- 15 hours ago
(1) Mountain Building: Volcanic eruptions, earthquakes, and ancient ice ages formed huge plateaus and mountain chains like the Rockies.
(2) Key Locations: The episode explores regions from the ancient Canadian Shield across the Grand Canyon.
(3) Future Changes: Tectonic shifts suggest that parts of California will eventually break off to become an island in the Pacific Ocean.
这部非凡的系列片宏大而全面地讲述了地球各大洲的崛起历程。它们是板块构造运动与地壳持续演变共同演绎的壮丽华尔兹的产物。随着陆块的聚合与分离，火山喷发与地震频发，山脉拔地而起，峡谷裂变生成。我们将透过地质学家及其他科学家的视角，见证这历经漫长岁月塑造而成的地球。
(2) Key Locations: The episode explores regions from the ancient Canadian Shield across the Grand Canyon.
(3) Future Changes: Tectonic shifts suggest that parts of California will eventually break off to become an island in the Pacific Ocean.
这部非凡的系列片宏大而全面地讲述了地球各大洲的崛起历程。它们是板块构造运动与地壳持续演变共同演绎的壮丽华尔兹的产物。随着陆块的聚合与分离，火山喷发与地震频发，山脉拔地而起，峡谷裂变生成。我们将透过地质学家及其他科学家的视角，见证这历经漫长岁月塑造而成的地球。
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TVTranscript
00:02Since its formation, our planet has undergone constant transformation.
00:11Stupendous collisions have created continents.
00:16Colossal forces have raised up ocean floors, forming dramatic mountain ranges.
00:26These movements on the Earth's surface can still be seen today as evidenced by volcanic eruptions, earthquakes and tsunamis.
00:38Tectonics sculpt our landscapes, alter the climate, change the course of oceans and can even influence the living world.
00:55For millions of years, fragments of the Earth's crust have come together and broken apart, resulting in volatile upheavals.
01:03Even today, the continent carries scars of its tumultuous past.
01:09From smoky craters to craggy mountaintops, specialists track these hidden clues.
01:17In their hands, every rock, every fossil becomes a word on the page in the story of North America.
01:24An exceptional testimony to the never-ending voyage of the continents.
01:48At its birth, 4.6 billion years ago, the Earth is a gigantic ball of lava.
01:55Then it cools, and rocky plates aggregate, forming the first fragments of the Earth's crust.
02:02Thus begins the first chapter of the history of the North American continent.
02:09In Montreal, located in eastern Canada, it so happens there's a researcher who studies these vestiges of our planet's infancy.
02:22Professor Don Francis works in the Department of Earth and Planetary Sciences at the prestigious McGill University.
02:31Every day, he rides his bike across Montreal's historic city centre to his laboratory.
02:40This area is ideal for geologists, because 90% of the province of Quebec is covered by what's called a
02:47craton,
02:49a fragment of the Earth's crust which has remained unchanged for billions of years.
02:58The rocks that crop out here are not the oldest.
03:02But for the scientist, each one will likely reveal an element of North America's story nonetheless.
03:12So all these rocks are much younger than the rocks of the craton, which normally are 2.7,
03:19and our team have discovered an area in the craton where the rocks are as old as 4.3 billion
03:25years old.
03:25This is very old age, and the rocks there tell us a lot of interesting things about that time.
03:33For example, we know that because there are pillow lavas there, that there was an ocean.
03:40This was at a time when the Moon was being bombarded by very large meteorites.
03:45All the big craters you see on the Moon were produced during this time.
03:48And in fact, it must have been happening on the Earth as well.
03:52So you have a marine environment where there are hot springs and there are big meteorites falling out of the
03:59sky.
03:59So it was a very unusual environment.
04:05Don Francis and his colleagues recently discovered these rocks dating back 4.3 billion years in northern Quebec.
04:14The announcement caused a sensation in the scientific community.
04:18These rocks are, in effect, the oldest specimens ever discovered.
04:25The study of their structure gives an unprecedented view of the environment that reigned on primitive Earth.
04:34But the geologists must still confirm the rocks' age in a definitive manner.
04:40To do this, they look for traces of a particular mineral inside the granite, zircon.
