1: Volcano | Earth: The Power of the Planet

00:00:20 “This is our planet -”
00:00:23 “the Earth.”
00:00:25 “It’s an amazing ever-changing world,”
00:00:28 “full of natural wonders,”
00:00:31 “but there’s more to Earth than this,”
00:00:33 “much more.”
00:00:35 “Because our planet is unique in the solar system,”
00:00:39 “perhaps even in the Universe.”
00:00:45 “Four and a half billion years”
00:00:47 “have made it a world of extraordinary landscapes”
00:00:51 “and a home to life.”
00:00:58 “My name’s Iain Stewart, and I want to show you”
00:01:02 “how our remarkable planet works.”
00:01:08 “In this series, I’m going to explore”
00:01:10 “the four powerful forces that have come together to create our world.”
00:01:18 “The oceans…”
00:01:20 “..that have the power of life and death over all living things.”
00:01:26 “The atmosphere…”
00:01:29 “..the most fickle of forces.”
00:01:32 “It drives our climate and protects and nourishes us.”
00:01:37 “Ice…”
00:01:38 “it has carved the world we know”
00:01:41 “and changed the course of human evolution.”
00:01:47 “But I’m going to start with volcanoes.”
00:01:52 “They’re terrifyingly destructive,”
00:01:55 “but they’re also the most fundamental force on the planet.”
00:02:03 “Volcanoes are part of a global system that continually reshapes our world.”
00:02:10 “They hold the key to the origins of life on Earth.”
00:02:15 “They saved the planet from the biggest crisis it’s ever faced.”
00:02:22 “And they’ve even formed partnership with life that keeps our planet habitable.”
00:02:53 “Ethiopia. Eastern Africa.”
00:02:58 “This is the Afar region, bandit country,”
00:03:02 “so I’ve hitched a lift with the Ethiopian military.”
00:03:13 “I’m off to one of the hottest and remotest places on the surface of our planet”
00:03:18 “to see the most powerful force on Earth in action.”
00:03:37 “We’ve got plenty of equipment because ahead of us, there is some serious climbing.”
00:03:49 “We’ve touched down on a dry brittle surface of recently cooled lava.”
00:03:58 “Once the helicopter leaves, we’re on our own for a couple of days.”
00:04:07 “This place has no water, no shelter, no life…”
00:04:13 “except, I’m told, for a few snakes,”
00:04:16 “but I think it’s really gonna be worth it.”
00:04:19 “I’ve come all this way to see one of the most remarkable volcanoes anywhere on the planet -”
00:04:27 “Erta Ale.”
00:04:38 “The name means “”the smoking mountain”” to the local Afar people.”
00:04:43 “It’s reckoned this volcano has been continuously erupting lava”
00:04:47 “for longer than any other on Earth,”
00:04:49 “but no-one’s quite sure because it’s only been properly studied for the last 40 years.”
00:04:56 “I’ve been lucky to see a lot of volcanoes in my time, and I’ve never seen one”
00:05:01 “that has a permanent lake of molten lava in its crater.”
00:05:07 “But there’s another reason why this volcano is very special.”
00:05:13 “And to see that, I need to get down into the crater”
00:05:17 “and see the lava up close. How does that feel? That’s fine.”
00:05:20 “The rocks here are very sharp and very brittle so it’s actually good”
00:05:24 “that we’re on an overhang and that we’re not gonna crash into it.”
00:05:28 “Nervous? Yeah, feeling a little bit nervous, apprehensive, really.”
00:05:32 “You know? It’s, you know, first time you’re ever gonna abseil,”
00:05:36 “you kinda didn’t want it to be down into an active volcano, but hey!”
00:05:45 “And then the ledge is…”
00:05:46 “So this is my…my one now.”
00:05:49 “Sit back, sit back.”
00:05:50 “After… After… OK.”
00:05:56 “That’s it, that’s good.”
00:06:01 “It’s a 30-metre vertical drop to reach a wide terrace below.”
00:06:08 “And the lava lake itself is a little further down.”
00:06:15 “I’ve waited until sunset to take a closer look”
00:06:18 “because the lava is at its most spectacular at night.”
00:06:21 “This is as close as I can safely get.”
00:06:24 “Oh, wow! Crikey.”
00:06:26 “That is magnificent! I mean, it’s taken us a hell of a journey to get here,”
00:06:31 “but THAT makes it all worth it. I’m standing on the edge of an active volcano”
00:06:36 “right next toa big pool of molten lava.”
00:06:45 “What makes this lava lake more than just pure spectacle”
00:06:49 “is that it’s a window that allows us to look deep into the Earth,”
00:06:53 “and it helps us understand the forces that shape our planet.”
00:07:09 “Just take a look at the motion of the lava lake speeded up.”
00:07:12 “Something intriguing is happening.”
00:07:15 “The movement of the lava follows a very distinctive pattern.”
00:07:22 “It wells upon one side of the crater”
00:07:25 “and forms a dark crust as it cools.”
00:07:29 “Then this crust moves across the surface of the lake”
00:07:32 “driven by the churning action of the lava below.”
00:07:38 “Finally, the crust sinks back down.”
00:07:43 “As we’ll discover, this process of molten rock”
00:07:47 “churning away below the surface affects our entire planet.”
