Deep Earth How Earth Made Us


Deep Earth

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Our planet is full of incredible natural wonders.

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Look at that!

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Whoo!

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It has immense power...

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..and yet, that's rarely mentioned in our history books.

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I'm here to change that.

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I'm looking at four ways the power of the planet

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has shaped our history.

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The power of fire...

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Oh...

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..that fuelled great technological breakthroughs.

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Wind...

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HE CHUCKLES

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..that has influenced the rise and fall of empires.

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Water...

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Our struggle to control it has directed human progress.

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But I'm going to start by looking inside the Earth itself.

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It's an unknown world, hot and extreme.

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HE CHUCKLES

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It's provided the raw materials for our conquest of the planet,

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but at a price.

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This is the great untold story of human history.

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Hidden unseen within the Earth,

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extraordinary geological forces are at work.

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Hi. Gracias.

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Forces that have shaped our history.

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To really understand and appreciate them,

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I've got to go deep into the Earth itself.

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This is the Naica mine in northern Mexico -

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the starting point for a journey to one of the most

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spectacular and extreme places on or in the planet.

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I'm really starting to feel it now.

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I'm getting hotter and hotter, the deeper in I go.

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This heat is just a taste of what lies ahead.

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Finally, I arrive at what they call "Base Camp".

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You know, where I'm heading is just so extreme, so oppressive

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that I'm going to need all of these people, all of these control systems

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and all of this kit over here just to get there.

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It's going to be like visiting another planet.

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Beyond here is a chamber that reveals the power of the inner Earth

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to influence human affairs.

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But to get there,

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they've had to develop some pretty esoteric equipment.

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Get this.

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It's like a chain mail of ice cubes.

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It's heavy, isn't it?

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The special refrigerated suit will keep me cool.

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What a palaver!

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-This brings down my core temperature?

-Yes.

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Oh, feels very cold suddenly.

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That's very odd!

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But it's not the heat alone that's potentially lethal.

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This is what? This is the oxygen?

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Yes, it's fresh air.

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-It's fresh air.

-Yes. You'll need it.

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The heat is combined with nearly 100% humidity.

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If I breathed that combination,

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moisture would begin to condense inside my lungs.

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After about ten minutes, I'd start to suffocate.

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-You're ready.

-I'm ready? I don't feel ready.

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OK.

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Without this suit, I could die.

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It seems a lot of effort,

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but inside there is one of the geological wonders of the world.

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HE BREATHES HEAVILY

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WONDROUS MUSIC

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That is unbelievable.

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This is just mad!

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Absolutely gorgeous, isn't it?

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This is la Cueva de los Cristales -

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for my money, the most spectacular cave of crystals

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discovered anywhere in the world.

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HE CHUCKLES

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You know, I've travelled around the world

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to see some of the most amazing geology,

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but this place - this place just tops it all.

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Look at it.

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It really looks perfect.

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You can see through them, they're so translucent.

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And there's different types.

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You can see these ones that are like roses building up

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and then these columns, these pillars - absolutely magnificent.

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Until recently, no-one knew this chamber existed.

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It was uncovered when miners broke through by chance.

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You know, these extraordinary crystals

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are made up almost entirely of a pretty ordinary mineral - gypsum -

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but it's the sheer scale of them that astounds you.

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This strange world is shaped by forces

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that have had a profound impact on human civilisation.

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HE PANTS

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Oh, this heat... This heat's just too much.

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It's unbearable.

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But, oh, hey, the heat - that's what it's all about.

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That's the whole point.

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It's this cauldron that's the reason that these crystals are here.

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It's so hot because only about 5km below the cavern...

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..is an area of the Earth's crust that is super-heated molten rock.

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This heats water, which dissolves minerals from the surrounding rock.

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Phenomenal pressure forces this mineral-rich water

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up through cracks in the rock and filled this giant cavern.

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Here, the conditions were perfect

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for the minerals to slowly crystallise back out of the water.

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The cave lay undisturbed for over half a million years,

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so the gypsum crystals just kept growing

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until the miners broke through and the cave was drained.

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But the hot inner Earth has done far more than create these crystals.

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This incredible hot world hidden just beneath the surface

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is a driving force for powerful geological events

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that have shaped the fate of peoples throughout history.

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This is the Timna Valley in Israel's Negev Desert.

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Today it's pretty well deserted.

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But over 6,000 years ago,

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this place witnessed

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one of the world's first great scientific breakthroughs.

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Up until this point,

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humans had made all their tools from stuff just lying around -

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stone, wood, bone,

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anything, really, that they could get their hands on.

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But then, between 6,000-7,000 years ago,

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our ancestors made an extraordinary imaginative leap.

