(old Japanese haiku)
Moments before dawn, a bright red flash lights the eastern and central skies over the island of Cypress. Nicosia Hodja, whose personal habit is to start each day with outdoor prayer, feels the earth roll beneath him. "I saw a brilliant reddish object," he later states, "like a huge globular lightning moving slowly toward the east."
The strange light Nicosia observed is one example of luminous phenomenon referred to as earthquake lights. Earthquake lights have been witnessed most often immediately after a powerful earthquake, but they have also been reported right before and during the quake. Generally lasting up to a minute, they typically appear as stationary hemispheres of bluish-white light, 20 to 200 meters in diameter. Some reports describe beams of light shining up like a search light from a point on the horizon, or as reddish or orange round spheres in a row floating in the sky. Still, others describe aurora-like lights or glowing mountaintops. Whatever the specific manifestation, geophysicists now accept the existence of earthquake-generated lights as real; however, scientists remain divided over exactly what causes the light show when the earth's surface jolts with explosive force.
"Very few scientists have worked on the problem [earthquake lights], and few today are willing to tackle it because most of the reports are personal observations of untrained observers, says John Derr of the U.S. Geological Survey. "Until recently, there were no hard data which could be subjected to scientific analysis." The lack of hard scientific data is not due to the scientists' lack of interest, but due to the nature of earthquake lights themselves. Their brief duration and random occurrence make collection and analysis of data exceedingly difficult. Consequently, several theories have emerged from limited and diverse observations that attempt to explain earthquake lights.
The theory that earthquake lights are a product of the great stresses along geological faults is known as the Tectonic Strain Theory and is the most widely accepted theory. Twelve major rock plates form a giant mosaic covering the outer surface of the earth. Called tectonic plates, they rest upon the soft inner core of the earth like a cracked eggshell on a hardboiled egg. Tectonic comes from the Greek word tektonikos, meaning to build. Lava from the earth's center continually oozes up through cracks in the mid-ocean regions, building new rock onto the existing plates. The new growth pushes the plates away from one another at a rate of several centimeters each year. However, as one plate moves, it presses into others creating strain at the point of contact. Such contact points are known as geological faults.
In addition, tectonic strain theorists are also considering an unusual property of some rocks to emit electromagnetic energy when squeezed as a possible source of the mysterious lights. These rocks share a similar structure: molecules which stack upon one another with the same alignment. This structure allows energy released by rock molecules to add under stress. The mineral quartz has such a structure. When squeezed, it releases its combined electro-magnetic energy in the form of radio waves-- much the same way squeezing a sponge releases water. Materials that do this are called piezoelectric - piezo coming from the Greek word piezein, to press.
A few special piezoelectric rocks also release energy in the form of light. Rocks capable of producing light do so in one of two ways: friction or fracture. Rubbing rock surfaces together with great force releases light energy, just like the flint in a manual charcoal lighter does by rubbing. This property of materials is called triboluminescence, from the Greek word tribien, to rub. But for some light-emitting rocks, rubbing is not enough force. They must be stressed to the point of fracture. Thus, they are known as fractoluminescent.
"There has to be some amount of impurity within the rock composition for sparks to fly, " says Linda Sweeting, professor of chemistry at Towson State University, Baltimore, Maryland. While conducting research into the triboluminescent properties of materials, Sweeting discovered that piezoelectric rocks with the most symmetrical construction, emit no light when stressed. Squeeze the same rock with a little impurity infused within its structure, and you get light -much the same way the presence of wintergreen oil added to sugar molecules produces light when Wint-O-Green Lifesavers are crushed.
Nobody knows this fact better than Sweeting, who has been credited with making the correlating discovery with Lifesavers. "I've gotten a lot of mileage out of that little pack of Lifesavers," she admits laughingly. "Of all the hard work I've invested over the past ten years, the Lifesaver thing has given me the most recognition." Over her desk she proudly displays a framed Peanuts cartoon autographed by artist Schultz. In it the characters are trying to produce enough light to read a map in the dark by munching on Lifesavers.
