How The Earth Was Made: From Molten Rock to Green Planet | Full Special | History

0:01[music playing]

0:04NARRATOR: Planet Earth is unique, an immense ball

0:09of rock 25,000 miles around.

0:13It is a refuge.

0:161/3 land, 2/3 water, and with an atmosphere rich in oxygen,

0:22it is the only known home in the universe for living creatures.

0:27But this blue-green oasis has not always been so welcoming.

0:31The planet bears the scars of a traumatic past,

0:35a past of extreme environments, and extreme catastrophes.

0:42Over the course of nearly five billion years,

0:45it has been a changing world, a world of fire, a world of ice.

0:52One of raging seas and poisonous skies.

0:58The life forms that now cling to its surface

1:01are the lucky survivors of a succession of deadly mass

1:05extinctions.

1:09For just over 200 years, determined scientists

1:12have explored the planet and unearthed its secrets.

1:16Their remarkable discoveries have

1:18led them to tell an incredible story, the story of "How

1:22the Earth was Made."

1:24[music playing]

1:34For thousands of years, humans had no knowledge

1:37of the true age and origin of the world,

1:40but just over 200 years ago, all this would change.

1:47Scotland, the Edinburgh coast.

1:50It was here one day in 1788 that the discovery

1:53of a small, rocky outcrop would completely rewrite the history

1:59of the Earth.

2:00[music playing]

2:10Geologist Geoffrey Boulton is on his way to the desolate Siccar

2:14Point where this discovery was made by a maverick

2:17Scottish farmer, James Hutton.

2:23Hutton was to become the father of modern geology.

2:27Hutton was a man who was enthusiastic in the pursuit

2:29of truth, a very enquiring mind.

2:32When he took over his father's farm,

2:34he saw underneath the soils rocks

2:36and wondered what these were.

2:38NARRATOR: Hutton spent years obsessed with understanding how

2:41the rocks of the Earth were made.

2:43His intrepid field expeditions took him all over Scotland,

2:46and they led him to realize that extremely slow processes could

2:50create the rocks he saw from layers of sediment.

2:55GEOFFREY BOULTON: He rode miles and miles on his horse

2:57to go to places where he thought he could find

2:59exciting geological experiences, even though he suffered

3:03terribly from saddle sores.

3:04NARRATOR: Hutton concluded that rocks could take hundreds

3:07of thousands of years to form, but his claims were

3:10speculative, and his radical ideas

3:12flew in the face of the accepted version of Earth history

3:17provided by the church.

3:20For generations, the Christian church

3:22had been the sole authority on all creation,

3:26based on the Book of Genesis.

3:31And using the biblical genealogies, church leaders

3:34were now confidently claiming they

3:36knew the exact age of the Earth itself.

3:41Archbishop Ussher in the 17th century

3:43had calculated that the Earth was 6,000 years old,

3:47and indeed, he calculated that it was made on October the 14th

3:51in the afternoon.

3:53NARRATOR: Hutton was convinced that the Earth had to be much

3:55older, and when his explorations led him to a Siccar Point

3:59in 1788, he would finally find the proof

4:02he was looking for in the unusual formation he

4:06discovered.

4:07[music playing]

4:12GEOFFREY BOULTON: These rocks are not just any old rocks,

4:14they're very special rocks.

4:16And the reason they're special is because of the story

4:20Hutton was able to tell from them.

4:23NARRATOR: Here, two layered rock formations

4:25stand at right angles to each other.

4:29He knew these rocks had once been laid down horizontally

4:33on the seafloor.

4:34They must then have been buried under great depth

4:37to re-crystallize.

4:38They must then have been tilted on end by great Earth forces,

4:41then they were eroded away and truncated,

4:44and these rocks were deposited on top.

4:46And he realized that that would not take hundreds of years,

4:50nor thousands of years, but many millions of years.

4:54NARRATOR: Hutton's discovery was a turning point.

4:57From that day forward, it was rock, not scripture,

5:01that would become the trusted guide to the distant past.

5:08And over the next two centuries, the study

5:10of rocks around the globe would lead to the awesome revelation

5:14that this blue-green planet has been on the most astounding

5:19journey, a journey that began in a world of fire.

5:27[music playing]

5:33It is now believed that the Earth was formed

5:35from collisions among the countless meteors that made up

5:39the early solar system.

5:41[meteor exploding]

5:46Back then, the surface was an ocean of molten rock,

5:50miles deep.

5:55Temperatures exceeded 8,000 degrees Fahrenheit, similar

5:59to the surface of the Sun.

6:06And huge meteorites rained down in a relentless bombardment.

6:11[music playing, explosions]

6:22The man who first proposed this hellish origin for the planet

6:27was the Victorian scientist Lord Kelvin.

6:30A British expert in thermodynamics, Kelvin

6:33believed that the Earth was slowly cooling down.

6:39The fires of the planet's interior,

6:41visible in volcanic eruptions, suggested to him

6:44that the planet had once been completely molten.

6:50Kelvin used thermodynamics to calculate

6:52a new age for the Earth.

6:55He reasoned that the molten planet would need nearly 20

6:58million years to cool to its present temperatures.

7:03Kelvin was correct about the Earth being molten,

7:06but not about its age.

7:08His figure was a colossal underestimate.

7:13Like all 19th century scientists,

7:15Kelvin was unaware of a key source of heat

7:18inside the early Earth that prevented the planet

7:21from cooling as he predicted.

7:24Radioactivity.

7:27In the early Earth, radioactive particles of uranium, thorium,

7:31and potassium were in huge abundance.

7:34The heat produced from the decay of these particles

7:37would keep the Earth extremely hot for an extremely long time.

7:42But although these particles confounded

7:44Kelvin's calculations, they would eventually prove the keys

7:48to unlocking the true age of the Earth.

7:53In the 20th century, rare particles

7:55of surviving radioactive uranium were collected together

7:58to create the first atomic weapons,

8:01but scientists had earlier found a different application,

8:04using the radioactive particles to accurately date the planet.

8:10In 1911, a gifted 21-year-old geology student, Arthur Holmes,

8:15used radiation to revolutionize our understanding of Earth

8:19history.

8:20After Holmes, geologists would talk in billions, not millions

8:25of years.

8:27Radiometric dating was simple in principle.

8:30It was based on the discovery that traces

8:32of the radioactive element, uranium,

8:34found throughout the rocks of the Earth,

8:36decayed into another element, lead.

8:40Like sand, trickling through an hourglass over hundreds

8:44of millions of years, and at a steady rate,

8:46a sample of radioactive uranium will decay to lead.

8:51By measuring the proportion of uranium

8:53to lead in crystals trapped in ancient rocks,

8:56Holmes could accurately calculate their ages.

9:02Collecting data from samples from all over the world

9:05would be a lifetime's worth.

9:09But as Holmes grew older, so did the Earth.

9:15Its calculated age extended first to one, then three, then

9:22finally, to 4.5 billion years.

9:28Today, 4.5 billion years is still

9:31the accepted age for the Earth.

9:35Time on this incredible scale is known to those

9:39in the business as deep time.

9:41GEOFFREY BOULTON: It's difficult to imagine

9:43how vast deep time is.

9:45Think of it this way, that's a grain of sand.

9:48If it represented a year, then the length of my finger

9:51would be equivalent to the whole of my lifetime.

9:54The tip of my finger to my elbow would take us back

9:56to the pilgrim fathers.

9:58From here to the rocky island you

10:00see on the horizon would take us back

10:02to the age of the dinosaurs.

10:03And if we were to turn around and go to the equator,

10:06then it would be equivalent to going back

10:08to the beginning of the Earth, 4 and 1/2 billion years ago.

10:15NARRATOR: The search for the age of the Earth was over,

10:18and the results had opened a window on the past.

10:21For the first time, scientists could put rocks

10:23in the correct order, look deep into the Earth's past,

10:27and tell its story.

10:29They would discover evidence of an epic journey

10:32with many twists and turns.

10:34But the most significant step may well

10:36have been taken within just a few million years of its birth,

10:41when the planet became a water world.

10:51[music playing]

10:524.5 billion years ago, the Earth was formed from the collisions

10:56of millions of meteors in the young solar system.

11:01Temperatures were so high that the planet's surface

11:04was a molten ocean.

11:07But even at that time, Earth was beginning to cool.

11:10The radioactivity that provided much of the heat

11:13was slowly declining, paving the way for the planet's

11:16first radical change, its transformation

11:20into a water world.

11:22[music playing]

11:26The Barberton Hills, South Africa.

11:30This remote region is home to some

11:32of the oldest rocks on Earth.

11:37South African geologist Gary Stevens

11:39is on the lookout for some of these incredibly rare survivors

11:43from the first billion years of Earth history,

11:46whose unique shape tells a story.

