0:00:40 > 0:00:46On this restless coastline, everything's on the move, even the land.
0:00:46 > 0:00:53The Isle of Wight seems so permanent and immoveable, and yet it's on a monumental journey.
0:00:53 > 0:00:57Nick Crane's crossing the Solent, in search of where the island's been,
0:00:57 > 0:00:59and what's happened to it
0:00:59 > 0:01:00along the way.
0:01:05 > 0:01:09Sailing around the Isle of Wight you get some sense of its size.
0:01:09 > 0:01:16At 23 miles across, it's England's largest island.
0:01:16 > 0:01:18It seems like a lost world.
0:01:18 > 0:01:22In fact, it's a time capsule containing
0:01:22 > 0:01:25clues to a journey the whole of the British Isles has been on.
0:01:26 > 0:01:34On a lost world you'd hope to find dinosaurs, and you wouldn't be disappointed.
0:01:34 > 0:01:36This is a dinosaur footprint,
0:01:36 > 0:01:39the beach is absolutely littered with them,
0:01:39 > 0:01:43they've fallen out of the cliff above me as the sea has eroded.
0:01:43 > 0:01:45It belongs to a four- or five-tonne Iguanodon.
0:01:45 > 0:01:48Look, you can see one articulated toe here, here's another one,
0:01:48 > 0:01:51the third toe has been snapped off, and here is the heel.
0:01:51 > 0:01:57These massive beasts tramped along this beach 130 million years ago,
0:01:57 > 0:01:59except that back then this land wasn't even here.
0:02:01 > 0:02:07And that's because the Isle of Wight has been on the move for ages, geological ages.
0:02:08 > 0:02:12And the evidence of its epic voyage is everywhere.
0:02:14 > 0:02:17This chalk is created from the remains of plankton which died
0:02:17 > 0:02:2378 million years ago in a very warm, very clear tropical sea.
0:02:25 > 0:02:33There certainly aren't tropical seas here now, so where was the Isle of Wight when the chalk was laid down?
0:02:33 > 0:02:37Well, a lot further south, and at the time it wasn't
0:02:37 > 0:02:39even an island.
0:02:40 > 0:02:4410,000 years ago it was part of the landmass of Britain.
0:02:44 > 0:02:51Step back 10,000 more and Britain was attached to the European mainland,
0:02:51 > 0:02:57but rewind a colossal 135 million years to the time of the dinosaurs
0:02:57 > 0:03:03when the continents were a lot closer together, Europe was 1,000 miles further south than now.
0:03:05 > 0:03:10The Isle of Wight has seen a lot of action on its journey north,
0:03:10 > 0:03:13and not surprisingly has picked up a few knocks along the way.
0:03:13 > 0:03:20You can see the bruises from those knocks in the landscape.
0:03:20 > 0:03:23Overlooking the multi-coloured cliffs at Alum Bay,
0:03:23 > 0:03:27geologist Alasdair Bruce is helping me get my eye in.
0:03:27 > 0:03:30What we're looking at it the huge fold in the Earth's crust.
0:03:30 > 0:03:35So if I elaborate by showing you this, that is essentially what we're looking at end-on.
0:03:35 > 0:03:39So this bit of the book is that peninsula sticking out in the sea?
0:03:39 > 0:03:41Yeah, those horizontal beds in the distance,
0:03:41 > 0:03:46and as you come further into the bay and into the Alum Sands themselves, they've now been tilted vertically.
0:03:46 > 0:03:51- And that's the vertical part. - That's the centre.- This bit here?
0:03:51 > 0:03:53- Indeed.- OK. So what caused the fault?
0:03:53 > 0:03:57Well, millions of years ago when Africa thundered into Europe to create the Alps.
0:03:57 > 0:04:00These are the plates covering the planet that shift around.
0:04:00 > 0:04:03Constantly moving. And as a result of that collision
0:04:03 > 0:04:07we all had to make way, geologically speaking, and our contribution
0:04:07 > 0:04:12in Britain was this large fold, and this essentially forms the backbone of the Isle of Wight.
0:04:12 > 0:04:15Switzerland got the Alps, the Isle of Wight got the fold.
0:04:16 > 0:04:23The chalk ridge running the length of the Isle of Wight, is in fact the last ripple of a colossal shockwave,
0:04:23 > 0:04:31the result of a continental car crash between Africa and Europe 65 million years ago.
0:04:31 > 0:04:36But even that didn't dislodge the Isle of Wight from the mainland of Britain,
0:04:36 > 0:04:42and you can still see the evidence of where it was connected, at The Needles.
0:04:43 > 0:04:48Alasdair, can you describe exactly what we'd have seen 10,000 years ago
0:04:48 > 0:04:51if we'd looked from here towards what is now Dorset?
