A history of glowing skies
Reports of strange lights appearing before or during earthquakes stretch back for millennia. One of the earliest documented accounts comes from ancient Greece, describing "immense columns of fire" that accompanied the destruction of the cities Helice and Buris in 373 BCE. In 869 CE, the court chronicle of Japan reported a "luminous phenomenon" in the sky during the devastating Jōgan earthquake. For centuries, these accounts were often dismissed. The advent of photography and video has provided tangible evidence. During a seismic swarm in Matsushiro, Japan, from 1965 to 1967, photographs captured recurring glows and bluish flashes, correlating them with seismic events and lending scientific credibility to the phenomenon.
These earthquake lights, or EQL, manifest in various forms: stationary or floating globes of light, flashes resembling lightning from the ground, and even low-flickering flames. Colors reported range from white and blue to pink and purple. One modern observation occurred 11 days before a powerful earthquake in Quebec in 1988, when people saw a bright purple-pink globe of light moving along the St. Lawrence River. Just seconds before the 2009 L'Aquila earthquake in Italy, witnesses described 10-centimeter-high flames flickering above a stone street. The first widely circulated video evidence came from the 2007 Peru earthquake, which captured luminous flashes over Lima as the ground shook.
The physics of stressed rock
The leading scientific model for many earthquake lights is not just piezoelectricity—where quartz-bearing rocks generate voltage under pressure. A more comprehensive theory, developed by physicist Friedemann Freund, centers on the activation of electrical charge carriers called "positive holes" within specific types of rock.
This process occurs predominantly in igneous and metamorphic rocks like basalts and gabbros. These rocks contain crystal defects called peroxy bonds. When tectonic stress builds before an earthquake, these bonds can break, releasing mobile, positively charged carriers known as p-holes. The charges can propagate through the rock at speeds up to 200-300 meters per second.
When this wave of positive holes reaches the Earth's surface, it creates a strong electric field. This field can ionize pockets of air at the rock-air interface, generating a plasma that emits light. This model explains why EQL are disproportionately observed in rift environments and near subvertical faults. A study of 65 documented EQL events found that 97% occurred adjacent to these types of faults, which provide a direct pathway for the charges to ascend from deep within the crust.