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At the Dee Estuary, an imaginary line in the mud | 0:00:25 | 0:00:29 | |
marks the boundary between the English and the Welsh. | 0:00:29 | 0:00:33 | |
You soon hit a high spot of Victorian resort building, Llandudno. | 0:00:36 | 0:00:42 | |
The town's nestled in the shelter of the Great Orme's imposing cliffs, which point our way westward. | 0:00:42 | 0:00:49 | |
Out towards my destination, the largest island in Wales, Anglesey. | 0:00:52 | 0:00:57 | |
Many make their way to these cliffs for the glorious sights looking out | 0:01:00 | 0:01:05 | |
to sea, but what's brought me here are the rocks beneath my feet. | 0:01:05 | 0:01:12 | |
On the island's edge you see a slice right through the Earth's geological history, | 0:01:12 | 0:01:16 | |
an extraordinary collection of rocks are exposed here. | 0:01:16 | 0:01:21 | |
Just to show you how different Anglesey is, | 0:01:21 | 0:01:24 | |
look at this geological map of southern Britain. | 0:01:24 | 0:01:27 | |
Great swathes of it are all the same colour, meaning they're all the same rock type. | 0:01:27 | 0:01:31 | |
Here's this great band of chalk running up here in green, | 0:01:31 | 0:01:34 | |
there's another huge band of limestone running down here. | 0:01:34 | 0:01:37 | |
But up here on Anglesey something different is happening. | 0:01:37 | 0:01:41 | |
There's an intense mosaic of different colours, meaning there are many different rock types. | 0:01:41 | 0:01:48 | |
Much of the mystery of Anglesey's formation is buried below the turf, | 0:01:48 | 0:01:53 | |
but the coast reveals the island's subterranean secrets. | 0:01:53 | 0:01:57 | |
The most stunning geological feature is the long channel of water | 0:01:57 | 0:02:02 | |
that separates Anglesey from the mainland, the Menai Strait. | 0:02:02 | 0:02:06 | |
To understand its significance I'm with David Schofield from the British Geological Survey. | 0:02:08 | 0:02:14 | |
What part does this gulf play in Anglesey geology? | 0:02:16 | 0:02:20 | |
Well, this is actually a long fault zone which we call the Menai Strait fault system. | 0:02:20 | 0:02:24 | |
It separates very much | 0:02:24 | 0:02:26 | |
older rocks to the north west than those to the south east. | 0:02:26 | 0:02:30 | |
It's a fundamental geological divide, which we know is still active | 0:02:30 | 0:02:33 | |
cos we're seeing some of Britain's biggest earthquakes happening along this fault line. | 0:02:33 | 0:02:37 | |
-Where we're standing? -Right where we're standing, yes. | 0:02:37 | 0:02:40 | |
So the shore we're on here is moving in relation to the shore over there. | 0:02:40 | 0:02:44 | |
It certainly is, at a very slow rate every year, | 0:02:44 | 0:02:46 | |
and every now and then it takes a bit of a jump and there's an earthquake. | 0:02:46 | 0:02:50 | |
Around 300 small earthquakes shake Britain each year, often felt | 0:02:51 | 0:02:57 | |
most strongly here, caused as the mainland grinds against Anglesey. | 0:02:57 | 0:03:02 | |
It's part of the bigger movement of landmasses around the globe. | 0:03:02 | 0:03:07 | |
The Earth's crust is made up of separate distinct plates | 0:03:07 | 0:03:11 | |
which are constantly moving against each other. | 0:03:11 | 0:03:14 | |
Where the edges of the plates move apart, new crust is created about as fast as your fingernails grow. | 0:03:18 | 0:03:25 | |
Deep on the ocean floor, as the plates tear apart, lava can ooze out. | 0:03:25 | 0:03:32 | |
This fiery business of planet building is exposed beautifully | 0:03:32 | 0:03:37 | |
on a small strip of Anglesey at Llanddwyn Island. | 0:03:37 | 0:03:41 | |
Local geologist Margaret Wood is my guide. | 0:03:41 | 0:03:46 | |
These are the world-famous pillow lavas of Llanddwyn. | 0:03:46 | 0:03:50 | |
All I can see is a grey rock. | 0:03:50 | 0:03:52 | |
It's beautifully bluey-grey, though. | 0:03:52 | 0:03:53 | |
We're looking at pillows which are lava which came up on the ocean bed. | 0:03:53 | 0:03:58 | |
They get into the water and immediately the outside will crack. | 0:03:58 | 0:04:01 | |
These huge great big rounded lumps here? | 0:04:01 | 0:04:03 | |
Each one of those is called a pillow. | 0:04:03 | 0:04:05 | |
It is astonishing the way that raw nature can produce these symmetries and shapes. | 0:04:05 | 0:04:10 | |
But having looked at those, | 0:04:10 | 0:04:13 | |
something even more extraordinary, on the other end of the island, | 0:04:13 | 0:04:17 | |