04:48This mineral is known to be exceptionally stable and to contain infinitesimal quantities of uranium,
04:55which over time, transform into lead.
04:59Thus, by calculating the proportions of lead and uranium in the zircon crystals,
05:04the exact age of the rock can be determined.
05:11Cut in very fine slices, the samples reveal their inner structure under the microscope's lens.
05:19There's one of these garnets in black.
05:22There's a filter in, but when you take the filter out, they're clear.
05:27And that's the way you identify the garnet.
05:32Up until recently, 3.8 were the oldest rocks.
05:36The result of that is a lot of people are now going back to 3.8 areas,
05:40of which there are not very many.
05:41You could probably count them on two hands, maybe less.
05:44But they've been going back into these areas, trying to see whether they can find the same anomaly that we
05:49found,
05:50and to see whether there are, in fact, more than one occurrence of very old rocks.
05:57Every day, Don teaches his students the history of the Canadian craton.
06:03Other tests are still necessary to assure that the oldest of the rocks are indeed 4.3 billion years of
06:09age.
06:11But if the results are confirmed, a new chapter will be added to the class syllabus,
06:16that of the birth of the North American continent's very first land mass.
06:24Later, fragments of the Earth's crust spread across the surface of the globe,
06:29migrating and combining with one another.
06:33When they collided, mountains were created.
06:36When they broke apart, oceans and seas were hollowed out.
06:45Then water and rain eroded their surface over millions of years.
06:52Traces of these ancient events are still visible today,
06:56notably on the Colorado Plateau in the heart of Monument Valley.
07:09Here, successive layers of strata testify to the never-ending evolution of the relief over millions of years.
07:22But the tectonic plates are always in motion.
07:26And 500 million years ago, the continental land masses in the northern hemisphere began to draw closer.
07:33Little by little, they began to collide with Africa.
07:39And about 100 million years later, a vast supercontinent was formed, the Pangaea.
07:48Today, the landscapes tell the story of Pangaea's birth,
07:51a major event in the history of North America.
07:57Southeastern Canada, in the province of Nova Scotia.
08:00The city of Passborough is located near the Appalachians.
08:05A vast mountain range born when America and Africa collided.
08:25Paul Olsen, a geologist and biologist at Columbia University in New York, knows the area by heart.
08:35He's roamed these coasts for many years in search of new clues to Pangaea's history.
08:45This is Nova Scotia in eastern Canada.
08:49300 million years ago, on this spot, North America and Africa collided, producing Pangaea, the last of the great supercontinents.
08:59This is really the center of the action.
09:01I'm going to show you with a drawing.
09:04Here is North America.
09:07And it's heading this way.
09:10And here comes Africa.
09:13And it's being shoved below North America.
09:16And when they finally collide, they produce an enormous mountain range, the Appalachians.
09:28Sprung from the earth 270 million years ago, today the Appalachians spread over more than 3,000 kilometers.
09:37A veritable open-air geological archive, it's the proof that long ago America and Africa formed one and the same
09:45territory.
09:47When the North America and African plates collided, they did so with tremendous force, so much so that they shoved
09:55the rocks up from their original flat-lying positions into these twisted and contorted forms that you can see here,
10:03barely recognizable from the way they were when they were formed.
10:06And you can find exactly the same kind of rocks in Africa today.
10:11So what actually happened?
10:14At about 50 million years later, the North American and African plates began to collapse.
10:20And as they collapsed, Africa began to pull away from North America.
10:26And the crust began to stretch and sink, forming a giant rift basin, when finally the Atlantic Ocean formed about
10:37200 million years ago.
10:41The opening of the Atlantic Ocean marks the end of Pangaea.
10:46But this fracturing makes for a bumpy ride.
10:49As the continents break apart, the Earth itself fissures in all quarters.
10:56In the interstices, astronomical quantities of magma rise from the depths of the mantle.
11:06Massive successive volcanic eruptions continue for more than 600,000 years.
11:16Now that rock is really interesting.
11:20On this side, you see red sediments deposited by streams and rivers.
11:24On this side, you have a completely different kind of rock.
11:28It's called basalt.
11:29It's basically hardened lava.
