Decoding Disaster A Timewatch Guide


Decoding Disaster

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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

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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

0:46:410:46:47

rushed over the low-lying sea defences.

0:46:470:46:50

Travelling at 30mph, the killer wave bore down

0:46:580:47:01

on the villages of Somerset and Monmouthshire.

0:47:010:47:04

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

0:47:160:47:20

Yet, for centuries,

0:47:210:47:22

this apocalyptic flood has been forgotten,

0:47:220:47:25

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

0:47:250:47:29

Was it just a huge storm

0:47:300:47:33

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

0:47:330:47:38

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.

0:47:540:47:57

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.

0:48:090:48:14

At Dunraven Bay in south Wales,

0:48:170:48:19

hundreds of boulders lie at the foot of the cliffs.

0:48:190:48:22

Some have obviously just dropped off the face,

0:48:220:48:25

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

0:48:450:48:48

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

0:49:010:49:03

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

0:49:030:49:06

what we call a boulder train,

0:49:060:49:08

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

0:49:080:49:11

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.

0:49:360:49:39

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.

0:49:590:50:03

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

0:50:120:50:14

from something of the 1970s,

0:50:140:50:15

the way that the evidence is presented.

0:50:150:50:18

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

0:50:180:50:21

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,

0:50:370:50:40

just a short distance off the British coast,

0:50:400:50:43

is an intriguing hypothesis and a scary one, too.

0:50:430:50:47

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.

0:50:540:50:57

This is the story

0:51:050:51:06

of how the greatest natural disaster

0:51:060:51:09

in human history might one day unfold.

0:51:090:51:12

The biggest wave ever seen...

0:51:140:51:16

..threatening death and devastation

0:51:170:51:20

on an unprecedented scale.

0:51:200:51:22

The power of this film lies in the fact

0:51:290:51:31

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.

0:51:410:51:44

Some scientists fear that an eruption

0:51:460:51:48

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

0:51:480:51:53

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

0:52:010:52:04

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.

0:52:130:52:17

Immediately in its path,

0:52:170:52:19

the highly populated island of Tenerife.

0:52:190:52:23

Locals and holiday-makers alike

0:52:240:52:26

do all they can to outrun it.

0:52:260:52:28

Within minutes,

0:52:420:52:43

the wave has claimed its first victims.

0:52:430:52:46

I don't think there's any doubt

0:52:470:52:50

that the initial wave will be

0:52:500:52:52

very catastrophic for the islands themselves.

0:52:520:52:55

So you're talking about thousands of people dead

0:52:570:53:00

and destruction on a scale that we've never seen

0:53:000:53:02

in this part of the world before.

0:53:020:53:04

Our mega tsunami's journey of destruction

0:53:060:53:09

has only just begun.

0:53:090:53:11

Over the following hours,

0:53:110:53:13

these waves will devastate the coastlines of Europe.

0:53:130:53:17

The emergency services have just three hours

0:53:190:53:22

before the wave strikes Britain.

0:53:220:53:25

The Environment Agency issues flood warnings

0:53:270:53:29

to the south coast

0:53:290:53:31

and rescue units are put on standby.

0:53:310:53:34

Police clear the streets of southern coastal towns,

0:53:360:53:39

evacuating schools and vulnerable communities.

0:53:390:53:44

A giant tsunami is spreading

0:53:440:53:46

throughout the Atlantic Basin.

0:53:460:53:47

Scientists estimate that the wave is travelling

0:53:470:53:50

at approximately 500mph.

0:53:500:53:53

Just three hours after the first UK warnings,

0:53:540:53:57

a wave up to 25 metres high

0:53:570:54:00

makes its first landfall in Britain...

0:54:000:54:03

..on Cornwall.

0:54:050:54:07

From Cornwall, the wave surges

0:54:180:54:20

through the English Channel,

0:54:200:54:22

engulfing much of Britain's south coast.

0:54:220:54:25

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

0:54:420:54:45

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

0:54:450:54:48

Towns such as Brighton would suffer serious disruption.

0:54:500:54:53

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,

0:55:010:55:04

by looking at what happened in the Indian Ocean in 2004

0:55:040:55:07

in places like Sri Lanka and Thailand.

0:55:070:55:09

The death toll was in the tens of thousands.

0:55:100:55:13

The population on the south coast of the UK

0:55:130:55:15

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

0:55:210:55:24

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,

0:55:470:55:50

we came up with roughly 4.5 million causalities.

0:55:500:55:53

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

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