you've got material that has actually gone down back into the crust, | 0:04:17 | 0:04:20 | |
and the fantastic thing is Llanddwyn Island is a complete mini-plate. | 0:04:20 | 0:04:27 | |
But that's amazing. I always thought that these plates on the surface | 0:04:27 | 0:04:30 | |
of the Earth really were the size of continents or oceans. | 0:04:30 | 0:04:33 | |
You're telling me that here on this beach in Anglesey there's an entire plate. | 0:04:33 | 0:04:38 | |
Absolutely. | 0:04:38 | 0:04:39 | |
This tiny island tells a big tale of how the Earth's built. | 0:04:39 | 0:04:45 | |
The plates of crust pull apart at one edge, but collide at the other edge. | 0:04:45 | 0:04:50 | |
As they crush into each other a jumble of different rocks is left behind, | 0:04:50 | 0:04:55 | |
which remarkably you can also see on Llanddwyn Island. | 0:04:55 | 0:04:59 | |
Wow, just look at that! Those colours, Margaret! | 0:05:02 | 0:05:07 | |
-It's fantastic, isn't it? -It looks like a great, big blancmange. | 0:05:07 | 0:05:10 | |
It's wonderful, isn't it? Those are quartz-rich rocks, you've got limestone over there, | 0:05:10 | 0:05:16 | |
and you've got schists, you've got conglomerate, and the colours are fantastic, aren't they? | 0:05:16 | 0:05:22 | |
-So this is two plates of the Earth crust colliding? -Exactly. | 0:05:22 | 0:05:26 | |
In the hundreds of millions of years Anglesey has been moving around the globe, | 0:05:26 | 0:05:31 | |
collisions and splits in the Earth's crust have created an astonishing array of rocks. | 0:05:31 | 0:05:37 | |
It's not just geologists who love this landscape, | 0:05:37 | 0:05:42 | |
it's a paradise for climbers, too. | 0:05:42 | 0:05:45 | |
The sea's worked away at the weaker rocks to create some of Britain's toughest cliff climbs. | 0:05:45 | 0:05:53 | |
Now I'm taking up the challenge to see these rocks as only climbers can. | 0:05:53 | 0:05:59 | |
But before the ascent, I've got an exhilarating 100-foot descent in prospect. | 0:05:59 | 0:06:05 | |
Fortunately, Libby Peter and Graham Desroy know their ropes. | 0:06:05 | 0:06:11 | |
Is it the nature of cliff climbing that you're always going | 0:06:11 | 0:06:14 | |
to start by going down before you can come up? | 0:06:14 | 0:06:16 | |
Normally you climb a mountain | 0:06:16 | 0:06:18 | |
and then abseil down again, but sea cliffs, it's the reverse. | 0:06:18 | 0:06:23 | |
You commit yourself by abseiling in and then you have to climb out again. | 0:06:23 | 0:06:28 | |
It does look amazing when you just disappear into the... | 0:06:28 | 0:06:32 | |
Yeah, it's like you're abseiling straight into the sea. | 0:06:32 | 0:06:34 | |
Yeah, it does. See you down there. | 0:06:34 | 0:06:36 | |
OK, will do. | 0:06:36 | 0:06:38 | |
Here goes. It's a very long way down. | 0:06:38 | 0:06:42 | |
The rock is now very dry and storm battered. | 0:06:48 | 0:06:52 | |
It's as if it's been scoured clear of vegetation. | 0:06:52 | 0:06:55 | |
That's pretty exciting. | 0:07:00 | 0:07:01 | |
-Is this where we start traversing round or... -That's right. | 0:07:01 | 0:07:05 | |
You know you're close to the sea when the spray starts whacking you in the face. | 0:07:08 | 0:07:12 | |
Hello, Libby. | 0:07:12 | 0:07:14 | |
What do you think? | 0:07:14 | 0:07:16 | |
Well, it beats sitting on a beach! | 0:07:16 | 0:07:18 | |
Just awesome, it's architecturally massive. | 0:07:18 | 0:07:22 | |
Takes your breath away. | 0:07:22 | 0:07:24 | |
The old heart's going. | 0:07:24 | 0:07:27 | |
The pros rate this climb as "very severe". | 0:07:29 | 0:07:33 | |
I can't tell you what I call it. | 0:07:37 | 0:07:38 | |
I can see all the incredible folds of rock, it's been bent like a piece of paper. | 0:07:42 | 0:07:48 | |
I mustn't get too distracted, I'm meant to be climbing. | 0:07:48 | 0:07:51 | |
I've been following this band of quartz all the way up. | 0:07:52 | 0:07:56 | |
Here it is, | 0:07:56 | 0:07:58 | |
glistening white in the sunshine. It's very beautiful. | 0:07:58 | 0:08:01 | |
Thank you so much. | 0:08:19 | 0:08:21 | |
That was sensational. | 0:08:23 | 0:08:25 | |
Thank you so much. It's such an honour to be taken up by the two of you. | 0:08:29 | 0:08:34 | |
I was so impressed with the way you climbed it. It was brilliant, it really was. | 0:08:34 | 0:08:38 | |
Subtitles by Red Bee Media Ltd | 0:08:38 | 0:08:42 | |
E-mail [email protected] | 0:08:42 | 0:08:44 |