11:52GARY STEVENS: This area of South African geology here

11:54on the eastern side of Mpumalanga

11:56is critical for our understanding of early Earth

11:58processes.

12:01NARRATOR: Gradual erosion along the trickling creek

12:03can occasionally expose these primordial rocks.

12:07Here, we have an interesting rock.

12:10The rounded shape of this rock over here

12:12is very different than the rounded shape of the rest

12:14of the rocks in this river.

12:18This is one of these 3.5 billion year old pillow lavas.

12:23The rounded pillow shape in the rock

12:25is the result of the lava that formed under water in an ocean

12:29approximately 3 and 1/2 billion years ago.

12:32NARRATOR: Pillow lavas are created today

12:35off the coast of Hawaii, where volcanic vents erupt

12:38into the Pacific Ocean.

12:42This unique pillow shape is only formed when lava solidifies

12:46under deep water.

12:50All rocks found from the period 3.5 billion years ago

12:53have been pillow lavas.

12:56By one billion years into the planet's existence,

12:58water had taken over, but geologists

13:01believe that it had already been around a long, long time.

13:05[music playing]

13:084.4 billion years ago.

13:12The Earth was around 100 million years old.

13:22Meteors still crashed into the planet,

13:25but gradual cooling of the core had allowed most of the surface

13:29to solidify into a crust of dark volcanic rock.

13:38And even then, at this early stage,

13:42water was forming on the surface.

13:47No rocks now survive from this most early period,

13:50but tiny crystals of zircon do.

13:54Uranium-carrying zircon is one of the crystals

13:57that help date the Earth, but these crystals

14:00can also retain the chemical fingerprints

14:02of water molecules.

14:04And these fingerprints are all over the most ancient zircons.

14:11But the origin of the majority of the planet's water

14:13remains a mystery.

14:16As the planet cooled, the surface rocks

14:18began spewing out tons of carbon dioxide.

14:22Some water vapor would have been vented during this process,

14:26but some believe it would not have been

14:27enough to cover the surface.

14:30DAN DURDA: Rocks, the material that

14:31accreted to form the Earth itself would have been

14:33too dry, too-- too close to the early hot Sun.

14:37We have this problem of trying to understand

14:39where-- where our water world got all of its water.

14:42NARRATOR: Impact expert Dan Durda supports the theory

14:45that the source of most of the Earth's water

14:48was extraterrestrial.

14:50DAN DURDA: The idea today is that the Earth's oceans arrived

14:52from above.

14:54They were brought in in the water-rich asteroids and comets

14:57which peppered the Earth during the tail

15:00off in its accretionary process.

15:02What I have here is a piece of an actual meteorite.

15:05This is the material from which the Earth itself formed.

15:08This primitive little meteorite contains about 5% water.

15:12It's that water in objects like this

15:14that was delivered to the Earth to form the Earth's oceans.

15:17NARRATOR: Scientists are divided on this,

15:20but wherever the water came from, when it did arrive,

15:23it changed the planet dramatically.

15:27As it evaporated off the surface,

15:29huge amounts of water vapor rose to join the carbon dioxide

15:33in the young atmosphere, forming thick, blanketing clouds.

15:37[music playing]

15:44This condensing water would trigger the greatest downpour

15:48the Earth would ever see.

15:50[thunder crashing]

15:55As thunderstorms rocked the skies,

15:57the rain began to fall on the rocky surface below.

16:02And it kept on falling.

16:06It would rain for millions and millions and millions of years.

16:13The result would be a water world.

16:21Four billion years ago.

16:24The Earth was now half a billion years old.

16:32Over 90% of its surface had become a vast ocean.

16:41Small volcanic islands poked out from the waves.

16:47The monstrous seas where iron-rich, making them an

16:51olive green color.

16:53Carbon dioxide filled the sky so thickly that they appeared red.

16:58The dense atmosphere produced enough pressure

17:01to crush a human body flat.

17:08And it was hot.

17:10Temperatures exceeded 200 degrees Fahrenheit.

17:16This toxic, hostile water world would remain

17:19for another half billion years.

17:22But dramatic transformations were on their way.

17:26Renewed volcanic activity would trigger the construction

17:30of the continents by creating a totally new kind of rock.

17:35Earth was about to become a granite planet.

17:443.4 billion years ago.

17:48The Earth was just over a billion years old.

17:55Huge, green oceans dominated.

17:57[music playing]

18:07None of the crumbling volcanic islands dotting the surface

18:11survived the punishing sea for long,

18:14but everything was about to change.

18:17An upsurge in undersea volcanic activity

18:20was about to create a tougher type of rock

18:23and give birth to the continents.

18:27In remote areas of the globe, the primeval cores

18:30of these first continents have been exposed.

18:35South Africa.

18:37Geologist Gary Stevens is climbing on some of the oldest

18:41continental rock on Earth.

18:45These rocks are special.

18:48We're standing here on ancient granite.

18:50This granite forms the nucleus of one of the world's oldest

18:53continents, and we can see it here in the Barberton area

18:57in South Africa.

18:59NARRATOR: These eroded outcrops of rock

19:01are the visible peaks of what is known as the Kaapvaal Craton,

19:05a titanic mass of ancient granite underlying

19:08southern Africa, a remnant of the early Earth.

19:123.5 billion years ago, granite was appearing everywhere.

19:18An upsurge of volcanism had fractured the crust

19:21of the Earth underneath the vast oceans,

19:24allowing water to plunge into the cracks alongside the molten

19:28lavas.

19:30The mixture of superheated water and basaltic lava

19:33produced the new rock, granite.

19:37It rose from the depths to form the first true continental

19:40crust.

19:41This is why granite is special and important.

19:44It's light.

19:45This rock, granitic rock, has a much lower density

19:48than this rock, a basaltic rock.

19:51The difference in density between these two rocks

19:54is greater than the difference in density between water

19:56and air.

19:58This rock would be typical for oceanic crustal material.

20:00This is typical of the continents.

20:02Continents are light and buoyant.

20:04Oceanic crust, denser and heavier.

20:07It literally floats on the mantle.

20:12NARRATOR: Granite crust was not only light, it was tough,

20:17tough enough to withstand the erosion of power of the oceans.

20:22[music playing]

20:27For the next couple of billion years,

20:29slowly, but surely, the granitoid protocontinents

20:32grew larger.

20:35On different parts of the globe, granite crust

20:38appeared that would one day form the hearts

20:41of the major landmasses.

20:44The dominance of the oceans was over.

20:48The continents had arrived.

20:54The slow expansion of the granite protocontinents

20:56was to change more than just the appearance of the planet.

21:00The shallow coastlines would bring life

21:02to the sunlit surface, and help trigger the production

21:05of oxygen. Almost since the arrival of the first oceans,

21:11it is believed that primitive, single-celled life forms had

21:14appeared, deep beneath the waves,

21:16living off the heat produced by the subsea volcanic fissures.

21:20But now, they were evolving and spreading upwards.

21:24On the continental coasts, an organism

21:26was appearing that was to transform the planet,

21:31the stromatolite.

21:33The stromatolite would live off sunlight,

21:37and it would fill the atmosphere with oxygen.

21:43This primeval organism can still be found today.

21:46[music playing]

21:56Western Australia.

21:58Martin Van Kranendonk is over 100 miles from the nearest town

22:02heading across the outback to a remote beach.

22:06We're going down this track to one of the most unique places

22:09in the world where you've got living stromatolites

22:11on the shoreline here at Shark Bay.

22:15On the narrow sandy coast of Shark Bay,

22:18a multitude of stromatolites fill the tidal shallows.

22:26Each of these unusual rocky mounds

22:28are up to 1 foot across and 2 feet high.

22:35It was only in the 1950s that the importance of Shark Bay

22:38was realized.

22:40Following trips to this remote site,

22:43Australian geologist Phillip Playford

22:45was the first to discover how stromatolites formed.

22:49Playford identified a rare bacterial algae found

22:52in a slimy film coating their surface as the creator

22:56of the mounds themselves.

22:58MARTIN VAN KRANENDONK: Stromatolites are made up

23:00of very thin layers of microorganisms that

23:04build up slowly, layer by layer, year by year,

23:08as they use light energy to gain their food,

23:11and as their waste product, they precipitate rock.

23:15NARRATOR: Other geologist recognized the significance

23:17of Playford's findings.

23:19Patterns they had seen in rocks billions of years old

23:22were, in fact, fossilized stromatolites.

23:25Playford's discovery had sparked off a fossil revolution.

23:29Once people knew that these kind of structures

23:31were made by living organisms, they

23:33went back into the rock record and found that they found

23:36the same kinds of structures, and therefore,

23:38could deduce that life occupied planet Earth 3 and 1/2

23:42billion years ago.

23:43These are really the ancestors of everything on Earth.

