Decoding Disaster A Timewatch Guide


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Decoding Disaster

Professor Danielle George uses five decades of BBC archive to find out how well disaster documentaries keep pace with scientific theories that advance every day.


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Natural disasters unleash forces

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that are, literally, earth-shattering.

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Whether it be an earthquake, a volcanic eruption, a tidal wave,

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each is terrifying.

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but fascinating too.

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Hollywood disaster movies make for a thrilling spectacle,

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but what about disaster documentaries?

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Surely we look to them to provide answers, not just entertainment.

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But to do that, programmes need to keep pace

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with science that advances every day.

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So, I've searched the archives

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of the ground-breaking history series Timewatch

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and 60 years of BBC documentaries,

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to see how film-makers have dealt with disaster,

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providing an extraordinary insight

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into one of the fastest-moving branches of knowledge.

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I'll see how rival theories keep emerging

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on the destruction of ancient Atlantis...

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It's normal, as a scientist that you guess, essentially,

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what might have happened, say, in Atlantis,

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based on the evidence at the time.

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..how there's still much to learn

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about history's most famous volcanic eruption at Pompeii...

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Science, if it's healthy, is a constant state of doubt.

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..how film-makers explore theories

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that sometimes sound barely believable.

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Was this killer wave of 400 years ago a British tsunami?

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These films do show that historians and scientists have made

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incredible advances in the study of historical disasters.

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Best of all, we can share that thrill of discovery

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and a new understanding of some of history's greatest calamities.

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As an engineer, I'm fascinated to discover how things work.

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But, as I've studied the film archive on disasters,

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I've realised we're still learning how the Earth itself works.

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The experts in this field keep turning up

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fresh evidence and new theories.

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What they thought was true just a few years ago

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may no longer seem certain today.

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But there's still something in me

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that wants to ask what actually happened to cause such and such?

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Was it X or was it Y? Surely somebody knows.

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For me, searching the film archive offers

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a unique opportunity to see how theories develop over time.

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I know that definite answers will be hard to find.

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For instance, this beach I'm on in south Wales was hit

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by a giant wave 400 years ago, causing huge loss of life.

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Some researchers say it was a massive storm surge.

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Much more controversially, others believe it was a tsunami,

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caused by an earthquake out at sea.

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I'll come back to that later,

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but it's just one example of how researchers,

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and the film-makers who document their work,

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are forever seeking new explanations

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for some of the greatest calamities to ever strike our planet.

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Since the dawn of time,

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we humans have been trying to understand how the Earth works.

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Specifically, the earthquakes and volcanic eruptions

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which can wipe out whole cities in moments -

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events so cataclysmic, they're still often simply called acts of God.

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Before we consider the disasters themselves,

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we need to look at the science behind them.

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The realisation that the Earth has a constantly moving crust

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is really very recent

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and it's completely changed our understanding of disasters.

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This has only really been an accepted theory

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since as late as the 1960s.

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Earthquake science is really quite novel and quite new

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and the last 30 years or so have shown incredible developments.

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And so, when this film appeared 45 years ago,

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it was proclaiming nothing less than a revolution.

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Nearly all earthquakes occur at the boundaries

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between the great plates of the Earth's outer shell.

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In the Middle East and the Mediterranean,

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the home of many ancient civilisations,

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there's an extraordinary jumble of large and small plates.

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Dan McKenzie of Cambridge University

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is one of the young revolutionaries of the Earth sciences.

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He played a pioneering part in first telling

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how the first great plates move as rigid units about the globe.

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Most of the worst earthquakes in the Mediterranean occur

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because Greece and Turkey are moving really quite rapidly westwards,

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at about 5cm a year.

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This means they've moved about 100 yards since the time of Socrates.

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This pair of scissors and a bobbin show what's happening.

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The bottom of the scissors is Africa and the top is Europe.

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Bobbin is Turkey.

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As Africa comes towards Europe, Turkey is squeezed out of the way.

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In this village, three-quarters of the population perished.

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An earthquake struck at 2.15 in the afternoon of 31st August, 1968.

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It killed 10,000 villagers and some of the bodies were never found.

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When the heavily-built roof of this communal wash house

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fell on them, 28 women died.

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The energy let loose in this earthquake was equivalent

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to an H-bomb of several megatons.

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The film shows how this new theory,

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that pieces of the Earth's crust collide

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and grind against each other,

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allowed scientists to understand even very recent disasters

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in a completely new way.

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Right across the world, in California,

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the San Fernando earthquake of 1971 awoke old faults

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that hadn't moved for thousands of years.

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It killed more than 60 people and gave warning

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of what more severe earthquakes might do to Californian cities.

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Earthquakes are part of a systematic remodelling of the Earth.

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That's the doctrine of a new generation of Earth scientists,

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like Tanya Atwater.

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She worked out how movements of the ocean floor have affected the land

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and so explain afresh much of the scenery of the western USA.

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When I was in school, I was taught that the Earth makes its mountains

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by a complicated sort of sinking and bobbing action,

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first down and then up again.

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That doesn't seem to be the case at all.

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Most mountains seem to be made

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by one piece of the Earth's outer crust

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pushing sideways against another.

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This is some of the damage from the recent San Fernando earthquake.

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The buckling here is just the latest step

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in the buckling of the Earth that made the mountains behind.

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Here, great plates are grinding.

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The coastal strip of California is edging

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past the rest of North America.

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This is three feet of mountain that was thrown up

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in the recent earthquake, just like the sidewalk was.

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It doesn't look like much, but you have to think about this happening

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over and over again, maybe once a century for thousands of centuries.

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If you look at the documentaries in the early '70s,

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they were still explaining plate tectonics to the audience.

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Now, if you look at more recent documentaries,

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plate tectonics is very broadly understood by the viewing public,

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I think, so they're starting from a different point.

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Once you know how recently the nature of the Earth's crust

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was still a mystery, it's easier to understand

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how theories are still being revised and refined.

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I'm going to look first at how this rapidly developing knowledge

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actually posed problems for film-makers.

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I've been looking at a series of films tackling the same subject,

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with each of them drawing a different conclusion.