11:31It's 201.6 million years old.
11:35And it's vivid evidence of the formation of the Atlantic Ocean, right here.
11:45If you look carefully, you can see little white dots.
11:48Those are minerals that filled in holes that were originally filled with gases.
11:52And those gases caused a mass extinction at exactly the time of the eruptions of these lavas.
11:58One that shaped the future of life on Earth and, in fact, allowed our ancestors very long ago to survive
12:06and fill the world.
12:14座風 Track
12:15One that sacrificial
12:29Animals and plants were quite different in different places.
12:31And there was a tremendous amount of diversity on the land.
12:35There were crocodile relatives that were dominating.
12:37the landscape over all of Pangaea. However, when North America and Africa began to split apart
12:44and the lava erupted in that enormous area, the gases that were produced by that eruption
12:51caused climate changes that killed off almost all of the crocodile relatives,
12:57leaving ecological space open for the dinosaurs to occupy. And after that is when dinosaurs
13:03actually took over the Earth and we begin the real part of the age of dinosaurs.
13:14200 million years ago, the tectonic plates resulted in a massive extinction of species.
13:23These are interesting. In total, half of the Earth's biological
13:28diversity disappeared, giving the dinosaurs free reign. Thus began their unrivaled dynasty on the planet.
13:39Along the banks of Nova Scotia, a few of these reptiles' fossil prints are still visible,
13:45the last remnants of their former domination.
13:57Cretaceous giants left other evidence of their passage.
14:13In the Canadian province of Alberta,
14:15the city of Drumheller houses the Royal Tyrell Museum, the largest in the world dedicated to dinosaurs.
14:25Gathered here are the skeletons of hundreds of specimens representing more than 35 different species.
14:34François Therrien is a paleontologist and geologist. His specialty, the study of the environment
14:40and behaviour of dinosaurs during the Cretaceous period.
14:47So, we're here in the storage room. It's here that plaster jackets containing the fossils
14:53are stored until they can be prepared. As you can see, there are a great many fossils.
14:59The oldest date back to 1962. And we'll probably never be able to prepare all of them.
15:05There are so many specimens. There's always a priority. We always prepare the nicest specimens before the others.
15:29And we're here in the storage room. And we're here in the storage room.
15:29Hi, Donna. How are you? Hello, I'm good. How are you?
15:33Good, good. What are you working on? I'm working on a gar block.
15:393D gar. Very rare. So far, I've found about 20 of them in here.
15:45Cool. Well, I was coming to ask you, do you want to go to the field? Go to the Tolman
15:49startups and dig site?
15:50Sure. Cool. Okay. Well, I'll have a few things to do and then I'll just meet you at the site
15:56then.
15:56Cool. Cool. See you there.
16:01The Alberta region is Francois Therrien's main excavation zone.
16:09The great majority of fossils exhibited in the museum come from an area called the Badlands.
16:20This valley, with its almost lunar scenery, draws a long scar across the Canadian west.
16:28It formed 100 million years ago.
16:32At that time, the face of North America was vastly different from these spectacular landscapes.
16:38About 180 million years ago, at the end of the Jurassic period,
16:42a subduction zone developed on the west coast of the North American continent.
16:47Because the crust fragments rose and pressed down on the North American,
16:51the continent started to sag, forming a huge depression in the middle of North America.
16:58Over millions of years, the marine level fluctuated in such a way that the ocean invaded the center of
17:05the North American continent, developing a great inside sea that connected the Arctic Ocean to the Gulf of Mexico.
17:13Great coastal plains rose up around this inside sea.
17:18These coastal zones were inhabited by the dinosaurs.
17:31Buried under the sediment, the skeletons of reptiles have traversed time and reappear today in a perfectly preserved state.
17:38Buried under the sea.
17:46Hey guys!
17:48How's it going?
17:50Good, good?
17:52Anything new? A skull or something?
17:59Since dinosaurs only lived between 230 and 66 million years,
18:04we have to find the rocks that were deposited here during that period.
18:08So south of Alberta is the best place on Earth because it meets these criteria.