23:47We're actually looking at our great, great, great, great,

23:49great, great, great, great, great grandmothers

23:51and grandfathers.

23:52[music playing]

23:55NARRATOR: The rock record shows that by 2.5 billion years ago,

23:59stromatolites were blossoming globally.

24:02All beaches on Earth would have resembled Shark Bay.

24:06[music playing]

24:12And as stromatolites filled the shallows,

24:15they began to fill the atmosphere with oxygen.

24:19Planet Earth and the solar system

24:21is the only planet that has an atmosphere composed

24:24of a large amount of oxygen. Geoscientists

24:27think that that oxygen came only from the reaction

24:31of stromatolites.

24:32NARRATOR: The algae turned sunlight into oxygen, a process

24:36known as photosynthesis.

24:40Over a period of two billion years,

24:42countless generations of stromatolites

24:44pumped out over 20 million, billion tons of oxygen.

24:49At first, the gas dissolved into the oceans, where it rusted out

24:53billions of tons of iron.

24:55But eventually, it would also fill the atmosphere

24:59and transform the planet.

25:02The planet's very appearance was dramatically altered.

25:06As the iron left the oceans, they changed from green

25:10to blue.

25:11When the oxygen moved on to the atmosphere,

25:14it diluted the remaining thick carbon dioxide

25:17and cleared the air.

25:19[music playing]

25:29After nearly two billion years of oxygenation,

25:33the blue planet was born.

25:39The Earth now had its blue oceans and its blue sky.

25:50Relics of this great transformative period

25:52survive today in immense layers of iron-rich sediment

25:57originally deposited on the floors of the ancient oceans.

26:02Scattered all throughout the globe,

26:04the banded iron formations, as they are known,

26:07are vital for today's economies.

26:11They are the major source of all the iron mined today.

26:17Following its oxygenation, the Earth was more recognizable.

26:22But before it would become the planet we know,

26:25a new cycle of cataclysmic events would take place.

26:29Over the next billion years, deep movements

26:32would wrench apart the crust, and life, which had just

26:36begun to make its mark, would face its toughest test yet.

26:50[music playing]

26:541.5 billion years ago.

26:57Planet Earth was almost three billion years old.

27:01For the first time in its history,

27:04it was beginning to resemble the planet we know.

27:07Newly arrived oxygen had turned the oceans blue,

27:11and the continents had grown to cover nearly a quarter

27:14of the surface.

27:16But their expansion was not over.

27:19And beneath the oceans, deep forces were at work,

27:22rearranging their positions.

27:24Imperceptibly, the continents were on the move.

27:29[music playing]

27:35Mark McMenamin is an expert in plate tectonics, the study

27:39of continental movement.

27:42Until the 1960s, this was radical science.

27:50MARK MCMENAMIN: In the 19th and early 20th century,

27:52the consensus view was that the continents were fixed.

27:56All geology was local, and the continents stay in one place.

28:01NARRATOR: But problems for this view had been mounting.

28:04One of the greatest mysteries was the geographic position

28:07of certain fossils.

28:10Trilobites, like the one on my left

28:12here, belong to the genus Paradoxides.

28:16NARRATOR: The Paradoxides really was a paradox.

28:19It was a freshwater creature with a curious distribution.

28:22MARK MCMENAMIN: This trilobite is found in the eastern part

28:26of North America.

28:28And also, in Britain, on the other side of the Atlantic

28:31Ocean.

28:33NARRATOR: The freshwater paradoxides could not have

28:35swum the vast, salty ocean.

28:40And they were not the only fossils

28:42showing bizarre intercontinental distribution.

28:46Geologists struggled for an explanation.

28:51In 1912, a radical new theory would emerge from Greenland

28:56that would lay the foundations for plate tectonics

28:59and shake Earth science to its foundations.

29:03The new theory was put forward by a German weather scientist,

29:07Alfred visionary Wegener, a man who

29:09had spent much of his career conducting atmospheric research

29:12in Greenland's frozen wastes.

29:15But Wegener had always been fascinated by the geologist's

29:18fossil paradox, and he boldly claimed that the answer was

29:22staring them in the face.

29:24MARK MCMENAMIN: Ever since accurate world maps were

29:26available, schoolchildren and others

29:28have pointed out the fit between the east coast of South America

29:32and the west coast of Africa, and this was always dismissed

29:36in reputable scientific circles as just a coincidence

29:39of no meaning, and so many disappointed children

29:42were turned away and told that their idea was wrong.

29:46Wegener proposed that the continents had indeed once

29:49been joined together, and had subsequently drifted apart.

29:56His observations in Greenland convinced him

29:59this continental drift was possible.

30:03I think that his inspiration was meteorological.

30:07Perhaps he saw a breakup of ice floes,

30:10and made what we would call an extrapolation to the hard rock

30:14part of the planet.

30:18NARRATOR: But few geologists could

30:19accept the radical theories of a mere meteorologist.

30:23MARK MCMENAMIN: There was complete rejection

30:25of what Wegener was saying.

30:28This is a tall order, to take a gigantic continent

30:31and shove it through the ocean floor

30:34to get it halfway across the globe.

30:39NARRATOR: Throughout his life, Wegener fought to gain evidence

30:43for his theory, but his brave attempts eventually

30:47led to his demise.

30:49In 1930, his last expedition to Greenland

30:52ended in tragedy when he lost his way in a snowstorm.

30:58MARK MCMENAMIN: In a icy situation on a glacier,

31:01it's difficult to find your way.

31:05Separated from both his base camp and the other members

31:08of his expedition, he basically got lost and died of exposure.

31:15NARRATOR: Wegener was dead, but his theory of continental drift

31:20lived on.

31:22[explosions, weapons firing]

31:25The breakthrough came after the US Navy produced a global map

31:29of the ocean floor, originally commissioned

31:32for submarine warfare during World War II.

31:37This detailed map revealed one of the Earth's greatest

31:40secrets, the fractured network of submarine mountain,

31:46volcanic rifts, and trenches that split the oceans

31:50into enormous plates of crust.

31:54These plates would be the building blocks

31:56for the new science of plate tectonics.

31:59The rifts and trenches would provide a solution

32:02to how continents drift by proving that the ocean

32:05floors are continuously being recycled.

32:10MARK MCMENAMIN: Plate tectonics is completely

32:12driven by the destruction of the old

32:16and the creation of the new.

32:19NARRATOR: Deep below the surface, mobile mantle rock

32:21is in continuous circular motion following convection currents

32:25of heat generated deep within the planet.

32:29Where these currents rise, the rifts form, and the plates

32:32are pushed apart, with new ocean crust created in the gap.

32:37Where the mantle currents sink back down into the Earth,

32:39they drag old oceanic plate down with them towards the interior.

32:44If the ocean plate moves, so do the continents.

32:48MARK MCMENAMIN: That oceanic plate drags the continent along

32:53with it.

32:54The process is like an escalator or a conveyor belt.

32:59NARRATOR: The process of ocean creation

33:00is visible today on a rocky island in the middle

33:03of the Atlantic, Iceland.

33:07Iceland lies on the mid-Atlantic ridge, a 10,000 mile long range

33:12of subsea volcanic mountains that mark one of the deep rifts

33:16in the Earth's crust.

33:20Iceland is really like a peak of this mountain chain.

33:23It's like a huge volcano sitting on top of it.

33:26NARRATOR: Seismologist P ll Einarsson studies the volcanism

33:29of this remote island, volcanism that is helping to expand

33:33the Atlantic Ocean.

33:35[music playing]

33:40Occasionally, an unusual type of volcanic eruption on Iceland

33:43confirms that plate tectonic process, a fissure eruption.

33:50A fissure eruption is a wall of fire.

33:53They could be 25 miles long, and spew lava hundreds of feet

33:57into the air.

33:59People fear eruptions.

34:00They respect the volcanoes.

34:03[music playing]

34:08NARRATOR: The fissures mark the path of the deep plate boundary

34:12that is creating the Atlantic.

34:14All across the island, running from northeast to southwest,

34:19are the remains of these fissure eruptions,

34:22scarring the rocky landscape with shallow canyons.

34:26These canyons are very slowly widening Iceland.

34:30[music playing]

34:36At their base, new crust is being created, pushing Europe

34:40and America apart.

34:43So here we are, located in the fissure between the two

34:46continental plates, the two crustal plates.

34:50Here, on my left, we have the North America plate,

34:53and on the other side, we have Europe.

34:56This fissure here is in a lava flow that's

34:59only about 8,000 years old.

35:01So in 8,000 years, that's how much the two plates have moved.

35:06DAN DURDA: The rate of continental drift averages

35:09about 2.5 centimeters per year, the rate at which fingernails

35:14typically grow.