00:07:53 “That’s because this lava lake”
00:07:55 “is connected toa gigantic source of heat”
00:07:58 “that lies deep inside the earth.”
00:08:02 “I think it’s fair to say that most of us”
00:08:05 “go about our daily lives completely unaware that underneath our feet,”
00:08:09 “our planet is incredibly hot.”
00:08:11 “I mean, we live on a thin skin of cool rock,”
00:08:15 “precariously located between the cold freezer of space up there”
00:08:20 “and a red-hot furnace down there.”
00:08:24 “And what a source of power this furnace is!”
00:08:27 “The Earth’s heat does far more than just fuel volcanoes.”
00:08:32 “It created the first atmosphere in the oceans.”
00:08:36 “It continually reshapes the planet’s surface,”
00:08:39 “builds great mountain ranges and moves entire continents.”
00:08:44 “And it created the conditions for life on Earth to begin.”
00:08:50 “In fact, you could say that the whole history of the planet”
00:08:54 “has been driven by the massive heat trapped inside it.”
00:08:59 “To understand where our planet’s inner heat comes from,”
00:09:02 “we have to go back four and a half billion years”
00:09:06 “to the time of Earth’s own birth.”
00:09:08 “It was a period called the Hadean, after Hades, the kingdom of hell,”
00:09:13 “which is a good name because this was a hot, hostile and violent world.”
00:09:30 “You may not recognise it,”
00:09:32 “but this is our planet in its very earliest days,”
00:09:37 “little more thana few pieces of rock”
00:09:40 “colliding as they circled the sun.”
00:09:43 “These impacts were so violent, they generated immense amounts of heat.”
00:09:50 “And they also delivered vast quantities of radioactive material to the earth.”
00:09:59 “Eventually, when the outer layers of the planet cooled,”
00:10:02 “these two powerful sources of heat were trapped in a huge hot core.”
00:10:13 “The centre of our planet isas hot as the surface of the sun.”
00:10:21 “This is the source of Earth’s vast heat energy.”
00:10:27 “And it’s what fuels volcanoes to this day.”
00:10:35 “Trapped within our planet, Earth’s hot core”
00:10:38 “has been continuously releasing unimaginable amounts of heat.”
00:10:42 “It gives you some idea how much”
00:10:44 “when you realise that even after four and a half billion years,”
00:10:48 “there’s still plenty left.”
00:10:56 “Earth’s inner heat makes the planet’s surface incredibly dynamic.”
00:11:02 “It has created a restless, continually changing landscape”
00:11:06 “unlike any other in the solar system.”
00:11:11 “It’s a world of destruction and renewal.”
00:11:29 “This is Iceland, a place that offers a great opportunity”
00:11:34 “to see exactly how Earth’s inner heat”
00:11:37 “is continually reshaping the planet’s landscape.”
00:11:44 “Molten rock usually lies hundreds of kilometres underground,”
00:11:49 “but here, as in Ethiopia, it’s much closer.”
00:11:56 “Yet the effect is very different.”
00:12:19 “Sulphurous fumes and bubbling hot pools”
00:12:22 “hint at the power that is just beneath the surface.”
00:12:34 “There are naturally heated pools everywhere on the island”
00:12:37 “which makes going for a dip something of a national pastime.”
00:12:43 “These hot springs are FABULOUS for relaxing in,”
00:12:47 “providing you don’t mind sharing your bath.”
00:12:49 “The mineral-rich water is meant to have therapeutic qualities.”
00:12:54 “But the people here might not be quite so relaxed”
00:12:57 “if they knew exactly how the water gets heated.”
00:13:00 “Right beneath us is a seething mass of red-hot molten rock.”
00:13:14 “Just 20 kilometres beneath Iceland”
00:13:17 “is a vast column of super-heated rock, known as a plume.”
00:13:22 “Recently, the shape of this hot plume of rock has been mapped.”
00:13:27 “It’s 100 kilometres wide and at least 600 kilometres deep.”
00:13:33 “Created more than50 million years ago,”
00:13:36 “the plume is sustained by heat continually rising up”
00:13:40 “from the Earth’s hot core.”
00:13:49 “But this giant plume of super-heated rock has done much more than just warm up Iceland’s hot springs -”
00:13:55 “it also created Iceland itself.”
00:14:00 “In 1963, we got to see how it must have happened.”
00:14:09 “A volcano, just below the sea’s surface,”
00:14:12 “blasted its way out of the water.”
00:14:20 “A new island, Surtsey, was born.”
00:14:24 “This is what Iceland must have looked like 50 million years ago”
00:14:28 “when it first burst above the surface.”
00:14:36 “But what makes Iceland so unusual”
00:14:39 “is not just that it sits above a hot plume.”
00:14:42 “This small island is also shaped by the Earth’s inner heat”
00:14:46 “in another much more powerful way.”
00:14:50 “This is Thingvellir.”
00:14:53 “It’s an important place in human history because in AD 930,”
00:14:58 “a group of Icelandic chieftains gathered hereto sort out their disputes.”
00:15:03 “This was the world’s first parliament which then sat here for the next eight centuries.”
00:15:10 “But there’s another reason why this is an important place.”
