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A Timewatch Guide S04E01 Decoding Disaster
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00:02Natural disasters unleash forces that are literally earth-shattering.
00:08Whether it be an earthquake, a volcanic eruption, a tidal wave, each is terrifying, but fascinating too.
00:19Hollywood disaster movies make for a thrilling spectacle.
00:24But what about disaster documentaries?
00:26Surely we look to them to provide answers, not just entertainment.
00:31But to do that, programs need to keep pace with science that advances every day.
00:38So I've searched the archives of the groundbreaking history series Time Watch and 60 years of BBC documentaries to see
00:46how filmmakers have dealt with disaster,
00:48providing an extraordinary insight into one of the fastest moving branches of knowledge.
00:56I'll see how rival theories keep emerging on the destruction of ancient Atlantis.
01:02It's normal as a scientist that you guess, essentially, what might have happened, say, in Atlantis, based on the evidence
01:09at the time.
01:09How there's still much to learn about history's most famous volcanic eruption at Pompeii.
01:17Science, if it's healthy, is a constant state of doubt.
01:21How filmmakers explore theories that sometimes sound barely believable.
01:31Was this killer wave of 400 years ago a British tsunami?
01:37These films do show that historians and scientists have made incredible advances in the study of historical disasters.
01:46Best of all, we can share that thrill of discovery and a new understanding of some of history's greatest calamities.
02:07As an engineer, I'm fascinated to discover how things work.
02:13But as I've studied the film Archive on Disasters, I've realised we're still learning how the Earth itself works.
02:22The experts in this field keep turning up fresh evidence and new theories.
02:29What they thought was true just a few years ago may no longer seem certain today.
02:37But there's still something in me that wants to ask, what actually happened to cause such and such?
02:44Was it X or was it Y?
02:46Surely somebody knows.
02:53For me, searching the film Archive offers a unique opportunity to see how theories develop over time.
03:03I know that definite answers will be hard to find.
03:07For instance, this beach I'm on in South Wales was hit by a giant wave 400 years ago, causing huge
03:15loss of life.
03:18Some researchers say it was a massive storm surge.
03:22Much more controversially, others believe it was a tsunami, caused by an earthquake out at sea.
03:29I'll come back to that later.
03:31But it's just one example of how researchers and the filmmakers who document their work
03:37are forever seeking new explanations for some of the greatest calamities to ever strike our planet.
03:43Since the dawn of time, we humans have been trying to understand how the Earth works.
03:51Specifically, the earthquakes and volcanic eruptions, which can wipe out whole cities in moments.
04:00Events so cataclysmic, they're still often simply called acts of God.
04:07Before we consider the disasters themselves, we need to look at the science behind them.
04:14The realisation that the Earth has a constantly moving crust is really very recent.
04:20And it's completely changed our understanding of disasters.
04:24This has only really been an accepted theory since as late as the 1960s.
04:29Earthquake science is really quite novel and quite new.
04:33And the last 30 years or so have shown incredible developments.
04:37And so when this film appeared, 45 years ago, it was proclaiming nothing less than a revolution.
04:45Nearly all earthquakes occur at the boundaries between the great plates of the Earth's outer shell.
04:52In the Middle East and the Mediterranean, the home of many ancient civilisations,
04:57there's an extraordinary jumble of large and small plates.
05:02Dan McKenzie, of Cambridge University, is one of the young revolutionaries of the Earth's sciences.
05:08He played a pioneering part in first telling how the great plates move as rigid units about the globe.
05:15Most of the worst earthquakes in the Mediterranean occur because Greece and Turkey
05:20are moving really quite rapidly westwards at about 5 centimetres a year.
05:24This means they've moved about 100 yards since the time of Socrates.
05:29This pair of scissors and the bobbin show what's happening.
05:33Bottom of the scissors is Africa, and the top is Europe.
05:37The bobbin is Turkey.
05:38And as Africa comes towards Europe, Turkey is squeezed out of the way.
05:46In this village, three quarters of the population perished.
05:49An earthquake struck at 2.15 in the afternoon of the 31st of August, 1968.
05:55It killed 10,000 villagers, and some of the bodies were never found.
06:01When the heavily built roof of this communal wash house fell on them, 28 women died.
06:07The energy let loose in this earthquake was equivalent to an H-bomb of several megatons.
06:14The film shows how this new theory, that pieces of the Earth's crust collide and grind against each other,
06:21allowed scientists to understand even very recent disasters in a completely new way.
06:27Right across the world in California, the San Fernando earthquake of 1971 awoke old faults that hadn't moved for thousands
06:35of years.
06:37It killed more than 60 people, and gave warning of what more severe earthquakes might do to Californian cities.
06:45Earthquakes are part of a systematic remodeling of the Earth.
06:48That's the doctrine of the new generation of Earth scientists, like Tanya Atwater.
06:53She worked out how movements of the ocean floor have affected the land,
06:56and so explain afresh much of the scenery of the Western USA.
06:59When I was in school, I was taught that the Earth makes its mountains by a complicated sort of sinking
07:06and bobbing action,
07:07first down and then up again.
07:08That doesn't seem to be the case at all.
07:11Most mountains seem to be made by one piece of the Earth's outer crust pushing sideways against another.
07:17This is some of the damage from the recent San Fernando earthquake.
07:20The buckling here is just the latest step in the buckling of the Earth that made the mountains behind.
07:27Here, great plates are grinding.
07:30The coastal strip of California is edging past the rest of North America.
