Category
📺
TVTranscript
00:00In an obscure corner of the universe, situated on a backwater arm of an unremarkable galaxy
00:22called the Milky Way, a fistful of planets wend their way around a rather standard-issue
00:28star. But take a closer look at the third planet out, and there it is. A restless blue
00:36planet with a red and violent soul. Powered by the molten rock that lies beneath, it explodes,
00:45slithers, jerks, and sloshes. And sometimes kills. Continents collide and shear apart
00:54again. Volcanoes erupt, mountains thrust skyward, and cities wait to die. All because of the liquid
01:05rock we call lava, and its parent, magma. Journey back in time to the Earth's molten origins, then
01:14join the wild ride through the jigsaw puzzle of our past. Fly into our violently beautiful present,
01:21and visit the explosive ring of fire. And contemplate, if you dare, the shattering
01:29nightmares the lava-driven world still has in store for us in the future. Mega-tsunamis,
01:36mega-thrust earthquakes, and the horror of the supervolcano. Join us for a dazzling and dangerous
01:45excursion, past, present, and future, on a place called Earth. A truly amazing planet.
01:54Welcome to heaven.
02:14With a window into hell. This is the big island of Hawaii.
02:20Home to Kilauea, one of the most active volcanoes on Earth, and perhaps the best
02:29place to see a planet's labor pains as it gives birth to itself. For the poet,
02:35this lovely dangerous stuff oozing and spitting out of the volcano might suggest
02:41a glowing lifeblood pumped from the red, red heart of a hot and vital Earth.
02:50A more apt comparison might be a bad case of indigestion. This is a planet that belches,
02:59vomits, shudders, heaves, and passes gas. Really nasty gas. Whether from a pulsing heart or a
03:14heaving gut, lava is our only concrete glimpse into the Earth's interior. Into an engine of
03:22creation and destruction that dwarfs all the mighty powers of the planet's human inhabitants.
03:28What lies beneath? We probably know more about the interior of the moon, the sun,
03:37and the stars than the heart of our own planet. So this red messenger is not only hypnotic,
03:45it's precious. Follow this lava back down the tube into its home and you're soon in the giant
03:56molten sphere that takes up the vast majority of the Earth's volume. The mantle. Made of
04:03superheated rock so dense and hot that it moves like glowing taffy. The mantle churns in extreme
04:10slow motion. It's about 2,000 miles down before you hit the Earth's cores and it may take millions
04:17of years for the molten round trip back up to the spewing spectacle that is Hawaii. For just a
04:25glimpse of what lava can do, drain away the ocean and sail by the Hawaiian island chain,
04:31all children of volcanoes. From south to north, the islands grow progressively and neatly older.
04:39The youngest is Loihi, now spewing lava, but which won't break the surface for another 50 or
04:47100,000 years. Then there's Hawaii's big island with its five volcanoes, from seafloor to top,
04:56as high as the Himalaya. The further north you go, the smaller they get,
05:02sinking and eroding over time, each one a little older than the last. And all of them,
05:10like all land on Earth, born of lava. What is immediately obvious is that lava creates paradise.
05:25Within months on the scorched new Earth, vegetation takes hold. The volcanic surface
05:35is rich with nutrients belched up from within. In just years, sun and moisture and microorganisms
05:44turn lava into soil, and life explodes. The gifts of the volcano have always lured humans
05:56onto its slopes. But what creates paradise here also creates mischief of unbelievable power
06:05elsewhere. Mount St. Helens in America, Vesuvius in Etna in Italy, Unzen in Japan,
06:22Pinatubo in the Philippines. A litany of awe and terror, not just from volcanic eruptions,
06:33but from those other terrible powers of the lava-driven world. Earthquakes,
06:39tsunamis, landslides, and a whole slew of other deadly phenomena.
