'Longest sediment flow ever measured in action'

Scientists are reporting what they say is the longest sediment avalanche yet measured in action.

It occurred underwater off West Africa, 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.

Prof Pete Talling from Durham University spoke with our science correspondent Jonathan Amos.

Read more: Underwater avalanche continued for two whole days