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One of the most enduring, most romantic mysteries of all

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is the search for the fabled island of Atlantis.

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Historians have argued whether the story of a lost civilisation,

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first told by the Greek philosopher Plato, around 350 BC,

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has a basis in fact, or whether it's merely a legend.

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Finally, in 1972,

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archaeologists discovered startling new evidence

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that Atlantis may have truly existed

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but was wiped out in a natural disaster.

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This is how Plato had described it.

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"In this island of Atlantis,

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"there was the fairest and noblest race of men that ever lived.

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"But they fell from grace

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"and were punished by the Earth shaker Poseidon.

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"And afterwards, there occurred violent earthquakes

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"and floods and, in one terrible day and night,

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"the island of Atlantis disappeared in the depths of the sea."

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The new evidence suggested

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that the disaster struck in the eastern Mediterranean

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on an island now crowded with tourists ever year,

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but which, in 1972, was a sleepy backwater -

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Santorini, sometimes known as Thera.

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A land of grapes and wine,

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one of the most enchanting of all the Greek islands of the Aegean,

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a picturesque, idyllic island on the surface but, underneath,

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there lurks a threat of terrible natural violence.

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For Santorini is an area of alarming geological instability.

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These cliffs are the walls of a caldera,

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a vast crater that formed when the erupting volcano collapsed,

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leaving a gaping hole to be filled by the sea.

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It was a Greek philosopher, Plato,

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who first wrote of the legend in the fourth century BC.

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It told of an ancient island civilisation.

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They became greedy and were punished by the gods

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and their land sank beneath the sea.

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What the archaeologists had just discovered was an entire city

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buried beneath tonnes of volcanic ash.

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And, remarkably, it seemed to match Plato's description

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of a wealthy, civilised society,

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with a taste for artistic expression.

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Perhaps the most exciting discoveries are the frescos,

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and we arrived at the site

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just as completely new wall painting was being uncovered.

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Skin divers and fishermen at work. One goes down with a hook.

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One might be collecting sponges.

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And, as the divers pick their way through the coral on the seabed,

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on the surface, a convoy of ships is on the move,

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led by a 50-oared galley.

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What's more, the eruption on Santorini also appeared

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to neatly solve another long-standing historical mystery.

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Experts already knew that, at almost the same time,

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sudden disaster had overcome the island of Crete,

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60 miles to the south.

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The wealthy and highly developed civilisation there,

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the Minoan kingdom, disappeared almost overnight,

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and for no obvious reason.

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But, armed with their new knowledge of the Earth sciences,

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archaeologists imagined that the volcano on Santorini

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had sent out a tidal wave big enough

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to cause wholesale destruction on Crete.

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Tidal waves of appalling violence, perhaps some 600 feet high,

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came raging in over the exposed northern coasts of Crete.

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Buildings had been dragged to the ground, as the waves receded.

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These waves had been created

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by the collapse of the volcano in Santorini,

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some 60 miles away to the north.

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This was a ground-breaking piece of historical detective work.

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Atlantis had been found and the mystery of the Minoans solved.

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Case closed.

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But in less than ten years, new evidence emerged,

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forcing the very same team of film-makers

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to backtrack on the tsunami theory.

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On islands much closer than Crete, especially the island of Melos,

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archaeologists found no evidence of a giant tidal wave.

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We saw no evidence at all

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of these great waves, tidal waves, tsunamis,

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whatever you want to call them, in Melos.

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If there were great tsunamis which were rushing across the ocean

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and going to flatten the palaces of Crete,

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we would have expected to find traces of that also in Melos.

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I have the feeling, therefore,

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that it wasn't as disastrous in the Aegean,

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as a whole, as is sometimes thought.

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But, if it wasn't a tsunami,

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what then caused the destruction of the Minoan civilisation on Crete?

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The film shows how archaeologists revisited all the clues,

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just like detectives reopening an old case.

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In particular, they looked again

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at the wall paintings they'd uncovered

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and now, built a theory that the Minoans were wiped out

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by invaders from the Greek mainland.

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It's a fascinating insight into the way that archaeologists

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necessarily use one piece of a jigsaw to imagine the whole picture.

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With the tidal wave theory crushed,

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the chief archaeologist on Santorini had to come up with a new narrative

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to explain those wall paintings of people in the sea.

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He first interpreted the figures in the water

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as underwater fishermen or sponge divers

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but later, he recognised them to be dead bodies,

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sinking to the bottom of the sea,

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casualties of some kind of naval engagement

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that seems to be taking place on the surface above them.

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The figures in the water may yet turn out to be

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evidence in favour of the invasion thesis.

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In the space of less than ten years, one important theory had emerged,

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been shot down and then replaced by another.

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It's very easy to look back and say they got it all wrong,

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but isn't this experimental approach

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what archaeology, science too, is all about -

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providing new answers to old questions

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with evidence that's constantly emerging?

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Science, if it's healthy, is a constant state of doubt.

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There are phrases like, "Scientists believe that..." -

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a phrase I hate because it doesn't represent

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this constant disagreement that has to go on in science or else it dies.

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And, of course, that wasn't the end of it.

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Discovering Atlantis is pretty much the Holy Grail

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for archaeologists and a perennial subject for TV documentaries.

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In 2002, film-makers once again reported that it HAD been found.

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But in a different part of Greece altogether.

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A separate team of archaeologists, digging on the Greek mainland,

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declared they'd found Atlantis...

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..and that it had been destroyed by a quite different natural disaster.

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This is the coast of Greece on the Corinthian Gulf,

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150km west of Athens.

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It is one of the most active earthquake regions in the world.

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According to old Roman texts,

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there was once a great Ancient Greek city here, called Helike.

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2,500 years ago, Helike was a thriving metropolis.

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Over 5,000 people lived and worked within its walls

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and pilgrims thronged to its temple of Poseidon.

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But on one cold winter's night, in 373 BC,

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the god of earthquakes and the sea turned on his own people.

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The ancient sources said the earthquake struck at night

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when most people were caught in their houses.

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A massive tidal wave or tsunami or sea wave came in...

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..and swept away all survivors.

