The phenomenon of earthquake lights has long been a subject of interest to those of a Fortean mindset - not surprising, given the crossovers with other Fortean areas including ufology and other 'earth lights'-related phenomena such as will o' the wisps etc (for a fascinating Fortean take on the phenomenon, see "Shaking Stars, an article by Geoff Falla that we featured in Darklore Vol 3). These mysterious lights have sometimes been reported as orbs or globes of light (for instance, on November 12 1988, a bright purple-pink globe of light moved along the St. Lawrence River near Quebec, just eleven days before a powerful earthquake), while on other occasions it has been reported simply as an odd glow, and even sometimes just as strangely illuminated clouds.
Happily, this week we've also seen some mainstream press coverage of new research into the topic which may just bring a greater understanding of when and how it happens: in a study published in Seismological Research Letters, a team of researchers looked at 65 earthquakes over the last four centuries that had earthquake light reports associated with them, and analyzed the geologic circumstances of each to look for any discernible patterns:
“We built a pretty large database of earthquakes with earthquake lights that happened around the world,” says [Robert] Thériault, a geologist with the Quebec Ministry of Natural Resources. “And eventually, when we started to look at them, we found a really striking pattern.”
Worldwide, roughly 95 percent of seismic activity occurs at the boundaries between two or more tectonic plates. But the vast majority of earthquake lights (85 percent) occurred in association with a quake within a tectonic plate at sites of continental rifting, a category that represents just five percent of all earthquakes. Additionally, most of the remaining 15 percent occurred with earthquakes caused by two plates sliding past each other (a transform fault), rather than one plate is pushed underneath another (a subduction zone).
Additionally, the scientists found that earthquake lights appear disproportionately before or during earthquakes, rather than afterward. They don’t yet have an explanation for the unusual location patterns of earthquake lights, but they think they can explain this trend in timing.
Their model, developed over the past few years by co-author Friedemann Freund of San Jose State University, also involves rocks conducting energy up to the surface, but not all the way up to the ionosphere.
“The process starts deep in the crust, where rocks are subjected to high stress levels, prior to the stress being released to produce an earthquake,” Thériault says. In certain types of rock, Freund has shown in lab experiments, this stress can break apart pairs of negatively-charged oxygen atoms that are linked together in peroxy bonds.
When this happens, each of the oxygen ions are released, and these can flow through cracks in the rock, towards the surface. At that point, the thinking goes, high-density groups of these charged atoms will ionize pockets of air, forming a charged gas (a plasma) that emits light.
Given that tectonic stresses build up over time before being released in the earthquake, the researchers suggest that these strange lights might be used in the future as an early-warning sign that a quake is imminent. Readers of this site will know this is not a new idea though - we've previously discussed (almost a decade ago) Michael Persinger's Tectonic Stress Theory, which covers much the same territory. The new paper, though, seems to have done a good job in narrowing down when and in what circumstances the strange phenomenon of earthquake lights tend to occur. See the links at the bottom of this post for more Daily Grail reading related to this fascinating topic.
Original Paper: "Prevalence of Earthquake Lights Associated with Rift Environments"
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