A strange and rhythmic shaking of the Earth that puzzled scientists back in 2023 has finally been explained, nearly two years later. The mystery began when sensitive equipment recorded tremors every 90 seconds for nine straight days, without any sign of an earthquake, volcano, or even visible damage.

Now, scientists from the University of Oxford have revealed the cause: a massive glacier-driven landslide in Greenland that led to a powerful, hidden tsunami.

In mid-2023, scientists across the globe noticed something unusual: tremors similar to an earthquake, but with no epicentre. Unlike regular quakes, there were no signs of volcanic eruptions, tectonic movements, or asteroid strikes. The tremors confused experts, and even satellites could not find anything unusual at the time.

With no clear answer, the incident remained a mystery until new technology brought the truth to light.

According to the new study published in Nature Communications, the source of the tremors was a massive landslide in the remote Dickson Fjord in eastern Greenland. A huge chunk, around 25 million cubic metres of rock and glacial ice, collapsed into the sea after being weakened by melting permafrost.

This sudden collapse created a tsunami with waves as high as 650 feet and caused a powerful water movement known as a “seiche”—a back-and-forth sloshing of water inside the narrow fjord.

These seiche waves were so strong, they shook the ground rhythmically every 90 seconds, creating the unusual tremors that were recorded worldwide. Scientists say the energy released was equal to launching 14 Saturn V rockets at once—about 500 gigawatts.

What makes this event more surprising is that no one saw it happen. A Danish military ship reached the area three days later and saw no unusual waves or signs of a tsunami.

The key to solving the puzzle came from the SWOT (Surface Water and Ocean Topography) satellite, a joint mission by NASA and France’s CNES. It carries a special tool called KaRIn (Ka-band Radar Interferometer) that can measure water heights even in narrow places like fjords.

Using SWOT’s data, scientists noticed that land on both sides of the fjord moved in opposite directions—clear evidence of a seiche. When they matched this with the ground-based seismic data and tidal measurements, the full story came together.

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This study does more than solve a mystery, it sends a strong message. As glaciers melt due to climate change, it’s not just sea levels that rise. Melting ice can also lead to giant landslides, tsunamis, and powerful tremors that affect areas far beyond the Arctic.

These hidden natural disasters may become more common as the Earth’s icy regions continue to warm. The event is a reminder of how much we still have to learn, and how modern technology is helping us see what was once invisible.