Greenland Rock Slide Rang the Earth
Mysterious, because it was seen by nobody except for perhaps a whale or a polar bear, the landslide and tsunami caused seismic instruments to vibrate all around the Earth, for 9 days.
GEUS, the Danish and Greenland Geological Survey broke the news yesterday, as a scientific article was published in the journal Science. GEUS writes:
A mysterious, globally observed and unprecedented 9-day-long seismic signal in September 2023 was caused by a massive landslide in Greenland. 25 million m3 of rock and ice fell into the remote Dickson Fjord and, in turn, caused a 200 metre-high mega-tsunami that continued sloshing back and forth - a phenomenon called a seiche - in the narrow fjord for 9 days. That is the conclusion of research published in the journal Science. This movement of a large mass of water generated vibrations through the Earth, shaking the planet and radiating globally observed seismic waves. Never before have scientists observed such an unusual mechanism causing a global seismic signal.
Picture of the area of the landslide, taken from the fjord, August 2023. (Photo: Søren Rysgaard). By GEUS
It is hard to gauge the actual dimensions in pictures from Greenland, but the mountaintop that collapsed was 1,200 meters high and the fjord runs between mountains that run up to more than 2,000 meters just a few kilometers inland. The tsunami was felt all the way out to the mouth of the fjord and ran ashore all the way to the end, flushing every lighter thing away, such as the scarce archeological remains of settlements and fishing huts. The island of Ella Ø about 80 kilometers away was inundated to a height of 4 meters and equipment stored near to the shore was washed away.
Retrieving equipment after the tsunami. Photo: Arctic command, Sirius Patrol.
The controversial traffic of cruise ships into this area has not stopped, although such a huge slide and tsunami could potentially have damaged even a ship at that size, either directly by the waves or by crashing the ship into rocks. We described the situation in a post, linked below, that a few days earlier last year, when the cruise ship Arctic Explorer ran aground in the neighboring Alpefjord, 80 kilometers away in a straight line, about twice as far when sailing.
The GEUS article says that luckily there was no cruise ship close to Dickson Fjord when the rock slide and tsunami happened, but it is still well documented that the Ocean Explorer was in Alpefjord and ran aground on 11 September which was five days earlier. And the ship was stuck there for several days. It was pulled off the ground by research vessel Tarajoq in combination with a pull anchor, on 14 September. Local sources also said that Ocean Explorer did not leave the fjord immediately. The captain was ordered to inspect the hull for possible damage, as customary for this kind of incidents. After a first inspection and permission to sail, the ship would go to a facility for further diver or dry dock inspections. The nearest harbor with adequate facilities is Reykjavik in Island.
This has not been emphasized by other news sources, but it seems clear enough that by coincidence, the rock slide and tsunami in Dickson Fjord occurred two days later, on 16 September. So it may be correct that there were no cruise ships in the vicinity of the fjord, but it was a close call. The Greenland government will have to look into the safety for cruise ship access once more.