Many natural events can happen during an earthquake—volcanoes, even a sonic boom—but the strangest event caused by a quake actually doesn’t even appear on the ground.
“Earthquake lights” is a luminous phenomenon that appears in the sky during, or even before, a quake. Sometimes white or bluish in hue but other times a full spectrum of colors, earthquake lights appear like an aurora over the area of the quake and can last from mere seconds to several minutes.
Ironically, for many years scientists didn’t believe earthquake lights even existed. It wasn’t until photographs were taken of them during the Matsushiro earthquake swarm (a swarm is a bunch of earthquakes happening in the same place over a short period of time) in the mid 1960s that they started taking them seriously.
The interesting thing is, scientists don’t exactly know how or why the lights appear. One theory is that the lights come from friction created from the tectonic movements of rocks containing quartz; another is that they come from a disruption of the ionosphere or magnetic field (this theory has been pretty much disproved, since the lights don’t appear during every earthquake). NASA scientist Friedmann T. Freund posited that igneous and metamorphic rocks contain electric charge carriers called positive holes which, when awakened by an earthquake, sparkle and glow. Still, none of these theories completely solves the riddle of this beautiful phenomenon.
One of the most spectacular occurrences of earthquake lights happened 30 minutes before the earthquakes that devastated China in 2008. Two people caught the lights on video: