Sometimes before an earthquake, strange bright orbs and glows are seen in the sky, like the scene visible in this video clip captured a half hour before the 2008 quake in Sichuan, China. You might think these are related to the UFOs that cause the quakes, but new research not only suggests a natural cause but also raises the possibility that the phenomena could be an indicator that a quake is coming. The scientists from Quebec Ministry of Natural Resources and San Jose State University suggest that rocks under high stress deep underground release oxygen ions that eventually make their way to the surface, ionizing air pockets above ground and creating a light-emitting plasma.
“If you see visible lights in the sky, and you live in an earthquake-prone area, they might be an early-warning sign that an earthquake is approaching,” geologist Robert Thériault says.
More in Smithsonian: "Why Do Lights Sometimes Appear in the Sky During An Earthquake?"