35:15NARRATOR: 2.5 centimeters, one inch per year,

35:19means that in one human lifetime,

35:21America and Europe will move just 6 feet further apart.

35:27But over millions of years, this speed of movement

35:30was enough to shift the continents thousands of miles.

35:35[music playing]

35:40Using plate tectonics as their guide,

35:42geologists such as Mark McMenamin

35:44have reconstructed the epic story of continental movement

35:48from the beginning.

35:49From samples taken from present day continental margins,

35:53they've compared fossils and microfossils,

35:55and matched up distinctive types of ancient rocks

35:58to reconstruct where the continents used to be.

36:02MARK MCMENAMIN: It's a tricky task.

36:04It's kind of like Humpty Dumpty, you've got all of these pieces.

36:07You need to use whatever clues you can,

36:09whatever fingerprints you had to put one continental margin

36:14against the other.

36:16NARRATOR: They are now confident that they can trace

36:18the movement of the continents back over a billion years

36:23to a time of a mass continental collision.

36:26[music playing]

36:30As the oceans between them were swallowed up,

36:32the large land masses drew together

36:35in what was to become a supercontinent, Rodinia.

36:44It is believed that Canada and the USA

36:46formed the supercontinent's heart, with other continents

36:52bunched around them.

36:57But Rodinia was unlike any continent seen today.

37:03It was a desolate, lifeless place.

37:06MARK MCMENAMIN: It would've been very

37:08much like being in the desert.

37:09It would've been similar to parts of the Sahara, Death

37:13Valley.

37:14There would have been no plants, no forests, no grasslands.

37:22Rodinia would've been a barren continent.

37:33NARRATOR: Rodinia may have been lifeless,

37:35but it was to have a profound effect on life in the oceans.

37:40In the oxygenated waters, primitive life forms

37:43were blooming alongside the stromatolites.

37:48But the huge supercontinent was about to give them

37:51a tremendous shock.

37:53Rodinia was to trigger what is now

37:56known as snowball Earth, the biggest freeze the world has

38:01ever seen.

38:03By around 700 million years ago, Rodinia's position

38:07was blocking the currents that brought warm water

38:09from the equator to the poles.

38:12Without this heat, the polar regions froze.

38:16The resulting ice reflected more of the Sun's rays away

38:19from the Earth, and in a catastrophic snowballing

38:21effect, temperatures dropped still further,

38:24and the ice advanced to cover the Earth.

38:27[music playing]

38:33Surface temperatures fell below minus 40 degrees.

38:37The oceans were covered in an ice sheet almost a mile deep.

38:42The only life on Earth, marine bacterias and algae,

38:46were trapped beneath in the darkness.

38:50The result was disaster.

38:53All but a tiny fraction of organisms

38:55were driven to extinction.

38:58The whole planet was dying.

39:09[music playing]

39:12650 million years ago.

39:17Climate changes triggered by the formation

39:19of the supercontinent Rodinia had left the surface

39:23of the Earth covered with a sheet of ice 1 mile thick.

39:28Temperatures hovered below minus 40 degrees Fahrenheit.

39:33Marine organisms, the only life on the planet,

39:37had almost been wiped out.

39:39The future of life on Earth hung in the balance.

39:42[music playing]

39:50But beneath the ice, the supercontinent was in turmoil.

39:56Vast volcanic eruptions were splitting Rodinia apart.

40:01It's thought that the accumulation of heat

40:03at the base of a supercontinent is what eventually leads

40:06to its undoing.

40:09It's like putting a blanket over the Earth.

40:12The heat that's generated from the Earth's interior

40:14will accumulate underneath that blanket.

40:17NARRATOR: The heat would spell the end of the snowball.

40:21As Rodinia ruptured, carbon dioxide

40:23released by the eruptions created a temporary greenhouse

40:27effect.

40:28The ice sheets drew back.

40:32Rodinia had broken into giant fragments.

40:38And the icy grip on life was broken.

40:44As shallow seas opened up in Rodinia's wake,

40:47and oxygen levels increased, the primitive organisms

40:51were free to take their next great step forward.

40:56They would become complex, and a lot more dangerous.

41:00[music playing]

41:04The Canadian Rockies.

41:06These remote mountains are home to a rare record

41:09of this key event in the evolution of life,

41:12the so-called Cambrian explosion.

41:15PAUL MCNEIL: For the first time in the history of life

41:17on Earth, we have some of the highest oxygen levels

41:20that we've had since the Earth was actually formed.

41:23Life bloomed.

41:25We see animals unlike we've ever seen before.

41:28NARRATOR: Paleontologist Paul McNeil

41:30is hiking up to a remote mountain quarry known

41:32as the Burgess Shale.

41:35The astonishing fossils in this quarry

41:38are a window on the world as it existed over

41:40500 million years ago.

41:43PAUL MCNEIL: If you surveyed all the people who

41:45study the history of life, you get almost unanimous agreement

41:47that this is one of the most important fossil sites

41:50in the world.

41:51[music playing]

41:56NARRATOR: The man who discovered the Burgess Shale was

41:58an American, Charles Doolittle Walcott, the president

42:02of The Smithsonian Institute.

42:04This fanatical fossil hunter, who was born into poverty,

42:08had lived the American dream.

42:11Armed only with a high school diploma,

42:13he had fought his way to the top of the American scientific

42:16establishment.

42:18But it was his tenacious fossil-hunting expeditions

42:22in the most remote mountains of North America that

42:24would lead to his most stunning achievement.

42:29This is the actual location where Walcott first

42:32made his amazing discovery.

42:34As the legend goes, it's August 31, 1909,

42:38riding along this very trail with his wife in a snow storm,

42:42and as they're riding along, a large slab of rock came down,

42:46blocked the trail, and they couldn't get by. ,

42:48Now being a gentleman, as all paleontologists are,

42:51he immediately leapt off his horse,

42:54flipped over the slab of rock, and found an incredibly

42:57well-preserved fossil.

42:58If it was down on the trail, where did it come from?

43:01Nowhere but up there.

43:03NARRATOR: The source of the rockfall

43:05was a section of the cliff no more than 100 feet across,

43:11a small area that became the celebrated Burgess Shale

43:15Quarry.

43:16[music playing]

43:23Walcott, often aided by his own family,

43:26eventually extracted over 60,000 fossils.

43:30And since Walcott, a further 100,000

43:32have been excavated from this uniquely rich cliff face.

43:38Quarrying the rocks of the mountain

43:40requires a tremendous amount of work,

43:42a lot of backbreaking labor.

43:45But it's also extremely exciting,

43:46because every time you split open a rock,

43:48you never know what you're going to find.

43:50Most of the time, you find nothing, but every once

43:52in a while, you find a new animal, one that's never been

43:56seen before, one that's been revealed for the first time

43:59in half a billion years.

44:00NARRATOR: The thousands of fossils found in the Burgess

44:03Shale revealed that starting 500 million years ago,

44:06life exploded with staggering diversity and complexity.

44:10PAUL MCNEIL: The preservation of these fossils

44:12is actually incredible in that they're actually preserved

44:15in three dimensions.

44:17You can excavate through the fossils themselves,

44:20see the internal organs, remove the organs,

44:23see the digestive tract.

44:27There's this fantastic preservation.

44:30Oh, look, it's starting to crack.

44:32And there goes a piece.

44:35What we have here is an actual Anomalocaris.

44:40These guys were up to a meter in length.

44:41That actually made them the T-Rex of the Cambrian.

44:45[music playing]

44:53NARRATOR: In the Cambrian seas, the oxygen-rich shallow waters

44:56were teeming with complex organisms.

45:00And creatures were feeding not just on plants,

45:04but on each other.

45:09PAUL MCNEIL: Cambria's actually one of most special times

45:12in the history of life.

45:13We see more different types of animals

45:15than we see in the rest of the entire history of life

45:19on Earth.

45:20NARRATOR: From this time onwards, with a biological arms

45:23race driving their evolution, creatures

45:26would become increasingly complex,

45:28with the development of hard shells, skeletons, eyes,

45:33and teeth.

45:36Modern animals had arrived on Earth.

45:41[music playing]

45:47The high level of oxygen that had triggered this explosion

45:50of life in the seas was also making a final modification

45:55to the atmosphere.

45:57Over the next 100 million years, oxygen reached today's

46:01high levels, a level dense enough

46:05to allow an ozone layer to form in the upper atmosphere.

46:11This layer was to free life forms from the oceans.

46:17Previously, powerful ultraviolet light

46:19would destroy any organism not protected by the water.

46:23Now, the ozone layer would act as a UV shield.

46:31[music playing]

46:36400 million years ago.

46:39The Earth is more than four billion years old.

46:43Over the next 100 million years, the continents would once again

46:47converge, and this time, thanks to the ozone shield,

46:52life was free to leave the oceans and conquer the land.