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Helike and all of its people were swept to the bottom of the sea,

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never to be seen again.

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Just a few short years after the disaster,

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the Greek writer Plato created the story of Atlantis.

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The archaeologists had been toiling here for 15 years,

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uncovering pottery and other artefacts,

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when they came upon structures

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which seemed to show signs of damage by tidal wave.

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Finally, in the walls below them,

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was possible evidence of the disaster itself.

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There were signs some huge force had struck the building.

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This wall has been knocked down toward the sea.

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That has the kind of pattern that you see when you have the backwash

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from the enormous wave going back to the sea...

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..and knocking them down in the direction of the sea.

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So, it seems that, after 15 long years of searching,

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their team may have succeeded

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where so many other archaeologists have failed.

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They believe these walls are just the first glimpses

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of the buildings that must lie in the ground around them.

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Beyond them, towards the hills, should lie the rest of the city,

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waiting to be uncovered.

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Now it seems the city whose destruction inspired

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the legend of Atlantis may finally have been found.

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So, was that the end of the quest for Atlantis?

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It's a mystery that just won't die.

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When Timewatch joined the search for Atlantis a decade later,

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the pendulum had swung right back to where it was in 1972.

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Historian Bettany Hughes went hunting for fresh evidence,

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homing in, once again, on the island of Santorini.

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Atlantis hunting is a fraught exercise

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but, precisely because it has generated so many wild theories,

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there's even more reason to try to sift the fact from the fiction.

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Fresh scientific evidence buttresses the idea that Plato's story

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was inspired by a real island and a real ancient civilisation

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that was destroyed by a real natural disaster...

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..an eruption on a scale the ancient world had never experienced before.

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This was an eruption that shook much of the planet.

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Ash was transported as far north as the Black Sea,

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as far east as central Turkey and as far south as the Nile Delta.

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Global temperatures dipped, stunting plant growth, even in Ireland.

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The early documentaries show a completely different picture

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from the modern ones, due to this advancement of science.

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New technologies, like satellite imagery, that we can now study,

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that give us a better global picture of what's happening,

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GPS, which records the relative movements on two sides of a fault

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before, during, after an earthquake.

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All of this instrumentation is providing us new data

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with which to study these natural events.

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For these film-makers, Santorini also seemed to fit perfectly

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with the description which Plato had provided.

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The first thing that strikes you is its really odd topography.

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The land just juts straight out of the sea

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and then you get these small islands, ringed by water,

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which are then, in turn, cradled

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by that massive semicircle of land up there.

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Now, just listen to what Plato has to say about his Atlantis.

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"There were circular belts of sea and land enclosing one another,

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"some greater, some smaller."

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Of course, that, in itself, doesn't prove anything.

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There could be loads of locations all round the world

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that match this description.

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But, nonetheless, this account

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and that landscape are really remarkably similar.

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Bettany's team had revived the 1972 theory

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that a massive tsunami had swept south from Santorini,

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smashing into the island of Crete.

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Evidence of the tsunami had now turned up on Crete itself.

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Archaeologist Sandy MacGillivray and tsunami expert, Costas Synolakis,

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are investigating the scale of the tsunamis

0:23:300:23:33

by mapping pumice on Crete's northern coastline.

0:23:330:23:37

Here's some. Here's a piece there.

0:23:370:23:40

That's so light, isn't it? Mm-hmm.

0:23:410:23:44

Cos it must have floated here, so... It's exactly what we like.

0:23:440:23:48

I mean, flotsam that comes out gives us an idea

0:23:480:23:51

of how high the wave reached.

0:23:510:23:54

So, the tsunami would have carried this up here to this headland.

0:23:540:23:57

At least to this point.

0:23:570:23:58

It could have carried it further up

0:23:580:24:00

and then it could have washed downriver

0:24:000:24:02

with the rain, with floods.

0:24:020:24:04

But this gives us, helps us bracket the size of the wave right offshore.

0:24:040:24:08

Costas has developed a computer simulation

0:24:100:24:13

of how the tsunamis would have travelled.

0:24:130:24:16

This is the initial wave.

0:24:160:24:18

We follow it all the way to Crete.

0:24:200:24:22

The first wave causes the shoreline to retreat, to move offshore.

0:24:220:24:26

We are less than an hour from the eruption

0:24:260:24:28

and the red on the south side of Crete

0:24:280:24:31

and the eastern Peloponnese are experiencing the big wave.

0:24:310:24:36

What do you think, Sandy, that says about what happened to Crete,

0:24:360:24:39

because most people live along the coast, don't they? I think so.

0:24:390:24:43

There was the city of Knossos which is inland

0:24:430:24:45

but, otherwise it's very much open coastline

0:24:450:24:48

and so, the death toll would have been staggering.

0:24:480:24:52

The hard evidence shows us

0:24:540:24:56

that here, there was a sophisticated trading civilisation

0:24:560:25:00

that flourished and was then swallowed by the sea,

0:25:000:25:04

ravaged by a disaster of legendary proportions.

0:25:040:25:08

Surely this is the root of Plato's Atlantis legend?

0:25:100:25:15

So, it's clear that theories come and go.

0:25:210:25:24

I suspect that's not the last we've heard of Atlantis.

0:25:240:25:27

Certainly, for the moment at least,

0:25:300:25:32

the evidence seems to favour Santorini

0:25:320:25:35

as the true location for Plato's Atlantis.

0:25:350:25:38

And it's brought home to me,

0:25:390:25:41

just how new much of the underlying science really is.

0:25:410:25:46

Tsunamis, in particular, are very poorly understood.

0:25:460:25:49

I don't think a lot of people realise

0:25:510:25:53

but, until the Indian Ocean tsunami, in 2004,

0:25:530:25:56

we didn't even know what a tsunami wave looked like.

0:25:560:25:58

It was only due to the complete chance of there being a vessel,

0:25:580:26:02

measuring the depth of water offshore of Thailand

0:26:020:26:04

when the tsunami passed under it, that we actually have a trace

0:26:040:26:08

of what a tsunami wave looks like, and that's 2004.

