During an earthquake, strange lights sometimes appear in the sky. Observers are baffled, and scientists aren’t sure what to make of it, either.
If you ever see these ominous lights, don’t panic. It is not the end of the world and aliens have not come to invade. Lately, images and footage have revealed strange luminescent phenomenon before, during, and after the 7.1 earthquake in Mexico City in early September 2021.
Theories ranged from sudden weather changes to UFOs. The topic went viral online. But this is not the first time that these odd lights have shown up in our skies during a major tremor.
The lights come in many shapes
Earthquake lights (EQL) have had many names over the years, including sheet lightning, ball lightning, and streamers. The scientific term is luminescence, or sometimes triboluminescence. The lights’ appearance tends to confuse people since they do not stick to one form or color. They can be balls of light, flames, bright streaks across the sky, and glowing hues of blues, reds, whites, violets, and pinks. They can last from a few seconds to several minutes.
Earthquake lights in New Zealand. Photo: Syrian Kiwi/Instagram
The first record of this phenomenon dates back to 869 AD when the Sanriku earthquake and subsequent tsunami devastated Japan. The quake was estimated to be above 8.0 on the Richter scale. A translation from Japan’s national historic record, called the Sandai Jitsuroku, said that a “large earthquake occurred in Mutsu Province with some strange light in the sky.”
The Japanese Historical Earthquake Archives noted around 55 instances of such lights throughout Japan’s history. The earthquake lights also appeared elsewhere around the world, particularly during earthquakes of 5.0 and higher. They occurred in the 1811-1812 earthquakes in Missouri, the infamous 1906 San Francisco earthquake, the 1988 Saguenay earthquake in Canada, the 2009 L’Aquila earthquake in Italy, the 2017 Chiapas earthquake in Mexico, and many more.
While scientists haven’t decided what causes these lights, it likely has something to do with the types of rock present. Yupik Enomoto of Shinshu University noticed that the lights appeared at the same time as landslides. He ran experiments on granite, limestone, pyroclastic rock, and others to determine whether light was emitted from fracturing, friction, or chemical reactions within the rock.
Different rocks, different colors
Enomoto fractured samples of rocks and found that granite had the most intense reaction. It sparked bright white. Other rocks behaved differently: Rhyolite emitted orange lightning; limestone, an intense red glow.
Enomoto also believes that rocks containing quartz are more prone to luminous reactions. It is possible that during an earthquake, as different rocks fracture and grind against one another, they create these kaleidoscopic displays. Nevertheless, it remains unproven that landslides are fully responsible.
Lights in the sky before an 8.0 earthquake in Sichuan, China, in 2008. Photo: YouTube
Some scientists suggest that the high levels of stress in rocks during an earthquake cause chemical bonds in rocks to break and the oxygen to ionize. These ions escape from the rock and travel into the atmosphere, where they emit light.
This ionization hypothesis was tested in a lab, and it does seem that rocks under stress release ions. The 9.0 Tohoku earthquake in 2011 further confirmed this. Here, a large number of electrons occurred in the atmosphere a few minutes before the shaking started. This theory is still under consideration, however.
The Earth’s magnetic field or ionosphere may also play a part: Perhaps a process similar to the aurora’s formation occurs in high-tension areas. However, this is a less popular theory.
Pent-up electrical charges?
Strangely enough, most of these lights happen in parts of the world where tectonic plates grind less past each other. One seismological study suggests that electrical currents from the Earth’s mantle escape through vertical faults in the rift. These currents are called positive holes. As they surface, ionization may emit glowing lights. Other vertical geological formations like dikes can also house electrical charges, which shoot into the air once released.
In 2014, Troy Shinbrot of Rutgers University pointed out that when grains of the same type of rock rub together, they create an electric charge. The charge reacts with the air, thereby electrifying it. This creates bright flashes of light. The tests were repeated and reproduced the same result. This breakthrough seems more in line with Enomoto’s hypothesis.
All these theories and findings are promising. But now that scientists are aware of the mystery, we’ll probably need a few more earthquakes before they can finally solve it.