06:45Take a look at the places on the planet where volcanoes erupt and earthquakes shake,
06:55and suddenly the world looks like something stitched together by Dr. Frankenstein. But
07:02these are not sutures. They're wounds in the world where the planet is literally ripping
07:07itself apart and spewing up its guts. And other places where it is smashing together
07:14and eating itself alive. It is at these scenes that the vast majority of earthquakes rage,
07:21and volcanoes explode. Why is the Earth so restless? What causes the ground to shake
07:32violently? Volcanoes to erupt with explosive force? And great mountain ranges to rise to
07:40incredible heights? The answer is plate tectonics. Lava is simply the surface signature of the
07:49powerful engine that drives it. All that molten magma beneath the crust. The Earth's surface is
07:58broken up into a dozen plus chunks of different sizes. Plates, all of which skate around like
08:05planetary bumper cars. The plates float despite their enormous mass, because there is denser
08:13material below. The continental parts of the plates are the lightest of all. They're granite-type
08:19stone, which may seem heavy enough to you and me. Might as well be styrofoam compared to what
08:25lies beneath. A boiling pressure cooker of melted rock. Magma. Most of the boundaries between
08:35individual plates cannot be seen, because they are hidden beneath the oceans. Thanks to satellites
08:42and sonar, we know where they are, and how impressive they are. Whisk away the oceans,
08:51and we see a long mid-ocean ridge, where the Earth is tearing itself apart, and spitting up some of the
08:57highest mountains on the planet. Here, plates move away from each other, like a pair of conveyor belts
09:04moving in opposite directions. A new crust is created as lava wells up to fill the void. Much of this
09:13underwater oozing takes the form of pillow lava. As the hot lava erupts on the cold ocean floor,
09:20a rounded bubble hardens instantly. As more lava pushes out from inside the flow, the pillow expands.
09:31New pillows burst through as the pressure increases. Equally spectacular are the smoking chimneys to be
09:40found along the ridge. Water that has seeped into the seafloor is heated by all this volcanic activity
09:48and blown upwards. At the remarkable Black Smokers, water reaching temperatures in excess of 350 degrees Celsius
09:58jets out. It's thought every drop of water in the world's oceans passes through a hydrothermal vent
10:06about once every 3 million years. There is one intriguing landscape where the Earth is ripping
10:16itself apart, and you don't need a submersible to see it. You don't even need to get your feet wet.
10:34This is Iceland, where a mid-ocean ridge managed to beach itself on land.
10:39Here, the Earth stews in its own juices, much to the delight of humans who welcome a dip into the
10:48geothermically heated spas that dot an often-forbidding landscape of black rock and blue-white ice.
10:56Here, too, you can stand with one foot in America and one in Europe, geologically speaking, because here at these cliffs
11:05lies the dividing line between the two plates. If you stood here for 40 years, your feet would be about six feet apart.
11:18At the foot of these cliffs lie the Parliament Plains, Þingvellir, the site of the ancient
11:23Icelandic Legislative Assembly, a democratic institution founded more than a millennium ago.
11:30In this natural amphitheater, laws were proclaimed and trials held, then announced to the throng
11:36assembled in the valley below. A short way north along the cliff is Drekengarheila,
11:43or Drowning Pool, a crystal-clear pool of water where unfaithful women were drowned.
11:53This is one of the most geologically active pools in the world, and it's one of the most
11:59geologically active places on Earth.
12:09Even under Iceland's spectacular glaciers, eruptions occur.
12:17And even seemingly placid pools of water tell of the grumbling violence that lies beneath the island.
12:24But if you wait a moment, once the water starts to bulge, it's a good idea to take a step back.
12:39The word geyser is Icelandic, which makes sense. And if you missed it,
12:48wait a couple of minutes.
12:52Standing here where Europe and North America meet, and looking east or west, you have to
12:57wonder what these plates are up to at their far edges. It stands to reason that if the Earth is
13:03spreading here, it's got to be colliding somewhere else. And it is, often fatally.
13:17Head about 5,500 miles east, and here's bustling Tokyo,
13:21smack above where the Eurasian plate hits the Pacific and Philippine sea plates.
13:27Let's try the other direction, about 4,000 miles west of Iceland.
13:32And here's the San Andreas Fault, where the American plate hits the Pacific plate
13:37and runs just offshore of San Francisco.
13:41Tokyo. San Francisco. What do these two places have in common?
13:46In geological terms, they are cities waiting to die.
13:51So how did we get to this place where many of our most storied cities are on the endangered
13:56species list? To answer that, we have to go back to the beginning.
14:02About 4.6 billion years ago, on the edge of a spiral arm of a pretty obscure galaxy,
14:09a lot of space rubble starts circling in a slow gravitational dance.
14:15These rocks and gas are the remains of several stars that exploded long ago.
14:21Perhaps about 100 million years later, this space junk begins to collect together
14:26under the force of gravity.
14:28Planetoids smash into one another, causing some to shatter, others to merge.