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They realised that the rock here contained a secret.

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These green bands are called malachite.

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And it was these malachite seams

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that around 6,500 years ago

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were at the centre of that incredible leap of human ingenuity.

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Like the gypsum inside the crystal cave,

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these bands of malachite

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formed when hot fluids rose from deep inside the planet

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and leaked into these rocks.

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But unlike gypsum,

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when malachite is heated up...

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..it does something special.

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It releases a metal.

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Copper.

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You know, in its day,

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this copper axe head would have been the pinnacle of technology.

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For a start, it's weighty.

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If you hit something or someone with this, it would leave a dent.

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For another thing, it's hard enough to take an edge.

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And if it gets blunt, you just sharpen it up.

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You can still see evidence of the ancient smelting pits at Timna.

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But the copperworkers left behind a more striking memorial to their work.

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A network of hundreds of tunnels, all carved by hand.

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This was the first large-scale mining anywhere on the planet.

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Those early copper miners

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would have squeezed through these narrow shafts on all fours,

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smashing their way through the rock

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and hauling their pails of copper-laced ore back to the surface.

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You know, the copper revolution

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changed our relationship with the planet

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in a really profound way.

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For the first time,

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we were transforming what the Earth offered us

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and in the process creating entirely new resources.

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And copper was just the start of things to come.

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About 5,000 years ago, tin was added to copper

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to form a new, more durable metal alloy - bronze.

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By 3,000 years ago, refinements to the smelting process

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meant iron could be smelted out of rock.

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Metal tools became the foundation for human civilisation.

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So it's clear we owe a huge debt to those first copper miners at Timna.

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But we also owe a debt to the deep Earth.

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The key to Timna's role in early history is its location.

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The Earth's crust is divided into huge pieces called plates.

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Where they meet are cracks known as fault lines.

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Timna is next to the Dead Sea fault,

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which separates Africa from Arabia.

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This fault also connects Timna to the deep, hot interior of the Earth.

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It's this hot interior

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that is ultimately the source

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of all the metals that have so radically changed our history.

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Fault lines allow them to rise to the surface...

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..just as they did at the crystal cave in Mexico.

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But fault lines began affecting human history

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even before the discovery of metals.

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In fact, we've been strangely drawn to these boundary zones

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ever since the dawn of civilisation.

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And you can see why

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in the barren wilderness of the Lut Desert in Iran.

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The landscape is covered in hundreds of holes arranged in rows.

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These holes in the desert

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can help explain our ancient attraction to fault lines.

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But that involves me going down one -

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something the locals seem a little bemused by.

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Hi.

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So this is it?

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HE SPEAKS LOCAL LANGUAGE

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That's tiny!

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I don't think I'll really fit.

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How deep is it?

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ROCK THUDS

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God! Apparently it's 50 metres.

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That's over 150 feet.

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OK, I guess we do it, huh?

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So we go down?

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And if this deep, dark hole wasn't scary enough,

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the method for going down is unconventional at best.

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So we take this, like a pulley?

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And this goes over the top, I guess.

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So do I go on this?

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You can't buy those, I bet you!

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I've never gone on a rope with a tripod pulled by a tractor before.

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So...

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TRACTOR ENGINE REVS

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Well, I think we should just do this before I change my mind.

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OK. What could possibly go wrong now?

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Blooming heck. It really is deep.

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Oh, this isn't natural.

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I'm getting lowered down into the bowels of the Earth here.

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I wasn't sure if I was claustrophobic

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but now I realise I think I am.

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It's so far up!

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Look at that.

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Oh, dear. I don't want to do this too many times.

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HE EXHALES

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METAL TAPS

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For over 2,000 years,

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local people have been digging shafts like this - by hand.

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And I get the sense I'm about to find out why.

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HE SIGHS

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All right, here we go.

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Hey hey!

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Ooh! Oof!

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WATER SPLASHES

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I misjudged it.

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Look at this!

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This is the answer.

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The essential ingredient of every civilisation on Earth.

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Cold, fresh drinking water.

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This is what made this remote corner of the Lut Desert

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one of the few places in the region that could sustain towns and cities.

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And I'll tell you...

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..after a trip like that, this is so nice to have.

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HE SIGHS

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Right. I'm off to explore a bit.

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I want to find where the water's coming from.

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This tunnel leading off the shaft is called a qanat.

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It's one of many in this region,

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hacked out of solid rock

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to capture ground water that's stored deep below the desert.

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I feel as if I'm in an underground rain shower.

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I've travelled about, I don't know, a couple of hundred metres now

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and it seems to be getting smaller and smaller.

