Earthquake lights are a rare phenomenon resulting from specific geological conditions. Rocks subjected to great stress produce electrical charges that can be channeled to the surface through deep vertical faults. This photos shows earthquake lights near Tagish Lake in Canada’s Yukon territory. Researchers looking at seismic records and found reports of the Cross Sound earthquake of July 1, 1973, which measured 6.7 on the Richter scale.(Photo: Jim Conacher)
(USA TODAY) -- They've been mistaken for UFOs or dismissed as hallucinations. Now
geologists have collected a near-definitive list of a rare but
fascinating phenomenon - earthquake lights.
Certain types of
earthquakes in certain areas can set off blazes of light seconds -
sometimes days - ahead of the actual quake. These can manifest
themselves as floating balls of light, bluish columns shooting up out of
the earth and even reverse lightning, reaching up into the sky from the
A study out Thursday in the journal Seismological Research Letters shows such quakes are tied to a specific type of temblor in areas where certain geological formations occur.
While rare, researchers were able to document 65 examples between 1600 and the present.
Seconds before the 2009 L'Aquila, Italy, earthquake struck, pedestrians
saw flames of light 4 inches high flickering above the stone-paved
Francesco Crispi Avenue in the town's historical city center.
Pisco, Peru, a naval officer saw pale-blue columns of light bursting
four times in succession out of the water on Aug. 15, 2007, as an
8.0-magnitude earthquake struck. Security cameras in the city captured images of the lights as well.
On Nov. 12, 1988, a bright purple-pink globe of light moved through the
sky along the St. Lawrence River near the city of Quebec, 11 days
before a powerful quake.
• And on April 18, 1906, blue flames were
seen hovering at the base of foothills west of San Francisco just
before the great earthquake hit. South of the city, in San Jose, one
street was seen to be ablaze with fire in a faint but beautiful rainbow
The mechanism that causes the phenomenon occurs only in specific and rare conditions, said Friedemann Freund, a professor of physics at San Jose State University and senior scientist at NASA Ames Research Center in Mountain View, Calif.
Rocks such as basalt and gabbro, created deep in the Earth's mantle, contain tiny defects in their crystals. When such rocks are stressed, those defects momentarily generate electrical charges, said Freund, one of the paper's authors.
"When a powerful seismic wave runs through the ground and hits a layer of such rocks, it compresses
the rocks with great pressure and speed, creating conditions under
which large amounts of positive and negative electrical charges are
generated," he said. These charges can then travel together, allowing
them to reach what's called a plasma state, which can burst out and
shoot up into the air.
Another necessary component for
earthquake lights to be produced in nature are deep vertical faults in
the Earth's crust, some of which can reach down 60 miles and more.
Magmas that solidify to become gabbros or basalts have risen along these
faults, forming dikes often tens to hundreds of feet thick.
speculate that the dikes act as a funnel, focusing the charges until
they become an ionized solid-state plasma," said Robert Thériault, lead
author on the paper and a geologist with the Quebec Ministry of Natural Resources in Canada.
"When the plasma bursts out into the air, it produces light," he said.
Fewer than 0.5% of earthquakes worldwide occur in the right places to create earthquake lights. The researchers combed through historical documents, many handwritten
and some in Latin, dating back centuries. They also looked at modern
scientific papers and surveillance-camera records that recorded
earthquake lights in real time.
Earthquake lights are
sometimes mistaken for UFOs, Thériault said. In the early 1970s, a Jim
Conacher was boating on Tagish Lake in Canada's Yukon territory with his
wife when they saw seven yellow luminous globes on the nearby flank of a
mountain. The nearer orbs slowly drifted up the mountain to join the
more distant ones.
Conacher took a photograph of the lights, which made its way to a website listing possible UFO sightings in Canada.
when the researchers looked through seismic reports, they found
records of the nearby Cross Sound earthquake of July 1, 1973, which
measured 6.7 on the Richter scale. There were also two aftershocks
measuring 5.2 and 4.1. Though the exact dating of the trip is uncertain
(the boaters have died), the researchers believe the lights appeared
just a few hours prior to the initial quake.
Areas that contain
these specific grouping of traits include Italy, Greece and the Rhine
rift, which stretches between France and Germany, as well as several
areas in South America. Researchers believe they exist in China as well.
lights aren't common enough in earthquake zones to be used as a warning
system, Thériault said. But they have sometimes functioned that way.
before Italy's L'Aquila earthquake, a man in his kitchen saw flashes
of brightness outside as intense as daylight. The light lasted for more
than a second. Because he had read a paper about earthquake lights
previously, he decided to take his family to a safer structure.
also knows a geologist in Canada who was living in China in 1976. On
July 28 that year, he saw earthquake lights, which prompted him to leave
his house. Soon thereafter, the devastating Tangshan quake hit. It is
believed to have killed hundreds of thousands of people. The geologist