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Submarine Geohazards - Landslides, Sediment Flows and Tsunamis

By far the largest landslides on our planet occur underwater. The Storegga Slide that occurred on the Norwegian continental margin about 8,200 years ago is larger than Scotland. Perhaps the most remarkable fact about the Storegga Slide (and indeed many other submarine landslides worldwide) is that they occur on sea floor gradients of just 1-3°. For comparison, a premiership soccer pitch has a 1° gradient to help water drain. This talk will explore current ideas on why huge submarine landslides might occur on such low gradients. The Storegga Slide generated a tsunami that ran up for over 5 m in places around the UK coastline. Collapse of volcanic islands can also generate extremely large submarine landslides, and the magnitude of the tsunamis they generate is also the subject of vigorous debate. The talk will continue by outlining recently collected field data sets that show how volcanic landslides are emplaced, which is the major unknown factor for predicting tsunami magnitude.

The talk will conclude by describing flows of sediment called turbidity currents that can run out for thousands of kilometres into the deep ocean. These include the longest run out sediment flows yet recognised on Earth, and a single turbidity current can transport more sediment than the annual sediment flux from all of the world’s rivers.

View this presentation online


Dr Pete Talling (National Oceanography Centre, Southampton)


Peter Talling leads the Submarine Geohazards Research Group at the UK National Oceanography Centre in Southampton. His recent work includes a publication in Nature showing how a newly recognised type of debris flow can start to deposit sediment hundreds of kilometres from an initial landslide.

Over the last ten years he has led the mapping of individual beds of ancient rock (each deposited by a single turbidity current) for 120 km across the Apennine mountain belt of Northern Italy. He also leads an ongoing series of (rather fast flowing) laboratory experiments that relate flow type to deposit type. He has acted as a consultant for submarine geohazards in many locations worldwide, and has just returned from being chief scientist for the first detailed marine geophysical survey of volcanic landslide deposits offshore from Montserrat in the Lesser Antilles.