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HE GROANS

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It's a bit narrow here.

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Well, this is it.

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This is the source of all this water.

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It's just pouring in from here.

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Underground water exists beneath most deserts.

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But it's usually so far down,

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there's no practical way of getting at it.

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The difference is, here there's a fault line.

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The fault is full of thick clay

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produced by the grinding of the surrounding rocks

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as they rub along the fault line.

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This forms a clay dam, which water can't penetrate.

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Water flowing down from the mountains

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pools against the dam,

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creating an underground reservoir

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through which a qanat is dug to channel the water.

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Gravity does the rest.

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So originally the water would've been banked up against this fault line,

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unable to penetrate through the clay-rich barrier.

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But what the locals did was to cut a qanat across the fault line,

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breaching the barrier and releasing the water.

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It was a simple but brilliant piece of engineering.

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OK.

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Qanats were an ingenious early example of a mains water supply.

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The shaft is simply a way

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to get access to the tunnel carrying the water, so it can be repaired.

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Today, the qanats still carry water from underneath the Lut Desert

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into the nearby city of Bam,

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as well as irrigating date orchards for which this area is famous.

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Oh! Oh, it's so good to see blue sky.

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Oh!

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Yeah, thank you.

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But this place isn't a one-off.

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In fact, if you look back at the ancient world,

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you see a strong link between fault lines,

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water and the growth of some of the first cities.

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More than 2,000 years ago, Petra in Jordan

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was the most important trade hub in the Middle East.

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It was built along a branch of the Dead Sea fault

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and was entirely dependent on natural springs,

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which rose along the fault and fed its irrigation system.

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Nearby is Jericho, said to be the oldest city in the world.

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It was first settled 10,000 years ago

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because deep ground water rose along fault lines

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to create fertile pastures in the desert.

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More unusual is the ancient Roman city of Hierapolis.

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It was built next to these terraces of white rock.

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Here, it wasn't just water that was important -

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minerals carried in the water were thought to have revitalising powers.

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So Hierapolis became an important healing centre

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in the Roman Empire.

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Whether it was minerals, metals or water,

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ancient civilisations were repeatedly drawn to the resources

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that fault lines brought up from the deep Earth.

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It's a connection which led 11 of the 13 most important civilisations

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of the ancient world

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unknowingly to build their cities close to a plate boundary.

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As the earliest civilisations developed,

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so the relationship between fault lines and human history

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became more sophisticated.

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They even played a role

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in the establishment of the most advanced early civilisation of all.

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4,000 years ago, in the Bronze Age,

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the island of Crete was home to the Minoans.

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Their showpiece was the palace of Knossos.

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You can see by the sheer scale and sophistication of Knossos

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that the Minoans weren't just another early civilisation.

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This, in a way, was the beginning of modern society.

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Certainly, this was a place

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that you and I would have felt reasonably at home.

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There was running water, a sewage system

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and large stores of food and wine.

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It all allowed the Minoans to create a new kind of society.

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For me, all this is a moment in history

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that is much under appreciated.

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What the Minoans represent is a great pivotal point

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when life switched from being dictated

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by the grim realities of survival

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into something that we could actually enjoy.

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What the Minoans invented was the day off.

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And the Minoans took their pioneering responsibilities

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in this area very seriously.

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Now, this may look like a car park,

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but, really, this is where the paraphernalia

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of the Minoan leisure society really took off

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because this is one of world's first sports stadiums.

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In its day, 500 spectators would cram in here

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to watch boxing, wrestling,

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and the Minoans' most peculiar sport, bull-leaping.

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The basic idea was that you wait for a massive bull to run at you,

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then at the crucial moment,

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you grab hold of the horns and flip yourself over the top.

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How do you practise that?

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No-one knows why the Minoans leapt over bulls,

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but this bizarre sport was a forerunner to bull-fighting.

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But the real legacy of the Minoans was how they made their wealth.

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This was the Bronze Age.

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To make bronze, you need two metals - copper and tin.

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The problem was finding them.

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For the Minoans, copper was relatively near at hand in Cyprus,

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thanks to the fault line beneath it.

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Tin was trickier.

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Inside the Earth's crust, only two parts per million are tin,

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so it's much rarer.

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The hunts for tin led to distant lands

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that were at the edge of the then-known world.

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One such place was so full of tin

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that it was called the Cassiterides - "the tin islands".

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Today...

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..we know it as Britain.

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But the centres of Bronze-Age civilisation

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were in the Mediterranean, 3,000km away.

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Tin was also found in other far-flung locations

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like Spain, Central Europe and even Iran...

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..which meant tin had to be traded,

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and for this, Crete was perfectly positioned.