00:15:14 “Although they didn’t know it, those early pioneers of democracy had set up their parliament”
00:15:19 “in the shadow of a most extraordinary rock face.”
00:15:35 “From the air, you can begin to see just how unusual this rock face is.”
00:15:42 “It’s a crack in the Earth’s surface”
00:15:44 “that runs for hundreds of kilometres.”
00:15:51 “But what we’re looking at”
00:15:53 “is just a tiny part of something much, much bigger.”
00:16:02 “This is the edge of a gigantic slab of the Earth’s crust”
00:16:06 “which runs unbroken for 7,000 kilometres,”
00:16:10 “right from this point, under the Atlantic,”
00:16:12 “across the USA, all the way to California.”
00:16:21 “It’s what’s known as the North American Plate.”
00:16:33 “The Earth’s surface is broken up”
00:16:35 “into seven major chunks called “”plates””.”
00:16:41 “They’re so enormous that they can carry an entire continent”
00:16:45 “and extend far under the sea.”
00:16:52 “Strip away the Atlantic Ocean and you can see a long boundary”
00:16:56 “between two of these plates that runs along the ocean floor”
00:17:00 “until it rises above the waves…”
00:17:05 “..cuts through Iceland…”
00:17:08 “..to eventually join up with the rock face at Thingvellir.”
00:17:19 “It’s possible to see this plate boundary”
00:17:22 “from a completely different perspective.”
00:17:38 “This is a very cold place to go scuba diving.”
00:17:41 “The water is just for degrees Celsius.”
00:17:44 “But it’s worth it because I’m actually swimming”
00:17:49 “in the gap between the two giant plates that run through Iceland.”
00:17:53 “To my left, the North American Plate”
00:17:57 “and to my right, Europe.”
00:18:03 “These sheer rock faces were once joined together,”
00:18:06 “but driven by immense geological forces,”
00:18:10 “the land was split apart create these deep chasms”
00:18:13 “which filled with water.”
00:18:26 “It’s hard to imagine a force that can move continents apart,”
00:18:30 “yet this is precisely what the Earth’s inner heat is able to do.”
00:18:39 “It happens because hot rock rises, heated by the Earth’s core.”
00:18:45 “Near the surface, the rock spread in two directions and goes sideways.”
00:18:50 “It begins to lose heat.”
00:18:52 “Eventually, the much cooler rock sinks back down.”
00:18:58 “Through this spreading process,”
00:19:00 “the Earth’s crust is very slowly dragged apart,”
00:19:04 “and it’s this that ultimately causes the continents to move.”
00:19:11 “The lava lake at Erta Ale”
00:19:13 “is an example of the same process but in miniature.”
00:19:18 “As we’ve seen, the movement of hot lava”
00:19:21 “drags the crust across the surface of the lake,”
00:19:24 “just as the continents are pulled across the Earth’s surface.”
00:19:30 “To appreciate the idea of continents moving,”
00:19:34 “you have to step outside human timescales”
00:19:37 “and think in terms of a completely different timeframe.”
00:19:41 “The continents here are drifting apart at two centimetres every year.”
00:19:46 “In my lifetime, we’re talking just a couple of steps.”
00:19:50 “Even in 1,000 years, that’s just 20 metres.”
00:19:54 “It’s only when you start to think in terms of millions of years”
00:19:58 “that you realise just what can happen.”
00:20:06 “225 million years ago, our planet looked very different.”
00:20:12 “All the continents were joined together”
00:20:14 “in a single supercontinent called Pangaea.”
00:20:20 “As the plates moved, this supercontinent broke up.”
00:20:24 “New oceans formed as continents drifted around the globe.”
00:20:31 “It’s this that has created the shape of the world we know today.”
00:20:37 “But the plates never stop moving.”
00:20:40 “In the distant future,”
00:20:42 “our continents will once again be reunited”
00:20:45 “in a new giant supercontinent.”
00:20:52 “We’ve seen what happens when the plates move apart…”
00:20:57 “..but when they crash into one another…”
00:21:01 “..the effects are even more dramatic.”
00:21:13 “The collision of the Earth’s plates is responsible”
00:21:16 “for the most spectacular mountain ranges on our planet.”
00:21:32 “To see how they’re created, I’ve come to New Zealand’s South Island.”
00:21:41 “These stunning peaks run 500kilometres along the west coast,”
00:21:46 “forming a dramatic spine down the island.”
00:21:54 “According to Māori legend,”
00:21:56 “these mountains are made of the petrified bodies of four gods”
00:22:01 “who got stranded hereon a canoeing trip to Earth.”
00:22:04 “As they were attempting to return to the heavens,”
00:22:08 “a big storm blew up and capsized the canoe.”
00:22:12 “They climbed on board and waited”
00:22:14 “for someone to rescue them, but no-one came.”
00:22:17 “As time passed, they slowly turned to stone.”
00:22:21 “As far as geology goes, there’s a slightly different explanation.”
00:22:25 “It may not be as romantic as Maoriland, but it’s every bit as epic.”
00:22:37 “What was to become New Zealand was once a group of scattered islands.”
00:22:44 “The collision of the Pacific and Australian plates”
00:22:47 “forced these islands together,”
00:22:49 “creating the familiar outline of New Zealand that we know today.”
