Climate change is increasingly causing extreme weather events and natural disasters that have left scientists alarmed. One such event occurred on September 16, 2023, when earthquake sensors around the world detected mysterious seismic tremors that lasted for nine days—an unusually long duration for any earthquake.
Researchers, who had no idea what was causing these seismic vibrations, classified the signal source as a “USO” – an unidentified seismic object, as per Scientific American. A year later, they finally had the answer to this mystery, and a study published in the journal Science revealed that the cause of the seismic signal was a massive rockslide that occurred in Greenland’s isolated Dickson Fjord. “When we set out on this scientific adventure, everybody was puzzled and no one had the faintest idea what caused this signal,” said Kristian Svennevig, a geologist and the study’s lead author, in a press release. “All we knew was that it was somehow associated with the landslide. We only managed to solve this enigma through a huge interdisciplinary and international effort.”
A team of 68 scientists from 40 institutions in 15 countries worked together to reveal that the mysterious reverberations were triggered after a 3,937-foot-high mountain collapsed in Greenland’s Dickson Fjord, per The Guardian. After the melting glacier was unable to hold the elephantine mass, more than 25 million cubic meters of rock and ice plunged into the fjord’s waters, further triggering a 656-foot-high mega-tsunami, and a phenomenon known as a “seiche.” A tsunami wave typically gets dissipated in the ocean or sea, but this wave got trapped inside the fjord, and the water kept sloshing back and forth rhythmically for almost nine days, sending seismic tremors throughout the planet.
The landslide and mega-tsunami were first observed in Eastern Greenland. Although no damage was caused to the locals, the disaster ended up smashing $200,000 worth of gear at an unoccupied research station on Ella Island.
Scientists attribute this entire phenomenon to the rapidly changing climate conditions. “Climate change is shifting what is typical on Earth, and it can set unusual events into motion,” said Alice Gabriel in the press release. This particular tsunami shed a voluminous mass of rock and ice that was “enough to fill 10,000 Olympic-sized swimming pools.”
To solve the mystery of this seismic reverberation, scientists combined information from a wealth of seismic data, satellite imagery, in-fjord water level monitors, and detailed simulations of how the tsunami wave evolved. When they analyzed the signal and reconstructed the chain of events that could have possibly triggered it, they noticed that it depicted two peculiar things. Firstly, it looked nothing like a typical earthquake on the seismograph, but oscillated with a 92-second interval between its peaks, too slow for humans to notice. Secondly, the signal didn’t seem to lose its strength for more than a week.
The study’s findings have now put another concern in the minds of scientists and geologists. As climate change appears more prevalent around the globe, especially in the arctic regions, events like these might be more frequent than ever. “This certainly won’t be the last such landslide-megatsunami. As permafrost on steep slopes continues to warm and glaciers continue to thin, we can expect these events to happen more often and on an even bigger scale across the world’s polar and mountainous regions. Recently identified unstable slopes in west Greenland and in Alaska are clear examples of looming disasters,” the researchers, including Stephen P. Hicks, told Scientific American and added that, while the ground beneath the feet of humans is shaking, they must adopt new ways of thinking to deal with these situations.