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The Minoans exploited their position

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at the crossroads of many different trading routes...

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..to become the world's first maritime superpower.

0:29:230:29:28

It may not seem like it today,

0:29:300:29:32

but in Bronze Age times, this island was at the centre of the known world,

0:29:320:29:37

with the mineral-rich heartlands

0:29:370:29:38

of Europe, the Middle East and North Africa all around.

0:29:380:29:42

For the Minoans, it wasn't so much about owning the raw materials

0:29:420:29:46

as knowing what to do with them, how to put them together.

0:29:460:29:50

They built an empire because they'd worked out how to exploit the geology

0:29:500:29:54

that their neighbours had on their doorsteps.

0:29:540:29:56

By the time of the Minoans,

0:30:030:30:05

fault lines had been a crucial factor

0:30:050:30:07

in the success of many early civilisations.

0:30:070:30:11

But the Earth extracted a price for these riches.

0:30:170:30:20

It was a price paid in full by the Minoans.

0:30:220:30:27

At the heart of the story was a small archipelago

0:30:280:30:32

100km north of Crete.

0:30:320:30:34

Today that island chain is known as Santorini,

0:30:380:30:41

famous for its pretty white houses and rugged coastline.

0:30:410:30:46

But at the time of the Minoans this was a busy port,

0:30:560:31:00

the key to their trading empire.

0:31:000:31:03

If Crete was the heart of the Minoan culture,

0:31:050:31:07

then this place was its backbone,

0:31:070:31:10

a centre of industry that helped fuel what was at the time

0:31:100:31:14

the most advanced civilisation on the planet.

0:31:140:31:17

But Santorini held a deadly secret.

0:31:200:31:23

Unknown to the Minoans,

0:31:260:31:27

it sat above one of the Earth's major plate boundaries.

0:31:270:31:31

Santorini formed when the African plate

0:31:350:31:38

started sliding below the European plate.

0:31:380:31:41

As the African plate melted inside the deep Earth,

0:31:430:31:47

molten rock rose back to the surface

0:31:470:31:50

to create what is actually a volcano.

0:31:500:31:52

OMINOUS RUMBLING

0:31:540:31:57

Around 3,500 years ago,

0:31:570:32:00

this volcano did what volcanoes tend to do -

0:32:000:32:04

it blew up.

0:32:040:32:05

Unluckily for the Minoans,

0:32:150:32:17

it was the biggest eruption of the last 10,000 years.

0:32:170:32:21

Today you can still trace why the eruption was so devastating

0:32:230:32:27

in the cliffs around Santorini.

0:32:270:32:29

This cliff is made entirely of ash and rock spat out by the volcano.

0:32:340:32:40

It's got distinct layers to it,

0:32:400:32:43

each of which are from different stages of the eruption.

0:32:430:32:46

In other words, this rock face is a timeline of events.

0:32:460:32:50

Climbing this cliff helps understand the disaster

0:32:530:32:56

that was unlike anything anyone had ever seen before.

0:32:560:33:01

This level here was the start of the eruption.

0:33:080:33:10

I'm kind of standing on the Minoan land surface.

0:33:100:33:14

And in the next five hours,

0:33:140:33:15

the eruptions threw out an enormous mushroom cloud of debris.

0:33:150:33:19

It just rained down ash after ash after ash.

0:33:240:33:26

This stuff is just like a silica glass.

0:33:320:33:35

It gets into your lungs and it just lacerates your lungs.

0:33:350:33:38

You just choke on it.

0:33:380:33:39

This innocent-looking gravel

0:33:550:33:57

was from the second and most lethal stage of the eruption.

0:33:570:34:01

Sea water invaded the volcano

0:34:040:34:06

and that mix of water with molten lava

0:34:060:34:09

produced a series of incredibly violent eruptions

0:34:090:34:11

that punched a jet of superheated gas and debris

0:34:110:34:15

high into the atmosphere.

0:34:150:34:16

As these clouds of hot gas and lava fell back to Earth,

0:34:240:34:27

they engulfed the outer edges of the island.

0:34:270:34:31

Ay!

0:34:310:34:33

But, incredibly, the worst was still to come.

0:34:360:34:41

Once the volcano had spewed out everything that was in its guts,

0:34:440:34:47

the weight of it collapsed into the void below,

0:34:470:34:50

producing the most enormous blast.

0:34:500:34:53

And in the death throes of that final blast,

0:34:530:34:56

there was one last catastrophic flourish.

0:34:560:34:59

The centre of the volcano crashed into the sea.

0:35:050:35:09

That sudden collapse created a gigantic tsunami...

