After submarine cables were cut in the Atlantic Ocean at Congo Canyon, the internet stopped working in many African countries.
The Congo Canyon is one of the world’s largest canyons. It starts inland, about halfway up the Congo River estuary, and extends about 280 kilometers out to sea. Sediment from the landslide that severed internet cables off Africa’s west coast travelled over 1,130 kilometers from the river’s mouth at a top speed of about eight meters per second.
After submarine telecommunications cables in the Atlantic Ocean were severed in January 2020, numerous countries experienced internet outages in Africa. The damage was caused by a massive underwater landslide, the largest ever recorded.
The continental shelf beneath the oceans is etched with underwater canyons that frequently dwarf their land-based counterparts. Sediment flows from the land, down canyons, and eventually settles on the deep sea floor. Storms, earthquakes, and river floods can all cause turbidity currents, which are powerful enough to bury, displace, or destroy deep-sea infrastructure.
Mike Clare, a marine scientist at Southampton’s National Oceanography Center, studies turbidity currents and landslides. He explains that “there were no direct measurements of how the processes work within submarine canyons until very recently.” It’s a difficult environment that often necessitates the use of expensive vessels and equipment to explore. ‘The poor sensors we installed to measure current were simply blasted with sand and mud over several days.’
Clare and his colleagues published a paper in 2022 revealing that a landslide had dammed the Congo Canyon, preventing megatons of organic carbon from being transported to the deep sea, where it sustains unique ecosystems home to species like the sea pig, which has long, tube-like feet that prevent it from sinking into the mud, and the pom pom anemone.
It is unclear what this means for those ecosystems. ‘Landslide dams have been reported from rivers, but never in a deep-sea canyon,’ Clare says. ‘For context, the sediment trapped by the underwater dam was nearly four times that of the Congo River’s annual sediment flux.’
There have been very few top-to-bottom surveys of submarine canyons. ‘There are probably only four places where we’ve gone more than once to get a sense of how the seafloor changes,’ Clare says. One of these locations is the Monterey Canyon on the west coast of the United States. The Monterey Bay Aquarium Research Institute has created a device called the benthic event detector, also known as the’smart boulder, which is a motion-sensing instrument that collects data as it moves across the sea floor.
However, Clare claims that we are only scratching the surface of understanding submarine canyons so far. ‘We still only have a handful of measurements, so it’s a real frontier in scientific exploration,’ says the researcher.
OceanIQ, a subsea cable data and route engineering firm, estimates that there are currently 2.8 million kilometers of subsea cable worldwide, with plenty more in the pipeline. ‘Sometimes, canyons are so long that you can’t go around them; you have to cross them,’ Clare says. ‘The Congo Canyon is a great example. As a result, it is critical to comprehend the potential threats they pose to critical infrastructure.’