0:26:080:26:13

I'm going to look now at how film-makers have tried to keep pace

0:26:150:26:19

with another branch of the Earth sciences.

0:26:190:26:22

Just as with tsunamis, our understanding of volcanoes

0:26:230:26:27

has massively increased in the last 40 years.

0:26:270:26:30

In 1972, film-makers explored

0:26:320:26:35

some of the brand-new discoveries in volcanology.

0:26:350:26:38

EXPLOSION

0:26:410:26:44

A volcano in eruption is undoubtedly the finest pyrotechnic display

0:26:440:26:48

that man can ever see.

0:26:480:26:51

These falls are twice the height of Niagara.

0:26:520:26:54

And the fire fountain rises to almost 1,000 feet.

0:26:560:26:59

Volcanoes can be docile or violent.

0:27:010:27:03

In fact, volcanoes can vary enormously.

0:27:040:27:07

Some lava flows like water, some is thicker than treacle.

0:27:070:27:11

Volcanoes may have a far greater effect on the formation of the globe

0:27:160:27:19

than the volcanologists at first suspected.

0:27:190:27:22

Starting at the South Pacific,

0:27:220:27:23

volcanoes spread right through Indonesia

0:27:230:27:25

and up the island chain to Japan, Siberia and Alaska,

0:27:250:27:29

down the west coast of America, with a loop round the Caribbean,

0:27:290:27:32

though Mexico, Peru and Chile.

0:27:320:27:35

It's not a random distribution. There are patterns.

0:27:350:27:39

The structure of the Earth's crust is a series of rigid plates.

0:27:400:27:43

Volcanoes help determine the plate boundaries.

0:27:430:27:46

The film advances the then novel theory

0:27:510:27:54

that all the land we now live on

0:27:540:27:56

was at one time spewed from the mouth of an erupting volcano.

0:27:560:28:00

The best information which we have available at the present time

0:28:030:28:06

suggests that all the world's volcanoes, between them,

0:28:060:28:10

are currently producing about three cubic kilometres

0:28:100:28:13

of new material per year.

0:28:130:28:15

At this rate, sustained through the course of geological time,

0:28:160:28:20

the Earth's volcanoes would be capable of building up

0:28:200:28:22

the whole of the continental crust.

0:28:220:28:25

I think it's possible that the continental crust is, indeed,

0:28:250:28:29

due to four and a half thousand million years of volcanism.

0:28:290:28:32

This new understanding of volcanoes helped historians

0:28:360:28:39

to better explain huge historic disasters,

0:28:390:28:42

in particular the incredible story of Pompeii.

0:28:420:28:47

This city in southern Italy, along with its neighbouring Herculaneum,

0:28:490:28:53

was destroyed by a vast eruption of Mount Vesuvius in the year 79 AD.

0:28:530:28:59

EXPLOSIONS

0:29:040:29:08

The way that Pompeii citizens, who perished in the disaster,

0:29:080:29:12

seem frozen in time has captured our imaginations.

0:29:120:29:16

Their body outlines, preserved in the ashes,

0:29:160:29:20

give a real sense of their final moments.

0:29:200:29:23

More than 50 years ago, in 1966,

0:29:270:29:30

presenter Robert Erskine introduced

0:29:300:29:33

this remarkable story to the TV audience.

0:29:330:29:37

Thousands of the townsfolk died, poisonous by the sulphurous fumes,

0:29:390:29:43

in the basements of the houses and in the streets,

0:29:430:29:45

because they couldn't make up their minds what to do.

0:29:450:29:48

At the first cataclysmic explosion,

0:29:480:29:51

the mountain split, split open,

0:29:510:29:54

and it spewed its hideous innards all the way down this gulley,

0:29:540:29:58

straight towards the town.

0:29:580:30:00

Well, the inhabitants took one look and ran.

0:30:010:30:06

Down these very streets, they fled in terror,

0:30:060:30:09

away from the mountain, leaving everything behind them,

0:30:090:30:12

doors and houses open, the wine bars precipitantly deserted,

0:30:120:30:16

everything left where it was dropped in the terror of the moment.

0:30:160:30:19

A blind panic flight, it must have been.

0:30:190:30:21

By the early '70s,

0:30:270:30:29

our new understanding of Earth science would deepen this knowledge.

0:30:290:30:32

So, by 1974, film-makers could give

0:30:340:30:38

a much more detailed account of the disaster.

0:30:380:30:40

On Mount Vesuvius, broad sheets of fire

0:30:420:30:44

and leaping flames blazed at several points.

0:30:440:30:47

Ashes were already falling.

0:30:480:30:51

The buildings were now shaking with violent shocks.

0:30:510:30:53

Outside, on the other hand,

0:30:530:30:55

there was the danger of falling pumice stones.

0:30:550:30:58

We now know what actually happened.

0:31:010:31:04

A violent blast of gas shot a huge cloud of ash and pumice

0:31:040:31:07

miles into the air.

0:31:070:31:09

Down fell a rain of lapilli, pieces of pumice,

0:31:090:31:11

which buried the city to a depth of about ten feet.

0:31:110:31:14

Some people fled, but many who sheltered in the houses

0:31:140:31:18

were killed by buildings crumbling under the weight.

0:31:180:31:20

Others were trapped and died.

0:31:200:31:22

Survivors emerged into the open.

0:31:250:31:27

It was then that a hurricane of scorching ash

0:31:270:31:31

swept down the mountain.

0:31:310:31:32

Those in flight, their lungs seared by the red-hot lava particles,

0:31:350:31:38

collapsed in their tracks.

0:31:380:31:40

About 2,000 bodies have been found so far, one-tenth of the population.

0:31:400:31:46

The last minor eruption of Vesuvius was in 1944.

0:31:480:31:52

For 30 years, the volcano has been silent, dangerously silent.

0:31:520:31:58

But for how long?

0:31:580:32:00

Vesuvius today looks like a volcano.

0:32:070:32:09

Although you can climb to the top, no-one can be in much doubt

0:32:110:32:14

of the explosive forces not very far below the surface.

0:32:140:32:17

Vesuvius is a particularly dangerous volcano, capable of great violence.