18:13There are rocky outcroppings that formed around 80 to 66 million years ago,
18:18deposited in the rivers and lakes,
18:20and we also have the advantage of a very arid climate,
18:24which limits plant growth.
18:26There are no big forests to cover the outcroppings,
18:29so there are a lot of rocky outcroppings,
18:31which means we can walk about the typical Badlands landscapes
18:34and discover other dinosaurs.
18:44François and his colleagues delicately probe the soil,
18:47looking for the tiniest fragments of fossilized bone.
18:51And like every year, the prospects look good.
19:04We see here, it's a bone poking out of the rock.
19:09It's the backbone of a horned dinosaur, a Ceratopsia.
19:23So in fact, we can say that tectonics aren't only responsible for forming the Great Plains of the North American
19:29continent,
19:30but tectonics are also responsible for providing ideal conservation conditions for all the dinosaur bones we find here.
19:37As the rocks rose and the Earth's crust sagged, there were a lot of rivers running towards this inside sea.
19:43These rivers overflowed the plains with alluvium and buried all the animals here.
19:47And it's thanks to this tectonic phenomenon that we can admire dinosaur bones in museums all over the world.
19:53It's a lot easier.
19:57Tirelessly, each year the researchers continue to unearth new bones.
20:05These fossils make it possible to deepen our knowledge about dinosaurs,
20:09but also of the history of the Great Plains,
20:12the swath of terrain born in the heart of North America more than 100 million years ago.
20:22But further west, the age of dinosaurs is marked by another major geological phenomenon.
20:31The continent drifts slowly, colliding with fragments of the continental crust
20:35dispersed across the ocean's surface.
20:39These tiny islets of land successively graft themselves to the North American plate,
20:44which grows little by little.
20:47This is how the four most westerly states on the continent,
20:50Nevada, Oregon, California, and Washington, were formed.
21:01Alan Glasner, geologist at the University of California,
21:05studies the history of these collisions that gave North America its final shape.
21:15He carries out his research in the heart of Yosemite National Park.
21:25With its mountains, lakes, and waterfalls that hurtle down the slopes,
21:30it's one of the most beautiful parks in all of the United States.
21:35The result of the encounter between North America and the future western states.
21:45The collisions caused a folding of the rock and provoked violent volcanic eruptions.
21:59Magma rose from the depths, and as it cooled, formed these gigantic granite domes.
22:17If you looked at western North America from space before Pangea broke up, it would have looked quite different.
22:22Much of today's Nevada, Oregon, Washington, California would have been underwater.
22:30But as subduction started, as North America moved westward, then suddenly the continent started to grow
22:36because you started adding things like the granite we're standing on.
22:40And if you look at it carefully, you can see lots of detail in it that shows you how different
22:47pockets of magma came up and cooled and crystallized to form this body here.
22:53And one of the most obvious examples of that are these late dikes that came in.
22:58As the magma cools, as it gets almost 100% crystallized, it cracks, and the very last liquid gets sucked
23:05into those cracks
23:06to form these beautiful dikes that show up so well on this glaciated surface.
23:16These veins of rock, which scientists call dikes, are proof of intensive volcanic activity in the past.
23:28So on the map, we've mapped out all these different pulses.
23:32Some of them are dark-colored, some are very light-colored stripes,
23:35and they allow us to work out a sequence of injections of magma into this area.
23:46Magma from the Earth's depths has thus infiltrated fissures in the rock to reach the surface.
23:58There was a time in history when Yosemite National Park, like the rest of the American West,
24:03was in fact located off the coast in the middle of the Pacific Ocean.
24:11But when pieces of the Earth's crust collided, they finished by melding into a single continent.
24:22Around these collisions, the Earth gave rise to California's highest mountain range,
24:28the Sierra Nevadas, which stretch more than 700 kilometers from north to south.
24:51In the field, Alan Glasner constantly analyzes clues to these past events
24:56to recover the details of the region's geological history.
25:04Today, he is joined by one of his students at the foot of the park's most famous monolith, El Capitan.
25:14Here, the granite cliff rises more than a kilometer high.
25:22Roger, how's it going?
25:24Going well.
25:30Yeah, check this out, Alan. Here's a piece of that apolite.
25:41What's the black? Biotite?
