In September 2023, the Earth experienced a seismic event caused by a massive landslide in Greenland. This event was linked to climate change and it created a mega-tsunami that not only causing local devastation but also triggered global vibrations, making the entire Earth vibrate for nine days.
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The event took place in eastern Greenland specifically in the Dickson Fjord. The collapse of a 1.2 km-high mountain peak into the fjord was triggered by the destabilization of a glacier at the mountain’s base.
This glacier had thinned due to climate change leading to the landslide. The landslide occurred on September 16, 2023. Around 25 million cubic meters of rock and ice were displaced by the landslide.
The initial wave produced by the landslide reached a height of 200 meters. As the wave traveled through the fjord, it reached up to 110 meters. However, the wave diminished to about 7 meters within a few minutes.
The tsunami stretched across more than 10 kilometers of the fjord. Due to the narrow, winding structure of the fjord, water continued to slosh back and forth for days.
An international team of 68 scientists from 41 research institutions took part in the investigation pooling together data from seismic recordings, satellite images, field measurements and supercomputer simulations. Led by Kristian Svennevig from GEUS, the team combined different forms of data to piece together what had caused this seismic anomaly.
The researchers found that a mountainside in Dickson Fjord, East Greenland had collapsed, triggering a mega-tsunami that reached an estimated 200 meters in height. The landslide displaced a huge volume of rock and ice, more than 25 million cubic meters equivalent to 10,000 Olympic-sized swimming pools.
The violent collision of the landslide into the fjord’s waters displaced approximately 4 billion gallons of water, unleashing a massive wave that reverberated within the narrow fjord for days.
The continuous sloshing of water, a phenomenon known as a seiche produced seismic waves that persisted for over a week.
As global temperatures rise, glaciers melt, destabilizing the geological structures they once supported. In this case, the melting of a glacier at the base of the mountain weakened the structure.
Alice Gabriel, a seismologist from UC San Diego’s Scripps Institution of Oceanography and a co-author of the study said that climate change is increasingly shifting Earth’s natural processes, triggering unusual and sometimes catastrophic events like this one.
The landslide occurred when a cliff face measuring approximately 40 acres in area fell from a height of over 1,000 feet. The falling debris composed of a mixture of rock and ice, crashed into the glacier below before plunging into the icy waters of Dickson Fjord, creating a debris flow that triggered the mega-tsunami.
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After the initial tsunami, smaller waves about 25 feet tall continued to reverberate inside the fjord for nine days, generating the seismic signals that perplexed scientists.
The topographical confinement of the fjord caused the waves to oscillate primarily along its north-south axis, dissipating more quickly in the east-west direction where the energy was absorbed by the open ocean.
The seismic vibrations caused by the mega-tsunami lasted for nine days and were detected globally by earthquake sensors. The seismic signal appeared as a single, monotonous hum, unlike typical earthquake signals, which are rich in frequency.
Initially labeled as a USO, the signal was later identified as being linked to the tsunami. The frequency of the water’s movement matched the seismic vibrations detected worldwide. The seismic waves traveled across the Earth’s crust, reaching even Antarctica in less than an hour.
The investigation involved 68 scientists from 40 institutions across 15 countries. They used a combination of seismic data, satellite imagery, field measurements and mathematical modeling to unravel the cause of the seismic signals.
The Danish military provided imagery of the collapsed mountain and the scars left by the tsunami, helping the researchers reconstruct the event.
The tsunami destroyed an uninhabited Inuit site that had existed for over 200 years suggesting that such an event had not occurred in at least two centuries.
A research base on the island of Ella Ø, located 70 km from the site also sustained damage. The Dickson Fjord is a popular route for tourist cruise ships. While no cruise ships were directly affected during the event, a cruise ship carrying 200 people had been stranded in mud in a nearby fjord just days before the tsunami struck.
While no people were present during the event, the waves caused approximately $200,000 worth of damage to an unoccupied research station on Ella Island.
The term megatsunami refers to waves that exceed 100 feet in height often caused by landslides, volcanic eruptions or meteor impacts.
Unlike typical tsunamis which are triggered by underwater earthquakes, megatsunamis result from the displacement of large amounts of water by massive external forces.
Past examples of megatsunamis include the 1958 Lituya Bay event in Alaska, where a 1,720-foot wave was triggered by a landslide following a 7.8 magnitude earthquake.
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