00:22:55 “Along the collision zone,”
00:22:58 “the land was buckled and a line of mountains rose up.”
00:23:11 “New Zealand’s mountains are around five million years old.”
00:23:15 “That may sound ancient, but it’s just a geological blink of an eye.”
00:23:20 “Yet even in this short timescale, these peaks have grown into giants.”
00:23:25 “All the world’s great mountain ranges form in this way”
00:23:29 “when continents collide.”
00:23:31 “You can really get a sense of how the surface of the Earth crumbles when you look down from space.”
00:23:38 “These are the European Alps…”
00:23:43 “..the South American Andes…”
00:23:47 “..and the Himalayas of Central Asia.”
00:23:55 “They’re all relatively young,”
00:23:57 “born out of recent collisions between plates.”
00:24:02 “Sometimes, you can actually see their growing pains.”
00:24:17 “Earthquakes are a horrific force of destruction.”
00:24:22 “Entire cities can be wiped out at terrible human cost.”
00:24:34 “But this is what happens when our planet”
00:24:37 “builds its great mountain ranges.”
00:24:39 “THEY SHOUT”
00:24:42 “In October 2005, a devastating earthquake hit the Western Himalayas”
00:24:48 “in Northern Pakistan.”
00:24:55 “The area around the town of Muzaffarabad”
00:24:58 “was completely razed to the ground.”
00:25:02 “But satellites measuring the height of the surrounding land before and after the earthquake”
00:25:08 “revealed that something else had happened as well -”
00:25:12 “the red and yellow colours show how the hills to the east of the earthquake’s epicentre”
00:25:17 “had actually risen as much as five metres during the earthquake.”
00:25:24 “This process, repeated thousands of times,”
00:25:28 “has helped build the Himalayas”
00:25:30 “into the greatest mountain range on Earth.”
00:25:34 “And it’s just as well that the earth’s inner heat continues to push mountains up.”
00:25:47 “Because huge though mountains are, they’re continually under attack.”
00:25:52 “Given enough time, there’s a force that can completely destroy them.”
00:25:57 “It might seem unlikely, but that force is nothing more than water.”
00:26:02 “THUNDER CLAPS”
00:26:08 “THUNDER RUMBLES”
00:26:17 “Ironically, mountains create the very rain that attacks them.”
00:26:21 “They’re high enough to disrupt the atmosphereand create their own weather.”
00:26:26 “The higher the mountains are pushed up,”
00:26:28 “the higher the air is forced to rise to cross them,”
00:26:31 “so the air cools and condenses into clouds”
00:26:35 “which produce rain.”
00:26:44 “And it’s surprising just how effective the power of water can be.”
00:26:49 “And forward!”
00:26:53 “And forward.”
00:26:59 “And get down!”
00:27:08 “LAUGHTER And hold on!”
00:27:14 “It’s only when you’re fighting the rapids”
00:27:17 “that you can begin to understand how powerful a river can be.”
00:27:23 “This gorgeous hundreds of metres deep”
00:27:26 “and yet it was cut by the river,”
00:27:27 “relentlessly wearing away at the rock, and it’s still getting deeper.”
00:27:34 “Rivers don’t just erode the rock -”
00:27:36 “they also carry it from the mountains to the sea”
00:27:39 “in the form of silt.”
00:27:41 “It happens on a massive scale.”
00:27:46 “In South America, the Amazon carries away over two billion tons”
00:27:51 “of the Andes every year and deposits it in the Atlantic ocean.”
00:27:59 “And on the Indian subcontinent,”
00:28:02 “the Ganges river, that starts high in the Himalayas,”
00:28:05 “grinds away around a billion tons of rock every year,”
00:28:10 “dropping it 3,000 kilometres down river in the Indian ocean.”
00:28:19 “If it wasn’t for the movement of the plates building new mountain ranges,”
00:28:23 “water would eventually erode away all the land on our planet.”
00:28:34 “It’s hard to imagine but…if the plates should ever stop moving,”
00:28:38 “our planet would become a water world.”
00:28:42 “It may take an unfeasibly long time,”
00:28:45 “but eventually the land would be worn down and washed out to sea”
00:28:49 “and Earth would be covered”
00:28:51 “in a vast ocean several kilometres deep.”
00:28:55 “So, it’s thanks to the collision of the plates continuallypushing the land up”
00:29:00 “that we’ve still gutters firma”” to stand on.”
00:29:10 “Our world is constantly reshaped a never-ending battle”
00:29:14 “between the Earth’s inner heat that pushes the land up”
00:29:18 “and the forces of erosion that wear it down.”
00:29:21 “But the Earth’s inner heat has made a profound difference”
00:29:25 “to our planet in another way,”
00:29:27 “perhaps in the most important way of all.”
00:29:39 “It began around four billion years ago.”
00:29:49 “This is Rotorua in the North Island of New Zealand.”
00:29:55 “It’s one of the most volcanically active places on the planet.”
00:30:01 “This is a landscape where you can travel back in time.”
00:30:05 “Rotorua is similar to how the early Earth would have looked.”
00:30:17 “In its early days, the planet looked very different.”
00:30:19 “Just like here, the ground was hot with perpetual volcanic activity.”
00:30:26 “Nasty chemicals brought up from below stained the land.”
