After a mountaintop collapsed into the sea in Greenland, a “megatsunami” as tall as a skyscraper shook the Earth for nine days straight, baffling scientists around the world.
No one was injured by the landslide or the resulting tsunami, but the 200-meter-high wave destroyed about $200,000 worth of infrastructure at an unoccupied research station on Ella Island.
Furthermore, the incident occurred near a route that is often used by cruise ships. If a cruise ship had been sailing there at the time, it could have caused a tragedy.
Until now, no one knew what caused the mysterious seismic activity that began in September 2023 and lasted for more than a week. It took an international team of scientists to trace it back to the landslide.
“When we embarked on this scientific adventure, everyone was baffled and no one had the slightest idea what was causing this signal,” said Kristian Svennevig, lead author of the study and a geologist at the Geological Survey of Denmark and Greenland.
Before and after the massive landslide that dumped 33 million cubic meters of ice and rock into a Greenland fjord, triggering a 650-foot-high ‘mega-tsunami’ that shook the Earth for nine days
Svennevig and his colleagues now believe that climate change set the stage for this landslide by melting a glacier at the base of the mountain and destabilizing enough ice and rock to fill 10,000 Olympic-sized swimming pools.
And as rising global temperatures continue to melt Earth’s polar regions, destructive landslides like this one could become more common.
The research team published their findings today in the journal Science.
When seismic monitoring networks first detected the activity, scientists were puzzled for two reasons.
For one, the signal was much more spread out than the typical tight squiggles an earthquake produces on a seismograph, a device used to record ground shaking.
“It oscillated with an interval of 92 seconds between its peaks, too slow for humans to perceive,” according to a statement from the University of California at San Diego, one of the institutions that contributed to the research.
Second, the signal remained strong for nine days straight. Typical seismic events decay much more quickly: the average earthquake lasts only a few seconds or minutes.
Scientists around the world quickly began working to get to the bottom of this strange signal.
Climate change set the stage for this landslide by melting a glacier at the base of the mountain and destabilizing enough ice and rock to fill 10,000 Olympic-sized swimming pools.
The megatsunami destroyed an estimated $200,000 worth of infrastructure at an unoccupied research station on Ella Island, but no one was injured.
Online discussions eventually resulted in reports of a massive landslide that occurred on a mountain overlooking a remote fjord in eastern Greenland on September 16, 2023.
To determine whether the landslide was related to the mysterious tremor, a team of researchers led by Svennevig digitally reconstructed the landslide and the resulting tremors.
They did this using a combination of seismic records from around the world, field measurements, satellite images and computer simulations.
Researchers also used supercomputers to simulate the 200-meter-high megatsunami triggered by 33 million cubic meters of rock and ice crashing into the fjord.
The waves moved back and forth inside the fjord in a phenomenon known as a seiche. Researchers concluded that this movement was what caused the nine-day period of seismic activity that shook the Earth last year.
“In the end, it took a huge amount of geophysical observations and numerical modeling by researchers in many countries to piece together the puzzle and get a complete picture of what had happened,” said co-author Robert Anthony, a geophysicist with the U.S. Geological Survey’s Earthquake Hazards Program, in a statement.
The findings demonstrate the “complex and cascading hazards” driven by the impact of climate change on Earth’s polar regions, according to the researchers.
“Climate change is changing what is typical on Earth and may lead to unusual events,” said co-author Alice Gabriel, a seismologist at the University of California, San Diego, in a statement.
Fortunately, there were no people in the area when the massive landslide and subsequent tsunami occurred, but the incident highlights the importance of monitoring the polar regions as climate change accelerates.