46:58Planet Earth had become a world of tropical swamps.

47:04[music playing]

47:06South Georgia, USA, the Okefenokee Swamp.

47:14FRED RICH: The Okefenokee is believed

47:15to be what we would call an analog, a modern analog

47:19for an environment that's very similar to the wetlands that

47:22existed on Earth in the past.

47:26NARRATOR: Fred Rich is an expert on prehistoric swamp land.

47:32Geologists like him believe that this freshwater swamp closely

47:37mimics the surface of the continents

47:39300 million years ago, in a period

47:42known as the Carboniferous.

47:45FRED RICH: Carboniferous was an unusual time,

47:48because it was the first period in Earth's history

47:52when large plants occupied Earth's surface, 40, 50,

47:5670 feet high that grew in dense groves

48:00and produced a vast forest canopy

48:03in a steamy, tropical jungle atmosphere that was something

48:06entirely new on the face of the Earth.

48:10NARRATOR: This dense tropical swamp land

48:12would dominate the Earth for the next 60 million years.

48:20The evidence is present on all of today's continents

48:24in the form of coal.

48:29The coal we use for fuel was formed from millions of years

48:32worth of accumulated plant matter, most of which

48:36existed less than 300 million years ago.

48:39[music playing]

48:45And it formed because of the unique way

48:47freshwater swamps decompose.

48:54PAUL MCNEIL: Okefenokee is derived

48:55from a Native American word that means

48:57land of the trembling earth.

48:59It's not very easy to walk through the swamp,

49:02because the subsurface is soggy plant remains.

49:07NARRATOR: The fresh water prevents the vegetation

49:09from decaying, allowing huge amounts to build up over time.

49:14Beneath me is not the regular sort of soil

49:17that you would have in your backyard.

49:20The soil that you see here is the plant material

49:22that accumulated last year, or perhaps five years ago.

49:28It's leaves, stems, twigs, there's still

49:31a good bit of water in this.

49:32But if we put this under tremendous amount of pressure

49:36and add some heat by covering over with layers of rock

49:40and leaving it in the ground for millions of years,

49:42eventually, it will change to this.

49:44This is a piece of bituminous coal,

49:46and it's on the order of 200 million years old.

49:50NARRATOR: As the dead plants were transformed to coal

49:53on land, the shallow waters surrounding the continents

49:56were preserving millions of generations

49:59of dead marine organisms.

50:02They would become our other major fossil fuels, oil

50:08and gas.

50:09Every year, mankind minds almost 5,000 megatons of coal,

50:1530 billion barrels of oil, and 3,000 billion cubic meters

50:20of gas.

50:21This fertile period of Earth history

50:24has given us much of the energy we use today.

50:28Without it, the Industrial Revolution

50:31may never have happened.

50:33[music playing]

50:36Plants were not alone in making a new life on the land

50:39300 million years ago.

50:42As time went on, first, enormous insects, then,

50:52ambitious amphibians, and finally, early reptilians

50:58left the seas to take their first steps

51:00on the muddy shorelines.

51:03The US east coast back then would

51:05have teamed with monsters, 3 foot millipedes on land,

51:102 foot dragonflies in the air, and protoalligators patrolling

51:14the nearby waters.

51:19The world was over 4 and 1/4 billion years old,

51:23and for the first time, the surface

51:25was host to a complete modern biosphere.

51:28[music playing]

51:40But the all-conquering life forms

51:42were about to experience a hell on Earth.

51:47Forces deep within were about to give life on the surface

51:50its sternest test ever.

51:53Enormous volcanic eruptions would

51:55herald the biggest mass extinction in the planet's

51:59entire history.

52:09[music playing]

52:11250 million years ago.

52:14For hundreds of millions of years, life on the surface

52:17had faced numerous challenges to its survival,

52:21but nothing on the scale of what was about to happen.

52:25[music playing]

52:29In what would one day become Siberia,

52:32the Earth's crust became a volcanic morass.

52:36The cause was a rare mantle plume eruption.

52:40No one knows for sure why they occur,

52:42but occasionally, huge masses of hot mantle from deep

52:46within the Earth surge upwards, melting and smashing the crust

52:51above.

52:53The eruptions continued for over one million years.

52:57They spewed out over 1 million cubic miles of molten rock,

53:04enough to bury the modern USA in a layer over 1,000 feet.

53:10Clouds of poisonous gases spread out

53:12and shrouded the entire globe.

53:20It was too much for most species of life.

53:23Over 95% were driven to extinction.

53:26[music playing]

53:31It was the most cataclysmic event

53:33the planet has ever witnessed.

53:39The planet that emerged from the chaos was much changed.

53:46A new supercontinent, the great Pangea, now dominated.

53:53And the climate was altering dramatically.

53:56Over the next 200 million years, oxygen and carbon dioxide

54:00would rise to new peaks, and under these conditions,

54:04the animals that had survived the extinction

54:06were to evolve into the most infamous creatures ever to walk

54:11the Earth, the dinosaurs.

54:16[music playing]

54:21Utah, USA.

54:26Paleontologist Reese Barrick is on the hunt for dinosaurs.

54:31In this dusty corner of the western USA,

54:35the rocks are packed with their bones.

54:38REESE BARRICK: Almost 1/3 of the history of life on this planet

54:41was dominated by dinosaurs.

54:43It really, truly is a dinosaur planet.

54:46We have, from the bottom of this slope,

54:49sediments that are 150 million years,

54:52and as you go up the slope, you actually

54:53end up in the Cretaceous at 125 million years.

54:57[music playing]

55:05How we doing, Barb?

55:06Doing great.

55:07Find anything fun?

55:08Small rib and some interesting fragments.

55:11Well, let's start for the day.

55:13NARRATOR: Compared to modern creatures,

55:15dinosaurs were enormous.

55:17The average mammal today is smaller than a dog.

55:20The average dinosaur was larger than a grizzly bear.

55:24[growling, music playing]

55:30Marvin, excellent, look at that.

55:33That is a spectacular therizinosaur claw.

55:36This animal's gonna have to be 300 kilograms,

55:40so it's about the size of a national football league

55:43lineman.

55:45These are absolutely fantastic, because they're

55:47very well-preserved bone.

55:50A perfect claw.

55:52Absolutely brilliant, Marvin.

55:54Nice job.

55:55[music playing]

55:58NARRATOR: The first recorded dinosaur fossil

56:00find was a bone discovered by young Mary Ann

56:03Mantell in England in 1822.

56:07Her husband, Dr. Gideon Mantell, was intrigued, and set

56:11about determining what type of creature it belonged to.

56:18The fossil was unlike anything he'd ever seen.

56:25After much research, he decided it was, in fact, a tooth

56:30from an enormous lizard.

56:33He named the beast iguanodon, after the iguana lizard

56:37he thought it resembled.

56:40Over the next few decades, across Europe and the USA,

56:43more and more huge bones were unearthed,

56:46and given their similarity to modern lizards,

56:49the name dinosaur, meaning terrible lizard, was coined.

56:53[music playing, growling]

57:02But many paleontologists today believe

57:04one of the reasons dinosaurs grew

57:06so large was that they weren't cold-blooded like today's

57:09lizards.

57:12They were lukewarm-blooded.

57:15This gave them the advantages of both cold-blooded lizards

57:18and warm-blooded mammals.

57:20REESE BARRICK: Dinosaurs were able to be active and collect

57:24food all year long, and yet, they could put a great amount

57:27of the food that the ate towards growing as opposed to just heat

57:31generation.

57:32NARRATOR: But another reason for their size

57:34may have been the sweltering oxygen-rich environment that

57:37came to dominate the dinosaur era,

57:40an environment triggered by volcanism.

57:43[music playing]

57:51Starting around 180 million years ago,

57:55a new upsurge in volcanic activity

57:57split apart the supercontinent.

58:01The continental fragments began their long journeys

58:04into the positions they occupy today.

58:08North America, South America, Africa, and Europe all

58:12went their separate ways.

58:15The Pangean supercontinent was no more.

58:20Each of the new continents still carried dinosaurs,

58:24and the steamy volcanic climate seemed to suit them.

58:29It was global warming gone wild.

58:33CO2 levels increased over 500%, and temperatures soared.

58:40In the greenhouse conditions this created,

58:42huge tropical forests spread across many of the continents.

58:48REESE BARRICK: The increasing amount of tropics

58:50means that there's a lot more lush vegetation, which means

58:52there's a lot more food for dinosaurs, which allowed them

58:56not only to specialize and evolve to specialize

58:58on different types of plant materials,

59:00but allowed them to get extremely large.

59:06NARRATOR: Many scientists believe

59:08that evolving for millions of years

59:09in this warm, oxygen-rich world allowed

59:12the lukewarm-blooded dinosaurs to reach their enormous sizes.

