An enormous underwater landslide 60,000 years ago produced the longest flow of sand and mud yet found on Earth. The landslide off the coast of north-west Africa dumped 225 billion metric tonnes of sediment into the ocean in a matter of hours or days. The flow travelled 1,500km (932 miles) - the distance from London to Rome - before depositing its sediment. The work, by a British team of researchers has been published in the academic journal Nature. The massive surge put down the same amount of sediment that comes out of all the world's rivers combined over a period...