07:36This is three feet of mountain that was thrown up in the recent earthquake, just like the sidewalk was.
07:42It doesn't look like much, but you have to think about this happening over and over again,
07:47maybe once a century for thousands of centuries.
07:52If you look at the documentaries in the early 70s, they were still explaining plate tectonics to the audience.
08:02Now, if you look at more recent documentaries, plate tectonics is very broadly understood by the viewing public,
08:10I think, and so they're starting from a different point.
08:17Once you know how recently the nature of the Earth's crust was still a mystery,
08:22it's easier to understand how theories are still being revised and refined.
08:29I'm going to look first at how this rapidly developing knowledge actually posed problems for filmmakers.
08:36I've been looking at a series of films tackling the same subject, with each of them drawing a different conclusion.
08:46One of the most enduring, most romantic mysteries of all is the search for the fabled island of Atlantis.
08:56Historians have argued whether the story of a lost civilization first told by the Greek philosopher Plato around 350 BC
09:03has a basis in fact, or whether it's merely a legend.
09:10Finally, in 1972, archaeologists discovered startling new evidence
09:15that Atlantis may have truly existed, but was wiped out in a natural disaster.
09:22This is how Plato had described it.
09:25In this island of Atlantis, there was the fairest and noblest race of men that ever lived,
09:30but they fell from grace and were punished by the earthshaker Poseidon.
09:39And afterwards, there occurred violent earthquakes and floods,
09:43and in one terrible day and night, the island of Atlantis disappeared in the depths of the sea.
09:57The new evidence suggested that the disaster struck in the eastern Mediterranean,
10:02on an island now crowded with tourists every year,
10:05but which in 1972 was a sleepy backwater.
10:10Santorini, sometimes known as Terra.
10:17A land of grapes and wine, one of the most enchanting of all the Greek islands of the Aegean.
10:22A picturesque, idyllic island on the surface,
10:25but underneath there lurks a threat of terrible natural violence.
10:29For Santorini is an area of alarming geological instability.
10:35These cliffs are the walls of a caldera,
10:38a vast crater that formed when the erupting volcano collapsed,
10:41leaving a gaping hole to be filled by the sea.
10:45It was a Greek philosopher Plato who first wrote of the legend in the 4th century BC.
10:51It told of an ancient island civilization.
11:02What the archaeologists had just discovered
11:05was an entire city buried beneath tons of volcanic ash.
11:11And remarkably, it seemed to match Plato's description
11:14of a wealthy, civilised society,
11:17with a taste for artistic expression.
11:22Perhaps the most exciting discoveries are the frescoes.
11:25And we arrived at the site
11:27just as a completely new wall painting was being uncovered.
11:32Skin divers and fishermen at work.
11:35One goes down with a hook.
11:38One might be collecting sponges.
11:42And as the divers pick their way through the coral of the seabed,
11:46on the surface a convoy of ships is on the move,
11:49led by a 50-odd galley.
11:55What's more, the eruption on Santorini
11:58also appeared to neatly solve another long-standing historical mystery.
12:05Experts already knew that at almost the same time,
12:09sudden disaster had overcome the island of Crete,
12:1260 miles to the south.
12:14The wealthy and highly developed civilisation there,
12:18the Minoan Kingdom,
12:19disappeared almost overnight,
12:22and for no obvious reason.
12:25But armed with their new knowledge of the earth sciences,
12:29archaeologists imagined that the volcano on Santorini
12:32had sent out a tidal wave,
12:34big enough to cause wholesale destruction on Crete.
12:39Tidal waves of appalling violence,
12:41perhaps some 600 feet high,
12:44came raging in over the exposed northern coasts of Crete.
12:48Buildings had been dragged to the ground as the waves receded.
12:52These waves had been created by the collapse of the volcano in Santorini
12:56some 60 miles away to the north.
12:59This was a groundbreaking piece of historical detective work.
13:04Atlantis had been found,
13:06and the mystery of the Minoans solved.
13:09Case closed.
13:11But in less than 10 years,
13:13new evidence emerged,
13:15forcing the very same team of filmmakers
13:17to backtrack on the tsunami theory.
13:21On islands much closer than Crete,
13:24especially the island of Melos,
13:27archaeologists found no evidence of a giant tidal wave.
13:33We saw no evidence at all of these great waves,
13:36tidal waves, tsunamis,
13:37whatever you want to call them in Melos.
13:40If there were great tsunamis
13:42which were rushing across the ocean
13:44and going to flatten the palaces of Crete,
13:47we would have expected to find traces of that also in Melos.
13:51I have the feeling, therefore,
13:53that it wasn't as disastrous in the Aegean as a whole
13:56as is sometimes thought.
13:59But if it wasn't a tsunami,
14:02what then caused the destruction
14:04of the Minoan civilization on Crete?
14:09The film shows how archaeologists revisited all the clues,
14:14just like detectives reopening an old case.
14:18In particular,
14:20they looked again at the wall paintings they'd uncovered
14:23and now built a theory that the Minoans
14:25were wiped out by invaders from the Greek mainland.
14:29It's a fascinating insight into the way that archaeologists
14:33necessarily use one piece of a jigsaw
14:35to imagine the whole picture.
14:38With the tidal wave theory crushed,
14:40the chief archaeologist on Santorini
14:42had to come up with a new narrative
14:44to explain those wall paintings of people in the sea.
14:48He first interpreted the figures in the water
14:51as underwater fishermen or sponge divers.