00:30:31 “And noxious gases bubbled up from steaming pools.”
00:30:39 “To us, the young Earth would have been a hellish place.”
00:30:43 “But ironically, this volcanic activity”
00:30:46 “helped create the right conditions”
00:30:48 “for the most important change in the history of our planet.”
00:30:53 “Ultimately, volcanoes provided the surface of our young planet”
00:30:57 “with warmth, water and a potent cocktail of chemicals,”
00:31:02 “and it was this combination which inadvertently prepared Earth”
00:31:06 “for an utterly remarkable event.”
00:31:09 “No-one’s sure exactly how it happened,”
00:31:11 “but around four billion years ago, our planet saw the birth of life.”
00:31:24 “These pools have a unique chemistry that is very similar to what would have existed on the early Earth.”
00:31:34 “Bruce Mountain has studied these pools for many years.”
00:31:39 “He’s going to show me how the first life on Earth might have begun.”
00:31:42 “We don’t have a time machine to take back, so the only thing we can do”
00:31:46 “is look at things we think are similar to what they were like,”
00:31:49 “and these hot springs are very, very close to those that would be found on the early Earth.”
00:31:54 “So, what’s the temperature of this water? Well, the water’s75 degrees Celsius so it’s…”
00:31:59 “You’d definitely get burned if you put your finger in there. And…”
00:32:02 “it’s full of hydrogen sulphide which is quite poisonous. There’s abet of arsenic in the water as well.”
00:32:08 “Surely there can’t be anything living in there!”
00:32:10 “There’s billions and billions and billions of organisms living in that water,”
00:32:15 “and they form these orange fibres. It looks like a fur that’s covering all the…rocks. Yeah.”
00:32:24 “For the microbes living within the orange fibres,”
00:32:27 “these toxic chemicals in the water are a rich soup of nutrients.”
00:32:34 “Pools like this were very common on the early Earth.”
00:32:37 “Fed by volcanic activity, they provided all the right chemicals needed for the emergence of life.”
00:32:46 “Deep down below us, there’s a body of magma that’s very hot.”
00:32:51 “Now, the magma itself is giving off gases like carbon dioxide and sulphur dioxide,”
00:32:55 “and that provides the food for these bacteria to grow.”
00:32:59 “So the volcanoes are like a supply chain providing all this?”
00:33:02 “They’re the heat engine that drives the whole process.”
00:33:11 “Volcanic pools like this one possible place where life might have begun.”
00:33:22 “But there is an alternative theory”
00:33:25 “as volcanoes created other places where life could have started…”
00:33:30 “like hydrothermal vents.”
00:33:34 “These too are the result of volcanic activity,”
00:33:37 “but they are found in the deepest parts of the oceans.”
00:33:42 “Today, they support an extraordinary diversity of life,”
00:33:47 “but four billion years ago, it’s thought that the combination”
00:33:51 “of high temperatures and rich chemicals that the vents produce”
00:33:55 “might have stimulated the emergence of life.”
00:34:07 “But the role of volcanoes went beyond just kick-starting life.”
00:34:11 “They have played a critical role in nurturing and protecting it too.”
00:34:20 “During Earth’s infancy, the sun wasn’t burning brightly as it does today.”
00:34:25 “In fact, it was about 30% cooler.”
00:34:28 “With a dimmer sun bathing the planet in weaker sunlight,”
00:34:32 “Earth was actually in danger of freezing.”
00:34:35 “It was volcanoes that provided the young vulnerable planet”
00:34:40 “with a way to keep warm, but not in the way that you might think.”
00:34:44 “Earth wasn’t warmed upby all that hot lava spewing out”
00:34:48 “but by an extraordinary gas that volcanoes pumped out,”
00:34:52 “and that gas…”
00:34:55 “..was carbon dioxide.”
00:35:05 “Today, we think of carbon dioxide a dangerous gas,”
00:35:09 “causing havoc through climate change.”
00:35:13 “But actually, carbon dioxide has always been vital to our planet”
00:35:19 “because it traps heat in the atmosphere that would otherwise be lost to space.”
00:35:30 “To see just how critical carbon dioxide is for Earth,”
00:35:34 “take a look at our near neighbours.”
00:35:40 “Mars is a frozen wasteland with an average temperature of minus 60 degrees.”
00:35:46 “That’s because its atmosphere doesn’t have enough carbon dioxide to keep it warm.”
00:35:54 “At the other extreme, temperature on the surface of Venus hot enough to melt lead,”
00:36:00 “not simply because it’s a bit closer to the sun, but because Venus has an atmosphere”
00:36:05 “with thousands of times more carbon dioxide than Earth.”
00:36:19 “The early Earth was much more volcanic than it is today”
00:36:23 “because its core was so much hotter.”
00:36:27 “This provided enough carbon dioxide to compensate for the weak sun.”
00:36:35 “It was volcanoes that prevented the young Earth from freezing over,”
00:36:41 “and so early life was able to survive.”
00:36:45 “But even this was not the end of what volcanoes have done for life on Earth.”
00:36:49 “About 600 million years ago, they also helped trigger”
00:36:54 “the greatest evolutionary leap in Earth’s history.”
00:36:59 “And a great evolutionary leap was certainly needed”
00:37:02 “because soon after life got started, it got stuck in a bit of a rut.”