0:32:190:32:25

Always the cities of the Bay of Naples must live in fear.

0:32:250:32:29

No-one can be sure when the mountain will split apart again.

0:32:290:32:33

And the learning process still continues,

0:32:370:32:40

fed by archaeology on one hand, volcanology on the other.

0:32:400:32:45

We have a particular volcanic eruption - Vesuvius, AD 79.

0:32:450:32:50

Our understanding of that is developing in two ways.

0:32:500:32:55

Firstly, more excavations are being done around Vesuvius.

0:32:550:32:59

But the other way is that we experience

0:32:590:33:03

other eruptions of similar types.

0:33:030:33:06

Therefore, you realise you can use the geophysical data,

0:33:080:33:12

the observational data, and so on,

0:33:120:33:15

of these different eruptions to understand AD 79.

0:33:150:33:20

It's clear how our understanding has increased

0:33:230:33:25

when you look at a much more recent film,

0:33:250:33:28

which adopted a rigorously forensic approach to the disaster.

0:33:280:33:32

In the early 1980s, a remarkable discovery was made

0:33:330:33:36

at Herculaneum, which lies only 7km from Vesuvius, closer than Pompeii.

0:33:360:33:42

300 skeletons were discovered, all victims of the volcanic eruption.

0:33:430:33:48

But, to work out exactly what killed them, scientists needed to study

0:33:510:33:55

another eruption that happened almost 2,000 years later.

0:33:550:33:59

The results appeared in a film, presented by Roman history scholar

0:34:010:34:05

and one-time Apprentice panellist Margaret Mountford.

0:34:050:34:09

What force was hot enough to reduce these poor people

0:34:130:34:16

to a pile of scorched bones?

0:34:160:34:18

We need to look at a volcano that erupted in North America

0:34:210:34:23

in the 1980s.

0:34:230:34:25

Mount St Helens National Park has

0:34:310:34:33

some of the most breathtaking scenery in the USA.

0:34:330:34:36

But on Sunday, May 18th, 1980, this peaceful world was transformed

0:34:380:34:44

when the Mount St Helens volcano erupted.

0:34:440:34:47

EXPLOSIONS

0:34:500:34:54

Volcanologists had seen eruptions before,

0:34:580:35:01

but this was the first time

0:35:010:35:03

they had managed to capture on film a little-known phenomenon.

0:35:030:35:06

The whole north face of Mount St Helens collapses.

0:35:080:35:12

As it does, it releases a searing-hot avalanche

0:35:150:35:18

of gas and dust that explodes down the sides of the mountain.

0:35:180:35:22

This is called a pyroclastic current.

0:35:240:35:27

The turbulent wave of gas measured 700 degrees Celsius

0:35:290:35:33

and travelled at nearly 500km an hour.

0:35:330:35:37

Can you explain what a pyroclastic current is?

0:35:380:35:42

A pyroclastic current is an avalanche

0:35:420:35:45

of searing-hot gas, ash and rock

0:35:450:35:48

that travels down the slopes of a volcano

0:35:480:35:50

at hundreds of kilometres an hour.

0:35:500:35:53

It's impossible to outrun and absolutely deadly.

0:35:530:35:56

When I think of an eruption, I think of streams of lava

0:35:560:35:59

coming down a mountain.

0:35:590:36:01

Well, the style of eruption - whether a volcano will erupt lava

0:36:010:36:05

or if it will erupt explosively -

0:36:050:36:08

is primarily a function of how much gas is in the magma.

0:36:080:36:12

If there is no gas in the magma,

0:36:120:36:14

then the magma will erupt as a lava flow or a lava dome.

0:36:140:36:18

And that is the actual magma,

0:36:180:36:19

the liquefied rock that's coming out as lava. Exactly.

0:36:190:36:23

And, in an explosive eruption,

0:36:230:36:24

the difference is the magma has gas bubbles

0:36:240:36:27

and as the gas in the magma makes its way to the surface,

0:36:270:36:31

the gas bubbles get bigger and bigger and bigger,

0:36:310:36:33

to the point where, when the volcano erupts,

0:36:330:36:36

the gases expand very quickly

0:36:360:36:38

and it rips the magma apart into very tiny pieces,

0:36:380:36:41

which are your ash and your pumice.

0:36:410:36:43

From what scientists witnessed at Mount St Helens,

0:36:450:36:48

and data gathered from other volcanic eruptions,

0:36:480:36:51

it's now possible to piece together

0:36:510:36:53

exactly what happened when Vesuvius erupted.

0:36:530:36:56

EXPLOSION

0:36:570:37:00

12 hours after the initial eruption,

0:37:000:37:03

the column above Vesuvius stretched nearly 32km high.

0:37:030:37:07

But under its own weight, it collapsed.

0:37:090:37:12

A pyroclastic current surged down the sides of the volcano

0:37:150:37:18

at speeds up 300km an hour.

0:37:180:37:21

Temperatures inside the explosive blast were over 500 degrees Celsius.

0:37:280:37:32

The wave of searing-hot gas and ash took less than five minutes

0:37:380:37:42

to strike Herculaneum 7km away.

0:37:420:37:46

The intense heat surge killed them instantly.

0:37:580:38:01

It vaporised their flesh.

0:38:050:38:08

And that is why all that remained

0:38:160:38:18

were blackened skeletons and cracked skulls.

0:38:180:38:22

This new insight into volcanoes gives historians a toolkit

0:38:260:38:31

with which to investigate previously unexplained events from the past.

0:38:310:38:36

We get new data all the time.

0:38:380:38:41

We didn't have a concept of the pyroclastic flow

0:38:410:38:44

and what pyroclastic flows did to people.

0:38:440:38:47

So, this constant drawing of information from other areas,

0:38:470:38:50

and comparisons and analogies,

0:38:500:38:52

means that the science is changing all the time.

0:38:520:38:55

The depth of knowledge which now exists

0:38:560:38:59

about the Vesuvius eruption shows

0:38:590:39:01

that with historians, scientists and film-makers working together,

0:39:010:39:06

it is possible to take an old mystery

0:39:060:39:09

and supply a definitive answer.