14:55But later, he recognized them to be dead bodies
14:58sinking to the bottom of the sea,
15:00casualties of some kind of naval engagement
15:03that seems to be taking place on the surface above them.
15:08The figures in the water may yet turn out
15:11to be evidence in favor of the invasion thesis.
15:17In the space of less than 10 years,
15:20one important theory had emerged,
15:22been shot down,
15:23and then replaced by another.
15:27It's very easy to look back and say
15:29they got it all wrong.
15:31But isn't this experimental approach
15:34what archaeology, science too,
15:36is all about?
15:38Providing new answers to old questions
15:40with evidence that's constantly emerging.
15:47Science, if it's healthy,
15:50is a constant state of doubt.
15:52There are phrases like
15:53scientists believe that,
15:56a phrase I hate
15:58because it doesn't represent
15:59this constant disagreement
16:01that has to go on in science
16:04or else it dies.
16:07And of course,
16:08that wasn't the end of it.
16:12Discovering Atlantis is pretty much
16:15the holy grail for archaeologists
16:16and a perennial subject for TV documentaries.
16:21In 2002,
16:23filmmakers once again reported
16:25that it had been found,
16:27but in a different part of Greece altogether.
16:30A separate team of archaeologists
16:33digging on the Greek mainland
16:34declared they'd found Atlantis
16:38and that it had been destroyed
16:40by a quite different natural disaster.
16:44This is the coast of Greece
16:46on the Corinthian Gulf,
16:48150 kilometres west of Athens.
16:50It is one of the most active earthquake regions
16:53in the world.
16:55According to old Roman texts,
16:57there was once a great ancient Greek city here
17:01called Heliki.
17:06Two and a half thousand years ago,
17:09Heliki was a thriving metropolis.
17:13Over 5,000 people lived and worked within its walls
17:17and pilgrims thronged to its temple of Poseidon.
17:24But on one cold winter's night in 373 BC,
17:29the god of earthquakes and the sea
17:31turned on his own people.
17:39The ancient sources say
17:41the earthquake struck at night
17:43where most people were caught in their houses.
17:48A massive tidal wave,
17:50a tsunami or sea wave came in.
17:59And swept away all survivors.
18:06Heliki and all of its people
18:08were swept to the bottom of the sea,
18:10never to be seen again.
18:15Just a few short years after the disaster,
18:18the Greek writer Plato
18:19created the story of Atlantis.
18:29The archaeologists had been toiling here
18:32for 15 years,
18:33uncovering pottery and other artefacts
18:36when they came upon structures
18:38which seemed to show signs of damage
18:40by tidal wave.
18:43Finally, in the walls below them
18:45was possible evidence of the disaster itself.
18:49There were signs some huge force
18:51had struck the building.
18:53This wall has been knocked down
18:55toward the sea.
18:58That is the kind of pattern
18:59that you see
19:00where you have the backwash
19:01from the enormous wave
19:03going back to the sea
19:07and knocking them down
19:08in the direction of the sea.
19:12So it seems
19:13that after 15 long years of searching,
19:15their team may have succeeded
19:17where so many other archaeologists have failed.
19:22They believe these walls
19:23are just the first glimpses
19:25of the buildings
19:26that must lie on the ground around them.
19:28Beyond them,
19:30towards the hills,
19:31should lie the rest of the city
19:33waiting to be uncovered.
19:36Now it seems
19:38the city whose destruction
19:39inspired the legend of Atlantis
19:41may finally have been found.
19:49So was that the end
19:51of the quest for Atlantis?
19:56It's a mystery
19:58that just won't die.
20:01When Time Watch
20:01joined the search for Atlantis
20:03a decade later,
20:04the pendulum had swung
20:06right back
20:06to where it was
20:07in 1972.
20:11Historian
20:12Bettany Hughes
20:13went hunting
20:14for fresh evidence,
20:16homing in
20:16once again
20:17on the island
20:18of Santorini.
20:21Atlantis hunting
20:22is a fraught exercise.
20:25But precisely
20:26because it has generated
20:27so many wild theories,
20:29there's even more reason
20:31to try to sift the fact
20:32from the fiction.
20:35Fresh scientific evidence
20:37buttresses the idea
20:39that Plato's story
20:40was inspired
20:41by a real island
20:42and a real ancient civilization
20:44which was destroyed
20:46by a real natural disaster.
20:52An eruption
20:53on a scale
20:54the ancient world
20:55had never experienced before.
21:02This was an eruption
21:04that shook
21:04much of the planet.
21:06Ash was transported
21:07as far north
21:08as the Black Sea,
21:09as far east
21:10as central Turkey
21:11and as far south
21:12as the Nile Delta.
21:14Global temperatures dipped,
21:16stunting plant growth
21:17even in Ireland.
21:24The early documentaries
21:26show a completely
21:27different picture
21:27from the modern ones
21:28due to this advancement
21:30of science.
21:32New technologies
21:33like satellite imagery
21:35that we can now study
21:36that give us
21:37a better global picture
21:38of what's happening.
21:39GPS,
21:40which records
21:41the relative movements
21:42on two sides
21:43of a fault
21:44before and during
21:45after an earthquake.
21:46All of this instrumentation
21:47is providing us
21:48new data
21:49with which to study
21:50these natural events.
21:53For these filmmakers,
21:55Santorini also seemed
21:56to fit perfectly
21:58with the description
21:59which Plato had provided.
22:04The first thing
22:05that strikes you
22:06is it's really odd
22:07topography.
