A mountainside of rock that collapsed and brought with it glacial ice, triggered a 200m wave that moved back and forth for 9 days
A massive landslide in a Greenland fjord caused a wave that “shook the Earth” for nine days, according to the BBC.
The signal last September was picked up by sensors around the world, leading scientists to investigate where it came from.
The landslide – a mountainside of rock that collapsed and brought glacial ice with it – triggered a 200m wave.
This wave was then “trapped” in the fjord and moved back and forth for nine days, creating vibrations.
Landslides like this, scientists say, are happening more often because of climate change, as the glaciers that support Greenland’s mountains melt.
An international team of scientists and the Danish Navy are involved in the investigation into this event, which is ongoing and published in the journal Science.
How the tsunami was connected to the mysterious tremor
“When colleagues first detected this signal last year, it didn’t look like an earthquake. We called it an ‘unknown seismic object’, recalls Dr Stephen Hicks from UCL, one of the scientists involved.
And he added that “It appears every 90 seconds for nine days.”
The group of curious scientists began discussing the confusing signal on an online chat platform.
“At the same time, colleagues from Denmark, who do a lot of field research in Greenland, received reports of a tsunami occurring in a remote fjord,” Dr Hicks explained.
“So we joined forces.”
The team used the seismic data to locate the source of the signal in Dickson Fjord in East Greenland. They then gathered other clues, including satellite images and photographs of the fjord taken by the Danish navy shortly before the signal appeared.
A satellite image showed a cloud of dust in a gully in the fjord. Comparing photos before and after the event revealed that a mountain had collapsed and swept part of a glacier into the water.
Researchers eventually discovered that 25 million cubic meters of rock – a volume equivalent to 25 Empire State Buildings – fell into the water, causing a “mega-tsunami” 200 meters high.
In “after” photos of the site, a mark left by the giant wave is visible on the glacier.
“We’ve never seen anything like this before”
Tsunamis, usually caused by underground earthquakes, disappear within hours in the open ocean. But this wave was trapped.
“This landslide occurred about 200 kilometers inland from the open ocean,” Dr Hicks explained.
The team created a model that showed how, instead of disintegrating, it fell back and forth over nine days.
“We’ve never seen this much movement of water over such a long period of time,” Dr Hicks said.
Scientists say the landslide was caused by warming in Greenland, which has melted the glacier at the base of the mountain.
“That glacier was supporting the mountain and it got so thin it stopped holding it up,” Dr Hicks said. “It shows how climate change is now affecting these areas.”
“We are seeing an increase in giant landslides that cause tsunamis, particularly in Greenland,” he told BBC News.
“While the Dickson Fjord event alone does not confirm this trend, its unprecedented scale highlights the need for more research.”
Source: Skai
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