0:04:51 > 0:04:55We'd have seen a line of white chalk cliffs, and behind that you'd have had cliff tops
0:04:55 > 0:05:00covered in primitive grasses, and as you walked away from that sort of coastal environment,
0:05:00 > 0:05:06you'd have walked into ancient woodlands and slowly down to shores of the estuary of the River Solent.
0:05:06 > 0:05:08- Sounds like a paradise.- Indeed.
0:05:09 > 0:05:13So how did that woodland paradise become an island?
0:05:15 > 0:05:1820,000 years ago, Northern Europe and most of Britain
0:05:18 > 0:05:23was covered with a layer of glacial ice over a mile thick.
0:05:23 > 0:05:28It started to warm up, the ice melted and water levels rose,
0:05:28 > 0:05:32but that wasn't the only thing that helped create the Isle of Wight.
0:05:34 > 0:05:38The other process is best illustrated by two men with an inflatable bed.
0:05:39 > 0:05:43OK, this is a primitive United Kingdom, we're going to have Scotland at one end,
0:05:43 > 0:05:46- and the Isle of Wight on the other end.- This is the North?
0:05:46 > 0:05:49It is, and it's very malleable as you can see.
0:05:49 > 0:05:54- So you're saying that the surface of the planet is this bendy in places?- Yes, geologically speaking.
0:05:54 > 0:05:5720,000 years ago, Scotland was covered with two kilometres thick of ice,
0:05:57 > 0:06:03- an enormous amount of weight, and I want you to be that weight, so in you go.- I'm Scotland, covered in ice.
0:06:03 > 0:06:06If I bring in the Isle of Wight, put that in place,
0:06:06 > 0:06:09then we wind the clock forward to about 12,000 years ago,
0:06:09 > 0:06:14the glaciers are melting away from Scotland really rapidly, so off you get.
0:06:14 > 0:06:19This drops, sinks down a bit, that is called "isostatic rebound".
0:06:19 > 0:06:23But what's happened to the Isle of Wight is, not only have we got sea levels attacking it,
0:06:23 > 0:06:26sea levels rise from all the glacial water going into the sea,
0:06:26 > 0:06:31but you've got the isostatic rebound happening, so the sea is now going to come churning around this particular
0:06:31 > 0:06:35lump of rock and turn it into the Isle of Wight that we see today.
0:06:35 > 0:06:37So it's being hit by a double-whammy.
0:06:38 > 0:06:42It was this combination of rising sea levels and the sinking landscape
0:06:42 > 0:06:46that would eventually separate the Isle of Wight from the mainland.
0:06:46 > 0:06:49The sea was rising, biting away at this chalk cliff,
0:06:49 > 0:06:53and at the same time the River Solent doing its thing at the back,
0:06:53 > 0:06:56so there would come a point where it would become a very narrow knife-edge blade
0:06:56 > 0:07:02going out across the sea, and then finally one stormy night it was breached, and the sea
0:07:02 > 0:07:06basically flooded into this area, and got rid of what was the River Solent.
0:07:09 > 0:07:15It took a few thousand years before the Isle of Wight was totally cut off as we see it today,
0:07:15 > 0:07:20but that's a blink of the eye compared to its multi-million-year trek,
0:07:20 > 0:07:25and this restless traveller is still moving, still evolving,
0:07:25 > 0:07:29part of the epic journey that the whole of the British Isles is on.
0:07:38 > 0:07:40'I'm also off out to The Needles.
0:07:42 > 0:07:47'It's not great conditions for studying rocks, but it is good for MY passion.
0:07:47 > 0:07:53'This is after all the sort of weather lighthouses were made for,
0:07:53 > 0:07:56'and I enjoy a good lighthouse, me!'
0:07:56 > 0:07:59So I couldn't resist a visit to this one, on The Needles,
0:07:59 > 0:08:02especially when I found out they're about to clean the lens.
0:08:09 > 0:08:13Everything about a lighthouse reminds us that we are connected to other shores.
0:08:20 > 0:08:26'Even the specialist lens used in lighthouses is an invention from across the Channel from France.'
0:08:27 > 0:08:31- How often does the lens get cleaned, then?- Just once a year.
0:08:31 > 0:08:34It's going to take about that long.
0:08:34 > 0:08:37I'd hate to be responsible for a smear.
0:08:41 > 0:08:43This really does feel like the edge of Britain,
0:08:43 > 0:08:50but of course the light from here continues on, travelling far beyond our shores and actually
0:08:50 > 0:08:53crossing the beam of the Gatteville lighthouse on the French coast.
0:08:53 > 0:08:56Even the light wants to bridge the gap.
0:08:56 > 0:09:00It kind of makes you want to reach out yourself and meet the neighbours.
0:09:18 > 0:09:20Subtitles by Red Bee Media Ltd