In September 2023, something unusual occurred on Earth, but it went largely unnoticed. Seismic stations around the world began picking up a soft but steady pulse. It occurred every 92 seconds, lasted nine days, and recurred briefly a month later. It wasn’t strong enough for people to feel, but the signal was so unusual that it caught the attention of scientists from Alaska to Australia. The question was: what caused it?
Now, thanks to NASA and the French space agency‘s joint mission called SWOT (Surface Water and Ocean Topography), scientists finally have the answer—and it’s both fascinating and terrifying.
The signal led scientists to a remote place in East Greenland called Dickson Fjord. It’s a narrow waterway surrounded by cliffs that rise as high as 3,000 feet. Using satellite images, researchers noticed something unusual: a large section of the mountain had vanished. This was the clue they needed.
On September 16, 2023, a massive rock and ice collapse took place at Dickson Fjord. More than 25 million cubic yards of material, enough to fill 10,000 Olympic-sized swimming pools, fell into the fjord from the mountain.
A Mega Tsunami Is Born
The impact of that massive collapse created something rare and powerful: a mega tsunami. Waves up to 650 feet high surged through the narrow two-mile fjord. These waves crashed into the cliffs, bounced back, and continued moving in a back-and-forth pattern. This created a phenomenon known as a seiche.
Unlike a regular tsunami that moves in one direction, a seiche causes water to oscillate, moving back and forth in an enclosed space, much like a giant sloshing bathtub. This sloshing motion sent low-frequency seismic signals through the Earth, which scientists around the world detected as the mysterious pulse.
The Role of SWOT in Solving the Puzzle
The key to solving the mystery was SWOT, a mission launched in 2022 to map and study Earth’s water bodies. It tracked small changes in water elevation, even just a couple of metres, and detected the precise wave patterns across the fjord. This matched what scientists expected from a seiche.
Researchers then used machine learning and computer simulations to model the wave behaviour over time. This helped them fill in the missing details and gain a full understanding of how the mega-tsunami and seiche occurred.
A Team Effort Across the Globe
“It was exciting to be working on such a puzzling problem,” said Robert Anthony from the US Geological Survey. He credited the success to a team of international scientists combining satellite data, seismic records, and computer models to put all the pieces together.
This discovery is not just about solving a mystery; it is also about uncovering a deeper truth. It shows us how climate change, geology, and powerful technology are all linked. As the Earth warms and glaciers melt, such mountain collapses and resulting mega tsunamis could become more common.
Thanks to science, we now understand this rare and dramatic event. And with missions like SWOT, we’re better prepared to spot and study similar disasters in the future.
