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full screen The mysterious signal was picked up all over the world.
Seismological measuring stations all over the world picked up the mysterious signal just over a year ago.
It lasted nine days – and no one understood what happened.
Until now.
On September 16 last year, the mysterious signal was picked up by the world’s seismologists.
They quickly realized that the vibrations were not caused by an earthquake. The frequencies of the tremors were not as varied and rapidly transient as in an earthquake. Instead, it was a kind of monotonous humming, and it would last – diminishing but measurable – for nine days.
– Some thought their instruments were broken. It was something completely unique, says Stephen Hicks, a seismologist at University College London to CNN.
The signal was quickly traced to East Greenland, but without an exact location.
– Everyone was stunned and no one had the faintest idea what caused the signal. It was longer and simpler than earthquake signals that normally last for minutes or hours. We labeled it a USO, an unidentified seismic object, says Kristian Svennevig, seismologist at Denmark’s Geological Institute Geus, to The Guardian.
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fullscreenBefore the landslide. Photo: London’s Global University
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full screen After the landslide. Photo: London’s Global University
Destroyed buildings
Shortly after the tremors began to spread across the Earth, the crew of a passing cruise ship discovered that several buildings on the island of Ella, an important landmark in the current part of Greenland, had been destroyed.
The cabins were empty but used normally, according to NBC Newsboth for research and as a Danish military base for sled dogs. But why had they been destroyed and what caused the mysterious vibrations across the world?
The answer has now been delivered in an almost year-long study involving 68 researchers in 15 countries and is presented in the scientific journal Science.
The signal came from a giant wave, a so-called seicheinfocloseseicheStanding wave in an enclosed space, comparable to water lapping back and forth in a bathtub., which was undulating back and forth in Dickson Fjord, about seven miles from Ella Island.
The wave movement was caused by the top of a roughly 1,200 meter high mountain collapsing into the fjord. Initially, the collapse triggered a massive local tsunami that first reached 200 meters up the mountainsides. But the wave height in the subsequent seich was after only a few minutes down to seven meters, writes The Guardian.
A few days later, the waves were only a few centimeters high and were not detected by the personnel of a Danish military ship photographing the area.
“Like discovering a new color”
However, the seismologists did not rest. The mysterious signal continued to be recorded and it is only now that the truth has been revealed through the international study.
– If I had said a year ago that a seiche could last for nine days, people would have shook their heads. It’s like discovering a new color in the rainbow, says Kristian Svennevig, who led the researchers’ work, to CNN.
The landslide and tsunami, one of the largest known to science, were caused by climate change, the researchers write.
The melting of the surrounding glacier caused the mountain to become unstable. Finally the top gave way and rock and soil enough to fill 10,000 Olympic swimming pools were hurled into the fjord.
Several independent experts hail the study and warn that landslides and mountain collapses will become more common in the Arctic world in the future.
– This is a sign that climate change is pushing these systems into unknown waters, says Kristian Svennevig.