On January 14, 2020, masses of sediment slid more than 1,100 kilometers and down to a depth of 4,500 meters off the African coast: one of the longest landslides that has ever been measured by humans. Peter Talling from Durham University and his team owe the fact that this was possible at all to a happy coincidence. Because the slide tore numerous measuring devices from their anchorage, which had been installed on site precisely because of such events. The working group describes their observations in »Nature Communications«.
The instruments were battery-powered and housed within buoys intended to allow them to drift across the ocean in the event the attachment failed. However, Talling and Co assessed it as relatively unlikely to find the football-sized buoys again. Wind and currents shifted them in different directions. Thanks to international cooperation and, above all, a lot of luck, it was still possible to collect the transmitters: a ship that happened to be passing fished some of the probes out of the sea. Others were recovered by other ships.
Just five months before the sediments left, the team had installed the measuring devices along the Congo Canyon in the Atlantic: it forms the continuation of the Congo River in the ocean. The masses of earth started to move at around 18 kilometers per hour and then accelerated to almost 30 kilometers per hour. In some cases, layers of 20 to 30 meters thick were removed. Talling and Co estimate the total volume of material that was transported deep at around 2.7 cubic kilometers with a total weight of up to 2675 megatons: In comparison, the Congo only drags up to 43 megatons of sediment into the sea every year.