14:35One planetoid will become the Earth. It suffers constant,
14:39cataclysmic bombardment and swells into a glowing, molten ball.
14:46About 100 million years after the Earth began to form, a change.
14:50Lava, literally the scum of the Earth at the time, the lightest part of the molten magma sphere,
14:56begins to cool and darken into a crust.
15:01For now, the crust will keep melting, but it's a start.
15:09Then something truly remarkable emerges.
15:12Lighter blobs of the molten Earth, called cratons, shoot to the surface and stick,
15:18giving rise to the beginnings of the Earth's permanent crust.
15:24Meanwhile, the lava of the primordial Earth's surface
15:28has been belching out water vapor and other gases.
15:33The crust is melting, and the lava is forming a crust.
15:37Eventually, the atmosphere gets so saturated with water vapor that it begins to rain,
15:44in a continual downpour that drenches the lava for as much as a million years.
15:58Flying past the Earth at this time, we see a vast gray ocean,
16:02Beneath a red-tinted sky, punctuated by volcanoes and small land masses.
16:09And unlikely as it seems, life may have gained a foothold already.
16:14That life in the oceans that gave birth to it may actually be vaporized many times
16:20by cataclysmic bombardments, which have slowed but not yet stopped.
16:25Earth has begun to take on its final form.
16:28A crust, a skin so thin it would be less than a sheet of paper,
16:32were the Earth the size of a basketball.
16:35And under that, a molten, semi-solid mantle that boils in extreme slow motion.
16:41And finally, two cores, a liquid iron core, pulsing out a magnetic field.
16:47By now, the remarkable process of plate tectonics has kicked into gear.
16:53Though how and when it started, exactly, we do not know.
16:58But we do know that the Earth is a very special place.
17:03And that's why we're here.
17:06We're here to help you.
17:09We're here to help you.
17:10We're here to help you.
17:12We're here to help you.
17:13We're here to help you.
17:15We do not know.
17:18For what follows next, you might want to strap yourself in.
17:23It's going to be a bumpy ride.
17:27Here's how it might have happened.
17:30At first, cratons and one continent called Ur had the planet all to themselves.
17:36Then, around a half billion years later, Arctica took shape.
17:41About another half a billion years passed before Atlantica formed.
17:45The continents roamed separately until, about 1.8 billion years ago,
17:50Arctica collided with what is now eastern Antarctica to form Nena.
17:57Then Nena, Atlantica and Ur collided one billion years ago,
18:02forming the supercontinent Rodinia.
18:08After about 300 million years, the three landmasses separated
18:13and came back together in a new configuration, Pangaea.
18:17Pangaea came apart too.
18:20When Pangaea split, Ur and Atlantica split up too.
18:26If you're confused, join the club.
18:29Even the Earth seems confused.
18:33All of this movement made for a host of unlikely neighbors way back when.
18:38North America's eastern seaboard once rubbed shoulders with Chile.
18:43California and Australia were neighbors, if not connected.
18:47And Brazil was either connected to Nigeria or very close.
18:52Run the Earth time machine backwards and you can see why.
18:56But no matter how many times you run the demolition derby of the continents,
19:01a question remains.
19:03What the hell is driving them?
19:07Hell, apparently.
19:09The force driving the plates is the slow movement
19:11of the super-hot semi-solid mantle that lies below the rigid plates.
19:17Like hot soup, magma boils in slow motion.
19:20Superheated magma rises to the surface, begins to cool,
19:24and then sinks back down to the bottom of the pot
19:27where it is reheated and rises again.
19:30This cycle is repeated over and over
19:33to generate what scientists call a convection cell or convective flow.
19:38But where's the heat source keeping our earthy soup performing its circular gymnastics?
19:44Well, most of it is left over from the spectacularly energetic collisions
19:48and gravitational crushing that created the Earth to begin with.
19:52It's still trapped down there and it wants out.
19:56And there's something else in the molten depths
19:58that makes it pretty hot real estate.
20:01Radioactive material.
20:03The belly of the beast has plenty of uranium and other radioactive elements,
20:09all of which release heat as they decay.
20:14That decay has significantly slowed the rate at which the Earth is cooling.
20:21So what does this mean at the surface?
20:24Two things.
20:25First, magma being burped up along the ridges.
20:29Those places like Iceland where the Earth is tearing itself asunder
20:32is pushing the plates in their respective continents apart.
20:38Second, what goes on at the other end of those plates,
20:42the collision zone, may be equally important.