25:43Yeah, all I can identify is biotite.
25:46That's a pretty rock.
25:48Yeah.
25:49We should definitely get a sample to analyze if it isn't in your database already.
25:55Mm-mm. Yeah, I don't have it from specifically here yet, so yeah, let's get one.
26:09I think one of the coolest pieces about the geology of El Capitan is that where we are right here
26:14at the base of El Cap
26:16was 10 kilometers below the Earth's surface, 104 million years ago,
26:21which is the same time as dinosaurs were roaming the Earth.
26:24So 10 kilometers above where we are now, there were dinosaurs walking around,
26:28which is just one of the coolest things.
26:29And there were big volcanoes going off at the same time, so those dinosaurs had a lot to worry about.
26:45Today, the Sierra Nevada's highest summit reaches an altitude of 4,400 meters.
26:56But this height pales in comparison to the colossal mountain that stood here in the past.
27:02Because over millions of years, water, wind and ice have worn down the rock.
27:15From the summit of Half Dome, Alan can contemplate the effects of this slow erosion.
27:25The Sierra Nevadas are now composed of a series of valleys and mountains with rounded peaks.
27:36When the Sierra Nevada forms a 90 million years and we're sitting here, you'd be about 10 kilometers down in
27:42the crust.
27:43There would be a very tall chain of volcanoes above you and there would be a subduction zone.
27:48Being subducted about the normal angle of the plate was going down at maybe 45 degrees.
27:54I'll make a sketch to illustrate that better.
28:00When the subducted plate gets to a depth of about 100 kilometers, then chemical reactions occur that produce magma.
28:09And so this magma rises, being less dense.
28:12Gets to the surface, it piles up and erupts, forms volcanoes and lava flows.
28:19It erupts volcanic ash and some of that magma gets trapped in the crust at depths of, well, let's say
28:2710 to 20 kilometers.
28:29And when it cools and hardens, it forms granite.
28:31And that's what we're standing in here.
28:34Erosion has taken off the upper layers of the crust and we're down within this magma factory.
28:41The Sierra Nevadas with its sumptuous landscapes is one of the places that best demonstrates the constant evolution of the
28:48continents.
28:49It was here, 100 million years ago, that North America extended westward to take on its current form.
28:59But during the same period, a different phenomenon was taking place a bit farther east.
29:04Another mountain range was also rising from the earth, the Rockies.
29:10This massif stretches for more than 4,800 kilometers from New Mexico all the way to northern British Columbia.
29:20The Rocky Mountains formed during the same period as the Sierra Nevadas.
29:25But for a long time, they mystified geologists the world over.
29:33Generally, mountain ranges are born at the edges of colliding plates.
29:38How then do we explain the presence of these peaks nearly 1,000 kilometers inland?
29:47Today, a hypothesis is at last taking shape.
29:51About 80 million years ago, a plate slid under the North American continent.
29:55But instead of dropping down at a 45-degree angle, as is usually the case,
30:01it wove its way in much closer to the surface.
30:05As a result, the rock didn't reach a sufficient depth to be melted by the heat.
30:12So the plate continued its journey, and jamming against the Earth's crust in its path gave rise to the Rocky
30:18Mountains.
30:23Today, not every detail of this event has been perfectly elucidated.
30:27But in all likelihood, the origin of the Rockies is a geological anomaly.
30:33A willful plate that suddenly refused to submerge.
30:44Backed up against the Rocky Mountains, another region was victim to the Earth's fitful rage for thousands of years.
31:01Yellowstone National Park, located in the state of Wyoming.
31:11Henry Heelsler is the park's geologist.
31:14Every day, he roams this immense natural reserve.
31:22His mission? Watch over the monster that sleeps just beneath the surface.
31:27A supervolcano of unimaginable strength.
31:33For years, specialists have tried to understand the origin of this supervolcano.
31:39They finally discovered that Yellowstone Park is situated on what is called a hotspot.
31:46These are zones where under the surface, the base temperature is unusually high.
31:54Thus, enormous quantities of magma rise from the depths and accumulate in a pocket several hundred kilometers under the ground,
32:02called a plume.
32:04When the magma is expelled, it pierces the Earth's crust and a volcano appears.
