Climate-triggered landslide and tsunami vibrated Earth for 9 days

A massive landslide in Greenland led to a mega-tsunami, which caused water to slosh back and forth across a fjord for nine days. This movement triggered vibrations that traveled through the Earth and were detected globally, according to a recent study.

The event, which occurred in September 2023, had initially puzzled seismologists when they observed a mysterious global seismic signal lasting for days. 

The research, published in the journal Science, reveals that the collapse of a 1.2 km-high mountain peak into the Dickson Fjord was responsible for the phenomenon.

Landslide produced a mega-tsunami 

The landslide, which occurred in a remote area, sent a wave of water 656 feet into the air, producing a tsunami that reached up to 360 feet high. 

This wave, which extended across more than 6 miles of the fjord, rapidly diminished to about 23 feet within a few minutes, and eventually settled down to just a few centimeters over the following days. 

By using advanced mathematical modeling, the researchers demonstrated how the narrow, winding fjord contributed to the prolonged back-and-forth sloshing of water. 

Global seismic vibrations

The frequency of this movement matched the seismic vibrations detected globally, helping to explain the baffling seismic readings.

According to the researchers, the landslide was triggered by the thinning of a glacier at the mountain’s base, which was no longer able to support the rock above. This destabilization was linked to climate change. 

First landslide and tsunami in Greenland

The event marks the first-ever landslide and tsunami recorded in eastern Greenland.

“When I first saw the seismic signal, I was completely baffled,” said co-author Stephen Hicks, an earth scientist at UCL 

“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.” 

Vibrations through Earth’s crust

Hicks noted that this is the first time that water sloshing has been recorded as vibrations through the Earth’s crust, traveling the world over and lasting several days.

The seismic signal detected was unlike the typical earthquake rumbles, which tend to be rich in frequency. Instead, it appeared as a single, monotonous hum. 

Initially labeled as a “USO” (unidentified seismic object), the signal was later linked to a large tsunami reported in the remote fjord of northeastern Greenland.

Piecing together the puzzle

To solve this mystery, 68 scientists from 40 institutions across 15 countries collaborated. They pooled together data from seismometers, infrasound recordings, satellite imagery, field measurements, and tsunami simulations. 

The Danish military also contributed imagery after inspecting the collapsed mountain and the scars left by the tsunami. This interdisciplinary effort allowed the team to piece together the sequence of events.

Study lead author Kristian Svennevig is a scientist at the Geological Survey of Denmark and Greenland (GEUS). 

“When we set out on this scientific adventure, everybody was puzzled and no one had the faintest idea what caused this signal. 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,” said Svennevig.

Destructive force of the landslide and tsunami 

The study revealed that the landslide displaced 25 million cubic meters of rock and ice – enough to fill 10,000 Olympic-sized swimming pools. 

The resulting tsunami waves, which were among the largest recorded in recent history, caused significant damage 70 km away from the site, including the destruction of cultural heritage sites and damage to a research base on the island of Ella Ø.

Although no cruise ships were in the area at the time, the researchers noted that Dickson Fjord is a popular route for tourist ships, and the consequences could have been devastating had any been nearby. 

Early warning systems are needed

Using high-resolution mathematical models, the team was able to precisely recreate the sloshing of water, which matched the seismic signals recorded around the world.

The study concluded that as climate change accelerates, it is becoming increasingly important to monitor regions previously considered stable and to develop early-warning systems for landslides and tsunamis. 

The role of global seismic networks 

Study co-author Thomas Forbriger from the Karlsruhe Institute of Technology emphasized the role of global seismic networks in the discovery. 

“We wouldn’t have discovered or been able to analyze this amazing event without networks of high-fidelity broadband seismic stations around the world, which are the only sensors that can truly capture such a unique signal,” said Forbriger.

According to Anne Mangeney from Université Paris Cité, the tsunami challenged the classical numerical models that we previously used to simulate just a few hours of tsunami propagation. 

“We had to go to an unprecedentedly high numerical resolution to capture this long-duration event in Greenland. This opens up new avenues in the development of numerical methods for tsunami modeling,” concluded Mangeney. 

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