59:17Huge dinosaurs may have been a biological response

59:21to a volcanically overactive planet.

59:25But size would not save the dinosaurs

59:28from what was to come.

59:31Their time on Earth would end in sudden, unstoppable

59:35devastation.

59:36[music playing, explosion]

59:53100 million years ago, planet Earth was ruled by dinosaurs.

1:00:07Huge beasts filled the land, the sea, and the air.

1:00:15They lived in a sweltering world defined

1:00:17by overactive volcanism.

1:00:22And before it was finished, this volcanism

1:00:24would bring to the surface some of the planet's most

1:00:28wondrous riches, diamonds.

1:00:31[music playing]

1:00:38Kimberley, South Africa.

1:00:40Jock Robey is chief geologist at De Beers, the largest diamond

1:00:45company in the world.

1:00:47JOCK ROBEY: Diamond is simply the high pressure form

1:00:49of the element carbon.

1:00:51This is a typical eight-sided crystal called on octahedron.

1:00:56Uncut, it is worth $2,000 a carat.

1:00:59As a cut stone, it would probably sell for $80,000.

1:01:04NARRATOR: For thousands of years,

1:01:05diamonds had been found worldwide washed up

1:01:08in sandy riverbanks, but their source

1:01:10had remained a total mystery.

1:01:14It was not until 1869 that huge, unique diamond discoveries were

1:01:18made in South Africa that their remarkable origin was revealed.

1:01:23JOCK ROBEY: What is special about the diamonds found

1:01:25in the Kimberley area is here, for the first time ever,

1:01:29they found a source rock of diamonds.

1:01:33This is a piece of rock mined from the Kimberlite,

1:01:36and as we turn it, it contains a diamond.

1:01:40NARRATOR: The diamond-bearing rock

1:01:41was extracted from strange vertical formations.

1:01:45JOCK ROBEY: As the miners were digging,

1:01:48they found that the diamonds were contained

1:01:50in the body of rock that had a shape of an ice cream cone.

1:01:55Slightly broad at the surface, yellow in color,

1:01:58tapering down to a narrower point.

1:02:01[music playing]

1:02:07NARRATOR: Henry Carvill Lewis, a visiting American mineralogist,

1:02:11put together the pieces.

1:02:14He realized these diamond mines were actually the mouths

1:02:17of ancient volcanoes.

1:02:21The miners were digging down into their roots

1:02:23through the diamond-bearing magma that remained.

1:02:30But these were clearly not normal volcanoes.

1:02:33They were over three times deeper,

1:02:36extending nearly 100 miles beneath the surface

1:02:39of the continent.

1:02:41Uniquely intense pressures and temperatures at this depth

1:02:44make it the only place that diamonds can form.

1:02:48The diamonds could only be brought up

1:02:49by uniquely intense eruptions.

1:02:52The diamond-bearing magma exploded out of the Earth

1:02:55at over 300 miles an hour.

1:02:58Imagine the force and the power of this volcano

1:03:01to cut the sheer vertical walls and blow this up another 1,000

1:03:05meters.

1:03:06This is the power of these volcanoes.

1:03:08[music playing]

1:03:16NARRATOR: When the Pangean supercontinent split apart over

1:03:19100 million years ago, scientists

1:03:21believe the enormous upheaval triggered

1:03:23these super eruptions.

1:03:26Because super continental breakups are rare,

1:03:28so are the diamonds they bring to the surface.

1:03:32The diamonds that erupted into the dinosaur world

1:03:35would survive unblemished until the present day.

1:03:39But the dinosaurs would not be so lucky.

1:03:43[music playing]

1:03:5065 million years ago.

1:03:55The planet was lush.

1:03:57Vegetation was thick on the surface.

1:04:01Living things were prospering like never before.

1:04:05But the dominant dinosaurs were about to be wiped

1:04:08from the face of the planet.

1:04:11REESE BARRICK: Dinosaur bones are found continuously

1:04:14throughout the sedimentary record

1:04:16from 230 million years ago, right up to 65 million years

1:04:20ago, and then instantaneously, they vanish.

1:04:26NARRATOR: Not only dinosaurs, but over 70% of species

1:04:30on Earth disappear.

1:04:33From plant life upward, something terrible

1:04:36had happened to the entire ecosystem of the planet.

1:04:39[music playing]

1:04:44This mass extinction remained a mystery

1:04:46for generations of paleontologists.

1:04:49But it is a mystery no longer.

1:04:54Colorado, USA.

1:04:57Dan Durda is taking samples from an exposed layer of rock

1:05:01exactly 65 million years old.

1:05:04Scientists now believe that it holds the answer.

1:05:09For Dan Durda, this powdery rock is an indication

1:05:12that the dinosaurs perished in a sudden astronomical

1:05:16catastrophe.

1:05:17Dinosaurs and 75% of all the other plants and animals

1:05:21that lived with them, this layer is their tombstone.

1:05:23This thin layer of clay is the important evidence

1:05:27of a violent event in the history of life on the planet.

1:05:32NARRATOR: The evidence held in the tombstone layer

1:05:34is a huge amount of an exceptionally rare element,

1:05:38iridium.

1:05:40The remarkable concentration of iridium

1:05:42was discovered accidentally in 1980

1:05:45by a father and son team of scientists, Lewis and Walter

1:05:49Alvarez.

1:05:51On the planet's surface, iridium is usually found

1:05:54in very small concentrations.

1:05:57Most of this rare element originates from space rock

1:06:00deposited from the multitude of small meteors

1:06:03vaporizing in the upper atmosphere every day.

1:06:06The Alvarezs were looking for variations in the strength

1:06:09of these tiny meteor showers, but when they realized

1:06:12this huge concentration was held in the infamous tombstone

1:06:15layer, they proposed a radical new theory for the extinction,

1:06:20death from above.

1:06:23The dinosaur planet had been hit by an enormous meteor.

1:06:28Their theory remained controversial for over 10

1:06:31years, until the final piece of the puzzle

1:06:33was discovered in Mexico, a hidden crater over 100

1:06:40miles across.

1:06:41DAN DURDA: In 1990, the Chicxulub impact crater

1:06:43was discovered, and its age, when finally dated,

1:06:46turned out to be precisely 65 million years old.

1:06:49It turned out to be it was the smoking gun for the Alvarez

1:06:52theory.

1:06:54NARRATOR: Worldwide, the tombstone layer

1:06:55contains an estimated 200,000 tons of iridium.

1:07:00This translates to a meteor over 6 miles in diameter.

1:07:06Its impact on the planet would have been devastating.

1:07:10You've got to imagine Mount Everest flying

1:07:12at you across the sky at 20 kilometers per second.

1:07:16[music playing]

1:07:28Several thousand cubic kilometers of the Earth's crust

1:07:31were vaporized and excavated and watched

1:07:35around the entire planet, slowly raining back down

1:07:38through the atmosphere to settle across the surface of the Earth

1:07:41as a thin layer of dust and debris.

1:07:47NARRATOR: But the meteor was not alone in wreaking destruction.

1:07:51Today, in India, ancient lava flows exist that are so thick,

1:07:55whole temples have been carved into their layers.

1:07:59The lavas were the result of a massive eruption that

1:08:02was occurring simultaneously with the meteor strike.

1:08:06Although not as extensive as the earlier Siberian eruptions,

1:08:09these lava flows in Western India could have buried the USA

1:08:13to a depth of over 600 feet.

1:08:16The huge clouds of toxic dust they produced

1:08:19would have rivaled those of the meteor.

1:08:2265 million years ago, the meteor impact and the eruptions

1:08:26would have been a deadly double blow.

1:08:30Whichever had the stronger effect,

1:08:32the combination of these events sounded the death knell

1:08:35for the dinosaurs.

1:08:36[MUSIC PLAYING, DINOSAURS ROARING]

1:08:41The dust cloud lingering high in the upper atmosphere

1:08:44and blocking the Sun devastated the life below.

1:08:49The huge dinosaurs, along with most other major species,

1:08:54were extinct.

1:08:55The new world that was to follow would

1:08:57be the world of the mammals, and the world of man.

1:09:09[music playing]

1:09:1250 million years ago.

1:09:15Life was slowly recovering after the cataclysmic extinction that

1:09:18obliterated the dinosaurs.

1:09:21The Earth had been around for over 4.4 billion years,

1:09:27but only now were the first mammals, our ancestors,

1:09:31beginning to flourish.

1:09:34Long before humans arrived, the continents

1:09:37continued to move and crash into one another.

1:09:40Slowly, but surely, the surface started to look familiar

1:09:44as plate tectonics and erosion created the dramatic landscapes

1:09:48we see today.

1:09:49[music playing]

1:09:57The Swiss Alps.

1:10:02Some mountain chains can be explained by volcanic eruption

1:10:06of rock from the depths of the Earth,

1:10:09but the greatest, including the Alps, contained no volcanoes.