20:46Here, where the heavier plates dive under the lighter ones,
20:50yanked downwards by gravity,
20:52they haul along their plates back into the oblivion of the mantle.
20:56That's what we know, or what we think we know.
21:00But the details of what's going on in the deepest parts of the Earth
21:04that drive the engine of plate tectonics, we may never know.
21:15But what practically all scientists agree on today
21:18is that virtually everything on our planet is being shaped by gravity.
21:23Everything on our planet is being shaped by plate tectonics,
21:28including the grand panorama of life itself.
21:34How momentous are these forces?
21:37A glimpse of the heady heights of Earth's most outstanding feature
21:41is most informative.
21:44These are the Himalaya, with Mount Everest their crowning glory.
21:48For those who attempt to climb it,
21:50it seems eternal, immobile, and mercilessly solid.
21:55But Everest and its Himalayan companions
21:58are creeping upwards even as we speak.
22:02Spectacular reminders that the demolition derby of the Earth's surface
22:07dwarfs any power that humans can generate.
22:14The Himalaya majestically lay claim to 96 of the 100 tallest mountains on Earth.
22:20And Everest, the highest of all, pokes a hole in the sky at 29,000 feet.
22:27High up on Everest, higher than the Seiner among us dare to go,
22:32you can find something fascinating.
22:34Fossils.
22:36Fossils of sea creatures from the trilobite family.
22:40Some more than 500 million years old.
22:44How did they end up at the cruising altitude of an airliner?
22:48This dramatic episode of Earth's soap opera might be called
22:51When Continents Collide.
22:54And the result gives new meaning to the term upward mobility.
23:00Let's rewind Earth's history by about 175 million years.
23:06Something that looks suspiciously like India
23:09breaks off the southeastern tip of Africa and begins drifting north.
23:13Then, 50 million years ago, boom.
23:17The leading edge of the Indian plate, which is oceanic crust,
23:21slams into the continental Eurasian plate.
23:25When the two continents meet head-on, the crust buckles upwards.
23:30The Eurasian plate crumples over the Indian plate.
23:35The collision of the two plates over millions of years
23:38has thrust the Himalaya and the Tibetan plateau to their present.
23:43Dizzying heights.
23:48And they're still growing.
23:50Where they will stop, no one knows.
23:56Global positioning devices planted on the summit
23:59show that Everest seems to be rising by an inch and a half a year.
24:04And that's how those little ocean-loving trilobites got all the way up there.
24:08They used to live in the sea that India squeezed shut
24:11just before it rammed into Asia.
24:19Believe it or not, the Himalaya are hardly without precedent
24:22in the history of the Earth.
24:25Let's rewind the Earth back to about 450 million years ago.
24:30Remember Pangaea, the supercontinent?
24:33Well, just before it was Pangaea, it was two supercontinents.
24:38One named Laurasia, and the other named Gondwana.
24:42When Laurasia and Gondwana collided,
24:45the resulting mountain range may have been the greatest the world has ever seen.
24:51Rivaling Everest and his brethren.
24:57In the wear and tear of time,
24:59erosion has since obliterated all traces of that mountain range's highlands.
25:07All that's left of the stumps, like worn teeth,
25:11in places like the Appalachian Mountains in the North American East.
25:19So much for when continents collide.
25:23But this is only the tip of the iceberg of our journey through earthly collisions.
25:28Sometimes continental plates smash into ocean floor plates.
25:33Sometimes sea floor hits sea floor.
25:37And sometimes plates simply grind against each other,
25:40like ships passing way too closely in the night.
25:44All to create topography as awesome as Mount Everest is tall.
25:51When the lighter continental plates crash into the heavier plates of the ocean floor,
25:57the ocean floor plunges underneath,
26:00creating the very deepest parts of the oceans, its trenches.
26:04Let's drain the planetary tub once again
26:07and take a glimpse at the Pacific floor off South America.
26:11Here the oceanic Nazca plate is ramming into and surging
26:15under the continental part of the South American plate.
26:19In turn, the lighter South American plate crumples upwards,
26:24creating the towering Andes, the backbone of the continent.
26:29It's a dangerous backbone.
26:31It's a dangerous backbone.
26:33Here legendarily strong earthquakes rumble and killer volcanoes spew.
26:40In some places, of course, ocean plate inevitably converges on ocean plate,
26:46and the result is a catastrophic downward mating dance that creates devastating earthquakes.