0:35:160:35:20

..which quickly spread out across the Aegean towards Crete.

0:35:220:35:27

WAVE CRASHES

0:35:300:35:33

For a civilisation whose strength was in their navy,

0:35:340:35:38

the tsunami would have been devastating.

0:35:380:35:41

It's thought that as the tsunami swept through the Aegean,

0:35:460:35:50

it engulfed the Minoan harbours,

0:35:500:35:52

and any boats in them would have been smashed into matchsticks.

0:35:520:35:57

So perhaps it's not that surprising that not a single boat

0:35:570:35:59

from the vast Minoan fleet

0:35:590:36:01

has ever been found.

0:36:010:36:03

This was a catastrophe from which the Minoans would never recover.

0:36:110:36:16

A long chalk-and-ash cloud and a giant tsunami

0:36:250:36:29

meant that this maritime power was on its knees.

0:36:290:36:33

With the fleet gone,

0:36:330:36:36

and their most strategic trading post obliterated,

0:36:360:36:40

the Minoans went downhill fast.

0:36:400:36:43

Within a century or so of the eruption,

0:36:430:36:45

this once-great civilisation was finished.

0:36:450:36:50

The eruption of Santorini

0:36:550:36:56

was an extreme event.

0:36:560:36:59

But ancient history is littered with

0:36:590:37:01

tales of cities destroyed along plate boundaries.

0:37:010:37:05

And it's not just volcanoes that do the damage.

0:37:110:37:15

Fault lines are also home to another deadly force of nature.

0:37:150:37:19

Earthquakes.

0:37:280:37:30

Recent events in Haiti are a reminder of just how devastating earthquakes can be.

0:37:300:37:35

The appalling disaster is a terrible example of how the destructive power of the deep Earth

0:37:350:37:42

can be concentrated along fault lines.

0:37:420:37:46

Over the past 10,000 years,

0:37:470:37:49

many cities first established to take advantage of fault lines

0:37:490:37:55

have been flattened.

0:37:550:37:58

Hierapolis, with its famous health spa,

0:38:000:38:04

was destroyed by a giant earthquake in AD 60.

0:38:040:38:08

Jericho, the oldest city in the world,

0:38:120:38:16

has been hit over 15 times by large earthquakes.

0:38:160:38:20

Some believe it was this

0:38:200:38:21

that famously brought its walls "tumbling down".

0:38:210:38:25

Likewise, Petra was abandoned

0:38:280:38:31

after an earthquake demolished its irrigation system in AD 360.

0:38:310:38:36

And it continues to this day.

0:38:410:38:44

In 2003, the city of Bam, famous for its qanats,

0:38:440:38:48

was devastated by a massive earthquake

0:38:480:38:50

which killed over 30,000 people.

0:38:500:38:53

It makes you realise that, in effect, much of human history

0:39:060:39:10

has centred on a bargain between us and the inner Earth.

0:39:100:39:14

Plate boundaries provide access

0:39:150:39:18

to resources from deep inside the planet.

0:39:180:39:21

But live near one, and you also live with the risk of a sudden catastrophic disaster.

0:39:250:39:31

But even the most advanced of our ancestors

0:39:350:39:38

had no way of explaining this strange coincidence.

0:39:380:39:41

In fact, it's only in the last 50 years

0:39:420:39:45

that scientists have finally understood

0:39:450:39:48

the bargain that was inadvertently struck all those years ago.

0:39:480:39:53

You can see the theory in action in the middle of the Pacific Ocean.

0:39:530:39:57

This is Kilauea on Hawaii's Big Island.

0:40:000:40:04

It's one of the most active volcanoes on the planet

0:40:080:40:11

because it's fed by a chamber of magma deep inside the Earth

0:40:110:40:15

called a hot spot.

0:40:150:40:17

The hot spot has effectively punched a hole in the Pacific plate -

0:40:270:40:32

the piece of the Earth's crust on which Hawaii sits.

0:40:320:40:35

But remove the ocean around Hawaii and something strange is revealed -

0:40:360:40:41

a chain of mountains stretching along the sea bed

0:40:410:40:44

for over 5,000km.

0:40:440:40:48

This line of extinct volcanoes is explained

0:40:480:40:51

when you realise that the Pacific plate is continually on the move.

0:40:510:40:56

As the plate drifts over this stationary hot spot,

0:41:000:41:03

a volcano forms,

0:41:030:41:06

but after about a million years,

0:41:060:41:08

the moving plate pulls the volcano away from the hot spot.

0:41:080:41:11

Meanwhile, another eruption begins, forming a new island.

0:41:120:41:17

Today, Kilauea is still growing, but it hasn't got long to go.

