Pebbles Coast


Pebbles

Nicholas Crane and a team of experts explore Britain's coastline and the relationship between people and the sea, and discover how the pebble makes detectives of us all.


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Three bounces.

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Irresistible, isn't it?

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You just know that early man stood on beaches like this,

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trying to see how many times

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he could make a flat stone bounce on water.

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The world record was set in 1992 with an amazing 38 bounces.

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Believe it or not, someone has actually worked out

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the optimum angle for a flat stone to hit the water,

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if it's going to get the maximum number of bounces.

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That angle is 20 degrees.

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But the real star of the show isn't the person skimming the stone,

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but the stone itself. The pebble.

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To help me find out where beach pebbles come from,

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I've met up with Twm Elias from the Snowdonia National Park

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and Professor Cynthia Burek of Chester University.

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It looks like a gigantic mud pie, Cynthia, but geologically,

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what is this?

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This is a glacial till, formed in very different conditions

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to those we have today.

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This formed about 17,000 years ago,

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in the last Ice Age when the area was covered

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by half a mile or a mile of ice, and as these pebbles all moved along on

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and in the ice, they all ground up against each other and bits fell off.

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And they are the bits that form the components of the till,

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this so-called mud and then it dropped it

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and the ice moved over the top, compacting this

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and making it so hard.

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And it's quite exotic looking, with the variety of pebbles in it.

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It reminds me of a sultana pudding

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with bits of raisins and currants in it.

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What's fascinating is the variety of the sultanas and raisins in here.

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Some are round, some are angular, different colours and so on.

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-Such an amazing concoction.

-Yes.

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Some are pre-formed pebbles, because they're already rounded.

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And some are pebbles waiting to be made.

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-So we can go from glacial debris to beach pebble over night.

-Absolutely.

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Especially in the winter when you get the big storm waves

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actually pounding against this cliff

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and the pebbles falling out onto the beach.

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That's tomorrow's beach pebble.

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To see tomorrow's pebbles today,

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Twm's been on a journey along the North Wales coast,

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starting up on Anglesea where glacial mud, or till, has already eroded

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to reveal huge quantities of pebbles, each with its own story.

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OK, Twm, show and tell!

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Hold on, I have one in me pocket, and here we have a basalt

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which has come from Northern Ireland, Giant's Causeway,

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that particular area.

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And it's very distinctive.

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It's a lovely black stone, especially when it's wet like that.

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-We also have a flint.

-Very toffee-coloured, isn't it?

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Yes indeed. And that probably came from the seabed

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between Ireland and the Isle of Man.

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And this bit of pink granite here, where's that from?

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Oh, yeah, that looks very much like the type of granite

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you'd get in Ailsa Craig.

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-The small island off south-west Scotland?

-Indeed.

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Listen to this one.

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PEBBLES CHIME AS THEY COLLIDE

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-That's a metallic ring, almost, isn't it?

-Yeah, it's like a bell.

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This is an ancient mud stone from Penmaenmawr to the east of Anglesea,

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and this actually came from the big quarrying areas above the beach.

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This was used by people in the Stone Age period for making stone axes.

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But more recently, in the 19th century,

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you got the granite quarries there as well.

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-This is a lovely smooth bit of granite.

-Yes indeed.

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These were used for making the cobbles you find on the streets,

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like Coronation Street, for a start.

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-So these are local pebbles?

-Indeed they are.

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And they've come down onto the beach and now they are being subjected

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to the same processes that's going on everywhere.

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You'd never think a single coast could produce

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such an incredible diversity of pebble.

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-That's the wonder of it.

-I want to find another piece of that lovely black basalt.

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It's my favourite. What's your favourite pebble?

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My favourite pebble? Oh...

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-It's like trying to choose between your own children!

-THEY LAUGH

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Subtitles by Red Bee Media Ltd

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Email [email protected]

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