1:10:14They appear to have risen as if by magic, up from the plains

1:10:18beneath.

1:10:22This famous range runs through the heart of Europe

1:10:26and reaches over 3 miles above sea level.

1:10:30How was such a huge mass of rock pushed up so high?

1:10:44Adrian Pfiffner is an expert on the structure of the Alpine

1:10:47chain, and he knows the answer.

1:10:51ADRIAN PFIFFNER: The scene we see in front of us

1:10:54is the result of a collision between two continents,

1:10:57the African continent and the European continent.

1:11:00[music playing]

1:11:05NARRATOR: A close study of the Alpine rocks

1:11:07can provide clear evidence of how the mountains were formed.

1:11:12The secret is revealed in quartz crystals that

1:11:15are extremely small.

1:11:18ADRIAN PFIFFNER: These slices are about 20/1000

1:11:21of a millimeter.

1:11:22At that thickness, you see through one single grain.

1:11:26NARRATOR: The tiny crystals in the rock

1:11:28revealed massive deformation.

1:11:30The quartz grains have been really stretched, elongated,

1:11:35and flattened.

1:11:37You need large stresses in order to deform these rocks.

1:11:40One process that is doing this is actually the collision

1:11:44of two continental plates.

1:11:47NARRATOR: For the last 45 million years,

1:11:50as the continents have continued to move,

1:11:52the African plate and subplates have been grinding into Europe.

1:11:58The continental crust along the collision point

1:12:00experiences extreme pressure, and the solid rock

1:12:04itself is warped and buckled.

1:12:07If you assume that my hands are two plates which

1:12:10are squeezing the rocks in between,

1:12:12you can see that some of the material escapes

1:12:14upwards and leads to the building of a mountain.

1:12:18NARRATOR: The twisted folds of the rock strata

1:12:20are exposed as the mountains are slowly

1:12:23squeezed higher and higher.

1:12:30One famous Alpine mountain demonstrates clearly

1:12:33this collision of the African and European

1:12:36continental plates, the Matterhorn.

1:12:42The Matterhorn is the child of two continents.

1:12:49ADRIAN PFIFFNER: What's amazing about the Matterhorn is

1:12:52the top pyramid of the Matterhorn

1:12:54is a piece of Africa, and it lies on Europe.

1:12:57NARRATOR: In the formation of this classic mountain,

1:13:00the two continental plates have actually overlapped.

1:13:04ADRIAN PFIFFNER: You can think of a car crash.

1:13:06If two cars crash with each other,

1:13:08maybe one car slides over the other one.

1:13:11The two continents moved together,

1:13:13and Africa moved on top of Europe.

1:13:17NARRATOR: Plate tectonics are responsible for all the Earth's

1:13:20mountain ranges, and over millions of years of growth,

1:13:24the only thing that has stopped them grinding

1:13:27inexorably skywards is erosion, erosion by snow,

1:13:34wind, and rain.

1:13:37This is the action of water that is eroding the mountains.

1:13:42Now, this might seem to be something very small,

1:13:45but actually, if you look at the entire Swiss Alps,

1:13:4850 million tons is eroded every year,

1:13:51and this corresponds to a small mountain roughly 1,000

1:13:55meters high, one every year.

1:13:57[music playing]

1:14:00NARRATOR: The height of mountains around the world

1:14:02are determined by these two opposing forces, uplift

1:14:07and erosion, changing them by fractions of an inch

1:14:11up or down each year.

1:14:16But plate movement and water erosion

1:14:18can also create the opposite of a mountain.

1:14:21Under the right conditions, the surface

1:14:23itself can be cut away, sometimes, spectacularly.

1:14:29[music playing]

1:14:34The Grand Canyon, over 1 mile deep, 10 miles wide, 277 miles

1:14:50long, and still growing.

1:14:53WAYNE RANNEY: One of the great stories of exploration

1:14:55is when the first Europeans saw the Grand Canyon in the year

1:14:591541.

1:15:00And a couple of those men came over to the rim,

1:15:02they saw the river down below, and they

1:15:04thought it was 6 feet wide.

1:15:07The explorer sent a couple of his men down,

1:15:09and they came back later and said the canyon is deeper

1:15:12than it looks.

1:15:16NARRATOR: Wayne Raney is an expert

1:15:18on this geological phenomenon.

1:15:20Its unique scale, the consequence

1:15:22of titanic forces of nature.

1:15:28Over the course of the last six million years,

1:15:31this spectacular canyon has been carved by the slow,

1:15:35winding Colorado River, in combination

1:15:38with dramatic uplifting of the Colorado Plateau.

1:15:42[music playing]

1:15:46Plate tectonic processes have pushed the whole plateau

1:15:49upwards.

1:15:51It now lies over 8,000 feet above sea level.

1:15:55WAYNE RANNEY: This uplift probably occurred

1:15:57with the Pacific plate coming into the North American plate

1:16:01and wrinkling the crust.

1:16:02Much like if you took a throw rug on a hardwood floor

1:16:05and pushed it along the hardwood floor,

1:16:07when the edge of that rug reaches the wall,

1:16:10you'll see this big bow up in the rug,

1:16:11and that's exactly what's happened to the western edge

1:16:14of North America.

1:16:16NARRATOR: The river looks too small to cut a canyon so deep,

1:16:21but its height above sea level means that the force of gravity

1:16:25gives it great power.

1:16:30WAYNE RANNEY: All you have to do is look at big rivers

1:16:32like the Amazon or the Mississippi.

1:16:35They have much more volume of water

1:16:36than the Colorado River does, and yet, they

1:16:38don't cut large canyons, because their landscape is not

1:16:41elevated.

1:16:43So uplift brings the rocks into an elevation where the river

1:16:46can then saw down through all of those layers

1:16:48and create the canyon landscape we see today.

1:16:53NARRATOR: Plate tectonics combined with erosion

1:16:55have sculpted many of the features

1:16:57on the surface of our planet, and as a general rule, the most

1:17:01jagged, tallest peaks and the deepest canyons

1:17:04are the youngest of these grand structures,

1:17:07all formed within the last 50 million years.

1:17:12But the final touches have been added by yet

1:17:16another major force of nature.

1:17:20Two million years ago, in East Africa,

1:17:22ancestors of modern humans were taking their first steps

1:17:26on Earth.

1:17:30At the same time, down from the North Pole,

1:17:33enormous, icy glaciers began to descend.

1:17:38The Earth was about to enter the ice ages.

1:17:47[music playing]

1:17:50Two million years ago, ancestors of modern humans

1:17:54had begun to spread out of Africa.

1:17:58But the earth around them was cooling down.

1:18:02Before long, much of the planet would

1:18:04be coated in huge glaciers.

1:18:07The ice ages had arrived.

1:18:10[music playing]

1:18:14The grand freezings were triggered

1:18:16when overflowing volcanoes in Panama

1:18:19created the land bridge joining north to South America,

1:18:23and radically altered global ocean currents.

1:18:27The polar seas cooled significantly.

1:18:32The result was that pronounced dips in global temperature

1:18:35could now tip the planet into ice ages lasting

1:18:39tens of thousands of years.

1:18:42[music playing]

1:18:50The Langjokull Glacier.

1:18:54In the highest, coldest parts of the planet,

1:18:57glaciers still reign supreme.

1:19:05Few venture out in these hostile terrains,

1:19:08but glacier climatologist Finnur Palsson and his team

1:19:12regularly battled the freezing elements.

1:19:17FINNUR PALSSON: When you're doing glacier field work,

1:19:19conditions can be very bad.

1:19:22NARRATOR: Outside, it is below minus 20 degrees Fahrenheit.

1:19:27FINNUR PALSSON: I like to work in harsh conditions.

1:19:32Difficulty is something you need to tackle.

1:19:35NARRATOR: Finnur is keeping tabs on the growth of the glacier.

1:19:40At present, it is over 350 square miles,

1:19:43the size of New York City.

1:19:46And although it may look static, in fact,

1:19:49it is in constant motion.

1:19:52Glaciers are formed initially by snowfall on high areas.

1:19:58The compacted ice is then dragged down

1:20:01by the force of gravity.

1:20:04The glaciers move like slow motion rivers.

1:20:08FINNUR PALSSON: You can think of ice

1:20:10as soft material, like toothpaste, flows.

1:20:16If you would make a big block of toothpaste on a plate,

1:20:20it will slowly sink down and flow away to the edges.

1:20:25NARRATOR: Finnur and his team in Iceland

1:20:27regularly check on the incremental movement

1:20:29of the ice.

1:20:35This is a satellite positioning system.

1:20:38You can calculate the position of this point

1:20:41with an accuracy of about 2 centimeters

1:20:44to calculate how fast the glacier moves.

