Earthquake lights: Why do they appear? 

Imagine this: It’s the weekend and you are out enjoying the sunset hour at a local park when you suddenly notice blue orbs of light at a distance, slowly hovering and then fading into the horizon. You watch, perplexed and you think it’s an optical illusion or maybe a shooting star. But in the very next moment, the ground starts to shake. You realise, it’s an earthquake! Fortunately, the earthquake stopped as quickly as it had arrived. You feel relieved to find that everyone is safe. But you are still wondering where those strange lights emerged from and where they vanished. You keep thinking, “Was there any connection to the earthquake?” Yes, you are right. Those were, what the scientist community refers to as earthquake lights.  

Earthquake lights: A sneak peek 
Earthquake lights (or EQL) have been visible for thousands of years and can be traced back to as early as 89 B.C. However, for ages, scientists had no clue as to what they were. In fact, these strange orbs of light have often been deemed as extra-terrestrial, something out of a science fiction. However, in the modern-times, thanks to technology, these lights have been sighted ahead of earthquakes and can be confirmed to be associated with them. 

Okay, so what do they look like? Well, that too varies from time to time. Usually, they are like floating orbs, but people have also reported them to be cloud-like streaks, mostly green in colour. Some have even said they look almost similar to lightning. Basically, this is a luminous aerial phenomenon that leads up to either a seismic activity or a celestial event.   

Interestingly, the earthquake lights were first captured on camera in 1965 during an earthquake in Japan. Later, they were also observed elsewhere, such as in China in 2008, Italy in 2009 and more recently Mexico in 2017.  

Okay, so what exactly causes earthquake lights? 
Before going onto understand what causes earthquake lights, let us tell you that these sightings are not only rare but also captivating. In fact, they do not always precede all earthquakes. Okay, so what are the possible logical explanations? Is it a mere reflection or something else?  

Turns out that earthquake lights don’t just appear, they are only seen near the time and epicentre of an earthquake, that is the area with the greatest amount of tectonic stress. Here’s the most intriguing part for you. According to research (after detailed analysis of 65 earthquake lights pattern) conducted by Friedemann Freund, an astrophysicist associated with NASA’s Ames Research Centre, these lights are formed when electrical charges are activated in the certain types of rocks (such as basalt and gabbro) underneath the earth’s outer surface. In other words, the surrounding tension breaks loose millions of negatively charged oxygen atoms forcing them out, giving them the shape of clusters and turning them into charged gas that emits light. It’s almost as if someone switches on a battery near the Earth’s crust.  

While this is the most popular explanation, there’s another study that revealed that the severe tectonic stress near the epicentres led to something called piezoelectric effect. In this case, quartz-bearing rocks are known to produce strong electric fields when they get compressed. But this theory has not been widely accepted.