26:53The Mariana Trench paralleling the Marianas Islands, for example,
26:57marks where the fast-moving Pacific plate converges against a slower-moving Philippine plate.
27:03The challenger deep at the southern end of the Mariana Trench
27:07plunges so deeply into the Earth's crust
27:10that you could flip Mount Everest upside down and fit it easily inside.
27:17Here, too, volcanoes are born.
27:20Over millions of years, the erupted lava has formed volcanic rock on the ocean floor
27:26that piles up until a submarine volcano rises above sea level to form an island volcano.
27:33Such volcanoes are typically strung out in chains called island arcs.
27:40The result of all the intricate plate tectonics fringing the giant Pacific plate,
27:45with the attendant bounding and plunging and scraping,
27:48geologists call the ring of fire.
27:53And they aren't kidding.
27:54The ring quakes and explodes up through Java, the Philippines, Japan, and Russia,
28:00rumbles east along the Aleutian island chain to Alaska,
28:03and then turns violently southward down the western coast of North, Central, and South America.
28:10Destructive earthquakes, volcanoes, and tsunamis all find a home in this ring of fire.
28:20So that leaves a compelling question.
28:22Where's an Earthling to go to find a nice, calm, geologically settled place to hunker down?
28:31Clearly not those places where the Earth is tearing itself apart
28:36and creating volcanoes and earthquakes.
28:41Or the places where the Earth is smashing together,
28:44creating often even worse volcanoes, earthquakes, tsunamis, and the like.
28:53Maybe we can safely retreat to the centers of the various plates
28:58and enjoy their quiet beauty in restful ways.
29:03The feel of solid and mobile rock beneath our feet, right?
29:10Wrong.
29:11Some of the scariest, most violent places on Earth lie smack in the middle of giant plates,
29:18which by all rights should just sit there,
29:20placidly ignoring what's going on at the faraway edges.
29:24And no one knows exactly why they don't.
29:29For a glimpse into what might be giving the nicely settled parts of the world major indigestion,
29:34let's return to paradise, Hawaii.
29:40It is thousands of miles from the ring of fire,
29:43right in the middle of the giant Pacific plate, far away from the action.
29:47So how did it get here?
29:52Hawaii, it seems, is just the tip of the iceberg,
29:56or make that the fireberg, of immense proportions.
30:00There are a handful of such places around the world, and like Hawaii,
30:05they usually make for benign and beautiful islands.
30:09They are called hotspots.
30:13But don't be lulled by Hawaii.
30:15There's one volcanic hotspot out there that's threatening to bring the world as we know it,
30:19to an end.
30:21Like to know which volcano is going to make for great vacation pictures?
30:26Which might kill hundreds of thousands of people?
30:30Which one has the potential to devastate life on Earth, including, perhaps, us?
30:37It's time to dive into those smoldering, explosive flagships of the lava-driven world.
30:42Volcanoes.
30:49So here we are, back in Hawaii,
30:52away from the hellish rims of the Pacific Ocean, known as the ring of fire,
30:58where volcanic eruptions are catastrophically explosive,
31:02and earthquakes can tear the Earth apart,
31:05level cities and hurl giant waves shoreward,
31:08taking hundreds of thousands of lives.
31:12Here, lava tends to seep and spit lazily out of restrained volcanoes.
31:18It eats everything in its path, including human habitation,
31:24but usually moves no faster than walking speed.
31:29Only rarely have Hawaii's volcanoes lashed out explosively.
31:33What's Hawaii's secret?
31:35It's a plume of magma, a hotspot, rising from deep within the Earth's molten mantle,
31:41that has somehow managed to break through the crust of the giant Pacific plate.
31:46It has created, in succession, the islands of the Hawaiian chain,
31:50until it reached here, under the Big Island and Luihi,
31:54the baby volcano that won't breach the surface for another 50,000 years.
31:58Because the Pacific plate is moving northwest, but the hotspot itself stays put,
32:04each island is carried away as another one forms.
32:10But the magma under Hawaii, rechristened lava once it emerges from its tube,
32:16is running, almost liquid.
32:20It's been flowing out from under the Pacific plate for over a century,
32:24almost liquid.
32:26It's been flowing out from under the Pacific plate for millions of years.
32:37Layer upon layer of almost flat lava fields,
32:42creating gently rounded volcanoes that have been slowly building up from the sea floor.
