A massive landslide in a Greenland fjord triggered a wave that “shook the Earth” for nine days.
The seismic signal last September was picked up by sensors all over the world, leading scientists to investigate where it had come from.
The landslide - a mountainside of rock that collapsed and carried glacial ice with it - triggered a 200m wave.
That wave was then “trapped” in the narrow fjord - moving back and forth for nine days, generating the vibrations.
Landslides like this, scientists say, are happening more frequently with climate change - as the glaciers that support Greenland's mountains melt.
#Greenland #Tsunami #BBCNews
The seismic signal last September was picked up by sensors all over the world, leading scientists to investigate where it had come from.
The landslide - a mountainside of rock that collapsed and carried glacial ice with it - triggered a 200m wave.
That wave was then “trapped” in the narrow fjord - moving back and forth for nine days, generating the vibrations.
Landslides like this, scientists say, are happening more frequently with climate change - as the glaciers that support Greenland's mountains melt.
#Greenland #Tsunami #BBCNews
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NewsTranscript
00:00Researchers say they've solved the mystery of the origins of the seismic signal that shook the Earth for nine days last September.
00:07They've pinned it down to a massive landslide which caused a tsunami in a remote fjord in Greenland.
00:13The risk of these Arctic landslides is increasing because of climate change, according to scientists, as Victoria Gill reports.
00:23A land continuously carved and moulded by vast glaciers.
00:27But in one fjord in the east of Greenland, a seismic event has transformed the landscape here forever.
00:33We're seeing here a simulation of how this seismic signal travelled around the world.
00:38When we run this, we'll start to see this wave.
00:42This animation shows the signal that baffled scientists for nine days in September of last year.
00:48The dots are seismic monitors around the world, picking up vibrations from something happening in Greenland.
00:55At the same time that scientists were puzzling over that, a team working in Greenland received a report of a large tsunami in the east of the country.
01:04These photographs show what caused it, a huge landslide into this fjord.
01:09Look at the mountaintop in this image taken before the event.
01:13And look at it afterwards. The top of the mountain is gone, collapsed into the fjord, taking part of the glacier with it.
01:20The scientists analysed the depth and shape of this narrow, 200km long fjord.
01:25And that revealed why the tsunami the landslide caused reverberated around the world for so long.
01:31The wave was essentially trapped.
01:33The energy of that wave just can't escape.
01:35So that wave has to just keep bouncing back and forth, sloshing back and forth in the fjord.
01:40It just can't go anywhere.
01:42Never before has such a long duration, large scale movement of water, over nine days in this case, been observed.
01:49Remote as it is, this is a location that cruise ships do visit.
01:53Fortunately, no vessels were in the area when the landslide happened.
01:56But scientists say the risk of these events is increasing with climate change.
02:01This glacier was holding up the mountain.
02:03Over decades it melted and thinned, and eventually millions of cubic metres of rock simply collapsed.
02:09It's a destructive side effect of climate change that was felt around the world.
02:14Victoria Gill, BBC News.