Researchers find massive mud flow off African coast

Sediment slunk 1,500km

It happened 60,000 years ago, so we'll concede that we're a bit late with the news, but scientists have uncovered evidence of the largest ever flow of sand and mud, off the coast of north-west Africa.

Researchers report in Nature that over the course of mere hours, or days, some 225 billion metric tonnes of sediment was dumped into the ocean after a landslide 60,000 years ago. The flow of debris travelled 1,500km before grinding and squelching to a halt.

The team says that the landslide responsible for the flow was probably not the largest ever known, however: landslides off the coast of Hawaii are known to have been bigger, and the Storegga slip off the coast of Norway also has it beat.

But in terms of sheer scale, the 1,500km long, 150km wide trail of sediment is in a class of its own. Researchers estimate that the flow dropped into the sea is ten times the amount of sediment carried by every river in the world each year.

"If you look at the distance it travelled and how much material it moved, it was at least as big as many volcanic eruptions," co-author Peter Talling from the University of Bristol, UK, told the BBC.

The researchers say that the blocks from the landslide would have broken up and become suspended in the water, flowing down the edge of the land mass, through an undersea canyon, and out to sea. Only a lessening of the gradient of the sea floor finally put the brakes on the huge volume of mud.

Dr. Talling said it would have been similar to an avalanche, where snow barrels down mountains in massive, deadly clouds. ®

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