32:48These volcanoes are called shield volcanoes, for their gently curved shape.
32:56Despite their tendency toward non-violence,
32:59one must not underestimate the tremendous power of these shield volcanoes.
33:04Mauna Loa on the Big Island, quiet now, but still stirring,
33:08is 13,681 feet above sea level,
33:12which means it rises more than 29,000 feet above the deep ocean floor.
33:19This magnificent geologic creature would be taller than Everest,
33:23if much of it were not underwater.
33:28Hawaii's slow and steady wins the race attitude,
33:32comes from that gentle lava,
33:35which comes in two forms,
33:37pahoehoe and a'alava.
33:39Pahoehoe is a smooth, ropey lava flow,
33:43and accounts for most of the lava splashed out of its volcanoes.
33:48A'a is a chunky, rough, broken lava flow.
33:52Legend has it that a'alava got its name
33:55from the noises barefooted people shouted
33:58while walking across its razor-edge, glass-tipped surface.
34:02It's only a legend.
34:04A'a actually means stony in the Hawaiian language.
34:10In human memory, the lavas of Hawaii have taken very few lives,
34:17perhaps five in the last century,
34:20and about a hundred people who happened to be in the wrong place
34:24at the wrong time, back in the 1700s.
34:29Compare that toll to other volcanoes elsewhere.
34:3236,000 killed by Krakatoa in Indonesia.
34:36The sound from its explosion
34:37was one of the loudest sounds humans ever heard.
34:4430,000 killed by Palai in the Caribbean.
34:48Thousands more by Vesuvius in Etna in Italy.
34:53These are tolls directly from the volcanoes.
34:56This doesn't take into consideration the hundreds of thousands
34:59who died through the ages from even larger volcanoes
35:02that affected climate, decimating crops for years afterwards.
35:08So why is it that the volcanoes whose names reverberate through history
35:12went boom instead of bloop?
35:15Why is it that the volcanoes whose names reverberate through history
35:19went boom instead of bloop?
35:21Why is this so terribly different from this, or this, or this?
35:29Now those look like real volcanoes,
35:32and they'll kill like real volcanoes.
35:36They're cones.
35:37They smoke, they brood, and then all hell breaks loose.
35:42Welcome to the deadly splendor of the composite volcano,
35:46also known as the volcano of the dead.
35:49Composite volcano, also known as a stratovolcano.
35:53Unlike Hawaii's shill volcanoes, which are flat and broad,
35:57composite volcanoes are tall, with steep sides, and they're violent.
36:05The steepness of their slopes hints strongly at their destructiveness.
36:13Other famous composite volcanoes include Mount Fuji in Japan,
36:17Mount Koropahi in Ecuador,
36:20Mount Shasta and Lassen in California,
36:23Mount St. Helens and Mount Rainier in Washington,
36:27Mount Pinatubo in the Philippines.
36:31Some slumber, some smoke, and some wait.
36:36Why?
36:39Lava apparently has a very different personality from place to place.
36:43And in some locations, it's positively explosive.
36:49This is the lava from Mount Unzen in Japan.
36:53Notice how it doesn't run or flow or splash
36:55or do anything that sounds remotely like fun.
36:59And here's Montserrat. Notice it just sits there.
37:04Chunky, glowering, bulging, and totally repressed.
37:09And if you asked it how it felt, it would say fine and turn away,
37:14seething and steaming.
37:16Even at high temperatures, it doesn't melt.
37:20It's too sticky. It bulges out into a dome,
37:25the smoking silo of a natural bomb.
37:28Apply more pressure from the Earth's mantle,
37:31and the lava shatters explosively,
37:35sending a plume of lava into the atmosphere.
37:38A plume of flaming ash hurling into the sky.
37:42And what goes up must come down.
37:45The ungodly return of the flaming ash to Earth
37:49is called a pyroclastic flow,
37:52a burning avalanche of stuff that's hotter than your oven
37:55and moving at the speed of a bullet train.
37:58It's what stopped time for the poor Romans of Pompeii,
38:02entombed by burning ash in their attempts to escape.
38:06It's what swallowed a Japanese town
38:09after killing some of the most experienced volcanologists in the world.
38:16It's also what left the capital of the Caribbean, Eden,
38:18called Montserrat, in ruins.
38:22And the smoking volcano belches threateningly to this day.
38:28All around the world, stratovolcanoes like these
38:32are stockpiling their explosives.
