In September 2023, uniform single frequency seismic waves were recorded at centres across the globe which lasted for nine days. These seismic waves were very much unlike waves generated by earthquake or volcano hence how they were formed remained unknown until recently. A latest study has found that a massive landslide triggered by climate change had created a mega-tsunami in the remote Dickson Fjord in east Greenland. The vibrations generated by back-and-forth sloshing of tsunami across the fjord were recorded globally as long-lasting monochromatic seismic waves last year.
Earthquakes generate seismic waves of varying (mixed) frequencies of short durations. Longer duration seismic waves lasting for minutes or hours are known to be associated with volcanoes.
On 16 September 2023, seismometers across the globe recorded uniform monochromatic seismic waves of single frequency that lasted for full nine days. These signals were originating from East Greenland but could not be attributed to an earthquake because they were not of mixed frequencies. These seismic signals could not be due to volcanic disturbance either because they lasted much longer than waves generated by volcanos. Since formation of these seismic waves could not be explained, they were classified as an USO (unidentified seismic object).
Researchers have now found how these strange seismic waves were formed.
Using various geophysical tools and simulation studies, the research team determined that a massive rockslide triggered by melting ice due to climate change was the beginning. A massive rock-ice avalanche of 25 × 106 cubic meters plunged into Dickson Fjord. The region is extremely remote, and the event was not seen by any human eye.
The massive avalanche in fjord led to formation of a 200-metre-high tsunami which stabilized into a 7-meter-high long-duration standing wave. Fjords have steep walls of rock on either side. The back-and-forth sloshing of high waves across the fjord generated the vibrations that spread across the globe as monochromatic long duration seismic waves.
Thus, the chain of events began with a large landslide. Global warming and climate change is contributing to melting of ice in polar regions which in turn is linked to large landslides. This study highlights cascading effects of climate change how sea and earth’s crust are influenced by events in polar ice regions.
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References:
- Svennevig K., et al 2024. A rockslide-generated tsunami in a Greenland fjord rang Earth for 9 days. SCIENCE. 12 September 2024. Vol 385, Issue 6714 pp. 1196-1205. DOI: https://doi.org/10.1126/science.adm9247
- UCL News – Climate-change-triggered landslide caused Earth to vibrate for nine days. Published 13 September 2024. Available at https://www.ucl.ac.uk/news/2024/sep/climate-change-triggered-landslide-caused-earth-vibrate-nine-days
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