22:10the land just
22:11just straight out
22:12of the sea
22:13and then you get
22:14these small islands
22:15ringed by water
22:16which are then
22:17in turn
22:18cradled by that
22:19massive semicircle
22:20of land up there.
22:23Now just listen
22:24to what Plato
22:24has to say
22:25about his Atlantis.
22:29There were circular
22:30belts of sea
22:31and land
22:31enclosing one another
22:32some greater
22:34some smaller.
22:37Now of course
22:38that in itself
22:39doesn't prove anything.
22:40I mean there could be
22:41loads of locations
22:42all around the world
22:43that match this description
22:44but nonetheless
22:46this account
22:47and that landscape
22:49are really remarkably similar.
23:04Bethany's team
23:05had revived
23:06the 1972 theory
23:07that a massive tsunami
23:09had swept south
23:11from Santorini
23:11smashing into
23:13the island of Crete.
23:15Evidence of the tsunami
23:17had now turned up
23:18on Crete itself.
23:21Archaeologist
23:21Sandy McGillivray
23:22and tsunami expert
23:24Costas Sinalakis
23:25are investigating
23:26the scale of the tsunamis
23:27by mapping pumice
23:29on Crete's
23:30northern coastline.
23:31Here's some.
23:32Here's a piece there.
23:34Oh.
23:36It's so light
23:37isn't it?
23:38Because it must have
23:39floated here so.
23:41This is exactly
23:42what we like.
23:43I mean the float sun
23:44that comes out
23:45gives us an idea
23:46of how high
23:46the wave reached.
23:48So the tsunami
23:49would have carried this
23:50up here to this headline?
23:51At least at least
23:51at this point.
23:52I mean it could have
23:52carried it further up
23:54and then could have
23:55washed down
23:55with the rain
23:57and with floods.
23:58But this gives us
23:59sort of a
23:59helps us bracket
24:00the size of the wave
24:02right offshore.
24:05Costas has developed
24:06a computer simulation
24:08of how the tsunamis
24:09would have travelled.
24:11You see this is
24:11the initial wave
24:14and we follow it
24:15all the way to Crete.
24:17See the first wave
24:18causes the shoreline
24:19to retreat
24:19to move offshore.
24:21We are less than
24:22an hour from the eruption
24:22and already the south side
24:24of Crete
24:25and the eastern
24:27Peloponnese
24:27are experiencing
24:29the big wave.
24:31What do you think Sandy
24:32that says about
24:33what happened to Crete?
24:34Because most people
24:35live along the coast
24:36don't they?
24:37I think so.
24:37It was the city
24:38of Knossos
24:38which is inland
24:39but otherwise
24:40it's very much
24:41open coastline
24:42and so the death toll
24:45would have been staggering.
24:48The hard evidence
24:50shows us
24:51that here
24:51there was a
24:52sophisticated
24:53trading civilisation
24:54that flourished
24:56and was then
24:57swallowed by the sea
24:58ravaged by a disaster
25:01of legendary proportions.
25:04Surely
25:05this is the root
25:07of Plato's
25:08Atlantis legend.
25:15So it's clear
25:16that theories
25:17come and go.
25:18I suspect
25:19that's not the last
25:20we've heard of Atlantis.
25:24Certainly
25:25for the moment
25:26at least
25:26the evidence
25:27seems to favour
25:28Santorini
25:29as the true location
25:31for Plato's Atlantis.
25:33And it's brought home
25:35to me
25:35just how new
25:37much of the underlying
25:38science
25:39really is.
25:41Tsunamis
25:41in particular
25:42are very poorly understood.
25:45I don't think
25:46a lot of people realise
25:47but until
25:48the Indian Ocean tsunami
25:49in 2004
25:50we didn't even know
25:51what a tsunami wave
25:52looked like.
25:53It was only due
25:53to the complete chance
25:55of there being
25:55a vessel
25:56measuring the depth
25:57of water
25:58offshore of Thailand
25:58when the tsunami
25:59passed under it
26:00that we actually
26:01have a trace
26:02of what a tsunami wave
26:03looks like
26:04and that's
26:062004.
26:09I'm going to look
26:11now
26:11at how filmmakers
26:12have tried
26:13to keep pace
26:14with another branch
26:15of the earth sciences.
26:17Just as with tsunamis
26:19our understanding
26:20of volcanoes
26:21has massively increased
26:23in the last 40 years.
26:26In 1972
26:28filmmakers
26:29explored some of
26:30the brand new discoveries
26:32in volcanology.
26:38A volcano
26:39in eruption
26:40is undoubtedly
26:41the finest
26:42pyrotechnic display
26:43that man can ever see.
26:46These falls
26:47are twice
26:48the height of Niagara
26:50and the fire fountain
26:51rises to almost
26:52a thousand feet.
26:55Volcanoes
26:56can be docile
26:57or violent.
26:58In fact
26:59volcanoes
27:00can vary
27:01enormously.
27:01Some lava
27:02flows like water.
27:04Some
27:04is thicker
27:05than treacle.
27:10Volcanoes
27:11may have
27:11a far greater
27:12effect
27:12on the formation
27:13of the globe
27:13than the volcanologists
27:14at first suspected.
27:16Starting
27:17in the South Pacific
27:17volcanoes
27:18spread right
27:19through Indonesia
27:20and up the island
27:21chain
27:21to Japan
27:22Siberia
27:22and Alaska
27:23down the west
27:24coast of America
27:25with a loop
27:26around the Caribbean
27:26through Mexico
27:28Peru
27:28and Chile.
27:30It's not
27:30a random distribution.