00:37:16 “Shark Bay in Western Australia”
00:37:18 “is home to some of the oldest life forms on Earth.”
00:37:24 “These strange domes are made up from layer upon layer of bacteria.”
00:37:29 “They’re called stromatolites.”
00:37:33 “For most of Earth’s long history,”
00:37:36 “this was the most advanced life on the planet.”
00:37:43 “For around two billion years,”
00:37:45 “stromatolites ruled our world unchallenged,”
00:37:50 “and there was nothing to suggest that this was ever going to change.”
00:37:56 “But Earth and the stromatolites were to face a catastrophe,”
00:38:00 “the most serious crisis life has ever faced.”
00:38:12 “Around 700 million years ago, our planet started to cool.”
00:38:28 “It was the beginning of an Ice Age, but with a difference.”
00:38:35 “No-one is quite sure why it happened, but it seems that ice advanced from the poles”
00:38:39 “until the entire world was plunged into an interminable frozen winter.”
00:38:56 “It’s been called the time of “”Snowball Earth”””
00:38:59 “because the whole planet would have appeared as an icy ball.”
00:39:05 “Travel out to Jupiter and you can get some idea of what Earth might have looked like.”
00:39:14 “Europa is one of Jupiter’s moons.”
00:39:16 “It’s completely covered in ice, just as Earth would have been at the time of the snowball.”
00:39:31 “But knowing what Earth looked like doesn’t convey just how terrible the conditions would have been.”
00:39:37 “A blizzard high in the Alps inmix-winter is as close as I can get.”
00:39:45 “The conditions must have been absolutely horrendous.”
00:39:50 “I don’t think I’ve been ever this cold in my life!”
00:39:55 “Temperature must be…minus 20degrees Celsius with the wind,”
00:40:00 “but the thing is during Snowball Earth,”
00:40:03 “things were much worse.”
00:40:18 “Today, the average…”
00:40:20 “..surface temperature of the planet”
00:40:23 “around the world is 15 degrees Celsius.”
00:40:27 “HE PANTS”
00:40:29 “During the time of the snowball, that average surface temperature”
00:40:33 “plummeted to minus 50,”
00:40:37 “5-0 degrees Celsius.”
00:40:42 “Those frozen conditions threatened the very existence…”
00:40:47 “..of life on Earth. HE GRUNTS”
00:40:52 “The scary thing about Snowball Earth is that our planet could have been trapped in the freezer for ever.”
00:41:07 “Once ice had almost completely covered the planet,”
00:41:10 “most of the sun’s heat was reflected back to space.”
00:41:14 “It looked like the Earth might never heat up again,”
00:41:18 “but clearly something happened which rescued our planet”
00:41:21 “from the icy grip of the snowball.”
00:41:29 “And what came to the rescue was volcanoes.”
00:41:34 “Even though ice covered the entire planet,”
00:41:37 “volcanoes continued to erupt,”
00:41:40 “blasting through the thick blanket of ice.”
00:41:46 “It must have been an extraordinary time.”
00:41:49 “The nearest we’ve experienced was in 2004 when an eruption was filmed”
00:41:54 “bursting through an ice sheet in central Iceland.”
00:41:59 “This is what would have happened during the snowball era,but on a global scale.”
00:42:07 “The heat from volcanoes would have melted holes in the ice,”
00:42:11 “but that’s not what saved our planet.”
00:42:14 “It was the tons of carbon dioxide gas it released that did the trick.”
00:42:26 “As volcanoes continued to erupt,”
00:42:28 “levels of carbon dioxide steadily built up in the atmosphere.”
00:42:34 “Until around 630 million years ago,”
00:42:38 “the layer of carbon dioxide became so thick that it trapped enough heat”
00:42:42 “to release the planet from the grip of the ice.”
00:42:50 “At last, a thaw began.”
00:43:03 “Fierce storms pounded the planet…”
00:43:06 “as ice house became hot house.”
00:43:10 “Temperatures swung from minus 50 Celsius to plus 50”
00:43:13 “in just a few hundred years,”
00:43:16 “as Earth endured the most extreme climate change in its history.”
00:43:28 “Fortunately, over time,”
00:43:30 “our planet’s climate stabilised and Earth slowly returned to normal.”
00:43:36 “It had been a close call,”
00:43:38 “but a few pockets of life had survived the snowball.”
00:43:43 “We’ve got a lotto thank volcanoes for.”
00:43:45 “They saved our planet from a desolate fate”
00:43:48 “as nothing more thana lifeless frozen wasteland.”
00:43:52 “But as if that’s not enough, when volcanoes triggered the end of Snowball Earth,”
00:43:57 “it set the stage for the greatest leap forward in the history of life on our planet.”
00:44:02 “DIDGERIDOO PLAYS”
00:44:16 “I’ve come to South Australia”
00:44:18 “to see what happened to the evolution of life”
00:44:21 “after Snowball Earth.”
00:44:23 “Palaeontologist Jim Gehling”
00:44:25 “is taking me to see some of the rarest and most ancient fossils in the world,”
00:44:31 “the remains of the creatures that finally ended the era of the stromatolites.”
00:44:35 “Jim, where exactly are we going?”
