Spectacular The Congo River flooded more abundantly than in half a century during the Central African rainy season in November–December 2019.
It dumped huge masses of silt into the Atlantic. In the early months of 2020, they triggered two huge seabed landslides. The researchers were able to measure the first one precisely before the upheaval ripped the equipment from the bottom.
The January 2020 avalanche cooled over 1,100 kilometers in the Congo canyon leading from the coast to the deep sea. As it went, it dredged up more and more sediment from the canyon and transported it to an area nearly five kilometers deep.
Se was the longest avalanche ever measured on Earth, says an international group of researchers Nature Communications in the journal.
It was also the first large seafloor landslide measured when it occurred. The more common small landslides pack more sediment into the canyons, but the rare large landslides wipe the canyons emptier and hollow them out deeper.
According to the researchers’ estimate, the pair of large landslides at the beginning of 2020 transported the amount of sediment that had taken many decades to accumulate from the Congo River.
A marathon promoted by the fact that the avalanche accelerated its speed.
In the first hundreds of kilometers, the speed was five meters per second, on the 1,000 kilometer climbs it was already over eight. This is special, because on the way the seabed became shallower.
The researchers had assumed that the large landslide would accelerate on its own, because the swirling clay bed gets denser and denser as it dredges the canyon. Now the phenomenon was measured in practice for the first time.
The huge landslides cut the communication cables between South and West Africa, which had been running across the Congo Canyon without problems for 18 years.
In addition, avalanches spelled the end of the world for countless seabed animals that happened to inhabit their path.
For marine life however, there was also joy. The bottom of the deep sea is a barren place, whose frozen darkness is enlivened by only a few hot springs and whale carcasses, which act as rapidly dwindling oases.
Daily food consists of organic particles that gradually sink from surface waters, i.e. “sea snow”. Large landslides made a buffet of organic material from the Congo River.