27:32There are patterns.
27:34The structure
27:35of the Earth's crust
27:35is a series
27:36of rigid plates.
27:38Volcanoes
27:39help determine
27:39the plate boundaries.
27:45The film advances
27:46the then novel theory
27:48that all the land
27:49we now live on
27:50was at one time
27:51spewed from the mouth
27:53of an erupting volcano.
27:57The best information
27:58which we have
27:59available
28:00at the present time
28:01suggests
28:01that all the world's
28:03volcanoes
28:03between them
28:04are currently
28:05producing
28:05about 3 cubic kilometers
28:07of new material
28:08per year.
28:10At this rate
28:11sustained
28:12through the course
28:13of geological time
28:14the Earth's volcanoes
28:15would be capable
28:16of building up
28:17the whole
28:17of the continental crust.
28:19I think it's possible
28:21that the continental crust
28:22is indeed due to
28:234,500 million years
28:25of volcanism.
28:30This new understanding
28:31of volcanoes
28:32helped historians
28:33to better explain
28:34huge historic disasters.
28:36In particular
28:37the incredible story
28:39of Pompeii.
28:43This city
28:44in southern Italy
28:45along with its
28:46neighbouring
28:47Herculaneum
28:48was destroyed
28:48by a vast eruption
28:50of Mount Vesuvius
28:51in the year
28:5279 AD.
29:03The way
29:04that Pompeii's
29:04citizens
29:05who perished
29:06in the disaster
29:07seem frozen in time
29:08has captured
29:09our imaginations.
29:11Their body outlines
29:12preserved in the ashes
29:14give a real sense
29:15of their final moments.
29:21More than 50 years ago
29:23in 1966
29:24presenter
29:26Robert Erskine
29:27introduced
29:28this remarkable story
29:29to the TV audience.
29:33Thousands of the
29:34townsfolk died
29:35poisoned by the
29:36sulfurous fumes
29:37in the basements
29:38of the houses
29:39and in the streets
29:39because they couldn't
29:40make up their minds
29:41what to do.
29:43At the first
29:43cataclysmic explosion
29:45the mountain
29:46split
29:47split open
29:49and it spewed
29:50its hideous innards
29:51all the way down
29:52this gully
29:53straight towards the tunnel.
29:55well, the inhabitants
29:57took one
29:58and ran
30:00down these very streets
30:02they fled in terror
30:03away from the mountain
30:04leaving everything behind
30:06the doors of the houses
30:07open
30:08the wine bars
30:09precipitately deserted
30:10everything left where it was dropped
30:12the terror of the moment
30:13a blind panic flight
30:15it must have been.
30:21by the early 70s
30:23our new understanding
30:24of earth science
30:25would deepen
30:26this knowledge
30:28so by 1974
30:30filmmakers
30:31could give a much more detailed account
30:34of the disaster
30:36on Mount Vesuvius
30:37broad sheets of fire
30:39and leaping flames
30:40blazed at several points
30:42ashes were already falling
30:44the buildings were now shaking
30:46with violent shocks
30:48outside on the other hand
30:49there was the danger of falling pumice stones
30:55we now know what actually happened
30:57a violent blast of gas
31:00shot a huge cloud of ash and pumice
31:01miles into the air
31:03down fell a rain of lapilli
31:04pieces of pumice
31:05which buried the city
31:06to a depth of about 10 feet
31:08some people fled
31:10but many who sheltered in the houses
31:12were killed by buildings
31:13crumbling under the weight
31:14others were trapped and died
31:19the survivors emerged into the open
31:21it was then
31:23that a hurricane
31:24of scorching ash
31:25swept down the mountain
31:29those in flight
31:30their lungs
31:31seared by the red hot lava particles
31:33collapsed in their tracks
31:35about 2,000 bodies
31:37have been found so far
31:38one tenth of the population
31:42the last minor eruption
31:44of Vesuvius
31:45was in 1944
31:46for 30 years
31:48the volcano
31:49has been silent
31:50dangerous
31:53but for how long
32:01Vesuvius today
32:02looks like a volcano
32:05although you can climb to the top
32:07no one can be in much doubt
32:08of the explosive forces
32:09not very far below the surface
32:13Vesuvius is a particularly dangerous volcano
32:16capable of great violence
32:19always the cities of the Bay of Naples
32:22must live in fear
32:23no one can be sure
32:25when the mountain will split apart again
32:31and the learning process still continues
32:34fed by archaeology on one hand
32:38volcanology on the other
32:40you have a particular volcanic eruption
32:43you have a particular volcanic eruption
32:43Vesuvius AD 79
32:44our understanding of that
32:47is developing in two ways
32:49firstly more excavations being done
32:52around Vesuvius
32:53but the other way
32:54is that we experience
32:57other eruptions
32:59of similar types
33:02therefore we realise
33:04ok we can use
33:05the geophysical data
33:06the observational data
33:09and so on
33:10of these different eruptions
33:11to understand
33:12AD 79
33:17it's clear how our understanding has increased
33:20when you look at a much more recent film
33:22which adopted a rigorously forensic approach to the disaster
33:27in the early 1980s
33:29a remarkable discovery was made at Herculaneum
33:32which lies only seven kilometers from Vesuvius
33:35closer than Pompeii
33:38300 skeletons were discovered
33:40all victims of the volcanic eruption
33:45but to work out exactly what killed them
33:47scientists needed to study another eruption
33:50that happened almost 2,000 years later
33:55the results appeared in a film
33:57presented by Roman history scholar
34:00and one-time apprentice panelist
34:02Margaret Mountford
34:07what force was hot enough
34:09to reduce these poor people
34:11to a pile of scorched bones?