0:39:090:39:11

Bur my trawl through the film archive shows there are still areas

0:39:120:39:16

where that's not at all true.

0:39:160:39:18

One of the deadliest disasters ever to strike the planet

0:39:180:39:22

still has no known cause.

0:39:220:39:24

Or at least no cause which experts can agree on.

0:39:250:39:29

It was an epidemic which killed tens of millions of people

0:39:310:39:35

and could, some experts fear, reappear today.

0:39:350:39:39

650 years ago, the so-called Black Death

0:39:400:39:43

is thought to have wiped out

0:39:430:39:45

something close to a third of Europe's population.

0:39:450:39:48

But, as Timewatch reported in 1984,

0:39:490:39:53

the epidemic raises maybe the biggest question in medical history.

0:39:530:39:58

The cause of that holocaust, historians believe, was plague -

0:40:000:40:03

more specifically, bubonic and pneumonic plague.

0:40:030:40:07

New biological research, however, is coming to a different conclusion.

0:40:070:40:11

The time-honoured theory was that bubonic plague had been spread

0:40:150:40:18

by black rats.

0:40:180:40:20

The fleas that live on the rats, but also feed on humans,

0:40:210:40:25

were thought to be the way the disease was transmitted.

0:40:250:40:28

But did this theory add up, in the light of new evidence?

0:40:280:40:32

The Black Death first arrived in Britain on the Dorset coast.

0:40:350:40:39

By the end of 1348, it had most of southern England in its grip.

0:40:400:40:44

Six months later, it had spread through Wales,

0:40:440:40:47

the Midlands and East Anglia.

0:40:470:40:49

By the end of 1349, it had reached the Scottish Highlands

0:40:490:40:52

and the North of Ireland.

0:40:520:40:54

It moved across the country at about a mile a day

0:40:540:40:56

or even a little more than that, depending whose account you follow.

0:40:560:41:00

Now, this just doesn't fit in with what we know of plague today.

0:41:000:41:03

The winter of 1348 to '49 was unusually cold.

0:41:030:41:08

But bubonic plague does not appear to thrive in low temperatures.

0:41:080:41:12

The black rat is an animal

0:41:120:41:14

that likes the warmth.

0:41:140:41:15

It comes from India, basically, in that region.

0:41:150:41:18

The flea is very temperature dependent.

0:41:180:41:21

It only breeds when the temperature gets

0:41:230:41:25

between 65 and 85 degrees Fahrenheit and when the humidity is right.

0:41:250:41:30

According to Dr Twigg, there just weren't enough rats and fleas

0:41:330:41:37

to spread bubonic plague across Britain so rapidly

0:41:370:41:40

and with such fearful loss of life.

0:41:400:41:42

But if it wasn't bubonic plague, what was it?

0:41:440:41:47

One disease that fits the bill rather well would be anthrax.

0:41:480:41:51

Unlike bubonic plague, it can spread from person to person.

0:41:530:41:56

It's found, to a great extent,

0:41:560:41:59

in domesticated animals - cattle and sheep.

0:41:590:42:02

But, in a human being, when the spore gets into the body,

0:42:030:42:06

haemorrhages occur.

0:42:060:42:08

The body oozes dark blood from all the bodily orifices.

0:42:090:42:14

The fact that anthrax, rather than bubonic plague,

0:42:170:42:20

might have been the culprit shows, perhaps,

0:42:200:42:22

how little we really know about this huge episode in history...

0:42:220:42:26

..and how difficult it is for film-makers

0:42:280:42:31

to offer a definitive account,

0:42:310:42:34

with research constantly being updated.

0:42:340:42:37

When Timewatch returned to the question in 2004,

0:42:370:42:41

yet another possible candidate

0:42:410:42:43

for the killer disease had entered the frame.

0:42:430:42:45

The biologist is convinced he's found the answer

0:42:470:42:50

to the mystery of the Black Death.

0:42:500:42:52

Historians have spent a lot of time

0:42:520:42:54

interpreting what went on,

0:42:540:42:57

in terms of rats and fleas, which is incorrect

0:42:570:43:01

and I think we need the record straightened out.

0:43:010:43:03

Professor Duncan's analysis is controversial

0:43:050:43:09

but he's willing to speculate on the actual identity of the killer

0:43:090:43:12

which terrorised Europe for over 300 years.

0:43:120:43:16

His guess is based on symptoms

0:43:160:43:18

mentioned in some of the 14th-century accounts.

0:43:180:43:22

"Sudden fever, spitting blood and saliva

0:43:230:43:26

"and no-one who spat blood survived it."

0:43:260:43:29

"Brought on by an affliction of the head of vomiting blood."

0:43:290:43:33

"The accompanying putrefaction of humours

0:43:330:43:37

"caused the victim to cough up blood."

0:43:370:43:40

Could these be medieval descriptions

0:43:430:43:45

of someone dying of internal haemorrhaging?

0:43:450:43:48

From the symptoms, it has got features in common with Ebola.

0:43:500:43:54

Ebola is one of the deadliest diseases on Earth.

0:43:570:44:01

It's caused by a tiny threadlike virus,

0:44:010:44:04

which was first isolated 30 years ago in Africa.

0:44:040:44:07

It causes a wide range of symptoms - fever, coughing up blood

0:44:090:44:14

and, occasionally, lumps under the skin.

0:44:140:44:17

The tragedy that was played out across medieval Europe

0:44:200:44:23

no longer seems to be easily explained

0:44:230:44:25

as an epidemic of bubonic plague, spread by fleas.

0:44:250:44:29

We are in the uneasy position of not knowing the cause

0:44:290:44:32

of the most deadly epidemic ever to strike humanity.

0:44:320:44:36

And until we know, we can't be sure we could stop it happening again.

0:44:370:44:42

So, now two possible new diagnoses.

0:44:490:44:51

One of this country's leading authorities on epidemics

0:44:530:44:56

believes the Black Death could even have been a series of diseases,

0:44:560:45:01

striking around the same time.

0:45:010:45:04

I don't place all that much reliance on anyone, myself included,

0:45:040:45:07

coming up and saying, "This is the answer.

