NASA reveals origin of lights that illuminated the Mexican sky during earthquake

The lights, which lit up Mexico City's sky during the earthquake that struck September 7, are a natural phenomenon caused by the electromagnetic charge generated by rocks, NASA scientist Friedemann Freund told the Mexican newspaper El Universal.

The severe earthquake measuring 8.4 magnitude shook Mexico, the country's Federal Civil Protection Unit said.

The shock of the tectonic plates produced earthquakes, but when "the stress level (among the rocks) is high, electronic loads arise that momentarily transform an insulating stone into a semiconductor," Freund noted.

Semiconductors are materials with level of electrical conductivity, between some metal and an insulator, and are used to make transistors.

Thus, during the earthquake, "the stones of the earth's crust grow and curve under the attack of the tectonic forces, the [electromagnetic] charges within it are released and generate a dazzling variety of phenomena that even form part of the folklore of earthquakes in regions of the world, "said Freund.