Just before the 6.8 magnitude earthquake rocked Morocco on Sept. 8, lights were captured on video that lit up the sky.

This phenomenon known as “earthquake lights,” or EQL, has been recorded at least 65 times in documents as early as the 1600s, geophysicist Friedemann Freund found in a published research paper published in Seismological Research Letters.

Witness accounts and videos show lights around the time of other major earthquakes such as the one that struck Guerrero in Mexico in 2021, per NOVA PBS.

Since the earthquake in Morocco happened at night, the lights would have been the chance to be “seen by people and maybe even recorded by cameras would be relatively high,” Freund told the Washington Post.

“It would be so bright that you can read the newspaper,” Freund told the Post. Freund has previously published several studies on earthquakes and earthquake lights, worked at NASA for 30 years and is currently a senior research scientist at the SETI Institute.

What are earthquake lights?

Described by the U.S. Geological Survey as lights that occur in the sky before, during or soon after an earthquake, earthquake lights can look like sheets of light, balls of light, streamers, or show a steady glow.

However, scientists are still fuzzy on further details since the phenomenon is difficult to track.

When have earthquake lights been seen in recent years?

Previous accounts collected by Freund and his team found that 80% of the EQL occurrences studied had a magnitude larger than 5.0.

Here are recent earthquakes with accounts of earthquake lights.

What causes earthquake lights?

Freund told the Post that just because an earthquake happens, lights don’t necessarily accompany it — “the connection is not totally guaranteed.”

There are several different theories about what causes earthquake lights including energy that builds up when the earth’s crust shifts, causing sparks of light.

Some geophysicists debate whether earthquake lights are a real phenomenon, blaming the light on destroyed power boxes and the like, per the USGS.

How rare are earthquake lights?

Less than 0.5 percent of earthquakes worldwide exhibit earthquake lights, according to National Geographic.

But if the lights do make an appearance, they usually show before or during the earthquake.

How could earthquake lights help predict earthquakes?

“If we could find some phenomenon that gives us information about the pressure build up in the Earth before the earthquake, that may help us to predict earthquakes,” John Ebel, a seismologist and professor of geophysics at Boston College told the Post.

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