'Completely unusual' signal detected as Earth shaken for nine days

Sixty-eight scientists worked for a year to investigate a mysterious incident that shook the Earth for nine days.

Background: A cloudy Sydney Harbour. Inset: A globe with dots showing where the vibrations were detected.
Vibrations were detected across every continent. Each dot on the map represents a seismic testing site where they were picked up. Source: Getty/Science

The world has been shaken continuously for nine days, a concerning new report has revealed. Ground zero has been pinpointed to be an icy fjord in remote Greenland, which collapsed triggering a 200-metre-high tsunami.

After an estimated 25 million cubic metres of rock and ice crashed into the fjord, the resulting wave oddly became stuck inside the narrow gap, generating vibrations as it moved back and forth for days during September last year. The unusual vibrations were detected across the globe, from Tokyo to Sydney and even the South Pole, so scientists scrambled to assemble a team to solve the mystery.

The collapse occurred close to a popular cruise ship route, and experts believe the incident could have caused chaos if one had been passing at the time. A research base was badly damaged at nearby Ella Ø Island.

It’s the first time such a long incident has been recorded, so understandably it’s taken a year for scientists to understand the circumstances that caused the “completely unusual seismic signal” which sounded nothing like a regular earthquake.

“It looked like nothing we had ever seen before. It came from somewhere in east Greenland and it spread around the world – from the Arctic to Antarctic in less than an hour. No place beneath our feet was immune to the tiny ground vibrations,” Dr Stephen Hicks from the University College London said.

Sadly it’s believed the problem will likely occur again. That’s because their findings, published in the journal Science this week, link the landslide directly to climate change, which is making polar regions increasingly vulnerable to glacial thinning and collapse.

"Our study of this event amazingly highlights the intricate interconnections between climate change in the atmosphere, destabilisation of glacier ice in the cryosphere, movements of water bodies in the hydrosphere, and Earth's solid crust in the lithosphere,” Hicks, an author of the study, said.

"This is the first time that water sloshing has been recorded as vibrations through the Earth's crust, travelling the world over and lasting several days."

The unusual reading on seismology equipment initially confused experts and it took 68 scientists from 40 institutions to figure out what occurred. “When I first saw the seismic signal, I was completely baffled. Never before has such a long-lasting, globally travelling seismic wave, containing only a single frequency of oscillation, been recorded,” Hicks added.

A mathematical model was used to trace the vibrations back to the event at Dickson fjord in eastern Greenland, which occurred on September 16, 2023. It predicted the water inside the fjord would have moved every 90 seconds and this matched the recordings of tremors in the Earth's crust.

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