38:35Brooding and smoking,
38:37awaiting the moment when the magma below them
38:40lights the lava fuse and detonates.
38:46Unbelievably, despite the destruction and death toll
38:49such volcanoes have visited upon mankind,
38:53they are minor compared to the violence
38:55that the lava world may have in store for us.
38:59And now we get to the three great time bombs of plate tectonics
39:03that lie somewhere in Earth's future.
39:06The supervolcano, the megathrust earthquake,
39:10and the mega tsunami.
39:19On the day after Christmas in 2004,
39:22the world reeled at one of the worst natural disasters of all time.
39:26A huge tsunami.
39:29The cause of so much devastation?
39:31The most powerful kind of earthquake on the planet.
39:35A megathrust earthquake deep in the Indian Ocean.
39:39It killed almost a quarter of a million people.
39:46But if a megathrust occurs closer to the surface,
39:50the toll could be much greater.
39:54Megathrust earthquakes occur when one of the Earth's plates
39:57subducts or plunges under the other.
40:02If the plunging plate becomes stuck against the upper plate,
40:05the pressure builds until the lower plate
40:07suddenly and catastrophically releases,
40:11and a huge megathrust earthquake occurs.
40:16Widely thought to be the largest earthquakes
40:18a planet can generate,
40:20they often measure 9.0 or more on the Richter scale.
40:25And if one should occur on land,
40:28in a populated area,
40:31what then?
40:35Welcome back to Tokyo,
40:37home to over 12 million people
40:40who live in a megathrust fault zone.
40:44Some 100,000 people died in the Great Tokyo Earthquake of 1923.
40:50The fault is overdue to slip again.
40:54Magma is pushing the Philippine Sea Plate
40:56and the Pacific Plate under the Eurasian Plate,
41:00once thought to be 24 miles below the surface.
41:05We now know that the tops of the plates
41:07are actually less than three miles down.
41:11That's why earthquake experts call Tokyo
41:14a city waiting to die.
41:18When the big one hits,
41:20will Tokyo be leveled?
41:25Tokyo's geological nemesis
41:27could generate a tsunami of immense proportions.
41:33But it turns out it's not just earthquakes
41:35that can trigger a megatsunami.
41:40Lying below the waves
41:41off the beautiful coast of Hawaii's Big Island,
41:44just out of sight,
41:46lie piles of rubble that extend miles out to sea.
41:51Apparently, that rubble didn't get there gradually.
41:55Instead, part of the giant Mauna Loa volcano
41:59may have collapsed catastrophically
42:01into the sea some 100,000 years ago,
42:05creating a megatsunami that rebounded on the islands.
42:10Reaching a height of nearly a third of a mile,
42:12the waves swept inland,
42:14tossing coral 1,600 yards up on the great volcano's flanks.
42:21It would have dwarfed the tsunami
42:23of 2004.
42:28Off the sheer cliffs of Maui,
42:30even more rubble lies underneath the sea,
42:33evidence of an even bigger landslide.
42:38Apparently, these happen every 200,000 years or so.
42:43So nothing to sweat about now, perhaps.
42:48But Hawaii isn't the only place
42:50where giant volcanoes are breaking erratically.
42:53They're eroding and leaning dangerously out to sea.
43:01This is the island of La Palma in the Canaries.
43:05In 1949, the southern volcano on the island erupted,
43:09cracking off a huge chunk of the volcano's western half.
43:14Eventually, that western flank could give way,
43:17hurling an area three times the size of Paris,
43:20a mile thick into the Atlantic Ocean.
43:23Pointing straight at North America.
43:27What could happen when the volcano on La Palma collapses?
43:31Some scientists predict a wave far bigger
43:33than anything ever witnessed in modern times.
43:37The resulting mega-tsunami could send a wave 20 stories high,
43:42racing across the Atlantic at the speed of a jetliner.
43:47Up to eight stories of water could crash
43:49into the east coast of the United States,
43:52swamping Boston, New York and Washington, D.C.
43:55in quick succession,
43:57before heading down the coast
43:59and inundating the Caribbean islands.
44:03It's hard to imagine that the Earth
44:05could have worse in store for us.
44:07But it does.
44:09And some say it's overdue.
44:17There is no landscape quite like this one.
44:20Here, more geysers erupt than anywhere else in the world.
44:29This is the world's first national park, Yellowstone.
44:35But America's most popular tourist attraction
44:38is also a time bomb of unimaginable proportions.
