When Earth Shook For 9 Days After Rockslide Triggered 650-Foot Tsunami

A massive landslide in Greenland's Dickson Fjord in September 2023 triggered a tsunami that sent shockwaves around the world, causing seismic tremors that lasted for more than a week.

New data from the international Surface Water and Ocean Topography (SWOT) satellite mission has revealed that these tremors persisted for nine days. This data is offering researchers critical insights into the tsunami's unique characteristics and widespread impact.

SWOT collected water elevation data in the Dickson Fjord on September 17, 2023, a day after the landslide. By comparing this data with measurements taken under calm conditions on August 6, scientists observed major differences in water levels, said a report published by NASA's Jet Propulsion Laboratory. 

The data, represented visually, showed water levels up to 1.2 metres (4 feet) higher along the fjord's north side than on the south. The tsunami was set in motion when around 25 million cubic metres (880 million cubic feet) of rock and ice plunged into the fjord, which lies in a series of waterways along Greenland's eastern coast.

According to a study published in Science Journal, the landslide created a wave of about 200 metres (650 feet) high.

The Dickson Fjord, with its steep walls towering over 1,830 metres (6,000 feet) and a depth of around 540 metres (1,772 feet), confined the tsunami's energy. In this confined space away from the open ocean, the tsunami's energy couldn't dissipate easily, causing the wave to move back and forth around every 90 seconds for nine days. This movement generated tremors that were detected by seismic instruments located thousands of kilometres away. This back-and-forth movement is called a seiche.

The SWOT mission, launched from California's Vandenberg Space Force Base in December 2022, played a major role in capturing this data. The mission was a collaborative effort led by NASA and the French space agency CNES, with support from the Canadian and UK space agencies.