Mysterious signals all over the world: "Something completely unique"

 

 

Tsunami
Mysterious signals were picked up - all over the world
The truth revealed after a year: "Like a new color in the rainbow"

Hans Österman

Updated 01.39 | Published 01.01

The mysterious signal was picked up all over the world.

Seismological measuring stations all over the world picked up the mysterious signal 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 repeated every 90 seconds. It could be traced fairly quickly 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.

His Swedish colleague Björn Lund at Uppsala University explains for Sveriges Radio what the vibration scales looked like.

- A very low-frequency signal, a bit as if the ground or the mountain hums or hums on a single note, he says.

Before the landslide. Photo: London's Global University

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 were normally used, according to NBC News, both 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 that involved 68 researchers in 15 countries and is presented in the scientific journal Science.

The signal came from giant wave, a so-called seiche, which heaved back and forth in the narrow Dickson Fjord, about seven miles from the island of Ella in the complex fjord system and 20 miles from the open sea.

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 shaken 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.

"Uncharted Waters"

Several independent experts praise the study and warn that landslides and mountain collapses will become more common in the Arctic world in the future, writes CNN.

- This is a sign that climate change is pushing these systems into unknown waters, says Kristian Svennevig.

When the tsunami was triggered, there was no cruise ship nearby and no people were killed or injured in the disaster. But the consequences can be big.

- The ice is retreating, the mountainsides are becoming unstable, and thus the risks in eastern Greenland must be assessed in a new way. Should we allow this cruise traffic to enter the fjords? And what should be done so that the population living in East Greenland will also be more prepared for the possibility that this could happen? says Björn Lund to SR.