00:44:38 “We’re going to a secret location in the Flinders Ranges.”
00:44:41 “This site is so valuable”
00:44:43 “that we have to actually be very careful about”
00:44:46 “who we take in there and who actually finds out about it.”
00:44:51 “We’re going to see one of the most fantastic things. It’s…”
00:44:54 “the place where you can geta look at the very first fossil evidence of complex life on Earth.”
00:45:06 “The area we’re about to visit was once at the bottom of the sea.”
00:45:10 “600 million years ago, the oceans were the only place where life could be found.”
00:45:17 “For a billion years,”
00:45:19 “all that the Earth had seen was microscopic single-celled creatures.”
00:45:24 “The best they could do was to form these domes of slime which we call stromatolites.”
00:45:29 “So then in comes the snowball, global glaciation and wipeout.”
00:45:34 “And how did life get affected by that?”
00:45:36 “Within a short time after the end of the snowball,”
00:45:39 “we see a revolution in the history of life.”
00:45:42 “We see a sudden increase in size and complexity of the single-celled creatures”
00:45:46 “and soon after, you find impressions on rocks”
00:45:50 “of the very first large creatures, things you can see with the naked eye,”
00:45:54 “which we believe are the oldest multi-celled creatures, the Ediacara fossils.”
00:46:02 “These fossils may represent the most important leap forward in the history of life on our planet,”
00:46:08 “but that doesn’t mean they’re easy to spot.”
00:46:12 “This is a very old surface. If we clean it off”
00:46:15 “and then push this putty onto the surface,”
00:46:19 “you can actually see the impression… Look at that!”
00:46:21 “..of a thing called Paracrine.”
00:46:24 “It looks like somebody’s signet ring. It’s like a trademark. Exactly, yeah!”
00:46:28 “And that’s really all the fossil is. It’s the impression of this soft-bodied creature”
00:46:33 “as it was preserved instantly on the sea floor about 560 million years ago.”
00:46:38 “These are nothing like the fossils I’m used to. That…”
00:46:41 “I would never, ever have spotted that.”
00:46:49 “Paracrine wouldn’t attract much attention today,”
00:46:52 “but this animal had Madea gigantic evolutionary leap.”
00:46:58 “Unlike single-celled microbes,”
00:47:00 “this was a complex creature with head, skin and internal organs.”
00:47:13 “Under here, we can actually see the imprint of quite a large creature,”
00:47:16 “at least the size of your hand.”
00:47:18 “This is Dickinsonia, and it has got the finest segments”
00:47:23 “that you can actually believe.”
00:47:25 “Oh, yeah, just as it catches the light….”
00:47:28 “Once you get it the right angle, you can actually the details of these body segments.”
00:47:33 “There are about three there. There’s another one there.”
00:47:36 “It’s like it was impressed yesterday. Every little detail is preserved on these sands. Beautiful.”
00:47:43 “Dickins onia could grow to over a metre long.”
00:47:47 “It’s thought they lived on the sea floor, soaking up nutrients through their skin.”
00:47:55 “Here for the first time, we’re seeing life that’s become multi-celled, it’s large.”
00:48:01 “These are the creatures that gave rise to the life that we know today.”
00:48:06 “For around 50 million years,”
00:48:08 “the Ediacarans lived in an ocean free of predators.”
00:48:12 “Slowly, they evolved into more complex animals,”
00:48:16 “but THAT came at a price.”
00:48:19 “These new animals now came equipped with rigid skeletons and shells,”
00:48:24 “gripping claws and protective armour.”
00:48:27 “The Earth had changed from soft peaceful Garden of Eden”
00:48:31 “into a savage world of predator and prey.”
00:48:36 “This intense competition now drove evolution at a frenetic pace.”
00:48:47 “For more than two billion years,”
00:48:49 “our world had been dominated by microbes.”
00:48:53 “Now, complex multi-celled life”
00:48:56 “exploded into many new shapes and sizes.”
00:49:01 “Emerging from the sea,”
00:49:03 “animals and plants went on to conquer the land…”
00:49:08 “..and the air.”
00:49:14 “Volcanoes had ended the terrible time of Snowball Earth”
00:49:18 “and in doing so, led toa great evolutionary leap forward.”
00:49:40 “But Earth’s powerful volcanoes had one further role to play”
00:49:45 “in the story of life on Earth.”
00:49:50 “It’s a role that’s still vital to the survival of complex lifelike us to this day.”
00:49:56 “It involves an amazing alliance,”
00:49:58 “a partnership between volcanoes and life”
00:50:02 “that regulates the temperature of the planet,”
00:50:05 “and once again it happens”
00:50:08 “because volcanoes have the power to change our atmosphere.”
00:50:18 “To show how this extraordinary partnership works,”
00:50:22 “I’m going to Sicily.”
00:50:29 “This is my favourite place on the entire planet.”
00:50:33 “I’m two and a half thousand metres above sea level on the island of Sicily,”
00:50:38 “and as you can see, this is pretty cold and windy,”
00:50:41 “but the Phoenicians called this place “”the furnace””.”
00:50:45 “The Romans called it “”the burning””,”
00:50:48 “and for the Arabs, it was “”the mountain of fire””.”
00:50:51 “We know it as Mount Etna.”
