A year ago, in September, earthquake monitoring equipment around the world picked up a seismic signal for nine days that puzzled science. Now, an international team of researchers has identified the source of the tremors.
“In September 2023, we discovered a signal that could be recognized worldwide,” 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 very different from an earthquake. The signal was an oscillation with a single dominant frequency, like a monotonous hum that decayed very slowly.”
Waves lapped back and forth in the fjord
It turns out that the collapse of a mountain peak that once towered 1,200 meters above the fjord caused a massive landslide in Greenland’s Dickson Fjord. This caused a huge tsunami that swept back and forth across the narrow fjord for nine days with a period of about 90 seconds. The wave, which initially was up to 110 meters high, stretched for ten kilometers and shrank to ‘only’ seven meters in just a few minutes.
“The amount of material that fell was enormous – more than 25 million cubic metres. “That’s enough to fill 10,000 Olympic-sized swimming pools,” explains Kristian Svennevig from the Geological Survey of Denmark and Greenland (GEUS), who coordinated the research.
Waves ran across the globe
The movements of the large body of water generated seismic waves that were measurable at the measuring stations for nine days. The waves traveled around the world and could be detected as far away as Antarctica, almost 20,000 kilometers away.
The study said the tsunami caused by the mountaintop collapse was one of the largest in recent history. Outside the fjord, waves measuring four metres high damaged a research base on Ella Island, 70 kilometres away, and destroyed cultural and archaeological sites throughout the fjord system.
Glaciers have become thinner due to climate change
The researchers also investigated how the massive landslide could have happened. Satellite images showed that the glacier at the foot of the mountain has thinned considerably in recent decades. The landslide and tsunami were also the first to be observed in northeastern Greenland. Scientists attribute the event to climate change. It shows that this is already having a strong impact there.
Source: Krone
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