44:44Something so deadly,
44:45it could conceivably bring civilization to its knees.
44:50The earliest geologists to visit Yellowstone
44:55understood that all of this beauty
44:57had uneasy geological underpinnings.
45:02But many speculated that because no volcanic peak
45:06or crater was visible,
45:08Yellowstone did not represent a threat.
45:11That's because they were looking at Yellowstone from the ground.
45:16Pull out from Yellowstone to a satellite view,
45:20and something awesome and frightening becomes clear.
45:23Almost the whole park is a volcanic crater or caldera.
45:29Roughly 50 miles in diameter.
45:34Yellowstone is one of the rarest
45:36and most terrible geological phenomena on Earth.
45:40The super volcano.
45:43It turns out that Yellowstone, like Hawaii, is a hotspot.
45:47With a plume of magna welling up from the mantle.
45:51Also like Hawaii, Yellowstone is always active on some level.
45:57Witness its magnificent sound and light shows.
46:02But unlike Hawaii, when Yellowstone blows, it really blows.
46:10Right now, the magna beneath the surface
46:12causes Yellowstone to breathe.
46:14The land here rises and falls, often by a couple of meters.
46:19Scientists predict that one day this bulging molten lava
46:22will burst through the Earth's crust.
46:26It's just a question of when.
46:30Yellowstone seems to erupt pretty much like clockwork
46:32every 600,000 years or so.
46:35And it last went boom about 640,000 years ago.
46:40Uh-oh.
46:42The last eruption of a super volcano
46:44was in Toba, Sumatra, 74,000 years ago.
46:49It was 5,000 times greater than Mount St. Helens
46:54and may have changed life on Earth forever.
46:57So much ash was hurled into the atmosphere
47:00that it obscured the sun.
47:04Everywhere in the world,
47:05Yellowstone erupted in the middle of the night.
47:09Everywhere in the world,
47:10global temperatures could have plunged.
47:13The rain would have been so poisoned by the gases
47:16that it would have turned strongly acidic.
47:20Plant life all around the world may have suffered.
47:24Man may even have been pushed to the edge of extinction.
47:28The population forced down to just thousands,
47:32which could explain our lack of genetic diversity.
47:38What if Yellowstone were to go today?
47:41Would humanity survive?
47:44No one really knows.
47:47The good news, though,
47:48even if mankind were blown to smithereens,
47:51the Earth would continue on as a living,
47:54breathing organism in its own right.
47:56The demolition derby of continents
47:59would continue unabated.
48:01Thanks to the momentum of plate tectonics,
48:03we can run time forward
48:05and get a glimpse of a possible future.
48:08If all continues on its current course,
48:10we may see California sailing away into the Pacific.
48:15The Pacific Ocean shrinks
48:16as the Atlantic grows to dominate the planet.
48:20Africa charges northward,
48:22squeezing the Mediterranean shut,
48:24crumpling the Italian boot,
48:26and sending mountains soaring from Paris to India.
48:31Australia crashes into Asia,
48:33the Red Sea parts,
48:35and becomes a new Atlantic-sized ocean.
48:39How high can Everest go?
48:42Everest continues to grow even taller,
48:45but scientists think it will likely begin to crumble
48:48under its own weight.
48:51Clearly, this is a dangerous planet
48:54we found ourselves on,
48:56thanks to the magma machine we skate on
48:58and its tendency to push, pull, and explode.
49:02But what to us is disaster upon disaster
49:06is another thing entirely to the Earth itself.
49:09The lava-driven world is a living,
49:11breathing, mobile organism in its own right,
49:15full of stresses and strains,
49:17always seeking peace and equilibrium
49:20despite its internal conflicts.
49:24Volcanoes release internal heat.
49:26Earthquakes relieve stress on its surface.
49:30Life may well have been born of lava,
49:32perhaps on some chemical wonderland
49:34created by smokers under a primordial sea.
49:38It almost certainly owes much of its diversity
49:41and hardiness to the plate tectonics
49:43that drives continents apart
49:45and smashes them back together again.
49:48Without lava,
49:49the world would be a cold, characterless stone in space.
49:54Instead, it blesses us with oceans
49:57and renews the surface of the Earth
49:59with rich, fertile land.
50:01Unknowing, unmoved, it moves us
50:04and holds our fate in its hands,
50:07glowing fingers and glowering fists.
50:31you