Greenland Landslide Triggered Seismic Event That ‘Shook the Earth’ for Nine Days

An enormous landslide of rock and glacial ice in a Greenland fjord last year led to a seismic wave that “shook the Earth” for nine straight days, reported BBC News.

The landslide triggered a 656-foot “mega-tsunami” inside the narrow fjord, where it moved back and forth, generating vibrations felt by sensors all over the planet.

“When colleagues first spotted this signal last year, it looked nothing like an earthquake. We called it an ‘unidentified seismic object,’” said Dr. Stephen Hicks, a researcher in the Department of Earth Sciences at University College London (UCL). “It kept appearing – every 90 seconds for nine days.”

Scientists say landslides like the one in Greenland are happening more often as climate change causes glaciers supporting Greenland’s mountains to melt.

“Even though we know seismometers can record a variety of sources happening on Earth’s surface, never before has such a long-lasting, globally travelling seismic wave, containing only a single frequency of oscillation, been recorded. This inspired me to co-lead a large team of scientists to figure out the puzzle,” Hicks said in a press release from UCL.

An international team of researchers, in collaboration with the Danish Navy, investigated the event, the results of which — “A rockslide-generated tsunami in a Greenland fjord rang Earth for 9 days” — were published in the journal Science.

For a year, dozens of scientists worldwide had been attempting to solve the puzzle of what the mysterious signal was, CNN reported.

Hicks told CNN that some of the seismologists picking up the repeating signal thought their instruments had broken. He said the vibrations didn’t give off the usual rumbles and high-pitched indicators seen with an earthquake, but rather a hum lacking in variation. Plus, signals associated with earthquakes normally go on for minutes, while the “unidentified seismic object” (USO) persisted for more than a week.

The signal was traced to eastern Greenland. To locate the exact location, the seismologists contacted their Denmark colleagues, who had gotten reports of a tsunami generated by a landslide in remote Dickson Fjord.

This led to a collaboration between 68 scientists from 15 countries over the course of almost a year. They sifted through satellite, seismic and land-based data, in addition to tsunami wave simulations to solve the mystery of the USO.

The glacier had been sitting 4,000 feet above Dickson Fjord for years, melting and thinning in the increasingly warming Arctic. The mountain collapsed in mid-September of 2023, sending rock and debris into the fjord.

The ensuing tsunami wave that became trapped in the narrow fjord created a “seiche,” or tightly enclosed wave moving rhythmically back and forth.

“This landslide happened about 200km inland from the open ocean,” Hicks explained, as reported by BBC News. “And these fjord systems are really complex, so the wave couldn’t dissipate its energy.”

Scientists had never known a seiche to last such a long time.

“Had I suggested a year ago that a seiche could persist for nine days, people would shake their heads and say that’s impossible,” said Dr. Kristian Svennevig, a researcher with the Geological Survey of Denmark and Greenland, as CNN reported.

The scientists discovered it was the seiche that led to the seismic energy deep below in Earth’s crust. The vibrations took roughly an hour to make their way from Greenland to Antarctica, Hicks said.

“Our study of this event amazingly highlights the intricate interconnections between climate change in the atmosphere, destabilisation of glacier ice in the cryosphere, movements of water bodies in the hydrosphere, and Earth’s solid crust in the lithosphere,” Hicks said in the press release. “This is the first time that water sloshing has been recorded as vibrations through the Earth’s crust, travelling the world over and lasting several days.”

There were no injuries reported from the tsunami, but an empty military base was damaged and cultural heritage sites that had been around for centuries were washed away, reported CNN. The location is frequented by cruise ships, and if any had been there, the authors of the study said “the consequences would have been devastating.”

Svennevig said a landslide and tsunami of that type had never been seen in East Greenland before.

The Arctic has been warming four times faster than other parts of the globe since 1979, which could mean more frequent mega-tsunamis triggered by landslides in the region.

“That glacier was supporting this mountain, and it got so thin that it just stopped holding it up,” Hicks said, as BBC News reported. “It shows how climate change is now impacting these areas.”