The researchers of theUniversity of Liverpool they managed to map and reconstruct the evolution of a giant underwater landslide happened about 60,000 years ago in the’Atlantic Ocean off the northwest coast of Africa. The landslide, with a volume of 150 km3has traveled 2000 km at the speed of 60 km/h covering a vast area of the seabed. Identifying and studying these events is very difficult and so far such a large submarine landslide has never been mapped. The study has revealed the dynamics of some submarine landslides, knowledge of which is very important for the consequences they can have, for example, on submarine cables that carry Internet traffic.
Study of the submarine landslide in the Atlantic
The researchers analyzed more than 300 carrots of sediments deposited by the landslide, collected over the last 40 years from the bottom of the Atlantic Ocean, off the coast of Morocco. In particular, to date the event, the fossils of marine organisms contained within them were studied. The data obtained, combined with the bathymetric data of the area, allowed to reconstruct the path taken by the landslide. The peculiarity of the phenomenon is that initially it was a landslide of relatively modest size whose volume, initially equal to 1.5 km3due to the material incorporated along the way it then grew by a good 100 times (much more than what happens with snow avalanches and terrestrial debris flows, which magnify 4 to 10 times).
The flow of material has reached the 200 m thick (the height of a skyscraper) and, moving with a speed of about 60 km/hswept away everything it encountered on the seabed. The landslide ran 400 km along the Agadir Canyonone of the largest underwater canyons in the world, carving out a trench 30 m deep and 15 km wideand another 1600 km on the seabed. Its sediments have invaded an area the size of Germany, covering it with a layer of sand and mud more than 1 m thick. This is the second largest submarine landslide ever documented (the largest was caused by a major earthquake in 1929 off the coast of Newfoundland, Canada) and the first of its magnitude to be reconstructed in any detail, including its evolution.
The importance of studying to understand the potential risks to Internet cables
Underwater landslides, which can be caused by events such as river floods, earthquakes and volcanic eruptionsare particularly difficult to locate and map, so our knowledge about them is limited. The reconstruction of the Atlantic landslide highlights the fact that landslides can occur on the ocean floor events of enormous magnitudepotentially destructive. In particular, it emerged that these phenomena may initially appear insignificant and only grow enormously in size along the way.
The consequences of submarine landslides can also affect us closely. For example, they can involve the submarine cables which carry all the global internet traffic and which constitute an increasingly extensive network on the seabed (just think that their total length is equal to 1.4 million kilometers). The breaking of these cables entails enormous inconvenience and costs for repair. This is what happened, for example, in 2006 in Taiwan when underwater landslides triggered by an earthquake broke the cables, with very serious damage to global markets and a cost of millions of dollars for repairs.
Landslides along submarine canyons are more or less frequent depending on the geographical position, but the climate change in progress could increase the likelihood of their occurrence.
