed, becomes a semiconductor.

He added: "Prior to earthquakes, huge volumes of rock — hundreds of thousands of cubic kilometres 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."

"It’s like switching on a battery, generating electrical charges that can flow out of the stressed rocks into and through unstressed rocks. The charges travel fast, at up to around 200 metres per second," he explained in a 2014 article for The Conversation.

Some other explanations also stated that static electricity is produced by the fracturing of rock and radon emanation, among many others.

There is no agreement on this phenomenon and this mystery is being studied by the scientists.

Freund expected that there may come a time when it would be possible to use earthquake lights, or the electric charge that causes them, to help forecast the approach of a major earthquake.