An earthquake light is a luminous aerial phenomenon that reportedly appears in the sky at or near areas of tectonic stress, seismic activity, or volcanic eruptions.

Earthquake lights are a phenomenon so unusual that they border on myth. The first known reports of them are from 89 BC, with spotty descriptions over the centuries.

Recently, they’ve been seen during foreshocks and the main earthquake in L’Aquila, Italy, in 2009, and as flashes of blue lightning over Wellington, New Zealand, in 2016.

Research into earthquake lights is ongoing; as such, several mechanisms have been proposed. Positive Holes is one such model. Another hypothesis involves intense electric fields created piezoelectrically by tectonic movements of rocks containing quartz. And a third explanation is a phenomenon called triboluminescence.