Pebbles Coast

Three bounces.

Irresistible, isn't it?

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

trying to see how many times

he could make a flat stone bounce on water.

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

Believe it or not, someone has actually worked out

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

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

That angle is 20 degrees.

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

but the stone itself. The pebble.

To help me find out where beach pebbles come from,

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

and Professor Cynthia Burek of Chester University.

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

what is this?

This is a glacial till, formed in very different conditions

to those we have today.

This formed about 17,000 years ago,

in the last Ice Age when the area was covered

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

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

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

this so-called mud and then it dropped it

and the ice moved over the top, compacting this

and making it so hard.

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

It reminds me of a sultana pudding

with bits of raisins and currants in it.

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

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

-Such an amazing concoction.

-Yes.

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

And some are pebbles waiting to be made.

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

-Absolutely.

Especially in the winter when you get the big storm waves

actually pounding against this cliff

and the pebbles falling out onto the beach.

That's tomorrow's beach pebble.

To see tomorrow's pebbles today,

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

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

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

OK, Twm, show and tell!

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

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

that particular area.

And it's very distinctive.

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

-We also have a flint.

-Very toffee-coloured, isn't it?

Yes indeed. And that probably came from the seabed

between Ireland and the Isle of Man.

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

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

you'd get in Ailsa Craig.

-The small island off south-west Scotland?

-Indeed.

Listen to this one.

PEBBLES CHIME AS THEY COLLIDE

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

-Yeah, it's like a bell.

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

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

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

But more recently, in the 19th century,

you got the granite quarries there as well.

-This is a lovely smooth bit of granite.

-Yes indeed.

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

like Coronation Street, for a start.

-So these are local pebbles?

-Indeed they are.

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

to the same processes that's going on everywhere.

You'd never think a single coast could produce

such an incredible diversity of pebble.

-That's the wonder of it.

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

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

My favourite pebble? Oh...

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

-THEY LAUGH

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