A landslide in a secluded area of Greenland triggered a massive mega-tsunami, reaching heights of 200 meters (650 feet), which then surged back and forth in a fjord for nine days. This ongoing movement created vibrations felt throughout the Earth, according to a recent study. The research, which involved UCL scientists, determined that these water movements were responsible for an enigmatic seismic signal detected globally, lasting for nine days and baffling seismologists in September 2023.
A remote landslide in Greenland resulted in a mega-tsunami that traveled back and forth across a fjord for nine days, producing vibrations across the Earth, as revealed in a new study with UCL researchers.
The findings, published in the journal Science, identified this water movement as the source of a perplexing global seismic signal that lasted for nine days, leaving seismologists scratching their heads in September 2023.
The landslide itself, which couldn’t be seen by the human eye, occurred when a 1.2-kilometer-high mountain peak collapsed into the remote Dickson Fjord below. This action created a massive water splash that reached 200 meters into the air and generated a wave as tall as 110 meters. Researchers estimated that this wave, which spanned 10 kilometers of the fjord, diminished to just seven meters within a few minutes and further dropped to a few centimeters in the days following the event.
The research team employed a sophisticated mathematical model that replicated the angle of the landslide and the fjord’s tight curves, illustrating how the water continued to rock back and forth for nine days with minimal energy loss.
According to the model, the water oscillated every 90 seconds, aligning with the recorded seismic vibrations that traveled through the Earth’s crust worldwide.
Researchers noted that the landslide was triggered by the thinning of the glacier at the mountain’s base, which could no longer support the overhanging rock. This phenomenon was ultimately driven by climate change. This event and the resulting tsunami marked the first such observations recorded in eastern Greenland.
Co-author Dr. Stephen Hicks from UCL Earth Sciences stated, “When I first noticed the seismic signal, I was utterly confused. While seismometers typically capture various surface movements, this was the first instance of a long-lasting global seismic wave that emitted only a single frequency. This prompted me to help lead a large team of scientists to unravel the mystery.”
“This study remarkably emphasizes the complex interrelationships between atmospheric climate change, destabilizing glacier ice in the cryosphere, movements in water bodies within the hydrosphere, and the solid crust of the Earth in the lithosphere.
“This marks the first time vibrations from water sloshing have been recorded as seismic signals traveling through the Earth’s crust for several days.”
The unusual seismic signal was detected by seismometers around the world, from the Arctic to Antarctica. Unlike the varied frequencies common in earthquake readings, this signal resembled a single, consistent hum.
Initially, when the study’s authors discovered the signal, they categorized it as a “USO”: unidentified seismic object.
Meanwhile, news emerged about a substantial tsunami in a remote fjord in northeast Greenland, reaching authorities and local researchers.
The researchers formed a unique multidisciplinary team consisting of 68 scientists from 40 institutions across 15 countries, combining data from seismometers and infrasound, field measurements, both on-site and satellite imagery, along with tsunami wave simulations.
The team also analyzed photographs taken by the Danish military, which explored the fjord shortly after the incident to examine the collapsed mountain and glacier, as well as the significant damage inflicted by the tsunami.
By merging local field data with expansive global observations, the team successfully pieced together the remarkable chain of events that transpired.
Lead author Dr. Kristian Svennevig from the Geological Survey of Denmark and Greenland (GEUS) remarked, “At the beginning of this scientific journey, everyone was perplexed, and no one had the slightest clue about the origin of this signal. We only knew it was somehow connected to the landslide. Ultimately, we were able to uncover this enigma through a major interdisciplinary and international collaboration.”
He added, “This study marks the first documented landslide and tsunami in eastern Greenland, illustrating the significant effects of climate change already at play in the region.”
The team estimated that 25 million cubic meters of rock and ice fell into the fjord, enough to fill 10,000 Olympic-sized swimming pools.
Using numerical simulations alongside local data and imagery, they verified that the tsunami was one of the largest recorded in recent history.
Four meters-high tsunami waves caused damage at a research facility on Ella Ø (island), affecting both cultural and archaeological sites throughout the fjord system, located 70 kilometers away from the landslide.
This fjord is frequently traversed by tourist cruise ships visiting Greenland. Fortunately, no cruise ships were in the vicinity of Dickson Fjord during the landslide and tsunami; had they been, the impact of such a large wave could have been catastrophic.
Mathematical models that accurately represented the fjord’s width and depth at a high resolution illustrated how the distinctive rhythm of moving water corresponded with the seismic signal.
The study concluded that as climate change accelerates, it is increasingly crucial to characterize and monitor areas once thought stable and to provide timely warnings for potential massive landslide and tsunami incidents.
Co-author Thomas Forbriger from Karlsruhe Institute of Technology stated, “We wouldn’t have been able to detect or analyze this extraordinary event without a network of high-quality broadband seismic stations worldwide, the only tools capable of capturing such a unique signal.”
Co-author Anne Mangeney from Université Paris Cité, Institut de Physique du Globe de Paris added, “This unique tsunami challenged the conventional numerical models we previously used for simulating short tsunami events. We needed to implement an unprecedented high level of numerical resolution to accurately capture this long-duration event in Greenland, paving the way for new developments in tsunami modeling methods.”
