Why Do Lights Sometimes Appear in the Sky During An Earthquake?

For decades, scientists have struggled to explain the mysterious flashes of light that occasionally accompany earthquakes, such as the ones captured in this photo taken at Tagish Lake, in the Yukon Territory, in 1972.
Today, in a study published in Seismological Research Letters, a team of scientists by Robert Thériault used an alternate strategy to figuring out the answer—they analyzed the geologic circumstances of 65 earthquakes starting in the year 1600 that produced reports of light to see what these events had in common.
The scientists found that earthquake lights appear disproportionately before or during earthquakes, rather than afterward. They don’t yet have an explanation for the unusual location patterns of earthquake lights, but they think they can explain this trend in timing.