1:20:47NARRATOR: Finnur's measurements tell him

1:20:49that this glacier is moving at over 150 feet per year.

1:20:55In today's mild temperatures, glacial advance

1:20:57is kept in check by glacial melting.

1:21:00But if global temperatures were to drop by just a few degrees

1:21:03for a long period, then the glaciers

1:21:05would grind slowly forward, and the Earth

1:21:08would enter another ice age.

1:21:11The existence of ice ages was first

1:21:13discovered by 19th century Swiss geologist Louis Agassiz.

1:21:18As he explored the Swiss Alps in the 1830s,

1:21:21Agassiz couldn't help but notice the immense boulders scattered

1:21:24over farmland, and the bizarre towers of gravel capped

1:21:30by stones that stood guard over some of the mountain valleys.

1:21:36To explain how the rocks arrived at these positions,

1:21:40he speculated that they had been carried

1:21:42and deposited by ancient glaciers that had once

1:21:45filled the Alpine valleys and covered

1:21:47the northern hemisphere.

1:21:51Initially ridiculed by his peers,

1:21:53Agassiz's ice age theory became accepted as telltale signs

1:21:57that these huge glaciers had indeed covered the continents

1:22:01were found all over the globe.

1:22:04The evidence is everywhere.

1:22:07[music playing]

1:22:14New York's Central Park.

1:22:16This oasis of green in the middle of Manhattan

1:22:19exposes part of the island's ancient bedrock.

1:22:23Many large outcrops are visible, and they contain the footprints

1:22:27of the glaciers.

1:22:28[music playing]

1:22:33Climate expert Joerg Schaeffer is looking for subtle traces

1:22:37of this frozen world.

1:22:38JOERG SCHAEFFER: It's actually something

1:22:40I bet that most New Yorkers do not know.

1:22:42You see the ice ages everywhere if you open your eyes.

1:22:48NARRATOR: Look closely, and the super hard bedrock

1:22:51is marked with scores of tiny parallel lines

1:22:55fractions of an inch deep.

1:22:58So this point here is actually one of the most amazing spots

1:23:01of evidence for an ice age in the middle of New York City.

1:23:05NARRATOR: The grooves were caused by small rocks caught

1:23:08under the massive weight of a moving glacier.

1:23:11These little rocks basically cut like a knife

1:23:13into this very hard bedrock.

1:23:16This is clear proof that once, enormous ice sheet

1:23:20was moving in this direction in the middle of New York City.

1:23:23[music playing]

1:23:28NARRATOR: The glaciers that hit New York were massive.

1:23:32They rolled down from the arctic and buried Manhattan

1:23:35under a huge depth of ice.

1:23:39JOERG SCHAEFFER: To give you an idea about the thickness

1:23:41of the Laurentide ice sheet in the Manhattan area,

1:23:44it was at least twice as thick as the Empire State Building's

1:23:49height today.

1:23:51NARRATOR: Over the last two million years,

1:23:53as the climate fluctuated, the huge ice sheets

1:23:56waxed and waned.

1:24:00With every pass, they gouged and crushed and reshaped the land

1:24:04beneath them.

1:24:08As the last glaciers retreated 10,000 years ago,

1:24:12they left behind a bruised and battered landscape,

1:24:15and created features we still see today.

1:24:20In the USA, Cape Cod and Long Island

1:24:23are built on immense piles of boulders dropped

1:24:25from the retreating edge of the North American ice sheet.

1:24:30And the great weight of the ice formed huge depressions that

1:24:34now make up the Great Lakes.

1:24:37In the warmer climate that followed

1:24:39the last glacial retreat, early humans

1:24:42had free reign over the surface.

1:24:44[music playing]

1:24:49In this brief period, a fraction of a fraction

1:24:52of 1% of the history of the Earth,

1:24:55the entire history of human civilization, has taken place.

1:25:01Human ingenuity has reshaped our planet.

1:25:04From our perspective, our achievements are breathtaking.

1:25:10But will we continue to survive and prosper?

1:25:14Humans have, with technology, dominated the planet

1:25:17more completely than perhaps did any other animal in the history

1:25:20of--

1:25:22of life, but we've done it for such a short period of time

1:25:24that we've got a long ways to go.

1:25:27NARRATOR: Over the past 4.5 billion years,

1:25:30the Earth has been on the most incredible journey.

1:25:34Over the eons of its existence, the planetary environment

1:25:38has undergone immense transformations.

1:25:42And since the arrival of life, these transformations

1:25:45have, in many ways, determined which organisms will survive,

1:25:51and which will be swept aside.

1:25:56If this turbulent past is any guide to the future,

1:25:59life, and humans in particular, will face further battles

1:26:02for survival as the planet continues along

1:26:05its path of change.

1:26:08Life is highly dependent on the Earth.

1:26:10What the Earth gives us is what we have to deal with.

1:26:15It's hard to separate completely

1:26:17the processes of geology and the processes of life.

1:26:22Life, in some ways, drives geology,

1:26:24and geology creates the environments in which life

1:26:27thrives.

1:26:31NARRATOR: Our first major challenge will be the climate.

1:26:36At the start of the 21st century,

1:26:38we may worry about global warming,

1:26:41but most scientists recognize that we

1:26:43are in a gap between ice ages.

1:26:46Our whole civilization has occurred

1:26:48in a brief warm period, 10,000 years so far.

1:26:53This warmth has proved crucial.

1:26:56It's definitely not a coincidence

1:26:57that civilizations developed over this period of time

1:27:00because the climate is so favorable to our species

1:27:03to develop and flourish.

1:27:05The period we live in the moment climate wise, over the last,

1:27:09let's say, 10,000 years, is exceptionally stable.

1:27:13It's almost unbelievably stable if you--

1:27:15if you look into the geological record.

1:27:17It certainly will not stay forever like that.

1:27:20NARRATOR: Even if our industrial economies affected

1:27:22global warming over the next couple of centuries,

1:27:25it can do no more than delay the inevitable.

1:27:28The continent's current positions

1:27:29keeping the polar oceans cool mean that in just 15,000 years,

1:27:34a new ice age may occur.

1:27:37MARK MCMENAMIN: The New York area

1:27:38is going to be completely changed

1:27:41by the next cycle of glaciation, and at some point,

1:27:44glaciers are going to move down and grind New York

1:27:48into the North Atlantic Ocean.

1:27:53NARRATOR: But even if we survive the big freezes,

1:27:56there will be greater challenges to come.

1:27:59As plate tectonics move the continents

1:28:01and end the ice ages, coastal regions will be engulfed,

1:28:05and whole countries will disappear.

1:28:10200 million years from now, a new supercontinent,

1:28:14Pangaea Altima, is due to take shape, as first

1:28:19the Mediterranean, and then the Atlantic Ocean

1:28:23are swallowed up.

1:28:25There will be continents eventually

1:28:27colliding with the east coast of North America,

1:28:30so New York, in the long run, will be destroyed

1:28:33in a continent to continent collision

1:28:35and will be completely crushed and thrust upward

1:28:40as a new mountain range.

1:28:42NARRATOR: The earth will once again

1:28:43be thrown into deadly turmoil.

1:28:46Oxygen levels and surface temperatures

1:28:48could fluctuate wildly and lead to new mass extinctions.

1:28:52But even the trauma of super continental disruption

1:28:55is nothing compared to what will follow.

1:28:57Everything will grind to a halt when the plate tectonic engine

1:29:01finally stops.

1:29:04The maintenance of habitability of this planet

1:29:07is involved with a plate tectonics cycle.

1:29:11It's not an infinite cycle.

1:29:14There is an end in sight.

1:29:15It's billions of years from now, but we know, eventually,

1:29:18the system will wear out.

1:29:20NARRATOR: The fires in the depths that have dominated

1:29:22activity on the surface will one day use up their fuel,

1:29:26and the story of planet Earth will be over.

1:29:33Without its burning heart, the Earth

1:29:36will share what many believe was the fate of Mars.

1:29:42The atmosphere and oceans will be stripped away,

1:29:45and the surface will become a bone dry, barren desert.

1:29:49The planet will be dead.

1:29:54But this is a picture of an incredibly distant future.

1:29:59For at least the next billion years, as the Earth continues

1:30:02its epic journey, some form of life should continue.

1:30:09But the human species, which have walked the Earth for over

1:30:12two million years, and mastered it only in the last 10,000,

1:30:17may be endangered.

1:30:19As the environment transforms, Earth could well become unfit

1:30:24for humans.

1:30:25If that happens in the distant future,

1:30:28rather than be forced to face extinction

1:30:30like our predecessors, technology

1:30:33may allow us to leave Earth in search of new homes,

1:30:37other blue-green planets on which to make a new start,

1:30:42leaving planet Earth to continue its amazing journey without us.