0:41:230:41:29

In a few thousand years, it will drift away from the hot spot

0:41:290:41:33

and eventually disappear beneath the waves.

0:41:330:41:36

The Hawaiian islands chain is a beautiful demonstration

0:41:470:41:51

of a big idea

0:41:510:41:54

that explains why plate boundaries

0:41:540:41:56

bring us extraordinary benefits and terrible hazards in equal measure.

0:41:560:42:02

It's called plate tectonics.

0:42:030:42:07

The key is that all the plates, which divide the Earth's surface

0:42:100:42:14

are continually on the move.

0:42:140:42:15

Where they collide, they crumple the land

0:42:170:42:20

to form great mountain ranges, like the Himalayas.

0:42:200:42:23

Where they pull apart,

0:42:270:42:30

oceans form in the gap.

0:42:300:42:33

The friction of this continual movement

0:42:370:42:39

means that plate boundaries become melting zones

0:42:390:42:42

where minerals are concentrated

0:42:420:42:44

and are able to rise towards the surface.

0:42:440:42:47

But the flip side is that huge amounts of energy

0:42:500:42:54

are concentrated along the plate boundaries.

0:42:540:42:57

When one plate slides underneath another, volcanoes form.

0:43:000:43:05

When two plates lock together and then suddenly break free,

0:43:160:43:20

the jolt causes devastating earthquakes.

0:43:200:43:23

So we now know that plate boundaries are so rich in resources

0:43:300:43:34

for exactly the reasons they're so dangerous.

0:43:340:43:38

Yet the strange thing is this groundbreaking discovery

0:43:410:43:45

has made little difference to where we live.

0:43:450:43:48

If you look at the plate boundaries,

0:43:530:43:56

it's clear that many cities are located close by.

0:43:560:43:59

In fact, 10 of the 20 largest cities in the world

0:44:010:44:05

are next to dangerous fault lines.

0:44:050:44:08

So why are we still building next to these danger zones?

0:44:090:44:12

In the rugged hills of central California

0:44:150:44:18

is part of the answer.

0:44:180:44:20

And to see it, I'm heading into the skies.

0:44:250:44:28

At least, I hope I am.

0:44:280:44:30

This is the dinkiest helicopter I've ever been in.

0:44:300:44:33

It'll be nice when it's finished.

0:44:350:44:37

MOTOR STARTS

0:44:410:44:43

I'm going to see

0:45:090:45:11

perhaps the most famous geological feature on the planet.

0:45:110:45:15

And this is the best way to find it.

0:45:150:45:17

Yeah, yeah, yeah, this is it. This looks fantastic.

0:45:210:45:26

It's this beautiful funnel cut right through these hills here.

0:45:300:45:34

That's amazing.

0:45:340:45:36

This line of hills with a trench cut through the middle

0:45:430:45:46

is the San Andreas Fault.

0:45:460:45:49

This fault is a boundary between the North American Plate to the east

0:45:510:45:55

and the Pacific Plate to the west.

0:45:550:45:57

For 25 million years, they've been grinding past each other

0:45:590:46:03

to create the largest earthquake fault in North America.

0:46:030:46:06

The San Andreas Fault starts up there in northern California,

0:46:090:46:13

then slices down through 700 miles through here

0:46:130:46:17

down to the border with Mexico.

0:46:170:46:19

As it goes, it cuts through cities and towns

0:46:190:46:22

and passes across a path of roads, bridges,

0:46:220:46:26

aqueducts and fibre-optic cables.

0:46:260:46:28

If ever there was a fault line

0:46:330:46:35

that cut through the very fabric of a modern society,

0:46:350:46:38

then it's this one.

0:46:380:46:40

But a good reason why over 20 million people

0:46:420:46:46

carry on living so close to this danger zone

0:46:460:46:49

is that this plate boundary has made California rich.

0:46:490:46:53

It began with the Californian gold rush.

0:46:570:47:00

These nuggets of gold might have been found in streams,

0:47:020:47:06

but the gold originally rose in hot mineral-rich fluids

0:47:060:47:10

forced up between the plates.

0:47:100:47:12

In fact, almost everything that makes California wealthy

0:47:180:47:23

is at least partly related to the San Andreas Fault.

0:47:230:47:27

Take, for example, the scenery.

0:47:280:47:31

It was the colliding plates

0:47:310:47:33

that forced up mountains along the Californian coast.

0:47:330:47:36

And this dramatic landscape attracts thousands of tourists every year,

0:47:400:47:45

who spend an estimated 2 billion on sightseeing alone.

0:47:450:47:50

Then there's the wine.