34:15we need to look at a volcano
34:16that erupted in North America
34:18in the 1980s
34:25Mount St. Helens National Park
34:28has some of the most breathtaking scenery
34:30in the USA
34:32but on Sunday
34:34May the 18th 1980
34:35this peaceful world
34:38was transformed
34:39when the Mount St. Helens volcano erupted
34:53Volcanologists had seen eruptions before
34:55but this was the first time
34:57they had managed to capture on film
34:59a little known phenomenon
35:02the whole north face of Mount St. Helens collapses
35:09as it does
35:10it releases a searing hot avalanche of gas and dust
35:13that explodes down the sides of the mountain
35:18this is called
35:19a pyroclastic current
35:31could you explain what a pyroclastic current is?
35:36a pyroclastic current is an avalanche of searing hot gas ash and rock
35:42that travels down the slopes of a volcano
35:45at hundreds of kilometers of an hour
35:47it's impossible to outrun
35:49and absolutely deadly
35:50when I think of an eruption
35:52I think of streams of lava coming down a mountain
35:55well the style of eruption
35:57whether a volcano will erupt lava
35:59or if it will erupt explosively
36:02is primarily a function of how much gas is in the magma
36:06if there is no gas in the magma
36:08then the magma will erupt as a lava flow or a lava dome
36:12and that is the actual magma
36:14the liquefied rock that's coming out
36:16that's lava
36:16exactly
36:16and in an explosive eruption
36:19the difference is
36:20the magma has gas bubbles
36:21and as the gas in the magma makes its way to the surface
36:25the gas bubbles get bigger and bigger and bigger
36:28to the point where
36:29when the volcano erupts
36:30the gases just expand very quickly
36:32and it rips the magma apart into very tiny pieces
36:35which are your ash and your pumice
36:39from what scientists witnessed at Mount St Helens
36:42and data gathered from other volcanic eruptions
36:45it's now possible to piece together exactly what happened
36:49when Vesuvius erupted
36:5412 hours after the initial eruption
36:57the column above Vesuvius stretched nearly 32 kilometers high
37:03but under its own weight
37:05it collapsed
37:09a pyroclastic current surged down the sides of the volcano
37:13at speeds up to 300 kilometers an hour
37:22temperatures inside the explosive blast were over 500 degrees Celsius
37:25temperatures inside the explosive blast were over 500 degrees Celsius
37:32the wave of searing hot gas and ash
37:35took less than five minutes to strike Herculaneum
37:38seven kilometers away
37:40seven kilometers away
37:52the intense heat surge killed them instantly
37:59it vaporized their flesh
38:10and that is why all that remained were blackened skeletons and cracked skulls
38:21this new insight into volcanoes gives historians a toolkit
38:25with which to investigate previously unexplained events from the past
38:32we get new data all the time
38:35we didn't have a concept of the pyroclastic flow
38:38and what pyroclastic flows did to people
38:41so this constant drawing of information from other areas and comparisons and analogies
38:46means that the science is changing all the time
38:50the depth of knowledge which now exists about the vesuvius eruption shows that
38:56with historians scientists and filmmakers working together
39:00it is possible to take an old mystery and supply a definitive answer
39:06but my troll through the film archive shows there are still areas where that's not at all true
39:13one of the deadliest disasters ever to strike the planet still has no known cause
39:19or at least no cause which experts can agree on
39:25it was an epidemic which killed tens of millions of people
39:29and could, some experts fear, reappear today
39:34650 years ago the so-called Black Death is thought to have wiped out something close
39:40to a third of Europe's population
39:43but, as Time Watch reported in 1984
39:46the epidemic raises maybe the biggest question in medical history
39:53the cause of that holocaust, historians believe, was plague
39:57more specifically bubonic and pneumonic plague
40:01new biological research, however, is coming to a different conclusion
40:09the time-honored theory was that bubonic plague had been spread by black rats
40:15the fleas that live on the rats but also feed on humans
40:19were thought to be the way the disease was transmitted
40:23but did this theory add up in the light of new evidence?
40:30the Black Death first arrived in Britain on the Dorset coast
40:34by the end of 1348 it had most of southern England in its grip
40:38six months later it had spread through Wales, the Midlands and East Anglia
40:43by the end of 1349 it had reached the Scottish Highlands and the north of Ireland
40:48it moved across the country at about a mile a day or even a little more than that
40:52depending whose account you follow
40:54now this just doesn't fit in with what we know of plague today
40:58the winter of 1348 to 49 was unusually cold
41:02but bubonic plague doesn't appear to thrive in low temperatures
41:06the black rat is an animal that likes the warmth
41:09it comes from India basically in that region
41:12the flea is very temperature dependent
41:16it only breeds when the temperature gets between 65 and 85 degrees Fahrenheit
41:22and when the humidity is right
41:27according to Dr. Twig there just weren't enough rats and fleas
41:31to spread bubonic plague across Britain so rapidly
41:34and with such fearful loss of life
41:38but if it wasn't bubonic plague what was it?
