A colossal landslide in eastern Greenland in September 2023 unleashed a series of unprecedented events, including a 200-meter-high tsunami and a mysterious nine-day seismic signal that baffled scientists worldwide. According to a new study published in Science, the landslide resulted from the collapse of a glacier in Dickson Fjord, a remote and rugged part of Greenland. The chain reaction from this event sent shockwaves through the scientific community, as a rare seismic phenomenon was detected globally.

Mysterious Signal Baffles Scientists after Greenland Landslide

The seismic activity, which was initially misunderstood, puzzled experts across the globe. "We were like, ‘Oh wow, this signal is still coming in. This is completely different to an earthquake,’" said Stephen Hicks, a seismologist at University College London, in an interview with CNN. What made this event even more unusual was its duration. "It kept appearing – every 90 seconds for nine days," Hicks added.

Typically, earthquakes produce vibrations that last a few minutes at most. However, the prolonged seismic activity—referred to as an unidentified seismic object (USO)—challenged conventional understanding. The signal was traced back to eastern Greenland, though pinpointing the exact cause initially proved difficult.

Landslide and Tsunami Uncovered as the Cause

Eventually, a team of researchers from Denmark connected the mysterious seismic signals to a landslide-triggered tsunami in Dickson Fjord. The event required the collaboration of 68 scientists from 15 countries to solve the puzzle of the nine-day seismic signal.

At the heart of the discovery was a massive cascading hazard, linked to the effects of climate change. The glacier, weakened by years of accelerated melting due to rising Arctic temperatures, had reached a critical thinning point. On September 16, 2023, a huge section of the mountain above the glacier collapsed, sending debris—enough to fill 10,000 Olympic-sized swimming pools—crashing into the fjord.

The resulting mega-tsunami, 200 meters high, was trapped in the narrow confines of Dickson Fjord. This trapped wave led to a phenomenon known as a "seiche," where water oscillates back and forth within a confined space, creating rhythmic movement. This sloshing effect, which persisted for nine days, generated seismic energy that was detected worldwide.

New Discovery in Seismic Science

"Had I suggested a year ago that a seiche could persist for nine days, people would shake their heads and say that’s impossible," remarked Dr. Kristian Svennevig from the Geological Survey of Denmark and Greenland, lead author of the study. He likened the discovery to "suddenly finding a new color in a rainbow."

This groundbreaking event not only highlights the potential hazards of climate change-induced glacial collapses but also opens new avenues of study in the field of seismology. The discovery of the nine-day seiche has broadened scientists' understanding of seismic phenomena, offering insight into how large-scale environmental changes can ripple through both the Earth’s oceans and its seismic systems.

The Greenland landslide and its seismic aftermath stand as a reminder of the powerful, interconnected forces at play in the natural world—forces that scientists are only beginning to fully understand.