‘Completely baffled’: 656-foot mega-tsunami that made Earth vibrate for 9 days stuns scientists

LONDON — Picture this: A tsunami taller than the Tower of Pisa, a fjord transformed into nature’s bathtub, and the entire Earth vibrating like a tuning fork for over a week. It might sound like the plot of a disaster movie, but it’s the reality of an extraordinary event that unfolded in Greenland, leaving scientists scrambling for explanations.

On September 16, 2023, a colossal mountain peak in the pristine wilderness of East Greenland crumbled into a remote fjord, unleashing a tremendous chain of events. This wasn’t just any landslide – it was a climate change-induced catastrophe that shook the Earth for an astonishing nine days.

The story begins with a mystery. Seismologists around the world detected an unusual signal rippling through the Earth’s crust. Unlike the typical “rumbles” and “pings” of earthquakes, this vibration sang a monotonous hum at a single frequency. It persisted for days, traveling from the Arctic to Antarctica, leaving experts scratching their heads. They dubbed it a “USO” – an unidentified seismic object.

Meanwhile, news trickled in of a massive tsunami in a remote Greenland fjord. As scientists pieced together the puzzle, they uncovered a sequence of events more dramatic than anyone could have imagined.

High above Dickson Fjord, a 1.2-kilometer-high mountain peak had been slowly destabilizing. As climate change caused the glacier at its base to thin, the rocky face lost its support. In a catastrophic moment, 25 million cubic meters of rock and ice – enough to fill 10,000 Olympic-sized swimming pools – came crashing down into the fjord below.

The impact, described in the journal Science, was cataclysmic. A wall of water shot 200 meters (an astonishing 656 feet!) into the air – nearly as tall as the Golden Gate Bridge. A tsunami wave up to 110 meters high (about 361 feet) surged across the fjord, gradually settling into a rhythmic sloshing motion known as a seiche.

What makes this event truly remarkable is how long this sloshing persisted. The seiche maintained a nearly constant frequency of 10.88 mHz (corresponding to a period of approximately 92 seconds), gradually decreasing in amplitude over nine days. This means that the water in the fjord was oscillating back and forth, completing one full cycle about every 92 seconds. This rhythmic motion transferred energy to the surrounding bedrock, generating seismic waves that traveled around the planet. The consistency and duration of this signal were unprecedented, allowing it to be detected by seismometers worldwide for over a week.

Dr. Stephen Hicks of UCL Earth Sciences, a co-author of the study, expresses his initial bewilderment. “When I first saw the seismic signal, I was completely baffled. Even though we know seismometers can record a variety of sources happening on Earth’s surface, never before has such a long-lasting, globally traveling seismic wave, containing only a single frequency of oscillation, been recorded,” he says in a statement.

The event’s far-reaching impacts were sobering. Seventy kilometers away, four-meter-high waves battered a research base on Ella Ø island, destroying valuable infrastructure and cultural heritage sites. Fortunately, the base was unoccupied at the time, but the incident points to the dangers to coastal communities and infrastructure. Moreover, had tourist cruise ships – which frequently ply these waters – been in the area, the consequences could have been devastating.

This incident marks the first documented large, tsunamigenic landslide in East Greenland, highlighting how climate change is reshaping polar landscapes in unexpected and potentially hazardous ways. As Dr. Kristian Svennevig from the Geological Survey of Denmark and Greenland notes, “As a landslide scientist, an additional interesting aspect of this study is that this is the first-ever landslide and tsunami observed from eastern Greenland, showing how climate change already has major impacts there.”

As glaciers thin and retreat due to warming temperatures, they can destabilize surrounding rock faces, increasing the likelihood of large landslides. When these landslides occur near water bodies, they have the potential to trigger tsunamis and long-lasting seiches, as dramatically demonstrated in this case.

The study of this extraordinary event was made possible by an unprecedented collaboration of 68 scientists from 40 institutions across 15 countries. They combined data from seismometers, infrasound sensors, field measurements, satellite imagery, and advanced computer simulations to reconstruct the cascade of events.