In September 2023, a colossal landslide in East Greenland triggered a mega-tsunami in distant Dickson Fiord. The vibrations had been felt around the globe for 9 consecutive days. For a 12 months, scientists have grappled with what triggered the incident.
The space the place the landslide and tsunami occurred is uninhabited, however monitoring stations internationally picked an enormous seismic sign. The readings confirmed waves ricocheting forwards and backwards by way of the fiord each 90 seconds.
Although nobody lives there, cruise ships do enter the fiord. Luckily, none had been there that day. However, one did enterprise into the fiord the next day and observed that on close by Ella Island, a analysis station’s boat and a delivery container, each often on land, had been washed out to sea. The station itself was additionally broken.
Unidentified Seismic Object
Kristian Svennevig from the Geological Survey of Denmark and Greenland (GEUS) suspected an earthquake or a tsunami. But the 9 days of reverberations baffled scientists. The vibrations didn’t match these of an earthquake or tsunami. They dubbed the incident a USO — an Unidentified Seismic Object.
D) Shows the place of the mountain ridge that collapsed in a large landslide. E) Shows the disappearance of the mountain ridge and markers of the tsunami triggered by the landslide. Photo: Okay. Svennevig et al.
Svennevig and 68 scientists from 15 international locations spent a 12 months making an attempt to determine it out. They used the whole lot from seismometer knowledge, satellite tv for pc imagery, subject measurements, and tsunami simulations to piece collectively what truly occurred.
The very first thing they checked out was satellite tv for pc imagery and aerial photographs. This revealed that vegetation alongside the shoreline of the fiord had been worn out. On Ella Island, vegetation had disappeared as much as 4 meters above the water line. This distance elevated as they checked out extra westerly photographs. This indicated that the waves should have come from the west and moved eastward.
Sloshed forwards and backwards for 9 days
Other satellite tv for pc photographs, taken on September 15 and 17, the times earlier than and after the tsunami, revealed {that a} mountain ridge west of the fiord had disappeared. Approximately 25 million cubic meters of rock and ice from the mountain had plunged into the ocean, producing a 200m-high tsunami that sped alongside the fiord at 160kph. The waves fell to seven meters inside a couple of minutes however bounced forwards and backwards for 9 days in opposition to the cliffs of the fiord, steadily getting smaller and smaller.
Tsunamis often dissipate after a number of hours however this one was trapped within the slender fiord and couldn’t.
“This landslide occurred about 200km inland from the open ocean, and these fiord programs are actually advanced, so the wave couldn’t dissipate its vitality,” Stephen Hicks, co-author of a paper on the occasion, advised the BBC. “We’ve by no means seen such a large-scale motion of water over such an extended interval.”
The examine concluded that local weather change triggered the preliminary landslide. The glacier subsequent to the fiord sits on the base of the mountain and helps it. As the glacier thinned from rising temperatures, it grew to become unable to help the overlying rock mass, resulting in the catastrophic collapse.
Nuggaatsiaq, Greenland two months after the tsunami. In the decrease photograph, be aware the 2 boats that the wave flung excessive above the seashore. Photos: Jerry Kobalenko
Another tsunami
The same occasion occurred in Greenland in 2017. A landslide fell 1,000m into Karrat Fjord and set off a 100m-high tsunami. By the time it hit the distant neighborhood of Nuggaatsiaq, it was 9 meters excessive. Four individuals had been killed and 9 had been injured. Buildings had been washed out to sea, boats landed 50 meters uphill. All residents had been evacuated, and the settlement is now deserted due to the continued menace of landslides.
Researchers are calling for enhanced monitoring of mountainous areas to guard individuals from comparable occasions, which is able to occur extra usually because the local weather warms and the ice that glues the frozen mountains collectively thaws.
