Researchers solve mystery

Mega-tsunami caused the earth’s crust to tremble for days in 2023

Images of the mountain peak (marked in yellow) and the glacier before (left) and after the massive landslide (right)

(Bild: Søren Rysgaard (links), Danish Army (rechts) / Collage: KIT/Elias Kobel)

In September a year ago, earthquake measuring devices around the world received a seismic signal for up to nine days, leaving scientists baffled. Now an international team of researchers has identified the source of the vibrations.

"In September 2023, we detected a signal that could be recognized globally," says Thomas Forbriger from the Geophysical Institute of the Karlsruhe Institute of Technology (KIT), who investigated the mysterious signal together with numerous other researchers. "It looked completely different from an earthquake. The signal was an oscillation with a single dominant frequency, like a monotonous hum that decays very slowly."

Waves sloshed back and forth in the fjord
As it turned out, the collapse of a mountain peak that had previously risen 1200 meters above the fjord caused a massive landslide in Dickson Fjord on Greenland. This triggered a huge tsunami that swept back and forth across the narrow fjord for nine days with a period of around 90 seconds. The wave, which was initially up to 110 meters high, extended over ten kilometers and shrank to "only" seven meters in just a few minutes.

"The volume of the falling material was enormous - more than 25 million cubic meters. That's enough to fill 10,000 Olympic swimming pools," explains Kristian Svennevig from the Geological Survey of Denmark and Greenland (GEUS), who coordinated the investigations.

Waves ran around the entire globe
The movements of the large mass of water generated seismic waves that were measurable at the measuring stations for nine days. The waves ran around the globe and could even be observed as far away as Antarctica, almost 20,000 kilometers away.

(Bild: Andrey VP - stock.adobe.com)

According to the study, the tsunami triggered by the collapse of the mountain peak was one of the highest in recent history. Outside the fjord, four-metre waves damaged a research base on the island of Ella, 70 kilometers away, and destroyed cultural and archaeological sites throughout the fjord system.

Glaciers thinned by climate change
The researchers also investigated how the massive landslide could have occurred. Satellite images showed that the glacier at the foot of the mountain had thinned out considerably in recent decades. The landslide and tsunami were also the first to be observed in north-east Greenland. Scientists attribute the event to climate change. It shows that this is already having a strong impact there too.