Last September's Nine-Day Tsunami That Shook the Earth

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A seismic event that puzzled scientists around the globe last September has been traced back to a massive landslide in a remote fjord in Greenland. The landslide triggered an enormous wave that generated seismic tremors, detectable worldwide, for an astonishing nine days. 

 

 

The event, which involved a mountainside collapse carrying glacial ice into Dickson Fjord in East Greenland, produced a 200-meter-high wave. This wave was "trapped" within the narrow confines of the fjord, repeatedly sloshing back and forth, generating vibrations that spread across the Earth. According to scientists, such events are becoming more frequent due to climate change, which is accelerating the melting of glaciers that support Greenland's mountains.

 

 

The results of the investigation, published in the journal *Science*, are the culmination of efforts by an international team of scientists and the Danish Navy. The seismic signal was first detected by sensors around the world, leading to a collaborative investigation into its origin. “When colleagues first spotted this signal last year, it looked nothing like an earthquake. We called it an ‘unidentified seismic object,’” recalled Dr. Stephen Hicks from University College London (UCL), one of the scientists involved in the study. The signal appeared repeatedly—every 90 seconds for nine days—leaving scientists baffled.

 

A group of curious scientists, communicating on an online platform, began to piece together the mystery. Meanwhile, researchers in Denmark, who frequently conduct fieldwork in Greenland, received reports of a tsunami in a remote fjord. “At the same time, colleagues from Denmark, who do a lot of fieldwork in Greenland, received reports of a tsunami that happened in a remote fjord,” explained Dr. Hicks. “So then we joined forces.”

 

By analyzing seismic data, the team was able to pinpoint the signal’s source to Dickson Fjord in East Greenland. They then gathered additional evidence, including satellite imagery and photographs taken by the Danish Navy just before the seismic activity began. One satellite image revealed a cloud of dust in a gully within the fjord. Comparing photographs taken before and after the event, the researchers confirmed that a mountainside had collapsed, sweeping part of a glacier into the fjord below.

 

The landslide involved 25 million cubic meters of rock, an amount equivalent to the volume of 25 Empire State Buildings, crashing into the water and generating the enormous wave. The force of the wave was so powerful that it left a visible mark on the glacier, created by the sediment it hurled upwards. 

 

Unlike typical tsunamis, which dissipate their energy within hours in the open ocean, this wave was trapped within the complex fjord system. “This landslide happened about 200 kilometers inland from the open ocean,” Dr. Hicks explained. “And these fjord systems are really complex, so the wave couldn't dissipate its energy.” Instead of dispersing, the wave continued to move back and forth within the fjord, generating seismic tremors for nine days. “We’ve never seen such a large-scale movement of water over such a long period,” added Dr. Hicks.

 

The scientists attribute the landslide to rising temperatures in Greenland, which have caused the glacier at the base of the mountain to melt and thin over time. “That glacier was supporting this mountain, and it got so thin that it just stopped holding it up,” said Dr. Hicks. “It shows how climate change is now impacting these areas.” While the event occurred in a remote area, these fjords are occasionally visited by Arctic cruise ships.

 

Fortunately, none were in the vicinity when the landslide occurred. However, Dr. Kristian Svennevig from the National Geological Surveys for Denmark and Greenland (GEUS), the lead researcher, emphasized that such events are becoming increasingly common in the Arctic. “We are witnessing a rise in giant, tsunami-causing landslides, particularly in Greenland,” he told the BBC. “While the Dickson Fjord event alone doesn't confirm this trend, its unprecedented scale underscores the need to carry out more research.”

 

Dr. Hicks further highlighted the significance of this event, stating, “It is perhaps the first time a climate change event has impacted the crust beneath our feet all the world over.” The Dickson Fjord landslide serves as a stark reminder of the far-reaching effects of climate change, extending beyond rising sea levels and melting ice caps to influence seismic activity across the globe.

 

Credit: BBC 2024-09-14

 

 

 

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[mfd101]

Would have been fascinating to actually see it happening. (From helicopter likely the only way, I guess. Given that it went on for 9 days, it should have been possible.)

[black tabby12345]

Gigantic Sea Surge from the mountain slide？

Reminds me of this.

1958 Lituya Bay Tsunami (wsspc.org)