How mysterious orbs Scientists link strange lights to movement in the Earth's crust
- These strange lights can appear before earthquakes but rarely afterwards
- They often occur near rifts caused by movement in Earth's tectonic plates
- Scientists believe the tension during this process creates an electronic charge, which turns into light when it reaches the surface
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They have been linked to UFOs and hallucinations and thought to be harbingers of doom.
Now scientists claim to have unravelled more details about a family of mysterious floating orbs, known as 'earthquake lights'
The lights, which take many forms and appear before or during earthquakes, could provide an early warning sign.
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Mysterious floating orbs of lights are harbingers of an imminent earthquake, scientists claim. These lights were seen before the 2008 Sichuan earthquake in China
For instance, seconds before the 2009 L’Aquila, Italy earthquake struck, pedestrians saw 10cm high flames of light flickering above the stone-paved Francesco Crispi Avenue in the town’s historical city centre.
In 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 in 1906, about 100km northwest of San Francisco, a couple saw streams of light running along the ground two nights preceding the devastating earthquake that destroyed much of the city.
The rare earthquake lights are more likely to occur on or near a rift, an elongated depression or trough in the Earth’s crust bounded on both sides by normal faults, than other faults.
VIDEO: Earthquake lights seen 30 minutes before 2008 Sichuan earthquake in China
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WHAT ARE EARTHQUAKE LIGHTS?
An earthquake light is a rare and unusual luminous phenomenon that appears before or during earthquakes but rarely afterwards.
They are more likely to occur on or near a rift - an elongated depression or trough in the Earth’s crust bounded on both sides by normal faults - than other faults.
Stress-activated mobile electronic charge carriers, termed positive holes, flow swiftly along stress gradients.
Upon reaching the surface, they ionise air molecules and generate the observed light.
Many sightings have confirmed that they have shapes similar to those of the auroras, with a white to bluish hue.
Scientists are still unsure why more earthquake light events are related to rift environments than other types of faults.
Stress-activated mobile electronic charge carriers, termed positive holes, flow swiftly along stress gradients.
Upon reaching the surface, they ionise air molecules and generate the observed light.
Continental rift environments now appear to be the common factor associated with earthquake lights.
Looking back at 65 of the best recorded incidents earthquake lights were recorded in American and European documents dating from the 1600s, 85 percent appeared spatially on or near rifts.
And 97 per cent appeared adjacent to a type of fault known as a subvertical fault
Intraplate faults are associated with just five per cent of Earth’s seismic activity, but 97 per cent of documented cases of earthquake lights.
Geologist Robert Thiriault of the Ministry of Natural Resources in Quebec said: 'Earthquake lights as a pre-earthquake phenomenon, in combination with other types of parameters that vary prior to seismic activity, may one day help forecast the approach of a major quake.
Scientists are still unsure why more earthquake light events are related to rift environments than other types of faults. However, they believe they can help warn of earthquakes in the future
'The numbers are striking and unexpected. We don’t know quite yet why more earthquake light events are related to rift environments than other types of faults.'
The earthquake lights described varied in shape and extent, though most commonly appeared as globular luminous masses, either stationary or moving, as atmospheric illuminations or as flame-like issuing from the ground.
Because they occur before or during the quakes it is suggested the processes responsible for earthquake lights formation are related to a rapid build-up of stress prior to fault rupture and rapid local stress changes during the propagation of the seismic waves.
Continental rift environments now appear to be the common factor associated with earthquake lights. This image of an earthquake light was taken in El Salvador
Eyewitness reports and security cameras captured a large number of light flashes during the 2007 8.0 magnitude earthquake at Pisco, Peru.
Together with seismic records obtained on a local university campus, the automatic security camera records allow for an exact timing and location of light flashes that illuminated a large portion of the night sky.
The light flashes identified as earthquake lights coincided with the passage of the seismic waves.
The study was published in Seismological Research Letters.
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