32:11But when the tectonic plate slowly floats above it, the hotspot doesn't move.
32:17It thus imprints its mark at regular intervals along the Earth's surface.
32:24In the last two billion years, the Yellowstone region was the site of three major eruptions.
32:31The last one dates back 642,000 years.
32:36Accumulated beneath the Earth's crust, the lava burst from its chamber and projected thousands of tons of molten rock,
32:43volcanic ash and sulfurous gases into the air.
32:49When material is forcefully erupted, not as a big blast, but basically vented through all the fissures and cracks that
32:59were forming in the Earth,
33:00it forms a caldera, which is a subsidence feature, and behind me you can see the evidence for that.
33:07Basically, the caldera starts almost exactly where I'm standing and then goes 72 kilometers directly behind me,
33:15where it's covered by more recent lava flows.
33:20In the heart of the National Park, the Yellowstone caldera forms a gigantic basin 72 kilometers long by 56 kilometers
33:28wide.
33:29It's all that remains of this colossal explosion, one of the most devastating in the history of the Earth.
33:36But today, the supervolcano is far from extinct. The Earth here rumbles non-stop.
33:44Geysers, gas and vapors, as well as other heat sources, punctuate the landscape, evidence of the intense activity that rains
33:52beneath the surface.
33:54The volcano is simply dozing, and it's potentially one of the most destructive on the planet.
34:05The super eruptions of Yellowstone, catastrophic for hundreds of kilometers around what currently is Yellowstone National Park.
34:16There would be no life left because of the force of the eruptions, the pyroclastic, the hot rock flows that
34:24come out tens of kilometers,
34:27the resulting ash clouds, the volcanic ash and volcanic gases that would be ejected high into the atmosphere and basically
34:36circle the entire globe,
34:38would cause a volcanic winter to cover the entire world.
34:54For many years, Yellowstone's supervolcano has been under close observation.
35:05The control center is located about 500 kilometers from there, at the University of Utah in Salt Lake City.
35:16The control center is located at the University of Utah at the University of Utah at the University of Utah
35:16at the University of Utah at the University of Utah.
35:22Jamie Farrell is a geologist. Every day his task is to analyze the volcano's slightest flutter,
35:28thanks to a network of sensors that measures deformations of the ground in real time.
35:35Recently, he also recreated the monster's history and constructed a model of the vast magma chamber that feeds it.
35:45So this is just a visualization tool that we use to kind of show the data that we record in
35:50Yellowstone.
35:51If you turn off the topography and we want to put on the earthquakes that we've recorded in Yellowstone as
35:57these red dots,
35:59what you can do here, you can zoom around and look underneath the ground and look at the patterns of
36:03earthquakes that have occurred from 1973 to the present.
36:07And again, there's roughly about 46,000 earthquakes here.
36:11If you want to look at a little bit of the bigger picture, we can turn on the Yellowstone plume,
36:17and that's this orangish-yellowish feature here. This is basically the Yellowstone hotspot.
36:21This is the feature that's providing all the heat and energy coming up from the mantle to feed the Yellowstone
36:27volcanoes.
36:28So you can see here it comes down, down into the mantle.
36:40So the Yellowstone hotspot manifests itself on the surface about 16 or 17 million years ago down in this area
36:47down here in the Nevada, Oregon.
36:49So this is kind of the track of the Yellowstone hotspot as the North American plate has moved over it.
36:54The western U.S. is stretching. We have an area called the Basin and Range where the crust is being
37:00thinned and stretched.
37:02The reason why the Yellowstone hotspot is here is because of that thinning and that may have provided a path
37:09for the hotspot to make it to the surface.
37:27Some 3,000 low-magnitude tremors shake the Yellowstone region every year.
37:34The Earth trembles. The ground is deformed. The composition of the gases evolves.
37:44But in the eyes of specialists, there is, for the moment, no proof of an imminent eruption.
37:58Change is the normal situation at Yellowstone with earthquakes, with ground deformation, with the geothermal system, with the gases.
38:07So roughly, the probability of another catastrophic eruption is very poorly understood because we've only had three in the past
38:182 million years.
