https://www.bbc.com/news/science-environment-57382529. . . , in a deep canyon leading away from the mouth of the Congo River.
Something in excess of a cubic kilometre of sand and mud descended into the deep.
This colossal flow kept moving for two whole days and ran out for more than 1,100km across the floor of the Atlantic Ocean.
The event would have gone unrecorded were it not for the fact that the slide broke two submarine telecommunications cables, slowing the internet and other data traffic between Nigeria and South Africa in the process.
And also because of the prescient action of researchers who had lined the length of the Congo Canyon with instruments capable of measuring current and sediment velocities.
5 m/s is about the speed of cooling water in the core of a PWR. It's not very fast, 16.4 ft/s, or 11.2 mph.The team had an early assessment of the speeds involved simply by noting the times when their sensors surfaced.
The recovery of the profilers, though, enabled the rough velocity calculations to be properly calibrated.
This showed the flow initially travelled at 5.2m/s in the upper canyon, but then continuously sped up to 8m/s by the time it reached the end of the channel.