Bizarre colorful cloud phenomenon in the sky - observed about 30 mins before the May 12, 2008 Sichuan earthquake. It was recorded in Tianshui, Gansu province ~450km northeast of the epicenter. One theory suggests that earthquake lights are a form of plasma discharge caused by the release of gases from within the Earth and are electrically charged in the air. Another possible explanation is local disruption of the Earth's magnetic field and/or ionosphere in the region of tectonic stress, resulting in the observed glow effects either from ionospheric radiative recombination at lower altitudes and greater atmospheric pressure or as aurora. Another explanation involves intense electric fields created piezoelectrically by tectonic movements of rocks containing quartz.