38:20But it's about the same as a large asteroid hitting the Earth and destroying it.
38:25So if you're concerned about a large asteroid hitting the Earth, then maybe you should be concerned about Yellowstone having
38:32a catastrophic eruption.
38:43The future of this volcano eventually is to become very, very cold and inactive.
38:49It will probably end with outpouring of basalts.
38:53The ground elevation will go down because it will no longer be very hot.
38:58So we'll have a very, very different looking terrain sometime into the future.
39:04It may be millions of years into the future.
39:07So the more interesting question for me is, will humanity even be around when Yellowstone changes a lot?
39:17One day, the supervolcano will thus disappear.
39:22Until then, the volcanic gases of this hugely powerful monster will continue to dance above the staggering beauty of these
39:29lands.
39:33But today, another large-scale phenomenon is in progress.
39:42An immense scar rips through the western region of North America.
39:47Baptized the San Andreas Fault, it runs for 1,300 kilometers through California.
39:54In this area, the Pacific Plate climbs northeast, while the North American Plate descends in the opposite direction.
40:03The result? These two fragments of the Earth's crust slide against one another, making the ground tremble at regular intervals.
40:14On the banks of the San Francisco Bay, specialists from the University of California keep careful watch over the San
40:21Andreas Fault seven days a week, 24 hours a day.
40:25Everyone here is used to the regular tremors produced by the Earth's movements.
40:31The fault line is part of everyday life for Californians.
40:38On the campus, geologist Roland Bergman teaches about the history of geology, but also of its future.
40:47Because inerexably, California is breaking off from the continent at a rate of five centimeters a year.
40:54In a million years, it will have become an island.
40:58The San Andreas Fault was born about 25 million years ago.
41:02Before that time, California was a place where subduction occurred.
41:06So the San Andreas Fault is a strike-slip fault.
41:10That means that motions of plaques or plates adjacent to the fault are parallel to the fault and horizontal in
41:18a strike-slip motion,
41:19rather than one plate moving on top of the other, as we might see in a subduction zone.
41:25And if we have the San Andreas Fault continue with its motion, and there's no reason to believe that it
41:34would stop,
41:34in another nine million years, we should be seeing the Los Angeles Basin offshore here and ruining our views.
41:46A squeaky valve between two plates of the Earth's crust, the San Andreas Fault gave birth to a complex system
41:53of fissures.
41:56Several secondary fault lines have appeared, and now run across the entire region.
42:03Among them, the Hayward Fault, which runs to the east, is particularly worrisome to seismologists.
42:12Aurelie Guillem is a post-doctoral candidate from France at the University of California at Berkeley.
42:18In the field, she's on the lookout for possible signs of movement along the Hayward Fault.
42:23So here we are in the city of Hayward, which has the same name as the Hayward Fault.
42:29It was here that the 1868 earthquake took place.
42:32In addition to powerful earthquakes, of a magnitude of about seven, that occur along this fault, the fault also causes
42:40slow slipping.
42:42We can observe this slow slipping on the sidewalks, like here, but also by the cracks along the streets.
42:50This sidewalk wasn't made like this.
42:54It was built straight, but since then has been deformed by the fault zone that runs through here.
43:00We can clearly see the movement in the relationship between these two blocks.
43:06This movement corresponds to the movement of the Hayward Fault, which has a right lateral strike slip,
43:12so the block propagates to the south in relation to this block here, which propagates to the north.
43:21The plates thus slide slowly against one another.
43:26But sometimes the accumulated energy suddenly cracks the fault.
43:31It ruptures, provoking an earthquake.
43:38We're at the Memorial Stadium on the Berkeley campus.
43:43This stadium was built in 1923, after the 1868 quake hit along the Hayward Fault.
43:52It measured 6.8 on the Richter scale.
43:56This stadium was built after that.
43:59And it has some deformation that can be seen on the top of the stadium here,
44:04where in fact the Hayward Fault cuts the stadium in two.
44:09So it's been affected over time, even since the structure was built.
44:14Deformation is about 40 centimetres, and it proves that the Hayward Fault slides continuously about 0.5 centimetres per year.
44:26It's a relatively new structure, but we can clearly see a large deformation with the naked eye.