To experience the phenomenon of tribo/fractoluminescence, Dr. Sweeting suggests, "Take a pack of Wint-O-Green Lifesavers into a dark room. Stand in front of a mirror and turn off the lights. After allowing a few minutes for your eyes to adjust to the dark, keep your mouth open and bite down on a lifesaver. A flash of blue light will be seen. But don't let the Lifesaver get wet. Moisture kills triboluminescence. "
Nature works on the same principle, but on a much grander scale. As tectonic plates continue to move and press against one another, forces build up between the rock surfaces. At some contact points, one plate moves downward while the other pushes over the top of it. According to Tectonic Strain theorists, light emitted from earthquakes with rubbing plate movement is triboluminescence. Light produced during quakes that severely fracture plate material is fractoluminescence. According to the same theorists, when light is emitted by a quake, both effects contributed in some combination.
Though Tectonic Strain Theory seems on the surface to offer a logical explanation for earthquake lights, critics argue that it has faults of its own. Scientists agree that ninety percent of all earthquakes happen along geological fault lines. This would lead rational thinkers to conclude that ninety percent of earthquake light sightings should occur along these faults. There have been many sightings of lights coinciding with earth tremors in regions hundreds of miles from any known faults. So, another theory has emerged that tries to explain the oddity. Proposed by computer programmer/analyst, and earthquake enthusiast, Timothy Kelly Ill, it has been growing in acceptance within the science community. Not surprisingly called the Fault-Free Earthquake Theory, it is also based on the piezoelectric property of rocks, but in reverse.
As previously stated, piezoelectric materials emit both radio wave and light energy when compressed. Interestingly, the process also works well in reverse: applying electric energy (charge) across a piezoelectric rock causes its physical size to change. If the polarity of the plus/minus charge applied across the whole rock is the same as the polarity on the individual molecules within the rock, expansion occurs; if it is opposite, compression occurs.
According to the Fault-Free Theory, whenever large electric charges in the atmosphere build up, usually during windless and dry periods, earth tremors occur. The constant bombardment of the earth by charged particles from the sun cause the electrical build-up in the atmosphere. When this electric charge between the atmosphere and the inner earth is applied across the tectonic plate (the piezoelectric material, in this case), the plate expands or rises slightly upward. At some point in time, the electricity in the atmosphere discharges into the earth, and the raised area compresses, or falls. The gradual rise and subsequent fall of a large land mass is what creates a fault free earthquake. Kelly believes that light observed with this type of quake comes from the sudden discharge of electricity, like lightning. It has been reported as flashes of light in the form of a column, or vortex; and, in rare instances, appearing as a large floating ball of light (like Nicosia saw).
Scientists B.T. Brady and Glen A. Rowell at the Department of the Interior Denver Research Center offer yet another theory. After conducting granite fracturing experiments, they are convinced that massive bombardment of nitrogen molecules by high-speed electrons (released by fracturing rock) best explains why some lights are reported seen as high as 200 meters above ground. Both scientists believe that piezoelectricity and triboluminescence only explain instances of dim earthquake light occurring close to the ground.
Brady and Rowell also have critics who seriously doubt in cases of deep fault earthquakes that electrons could reach the surface of the earth in great enough numbers to ionize the air. Yet there are many documented cases of significant earthquake lights associated with deep quakes. They admit that their theory has some flaws but argue that countless smaller cracks may have formed over time, providing conduits for the passage of electrons upward and outward.
Whose theory can best explain the atmospheric illuminations associated with quakes occurring out at sea? Not the Tectonic Strain Theory people. Sweeting said that moisture kills triboluminescence. Not the Fault Free Earthquake Theory people. The air over the sea is too humid for sufficient static charge to form. Not the high-speed electron people. They rely on air ionizing where it contacts the cracks in the earth, not above sea water.
Other theorists contend that some earthquake lights, especially the higher altitude ones, over both land and sea, may be auroras. They include consideration of solar disturbance and its effect on the earth. These theorists believe that magnetic coupling (the transfer of energy) between solar plasmas blown toward the earth and the earth's magnetic field may momentarily place a drag on the earth's rotation, jarring the already over-stressed faults. The associated lights occur as highly charged particles from the solar plasma ionize air in the upper atmosphere.
Earth, sun, stress, fracture, electrons -- there seem to be as many theories as there are tectonic plates. But at least the plates, like pieces of a puzzle, have managed to fit together and produce something – like the surface of the earth. By cleverly piecing together the present theories, the explanation for earthquake lights may one day be revealed. Meanwhile, Nicosia Hodja's memory of a drifting reddish glob in the sky remains a mystery.