0:47:510:47:53

That's partly down to the San Andreas too.

0:47:530:47:55

California is mostly desert

0:47:570:47:59

but when moist air rolls in off the ocean and hits the mountains,

0:47:590:48:03

it rises to form rain that irrigates this otherwise arid landscape.

0:48:030:48:08

It's a microclimate that has made this

0:48:120:48:14

one of the most productive farming regions in America.

0:48:140:48:17

But the ultimate gift of the San Andreas is this.

0:48:210:48:25

HISSING

0:48:280:48:30

Oil.

0:48:350:48:37

Black gold.

0:48:380:48:39

This is an oil seep,

0:48:390:48:42

which is when oil leaks to the surface, like a natural spring.

0:48:420:48:45

HISSING

0:48:470:48:49

Except this is black and gooey.

0:48:490:48:53

Look at that.

0:48:530:48:55

150 years ago, when the first people were looking for oil,

0:48:550:48:58

even the most witless prospector

0:48:580:49:01

realised that places like this were a good place to drill.

0:49:010:49:05

And drill they did.

0:49:070:49:11

Over the years, around 200,000 wells have been sunk here.

0:49:120:49:18

Most people probably think of Texas as America's oil state

0:49:250:49:29

but California was and still is one of the world's biggest oil producers,

0:49:290:49:35

drawing more than 700,000 barrels of crude oil

0:49:350:49:38

out of the ground every day.

0:49:380:49:41

The oil formed millions of years ago, deep inside the Earth.

0:49:480:49:51

But it was the San Andreas Fault which split the rock

0:49:510:49:55

and brought it close enough to the surface to be exploited.

0:49:550:49:59

So it seems that the San Andreas Fault

0:50:040:50:06

has brought California some serious economic benefits.

0:50:060:50:09

Its shaping of the land has created the conditions for oil,

0:50:090:50:13

for agriculture, for wine and even for tourism.

0:50:130:50:17

But how much is that really worth?

0:50:170:50:19

The money men have done the sums.

0:50:240:50:28

They reckon this state earns around 100 billion every year

0:50:280:50:33

because of the San Andreas Fault.

0:50:330:50:35

California's geology is a licence to print money.

0:50:380:50:43

Earthquake geologists like me

0:50:450:50:47

know that California gets struck by a big seismic shake

0:50:470:50:51

every 100 to 150 years.

0:50:510:50:53

And those major quakes are hugely destructive.

0:50:530:50:56

That doesn't seem to dampen the spirits

0:50:560:50:59

of the number-crunchers that are in these skyscrapers.

0:50:590:51:02

It's worked out that in a city like LA,

0:51:020:51:05

a major earthquake will cause up to 250 billion worth of damage.

0:51:050:51:10

Now, that is a huge sum.

0:51:100:51:12

But averaged out over a century, you're still in profit.

0:51:120:51:16

You've got 100 billion a year coming in,

0:51:160:51:19

versus a one-off hit of 250 billion.

0:51:190:51:22

That's a gain of 40 to 1.

0:51:220:51:25

Any economist will tell you that's a pretty decent return.

0:51:250:51:29

10,000 years

0:51:320:51:33

after our ancestors first settled along plate boundaries,

0:51:330:51:37

the benefits of living along a fault line are as potent as ever.

0:51:370:51:41

The point is that in pure economic terms,

0:51:480:51:51

we're still financially better off living along a fault line than not,

0:51:510:51:56

even when it's one of the most active in the world.

0:51:560:51:58

But the problem that I have with that equation

0:51:580:52:01

is that life's not just about money.

0:52:010:52:05

Istanbul, the only city in the world to straddle Asia and Europe.

0:52:130:52:21

This location at the crossroads of two continents

0:52:210:52:24

has made it a trading hub for centuries.

0:52:240:52:28

That's why I find it so exciting.

0:52:300:52:32

It's a vibrant, bustling, cosmopolitan place.

0:52:320:52:35

But Istanbul's location also brings with it great danger.

0:52:400:52:46

Nearby lies the North Anatolian Fault,

0:52:520:52:55

one of the most seismically active plate boundaries on the planet.

0:52:550:52:59

Scientists reckon a major earthquake is due here any time.

0:52:590:53:05

There's little doubt that in the very near future,

0:53:090:53:12

Istanbul will be struck by a big earthquake.

0:53:120:53:15

It's a strange feeling

0:53:150:53:17

that this city that I love could be destroyed in my lifetime.

0:53:170:53:22

But it doesn't have to be.

0:53:240:53:26

Here, they're starting to rewrite the terms

0:53:290:53:33

of our ancient bargain with fault lines.