0:45:070:45:10

"It's not the plague bacillus, it's the anthrax bacillus

0:45:100:45:13

"or it's Ebola, or it's this or it's that or it's something else."

0:45:130:45:16

It's bad enough to get things diagnosed today, and I mean today.

0:45:160:45:20

Imagine what it's like 800 years ago.

0:45:200:45:22

I suspect, myself, there were deaths of all kinds of things,

0:45:240:45:27

all kinds of things,

0:45:270:45:29

and it's too easy to throw them all into the bubonic plague pot.

0:45:290:45:33

That's why I'm sceptical about it.

0:45:330:45:35

It would be wrong to be too harsh about these conflicting diagnoses.

0:45:380:45:43

After all, the second opinion is a long-established tradition.

0:45:430:45:47

But it does serve as a warning

0:45:480:45:51

about looking for certainty where it simply may not exist.

0:45:510:45:55

After studying these films, I think one of the reasons

0:45:560:45:59

why disaster documentaries are so fascinating

0:45:590:46:02

is that they make you wonder, "Am I safe? Could it ever happen here?"

0:46:020:46:08

Could a lovely beach like this, Dunraven Bay in south Wales,

0:46:100:46:13

really be the location for a huge natural disaster?

0:46:130:46:17

Timewatch revealed that's not as farfetched as it sounds.

0:46:200:46:24

400 years ago, the entire coastline of the Bristol Channel

0:46:270:46:31

was engulfed by an enormous flood.

0:46:310:46:33

The question is, what caused it?

0:46:350:46:37

On 20th January, 1607, a wall of water up to ten metres high

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rushed over the low-lying sea defences.

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Travelling at 30mph, the killer wave bore down

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on the villages of Somerset and Monmouthshire.

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It came without warning and left 2,000 dead in its wake.

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Yet, for centuries,

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this apocalyptic flood has been forgotten,

0:47:220:47:25

and only now are scientists piecing together the evidence left behind.

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Was it just a huge storm

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or was the killer wave of 1607 in fact a British tsunami?

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It was a very timely question when this film appeared in 2005.

0:47:430:47:48

The terrible Boxing Day tsunami off Indonesia,

0:47:490:47:52

with a quarter of a million people dead,

0:47:520:47:54

was still fresh in everyone's mind.

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The film looks at new research,

0:48:030:48:05

suggesting the flood had many of the characteristics of a tsunami,

0:48:050:48:09

in particular, the way the rocks are laid out on this beach.

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At Dunraven Bay in south Wales,

0:48:170:48:19

hundreds of boulders lie at the foot of the cliffs.

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Some have obviously just dropped off the face,

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but others are less easy to explain.

0:48:250:48:28

This particular boulder, I'm pretty sure,

0:48:280:48:31

has been moved off the beach.

0:48:310:48:33

It's got some fossils in it which you don't normally associate

0:48:330:48:36

with the older limestones

0:48:360:48:38

which you find on the cliffs here.

0:48:380:48:39

So, it looks like this quite big boulder

0:48:390:48:41

has come from over there on the beach.

0:48:410:48:44

The force of water needed to move seven-tonne boulders

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could easily be produced by a tsunami.

0:48:480:48:51

The way the boulders are lying gives Simon another clue.

0:48:510:48:55

That's 270 degrees west.

0:48:560:48:59

Certainly storms can move the odd boulder

0:48:590:49:01

and can fling boulders up onto the top of cliffs

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but, given that we've got so many boulders in a train,

0:49:030:49:06

what we call a boulder train,

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and they're all pointing back in the same direction,

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that suggests to us a constant flow over time.

0:49:110:49:15

It would only have taken a five-metre tsunami wave

0:49:170:49:20

to shift these boulders.

0:49:200:49:21

For a storm to do the same thing, they calculate it would have taken

0:49:210:49:26

a wave at least 20 metres high, over 60 feet.

0:49:260:49:29

Yet the very idea of a tsunami laying waste to the Bristol Channel

0:49:310:49:34

goes against every assumption we have

0:49:340:49:36

about Britain being geologically safe.

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The big surprise is that the seabed off the southwest tip of Ireland

0:49:400:49:45

is the location of an ancient but massive faultline.

0:49:450:49:48

On 8th February, 1980, sensors recorded an earthquake

0:49:500:49:54

from exactly this area, 4.5 on the Richter scale,

0:49:540:49:59

violent enough to give fresh impetus to the tsunami theory.

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I think I've got the dark layer here.

0:50:060:50:09

I really like that style of film-making.

0:50:090:50:12

I think that's quite a change

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from something of the 1970s,

0:50:140:50:15

the way that the evidence is presented.

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Quite thin here. It's coming to about ten centimetres.

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The dilemma scientists actually have themselves about the evidence

0:50:210:50:25

which, of course, has a great deal of uncertainty about it.

0:50:250:50:28

The film-makers are careful to say that much more evidence is needed

0:50:280:50:33

before the theory is widely accepted.

0:50:330:50:35

But the thought of an undersea earthquake zone,

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just a short distance off the British coast,

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is an intriguing hypothesis and a scary one, too.

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The last film I'm going to look at is especially chilling

0:50:490:50:52

because it assembles compelling evidence

0:50:520:50:54

for disaster that's yet to happen.

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This is the story

0:51:050:51:06

of how the greatest natural disaster

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in human history might one day unfold.

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The biggest wave ever seen...

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..threatening death and devastation

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on an unprecedented scale.

0:51:200:51:22

The power of this film lies in the fact

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that it's based on a genuine scientific hypothesis,

0:51:310:51:35

yet it uses all the visual tricks

0:51:350:51:38

of the classic disaster movie.

0:51:380:51:40

The film reports a study of a volcano in the Canary Islands.

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Some scientists fear that an eruption

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would cause the volcano to crumble, producing a huge landslide.

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That, in turn,

0:51:530:51:55

could displace enough water to trigger a mega tsunami.

0:51:550:52:00

The film goes on to imagine the terrible consequences

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if a disaster like that happened for real.

