Portents of doom? (Image: KPA/Zuma/Rex Features)
Read more: “Strange skies: Seven wonders of the atmosphere“
Glowing orbs that drift through the air; blue-white sheets of light; sparks and flashes and flames licking up from the ground… all may be signs of disaster to come. For millennia, people have reported strange, baleful lights appearing before and during earthquakes. In 1746, for example, the flames dancing on San Lorenzo Island in Peru impressed prison governor Manuel Romero so much that he briefly released the detainees to let them watch. Three weeks later a huge quake hit nearby Lima and a tsunami washed 5 kilometres inland.
“For millennia, people have reported strange, baleful lights appearing before and during earthquakes”
There is plenty of photographic evidence for earthquake lights. They tend to accompany large quakes – with magnitudes above 6 – centred at fairly shallow points in the Earth’s crust. It is not clear how the lights are produced, but Friedmann Freund of NASA’s Ames Research Center in Moffett Field, California, thinks that when rocks in the crust are squeezed, chemical bonds break to produce a pulse of electrical charge that travels up to the surface. “The rocks become like a battery and produce an enormous amount of electric power,” he says.
This process only generates a low voltage, but Freund thinks that the charge forms an ultra-thin layer at the surface. Since the charge is concentrated over a small distance, it would create a strong electric field, perhaps enough to ionise the air and create a luminous discharge that travels up away from the ground – explaining the orbs, flames …
