Mysterious 9-day seismic event triggered by 650-foot tsunami

A tsunami stemming from a landslide in a Greenland fjord, caused by melting ice , was behind a surprising seismic event last year that shook the earth for nine days, a researcher told AFP on Friday.

According to a report recently published in the scientific journal Science, tremors that were registered in September 2023 originated from the massive wave rocking back and forth in the Dickson fjord in Greenland's remote east.

"The completely unique thing about this event is how long the seismic signal lasted and how constant the frequency was," one of the authors of the report, Kristian Svennevig, from the Geological Survey of Denmark and Greenland, told AFP.

"Other landslides and tsunamis have produced seismic signals but only for a couple of hours and very locally. This one was observed globally all the way to the Antarctic," he said.

The phenomenon initially surprised the scientific community, which began by defining it as an "unidentified seismic object" before determining that the source was the landslide.

In September 2023, 882 million cubic feet of rock and ice — a volume equivalent to 25 Empire State Buildings — fell into the fjord in the remote and uninhabited area, about 124 miles from the ocean.

The landslide triggered a 650-foot-high mega-tsunami at its epicenter.

Over 40 miles away, tsunami waves over a dozen feet high damaged a research base on the island of Ella.

"When colleagues first spotted this signal last year, it looked nothing like an earthquake," Stephen Hicks, a scientist who has a doctorate in earth sciences and was involved in the report, told BBC News . "It kept appearing — every 90 seconds for nine days."

A group of scientists started to discuss the strange signal on an online chat platform, according to BBC News.

The team created a model that showed how the wave sloshed back and forth for nine days.

"We've never seen such a large scale movement of water over such a long period," Hicks told BBC News.

The collapse was caused by the thinning of the glacier at the base of the mountain, a process accelerated by climate change , according to the report.

"With the Arctic continuing to warm we may expect the frequency and magnitude of such events to increase in the future," Svennevig said.

"We have no experience with dealing with an Arctic as warm as we observe now," he added.

He stressed the need for early warning systems to be put in place, but noted that it was a challenge in such extreme environments.