In September 2023, scientists worldwide noticed something unusual. Seismometers on every continent detected a strange hum from deep within Earth’s crust. The signal pulsed every 90 seconds and lasted for nine straight days. This wasn’t an earthquake or any known geological event.
The frequency measured exactly 11.45 millihertz, creating a rhythm that had never been seen before. Teams from Tokyo, Berlin, and dozens of other research centers scrambled to find answers. They ruled out volcanoes, underwater earthquakes, and even solar activity. Nothing in their databases matched this mysterious signal.
The planet seemed to ring like a bell that had been struck by an invisible hammer. Some experts wondered if human activity caused it, while others suspected an unknown natural process. Media outlets began referring to it as the “unidentified seismic object.” The world watched and waited for an explanation.
Greenland’s Hidden Disaster
Scientists eventually traced the signal to a remote fjord in northeast Greenland, known as Dickson Fjord. This narrow waterway is situated 124 miles from the open ocean, surrounded by mountain peaks that reach heights of 4,000 feet. The fjord stretches 1.7 miles wide and plunges 1,772 feet deep, creating a natural basin with steep walls.
Climate change has been warming the Arctic rapidly for decades. Glaciers in the region were melting and thinning, thereby removing support from ancient mountain slopes. On September 16, 2023, at 12:35 UTC, disaster struck. A massive section of mountain—containing 25 million cubic meters of rock and ice—broke loose and crashed into the fjord below. The landslide moved at 138 feet per second, hitting the water with tremendous force.
This impact created a mega-tsunami with an initial wave height of 656 feet. Only Alaska’s 1958 Lituya Bay tsunami, which reached 1,720 feet, was taller in modern records. The fjord’s narrow shape trapped the wave, preventing it from escaping into the Atlantic Ocean. Instead, the water began sloshing back and forth like liquid in a bathtub. This created what scientists call a seiche—a standing wave that can last for hours or even days.
Climate Change Creates New Threats
NASA’s SWOT satellite provided the key evidence that solved the mystery. The satellite detected water slopes up to 6.6 feet that kept reversing direction inside the fjord. The trapped wave slammed repeatedly against the fjord walls, creating a 90-second pulse that seismometers detected worldwide. Lead seismologist Stephen Hicks called it unprecedented prolonged water movement.
The event destroyed $200,000 worth of monitoring equipment located 45 miles away on Ella Island. Remarkably, no one died because Dickson Fjord has no nearby settlements. But scientists worry about the future. A second mega-tsunami hit the same location in October 2023, proving this wasn’t a one-time event. Glacial retreat continues to destabilize mountain slopes across the Arctic. In places like Canada’s Banks Island, permafrost is thawing and creating retrogressive slumps that advance 16 to 49 feet each year.
Researchers have identified dozens of similar high-risk fjords in Greenland, Alaska, and Svalbard. These locations combine narrow geometry with thinning ice, creating perfect conditions for future landslides. Traditional earthquake warning systems can’t detect these events in time. Tourists visiting the Arctic on cruise ships face growing dangers from unexpected tsunamis. Scientists now push for better monitoring systems, including glacier surveillance and slope assessments. The dual 2023 events show how climate change creates new geological hazards that can shake the entire planet.
Sources:
Science Journal (Svennevig et al.), Peer-reviewed study on Greenland landslide and seismic signal, 11 September 2024
BBC, Massive Greenland tsunami shook Earth for nine days, 12 September 2024
University College London, Climate-change-triggered landslide caused Earth to vibrate for nine days, 12 September 2024
Nature Communications (Monahan et al.), Observations of the seiche that shook the world, 3 June 2025
University of Manchester, Climate change triggered landslide rocked the Earth for 9 days, 16 July 2025
Geological Survey of Denmark and Greenland, Dickson Fjord landslide investigation and global impact analysis, 2024