41:43one disease that fits the bill rather well would be anthrax
41:47unlike bubonic plague it can spread from person to person
41:50it's found to a great extent in domesticated animals, cattle and sheep
41:57but in a human being when the spore gets into the body
42:01hemorrhages occur
42:03the body oozes dark blood from all the bodily orifices
42:11the fact that anthrax rather than bubonic plague might have been the culprit
42:15shows perhaps how little we really know about this huge episode in history
42:22and how difficult it is for filmmakers to offer a definitive account
42:28with research constantly being updated
42:31when Time Watch returned to the question in 2004
42:35yet another possible candidate for the killer disease had entered the frame
42:41the biologist is convinced he has found the answer to the mystery of the Black Death
42:47historians have spent a lot of time interpreting what went on in terms of rats and fleas
42:54which is incorrect
42:55I think we need the record straightened out
43:00Professor Duncan's analysis is controversial
43:02but he's willing to speculate on the actual identity of the killer
43:06which terrorized Europe for over 300 years
43:11his guess is based on symptoms mentioned in some of the 14th century accounts
43:17sudden fever spitting blood and saliva and no one who spat blood survived it
43:23brought on by an affliction of a head of vomiting blood
43:28the accompanying putrefaction of humors caused the victim to cough up blood
43:37could these be medieval descriptions of someone dying of internal hemorrhaging
43:44from the symptoms it has got features in common with Ebola
43:51Ebola is one of the deadliest diseases on earth
43:55it's caused by a tiny thread like virus which was first isolated 30 years ago in Africa
44:03it causes a wide range of symptoms
44:06fever coughing up blood and occasionally lumps under the skin
44:14the tragedy that was played out across medieval Europe
44:17no longer seems to be easily explained as an epidemic of bubonic plague spread by fleas
44:23we are in the uneasy position of not knowing the cause of the most deadly epidemic ever to strike humanity
44:31and until we know we can't be sure we could stop it happening again
44:42so now two possible new diagnoses
44:47one of this country's leading authorities on epidemics
44:51believes the black death could even have been a series of diseases
44:55striking around the same time
44:58I don't place all that much reliance on anyone
45:00myself included coming up saying
45:02oh this is the answer
45:04it's not the plague bacillus
45:06it's the anthrax bacillus
45:07or it's Ebola
45:08or it's this or it's that
45:10or it's something else
45:10it's bad enough to get things diagnosed today
45:13and I mean today
45:14imagine it was like 800 years ago
45:17I suspect myself there were deaths of all kinds of things
45:21all kinds of things
45:22and it's too easy to throw them all into the bubonic plague pot
45:27that's why I'm skeptical about it
45:32it would be wrong to be too harsh about these conflicting diagnoses
45:36after all the second opinion is a long established tradition
45:42but it does serve as a warning about looking for certainty
45:47where it simply may not exist
45:50after studying these films
45:52I think one of the reasons why disaster documentaries are so fascinating
45:57is that they make you wonder
45:59am I safe?
46:00could it ever happen here?
46:04could a lovely beach like this
46:06Dunraven Bay in South Wales
46:08really be the location for a huge natural disaster?
46:14Time Watch revealed
46:15that's not as far-fetched as it sounds
46:21400 years ago
46:22the entire coastline of the Bristol Channel
46:25was engulfed by an enormous flood
46:29the question is
46:30what caused it?
46:36on the 20th of January 1607
46:38a wall of water up to 10 metres high
46:42rushed over the low-lying sea defences
46:52travelling at 30 miles an hour
46:54the killer wave bore down on the villages of Somerset and Monmouthshire
47:10it came without warning
47:12and left 2,000 dead in its wake
47:15yet for centuries this apocalyptic flood has been forgotten
47:19and only now the scientists piecing together the evidence left behind
47:24was it just a huge storm?
47:27or was the killer wave of 1607
47:30in fact a British tsunami?
47:37it was a very timely question
47:39when this film appeared in 2005
47:42the terrible Boxing Day tsunami off Indonesia
47:46with a quarter of a million people dead
47:48was still fresh in everyone's mind
47:56the film looks at new research
47:59suggesting the flood had many of the characteristics of a tsunami
48:04in particular the way the rocks are laid out on this beach
48:11at Dunraven Bay in South Wales
48:14hundreds of boulders lie at the foot of the cliffs
48:16some have obviously just dropped off the face
48:19but others are less easy to explain
48:22this particular boulder has
48:24I'm pretty sure has been moved off the beach
48:27it's got some fossils in it
48:29which you don't normally associate with the older limestones
48:32which you find on the cliffs here
48:33so it looks like this quite big boulder
48:36has come from over there on the beach
48:40the force of water needed to move seven-ton boulders
48:43could easily be produced by a tsunami
48:46the way the boulders are lying
48:47gives Simon another clue
48:50okay that's 270 degrees west
48:53certainly storms can move the odd boulder
48:55and can fling boulders up onto the top of cliffs
48:57but given that we've got so many boulders in a train
49:00what we call a boulder train
49:02and they're all pointing back in the same direction
49:04that suggests to us a constant flow over time
49:11it would only have taken a five-metre tsunami wave
49:14to shift these boulders
49:16for a storm to do the same thing
49:18they calculate it would have taken a wave
49:20at least 20 metres high
49:22over 60 feet
49:25yet the very idea of a tsunami
49:27laying waste to the Bristol Channel
49:28goes against every assumption we have
49:31about Britain being geologically safe
49:35the big surprise is that the seabed
49:38off the southwest tip of Ireland
49:39is the location of an ancient but massive fault line
49:45on the 8th of February 1980
49:47sensors recorded an earthquake from exactly this area
49:504.5 on the Richter scale
49:53violent enough to give fresh impetus