0:53:330:53:36

The aim is to enjoy the benefits of living along this plate boundary

0:53:360:53:40

without having to pay a price in human life.

0:53:400:53:43

Below the waters of the Bosphorus,

0:53:460:53:49

the channel that separates Europe from Asia,

0:53:490:53:51

is a clue to the solution.

0:53:510:53:53

You know, this is such an eerie feeling.

0:54:090:54:12

I'm 35m below the level of the Bosphorus

0:54:120:54:14

and I'm walking parallel

0:54:140:54:16

to one of the most active earthquake zones in the world.

0:54:160:54:19

So not the kind of place you expect to find a major engineering project,

0:54:190:54:23

and yet that's exactly where

0:54:230:54:24

the Turkish authorities decided to build an underground train line.

0:54:240:54:29

This tunnel, which will one day link Asia to Europe,

0:54:310:54:35

is the deepest tunnel of its kind on Earth

0:54:350:54:37

and yet it runs alongside

0:54:370:54:39

one of the most dangerous earthquake faults in the world.

0:54:390:54:43

These engineers are confident they've got the risks covered.

0:54:480:54:52

Through some technical wizardry,

0:54:520:54:54

the whole tunnel's designed to absorb the vibrations

0:54:540:54:56

of even the largest of earthquakes.

0:54:560:54:58

What these guys are doing, effectively,

0:54:580:55:01

is confronting the earthquake threat head-on.

0:55:010:55:03

This technology won't allow us to stop earthquakes,

0:55:060:55:09

but it shows

0:55:090:55:11

that if we really want to protect against their consequences, we can.

0:55:110:55:15

Unfortunately, in Istanbul, this tunnel is only half the story.

0:55:150:55:22

You know, high-tech underground train tunnels are all very well,

0:55:240:55:27

but the reality is that most people who'll die in the next earthquake

0:55:270:55:31

will die because the buildings that they live and work in collapse.

0:55:310:55:35

And in that sense, Istanbul is completely unprepared.

0:55:350:55:39

It's reckoned that when the next earthquake comes,

0:55:390:55:42

it might bring down a quarter of the city.

0:55:420:55:45

And the thing is, it doesn't have to be like that,

0:55:450:55:47

because we have the technical know-how to keep buildings standing.

0:55:470:55:52

The irony is Istanbul already has a building

0:55:530:55:57

that has survived earthquakes for centuries.

0:55:570:56:00

This magnificent building is the Hagia Sophia.

0:56:090:56:13

It's got to be my favourite place in the city.

0:56:130:56:15

For the tourists that come here,

0:56:150:56:18

this is a fitting symbol of Istanbul's reputation

0:56:180:56:21

as a crossroads of different civilisations.

0:56:210:56:24

In its 1,500-year history, it's been a church and a mosque

0:56:240:56:28

and now a museum.

0:56:280:56:30

The Hagia Sophia has stood through more than a dozen earthquakes,

0:56:320:56:37

without the benefit of modern technology.

0:56:370:56:39

It was built on such a massive, monumental scale

0:56:390:56:43

that even the biggest earthquakes never managed to knock it down.

0:56:430:56:48

You know, it's no accident that when the earthquake does strike,

0:56:580:57:01

the two things that'll probably survive

0:57:010:57:04

are one of the oldest buildings in the city and one of the newest.

0:57:040:57:08

And that's because they're both structures

0:57:080:57:11

that we've decided are worthy of looking after.

0:57:110:57:14

Today, we have the technology to protect every building -

0:57:170:57:21

whether it's flats, factories or offices...

0:57:210:57:25

..if we choose to.

0:57:260:57:28

For 10,000 years,

0:57:330:57:36

we've lived with the benefits and the dangers of fault lines.

0:57:360:57:39

You know, it's clear that people

0:57:470:57:50

are going to continue to live along fault lines -

0:57:500:57:53

probably for the next 10,000 years.

0:57:530:57:55

But now we have two clear options -

0:57:550:57:58

stick with the old regime and take our chances

0:57:580:58:01

or embrace the new and take some kind of control.

0:58:010:58:06

The trouble is, protection doesn't come cheap.

0:58:060:58:10

Reinforcing every building in an earthquake zone would be massively expensive.

0:58:100:58:16

So even with all our knowledge,

0:58:160:58:19

the deep Earth is going to continue to confront us with some tough choices

0:58:190:58:23

for years to come.

0:58:230:58:26

Next time - the magic of water.

0:58:290:58:33

It's constantly transforming itself,

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shifting between guises and from place to place.

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Our struggle to control it has shaped the destiny of some of the greatest civilisations in history.

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E-mail [email protected]

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