44:32It's a beautiful deformation visible to the eye.
44:38April 18th 1906, another earthquake registering 8.2 on the Richter scale hit the city of San Francisco.
44:50There were 3,000 victims, and it transformed the city into a vast field of ruins.
44:58This same phenomenon took place on October 17th, 1989.
45:0363 people died, nearly 4,000 others were wounded, and material damage reached almost $6 billion.
45:15Today, what everyone fears is the big one.
45:19The megathrust earthquake that's supposed to hit California in the next 30 years.
45:30For Richard Allen, director of UC Berkeley's seismological laboratory, residents must definitely prepare for this disaster scenario.
45:41So here we're on the UC Berkeley campus, and the Hayward Fault actually goes across the Berkeley campus.
45:47So if we have an earthquake on that fault, then we expect fairly significant damage in this area.
45:52Most of the buildings on campus here have been retrofit so that they should not collapse during an earthquake.
45:58However, many may be seriously damaged, and we won't be able to use them following the event.
46:07So while we can't predict the exact time at which an earthquake is going to occur, we know that we're
46:13going to have big earthquakes in this region over the next few decades.
46:16In fact, it's about a two in three chance of a major damaging earthquake in the Bay Area in the
46:21next 30 years.
46:22So that's how we can then get ready for these earthquakes by building buildings.
46:26But the other thing that we can do is we can use the very beginnings of an earthquake, the P
46:31waves that radiate from a fault, to say something about the shaking that's coming and provide a few seconds warning
46:37to people before they feel the shaking.
46:47Will the famous Golden Gate Bridge stand up to the big one when it hits?
46:53One thing is certain, the population must prepare itself for the next tragedy.
46:59Aurelie Guillem studied the possible consequences of a megaquake in the San Francisco Bay Area.
47:06And it's from this promontory overlooking the Bay that the amplitude of potential damage is most visible.
47:14From here, we can get an overview of the Hayward Fault.
47:20So, behind the hill is Berkeley with the Memorial Stadium, in front of us is San Francisco, and right there
47:26is Oakland.
47:30During a future quake, the Hayward Fault will break at this spot here with serious consequences.
47:38Below us, there's a big highway network.
47:41The Hayward Fault will cut the highway in two.
47:47This region is also very populated.
47:51And facing us, there's a gas factory right next to the fault.
47:57We imagine there'll be problems with electricity distribution in the weeks following a future quake.
48:07Something else that can't be seen here are water pipelines in that area,
48:13running east to west and thus crossing the fault line.
48:17So, we can't really identify the world.
48:25During the 1906 earthquake, broken water mains prevented firemen from putting out dozens of fires that ravaged the city.
48:40If the water lines here are blocked or shut down, as well as the highways, and the electricity is out,
48:49we are looking at a pretty big natural disaster in this highly populated region.
48:59Every day, experts are on the lookout for the slightest tremor, ready to sound the alert in the case of
49:05an imminent quake.
49:10But until then, San Francisco keeps its cool.
49:16As if the all-powerful tectonic forces couldn't mar one of the most beautiful cities in the world.
49:30North America as we know it today represents only an ephemeral stage in the planet's history.
49:39In the future, the Earth's terrible fits will continue to mold its landscape.
49:43Earthquakes and volcanic eruptions threaten one day to wreak long-lasting consequences on the entirety of the living world.
49:52And in several million years, the continent will be ripped in two.
49:56California will detach and drift at length through the Pacific Ocean.
50:03The colossal forces of the tectonic plates have not yet finished sculpting the surface of the North American continent.
50:24California will be Patton'sonsin.
50:24California will be partly organized by the Pacific Ocean.
50:30The greater global field of the European Union is from the North America.
50:30It's New France-Pacific and the European Union.
50:32The United Nations has been fueled by the European Union.
50:32The entire world of the European Union has been in Ottawa, where we have created a large number of nations.
50:35The world's biggest security of the American people that are in the world, the America of France has been in.
50:36The largest pirates must be in the area since theumu-wide.
50:40The plateau of the ocean itself has been lysed in between the sights and the development-believers in the internet.
51:07Transcription by CastingWords