49:56to the tsunami theory
50:00I think I've got that dark layer here
50:03I really like that style of filmmaking
50:07I think it's quite a change from something of the 1970s
50:10the way that the, you know, the evidence is presented
50:13in here it's coming to about 10 centimetres
50:16the dilemmas scientists actually have
50:18themselves about the evidence
50:19which of course has a great deal of uncertainty
50:21about it
50:22the filmmakers are careful to say
50:25that much more evidence is needed
50:27before the theory is widely accepted
50:31but the thought of an undersea earthquake zone
50:34just a short distance off the British coast
50:37is an intriguing hypothesis
50:39and a scary one too
50:42the last film I'm going to look at
50:44is especially chilling
50:46because it assembles compelling evidence
50:49for disaster that's yet to happen
50:59this is the story of how the greatest natural disaster
51:03in human history might one day unfold
51:08the biggest wave ever seen
51:11threatening death and devastation
51:14on an unprecedented scale
51:23the power of this film lies in the fact
51:26that it's based on a genuine scientific hypothesis
51:29yet it uses all the visual tricks
51:32of the classic disaster movie
51:34the film reports a study of a volcano
51:37in the Canary Islands
51:40some scientists fear that an eruption
51:43would cause the volcano to crumble
51:45producing a huge landslide
51:48that in turn could displace enough water
51:51to trigger a mega tsunami
51:55the film goes on to imagine the terrible consequences
51:59if a disaster like that happened for real
52:04travelling at up to 800 miles an hour
52:07the giant wave surges out in all directions
52:12immediately in its path
52:14the highly populated island of Tenerife
52:18locals and holiday makers alike
52:20do all they can to outrun it
52:36within minutes the wave has claimed its first victims
52:42I don't think there's any doubt
52:44I don't think there's any doubt
52:44that the initial wave will be very catastrophic
52:47for the islands themselves
52:52so you're talking about thousands of people dead
52:54and destruction on a scale that we've never seen in this part of the world before
53:00our mega tsunami's journey of destruction has only just begun
53:05over the following hours these waves will devastate the coastlines of Europe
53:13the emergency services have just three hours before the wave strikes Britain
53:20the environment agency issues flood warnings to the south coast
53:25and rescue units are put on standby
53:30police clear the streets of southern coastal towns
53:34evacuating schools and vulnerable communities
53:37a giant tsunami is spreading throughout the Atlantic basin
53:42scientists estimate that the wave is travelling at approximately 500 miles per hour
53:48just three hours after the first UK warnings
53:52a wave up to 25 meters high makes its first landfall in Britain
53:59on Cornwall
54:12from Cornwall the wave surges through the English Channel
54:16engulfing much of Britain's south coast
54:27In our scenario, London, our capital, tucked in from the North Sea, is safely sheltered
54:37Models differ on what the wave might do to our southern cities as it works its way east
54:44Towns such as Brighton would suffer serious disruption
54:53We can get some idea of the impact of a 7 to 10 meter wave on the UK south coast
54:58by looking at what happened in the Indian Ocean in 2004 in places like Sri Lanka and Thailand
55:04The death toll was in the tens of thousands
55:07The population on the south coast of the UK is probably quite a bit higher
55:11So that sort of wave would be immensely destructive in the UK
55:15But the greatest carnage would be inflicted on the USA
55:19With east coast cities like New York directly in the path of the tsunami
55:24New York, Boston, Washington, Miami
55:30Entire cities have been destroyed
55:34The number of casualties is really hard to get at in something like this
55:39For the 25 meter scenario with maybe 3 to 4 hours of warning
55:44We came up with roughly 4.5 million casualties
55:49Around the world, there may be one of these enormous events
55:53Maybe once every 20,000 years
55:55Maybe only once every 50,000 years
55:59We can't say when the collapse is going to occur
56:03It seems to already be close to failure
56:09So the crucial question is not a matter of if, but of when
56:26If the worst were to happen, then at least we'd have some warning
56:32Unlike the people of Pompeii, or maybe Atlantis
56:35Who were suddenly overwhelmed by forces
56:38They could only ascribe to the angry gods
56:44Given that we've only just begun to understand what's happening beneath the Earth's surface
56:49In the past few decades
56:50It's little wonder that they looked for supernatural explanation
56:55More than 3,000 years ago
56:57My troll through the film archive clearly shows that we've learnt a huge amount about natural disasters in the last
57:05half century
57:06And we've learnt so fast that it's hard for filmmakers to keep up
57:11It's our scientific responsibility to be very humble about the limitations of this knowledge and what it's based on
57:17But also invite debate
57:19It's important that new discoveries, that new theories are debated
57:24There has to be an acknowledgement that science changes
57:26As a scientist, I treat these films as a snapshot
57:31That captures our understanding at a certain point in time
57:35These documentaries, whatever their imperfections
57:39Their flaws and their distortions
57:42And all the complaints
57:43Things aren't being represented
57:45It's not certain science
57:47But it's describing possibilities
57:50The knowledge of which
57:53May save lives
57:55As these films evolve
57:57It's like actually being an observer during the discovery process
58:02And I'm all in favour of that
58:06As the years go by
58:08We understand more and more
58:10So I don't think we've seen the last documentary on what happened 3,000 years ago at Atlantis
58:16Or Pompeii
58:18Or even here
58:24On the provenance of the film
58:24The film is a national discovery
58:24And we are pretty fun
58:31The film is a film
58:31That's the film is a film
58:33The film is a film
58:33For the film is a film
58:33With the film, the film is a film
58:33Of the film is a film
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