Shetland Tsunami Coast


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Shetland Tsunami

Nicholas Crane discovers evidence of a giant tsunami, a tidal wave which devastated Britain and reshaped the Shetland coast about seven thousand years ago.


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I'm on the coast of Eshaness,

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one of the most remote spots in the British Isles.

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One one side, hundreds of acres of bog and moor.

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On the other side, the North Atlantic.

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Between and sea and the land, a narrow coastal battleground.

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On the defence, the ancient rocks of Shetland,

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on the attack, the power of waves.

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This is the Grind o' da Navir.

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The rock was created millennia ago by a volcanic lava flow.

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Now, all that remains of the clifftop

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is a spectacular amphitheatre hewn out of the rock

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by gigantic storm waves.

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I want to know how the titanic battle between sea and rock

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reshapes this coast.

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This coast is strewn with clues,

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clues which reveal the terrifying power of the sea.

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You just have to know where to look.

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'Across the loch from one of the UK's biggest oil terminals,

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'I'm on the hunt for signs of a cataclysmic event

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'which hit these islands thousands of years ago.'

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Thanks, Mick!

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'Apparently, the evidence is hidden in the peat banks of Sullom Voe.'

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-Lovely beach you've brought me to, Adrian.

-Oh, yes!

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'Geomorphologist Adrian Hall is going to show me what to look for.'

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-This is peat.

-Well, I know that!

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Yes! It's got a wonderful environmental history locked in here.

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-The turf up here with the modern vegetation...

-Where we are today.

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And here we've got the dried-out peat.

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And then we've got some very clear layers in the peat,

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and then when we get down to about here,

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we've got a very, very clear change. It's mainly sand,

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-but as you can see, there are lumps of gravel.

-Yeah. Sudden change

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of colour, isn't there? And texture.

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But even more striking are these lumps of peat

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which clearly have been torn up

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from some pre-existing peat bank.

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Let's just have a look at that.

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See, the sand layer is really quite thick.

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It's got tiny marine organisms in it,

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so we've got to have a process that brings this material from the seabed

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-and up onto the land.

-So what is it?

-There's only one thing

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that can produce deposits of sand 20 metres above sea level

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-and that's a tsunami.

-A tidal wave?

-A tidal wave.

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The sand layer buried in this peat

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is evidence of a tsunami that hit this coastline 7,000 years ago.

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It was caused

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by a gigantic underwater avalanche

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on the continental slope off Norway.

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When a mass of sediment collapsed onto the seabed,

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it generated killer waves destined for Shetland 250 miles away.

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The first hunter-gatherers

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were already on Shetland 7,500 years ago,

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so we've got to imagine this as a broad open valley,

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the sea far, far out there.

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And then suddenly, on the horizon, there would be a wall of water,

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and it would be moving very rapidly.

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-So it funnelled down Sullom Voe, got constrained between the two shores.

-It would build

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and grow until, eventually, you were looking at a wall of water

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20 metres high.

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And then it would break and surge forward into this area,

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carrying the debris and hurling it against the land.

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The low-lying parts of Shetland would have been completely overwhelmed.

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This ancient tsunami reached as far south as the English border.

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The tsunami which struck these islands was a freak event,

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but the waves being generated by North Atlantic weather patterns are not,

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and they can be just as ferocious.

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Big waves are going to reach further inland.

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Life on the edge could get a lot more precarious.

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