During an earthquake, strange lights sometimes appear in the sky. Observers are bewildered and scientists also don’t know what to make of it.
If you ever see these ominous lights, don’t panic. It is not the end of the world and the aliens have not come to invade it. Lately, images and footage have revealed strange luminescent phenomena before, during and after the 7.1 earthquake in Mexico City in early September 2021.
Theories ranged from sudden weather changes to UFOs. The subject went viral online. But this is not the first time that these strange lights have appeared in our sky during a major earthquake.
Lights come in many forms
Seismic 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 appearance of lights tends to confuse people because they don’t stick to any shape or color. They can be balls of light, flames, brilliant streaks in the sky, and vibrant hues of blue, red, white, purple and pink. They can last from a few seconds to several minutes.
The earliest record of this phenomenon dates back to AD 869 when the Sanriku earthquake and subsequent tsunami devastated Japan. The earthquake was estimated to be over 8.0 on the Richter scale. A translation of the National Historic Register of Japan, called the Sandai Jitsuroku, said that a “great earthquake occurred in Mutsu province with a strange light in the sky.”
The Japanese historical earthquake records have noted around 55 cases of such lights throughout the history of Japan. Earthquake lights have also appeared elsewhere in the world, especially during earthquakes of 5.0 and above. They occurred during the 1811-1812 earthquakes in Missouri, the infamous 1906 earthquake in San Francisco, the 1988 earthquake in Saguenay in Canada, the L’Aquila earthquake in 2009 in Italy, the Chiapas earthquake in 2017 in Mexico, and many others.
While scientists have yet to decide the cause of these lights, it likely has something to do with the types of rocks present. Yupik Enomoto from Shinshu University noticed that the lights appeared at the same time as the landslides. He conducted experiments on granite, limestone, pyroclastic rock, and others to determine if light was emitted by fracturing, friction, or chemical reactions inside the rock.
Different rocks, different colors
Enomoto fractured rock samples and found that granite had the most intense reaction. It sparkled brilliantly white. Other rocks behaved differently: the rhyolite emitted orange flashes; limestone, an intense red glow.
Enomoto also believes that rocks containing quartz are more prone to light reactions. It’s possible that during an earthquake, when different rocks fracture and rub against each other, they create these kaleidoscopic displays. However, it is not proven that landslides are fully responsible.
Some scientists suggest that the high stress levels in rocks during an earthquake cause chemical bonds in rocks to break down and oxygen to ionize. These ions escape from the rock and travel through the atmosphere, where they emit light.
This ionization hypothesis has been tested in the laboratory, and it seems that rocks under stress release ions. The Tohoku 9.0 earthquake in 2011 further confirmed this. Here, a large number of electrons were produced in the atmosphere a few minutes before the start of the tremors. This theory is however still under study.
The Earth’s magnetic field or the ionosphere may also play a role: perhaps a process similar to the formation of auroras occurs in high voltage areas. However, this is a less popular theory.
Electrical charges accumulated?
Oddly enough, most of these lights occur in parts of the world where tectonic plates rub less against each other. A seismological study suggests that electric currents in the Earth’s mantle escape through vertical faults in the rift. These currents are called positive holes. On their surface, ionization can emit incandescent lights. Other vertical geological formations such as dikes can also harbor electrical charges, which soar into the air when released.
In 2014, Troy Shinbrot of Rutgers University pointed out that when grains of the same type of rock rub against each other, they create an electrical charge. The charge reacts with the air, electrifying it. This creates lightning flashes. The tests were repeated and reproduced the same result. This breakthrough seems more in line with Enomoto’s hypothesis.
All of these theories and findings are promising. But now that scientists are aware of the mystery, we’ll likely need a few more earthquakes before we can finally solve it.
About the Author
Kristine De Abreu
Kristine De Abreu is a writer (and occasional photographer) based in sunny Trinidad and Tobago.
Since graduating with a BA in English and History from the University of Leicester, she has pursued a full-time writing career, exploring multiple niches before embarking on travel and exploration. While studying for an additional travel journalism degree with the British College of Journalism, she began writing for ExWeb.
Currently, she works in a travel magazine in Trinidad as an editorial assistant and is also the Weird Wonder Woman of ExWeb, reporting the natural quirks of the world as well as general stories from the world of exploration.
Although not a climber (yet!), She hikes in the bush, is known to befriend iguanas, and quotes The Lord of the Rings trilogy from start to finish.