0:52:040:52:07

Travelling at up to 800 millions an hour,

0:52:100:52:13

the giant wave surges out in all directions.

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Immediately in its path,

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the highly populated island of Tenerife.

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Locals and holiday-makers alike

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do all they can to outrun it.

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Within minutes,

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the wave has claimed its first victims.

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I don't think there's any doubt

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that the initial wave will be

0:52:500:52:52

very catastrophic for the islands themselves.

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So you're talking about thousands of people dead

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and destruction on a scale that we've never seen

0:53:000:53:02

in this part of the world before.

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Our mega tsunami's journey of destruction

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has only just begun.

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Over the following hours,

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these waves will devastate the coastlines of Europe.

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The emergency services have just three hours

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before the wave strikes Britain.

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The Environment Agency issues flood warnings

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to the south coast

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and rescue units are put on standby.

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Police clear the streets of southern coastal towns,

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evacuating schools and vulnerable communities.

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A giant tsunami is spreading

0:53:440:53:46

throughout the Atlantic Basin.

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Scientists estimate that the wave is travelling

0:53:470:53:50

at approximately 500mph.

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Just three hours after the first UK warnings,

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a wave up to 25 metres high

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makes its first landfall in Britain...

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..on Cornwall.

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From Cornwall, the wave surges

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through the English Channel,

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engulfing much of Britain's south coast.

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In our scenario, London, our capital,

0:54:330:54:36

tucked in from the North Sea, is safely sheltered.

0:54:360:54:40

Models differ on what the wave might do

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to our southern cities, as it works its way east.

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Towns such as Brighton would suffer serious disruption.

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We can get some idea of the impact

0:54:580:55:01

of a seven to ten-metre wave on the UK south coast,

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by looking at what happened in the Indian Ocean in 2004

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in places like Sri Lanka and Thailand.

0:55:070:55:09

The death toll was in the tens of thousands.

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The population on the south coast of the UK

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is probably quite a bit higher,

0:55:150:55:17

so that sort of wave would be immensely destructive in the UK.

0:55:170:55:21

But the greatest carnage would be inflicted

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on the USA, with east coast cities like New York,

0:55:240:55:27

directly in the path of the tsunami.

0:55:270:55:30

New York, Boston, Washington, Miami.

0:55:300:55:35

Entire cities have been destroyed.

0:55:350:55:38

The number of casualties

0:55:400:55:42

is really hard to get at in something like this.

0:55:420:55:44

For the 25-metre scenario,

0:55:440:55:47

with maybe three to four hours' warning,

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we came up with roughly 4.5 million causalities.

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Around the world, there may be

0:55:550:55:57

one of these enormous events

0:55:570:55:59

maybe once every 20,000 years, maybe only once every 50,000 years.

0:55:590:56:04

We can't say when the collapse is going to occur.

0:56:050:56:08

It seems to already be close to failure.

0:56:090:56:13

So, the crucial question is not a matter of if, but of when.

0:56:150:56:21

EXPLOSION

0:56:210:56:24

If the worst were to happen, then at least WE'D have some warning,

0:56:320:56:37

unlike the people of Pompeii or maybe Atlantis,

0:56:370:56:41

who were suddenly overwhelmed

0:56:410:56:43

by forces they could only ascribe to the angry gods.

0:56:430:56:47

Given that we've only just begun to understand

0:56:500:56:53

what's happening beneath the Earth's surface in the past few decades,

0:56:530:56:56

it's little wonder that they looked for supernatural explanation

0:56:560:57:00

more than 3,000 years ago.

0:57:000:57:02

My trawl through the film archive clearly shows

0:57:030:57:06

that we've learnt a huge amount about natural disasters

0:57:060:57:09

in the last half-century,

0:57:090:57:12

and we've learnt so fast that it's hard for film-makers to keep up.

0:57:120:57:16

It's our scientific responsibility to be very humble

0:57:160:57:19

about the limitations of this knowledge

0:57:190:57:21

and what it's based on, but also invite debate.

0:57:210:57:25

It's important that new discoveries, that new theories are debated.

0:57:250:57:30

There has to be an acknowledgement that science changes.

0:57:300:57:32

As a scientist, I treat these films as a snapshot

0:57:320:57:37

that captures our understanding at a certain point in time.

0:57:370:57:41

These documentaries, whatever their imperfections, their flaws

0:57:410:57:45

and their distortions and all the complaints, you know,

0:57:450:57:49

"Things aren't being represented, it's not certain science,"

0:57:490:57:52

but it's describing possibilities,

0:57:520:57:55

and it's possibilities the knowledge of which may save lives.

0:57:550:58:00

As these films evolve, it's like actually being an observer

0:58:010:58:05

during the discovery process and I'm all in favour of that.

0:58:050:58:10

As the years go by, we understand more and more,

0:58:120:58:16

so I don't think we've seen the last documentary

0:58:160:58:19

on what happened 3,000 years ago in Atlantis, or Pompeii or even here.

0:58:190:58:25

Detective Griffin?

0:59:020:59:04

Are you good? You all right?

0:59:040:59:05

Pleased to be back.

0:59:050:59:06

Your baby has been loved by me very much.

0:59:060:59:09

I'd like to say thank you.

0:59:090:59:10

I like you.

0:59:110:59:13

We have a report there's a suitcase washed up.

0:59:130:59:15

There's black human hair coming from the inside.

0:59:150:59:18

From earthquakes to tsunamis to volcanic eruptions, natural disasters are both terrifying and fascinating - providing endless fresh material for documentary makers. But how well do disaster documentaries keep pace with the scientific theories that advance every day? To try and answer that question, Professor Danielle George is plunging into five decades of BBC archive. What she uncovers provides an extraordinary insight into one of the fastest moving branches of knowledge. From the legendary loss of Atlantis to the eruption that destroyed Pompeii, Danielle reveals how film-makers have changed their approach again and again in the light of new scientific theories. While we rarely associate Britain with major natural disaster, at the end of the programme Danielle brings us close to home, exploring programmes which suggest that 400 years ago Britain was hit by a tidal wave that killed hundreds of people, and that an even bigger tsunami could threaten us again.