Friday, 25 July 2014

Trænadjupet Slide

So we've heard about the Afen Slide and seen some of the great cores from the Trænadjupet Slide, as well the wide array of sediment types that exist within them. Here's a little background on why the Trænadjupet Slide is important and what the cores might tell us.

Extent of the Trænadjupet Slide (Courtesy of SpringerLink)

We know from recent submarine landslides (Grand Banks, 1929), and from the geological record (Storegga, ~6000 BC), that submarine landslides have the potential to cause tsunami evens similar to the 2004 Christmas tsunami in the Indian Ocean. Despite this tsunami-causing potential, the Trænadjupet Slide appears to have left little or no evidence of a tsunami on nearby coastlines as one might expect. Tsunamis often deposit marine sand much higher up on land than normal coastal processes and thus we have a record of the event stored for us to study. There are some potential deposits being explored, but there is still some debate about the significance of these deposits. Much of the uncertainty arises due to a lack of sufficient age-control on when the Trænadjupet Slide took place. Uncertainty also surrounds how fast the collapse happened and how fast it moved.  Fast moving landslides will tend to have more of an impact than those that move slowly or those that fail in multiple smaller stages. 

Schematic of how underwater landslides can cause tsunami waves (Courtesy of IranPetroTech)

So, where do the cores come in? Cores will be used to radiocarbon date marine background sediment which has accumulated on top of the landslide debris, and help constrain how old it is. Cores also allow us to look at the internal morphology of the slide and how the debris is distributed both spatially and in time. If the slide took place in numerous small stages rather than as one large failure, it may not have had enough energy to create a tsunami. The cores and radiocarbon dating will help us to better understand why this slide might not have generated a tsunami which will assist in assessing the tsunami risk to countries with nearby continental margins. 

Tsunami deposits within terrestrial soil on The Shetland Islands
Josh Allin

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