00:50:56 “And even after thousands of years,”
00:50:59 “it’s still one of THE most active volcanoes in the world.”
00:51:15 “It’s maybe hard to believe that volcanoes as destructive as Etna”
00:51:20 “could ever develop a partnership with life.”
00:51:23 “But in fact working together, they fine-tune the Earth’s temperature”
00:51:28 “by controlling the amount of carbon dioxide in the atmosphere.”
00:51:37 “This process begins in an unlikely place…”
00:51:42 “..the oceans, with tiny creatures called plankton.”
00:51:49 “They may be individually microscopic,”
00:51:54 “but they’re so abundant that when they come together,”
00:51:57 “they can be seen from space.”
00:52:01 “Every year, they proliferate into huge blooms”
00:52:05 “that colour the ocean green.”
00:52:08 “And it’s because the plankton are so abundant”
00:52:10 “that they can help regulate the climate of the planet.”
00:52:15 “The oceans absorb carbon dioxide from the atmosphere”
00:52:20 “and the plankton this carbon to grow.”
00:52:25 “When the plankton die, they fall to the sea floor and here,”
00:52:30 “over thousands of years, they are slowly transformed into rock.”
00:52:36 “In this way, huge amounts of carbon dioxide, the very gas that keeps our planet warm,”
00:52:41 “are removed from the atmosphere and locked away on the sea floor.”
00:52:50 “So if that was the end of the story, our planet would steadily get colder and colder.”
00:52:59 “Fortunately, volcanoes like Etna don’t allow that to happen.”
00:53:04 “Etna is a special type of volcano.”
00:53:08 “It’s formed where two of the Earth’s plates are colliding,”
00:53:11 “in this case, the African plate with the European one.”
00:53:17 “What happens is that one plate gets forced down or “”subducted” “underneath the other.”
00:53:22 “That action produces volcanoes and subduction volcanoes”
00:53:26 “produce some of the largest and most powerful eruptions on the planet.”
00:53:32 “Where the plates collide, the rock on the sea floor containing carbon”
00:53:36 “from the dead plankton carried deep into the Earth.”
00:53:42 “As it descends, this layer of rock is heated”
00:53:46 “so the rock melts, releasing carbon dioxide.”
00:53:52 “And gas is returned back into the atmosphere during an eruption.”
00:54:07 “The remarkable cycle is complete.”
00:54:15 “It’s uncanny how working together, life and volcanoes”
00:54:20 “keep just the right amount of carbon dioxide in our atmosphere,”
00:54:24 “maintaining our planet at a comfortable temperature.”
00:54:32 “But this process that has sustained life on the planet”
00:54:36 “comes at an enormous cost.”
00:54:43 “Subduction volcanoes are the most violent on Earth.”
00:54:51 “You can see just how explosive they are”
00:54:54 “by looking at one of the most famous eruptions ever recorded.”
00:54:59 “On May 18th 1980,”
00:55:01 “Mount St Helens in the United States was ripped apart.”
00:55:08 “Within minutes, 2.8 billion cubic metres of the volcano”
00:55:14 “were blasted out over the surrounding countryside.”
00:55:21 “For the last 25 years, Mounts Helens has been fairly quiet.”
00:55:29 “But inside its vast crater, a giant cone of rock is growing.”
00:55:36 “Forced up by the pressure from beneath,”
00:55:39 “Mount St Helens is building for another eruption.”
00:55:52 “The irony is that subduction volcanoes are so highly explosive”
00:55:56 “and destructive because they’re so gassy,”
00:55:59 “yet it’s the release of the gas that’s crucial to the Earth.”
00:56:03 “That’s the key to recycling carbon that’s locked in the rocks back into the atmosphere.”
00:56:10 “The whole elaborate system works like a finely-tuned thermostat,”
00:56:15 “maintaining the right temperature for life.”
00:56:22 “But, of course, it must be hard to accept”
00:56:25 “just how important volcanoes are to our world”
00:56:29 “when it’s your own home that gets destroyed.”
00:56:38 “In 1992, a few months before I first came here,”
00:56:42 “the volcano spewing masses of lava.”
00:56:46 “I remember the news footage of the farmer who lived in this house here.”
00:56:51 “With the lava coming up to his front door,”
00:56:55 “he sits down for a farewell meal,”
00:56:57 “drinks a final glass of red wine, daubs a sarcastic remark,”
00:57:01 “””Grazie, Governo””, on the wall and leaves his home to the lava.”
00:57:29 “Ever since the planet formed four and a half billion years ago…”
00:57:36 “..Earth’s inner heat has been continuously struggling to escape.”
00:57:47 “We see the result as volcanoes, but that’s just one part of it.”
00:57:58 “To me, nothing has been more important”
00:58:00 “to the history of our planet than the heat trapped inside it.”
00:58:09 “No force on Earth is more dramatic, more destructive, more violent than volcanoes,”
00:58:15 “but they’re so much more than just a force of destruction -”
00:58:19 “they’re the life force of our planet.”
00:58:21 “Quite simply, without volcanoes I wouldn’t be here…”
00:58:26 “and neither would you.”
00:58:32 “Next time – the atmosphere.”
00:58:35 “It’s immensely powerful,”
00:58:38 “but at the same time, highly sensitive.”
00:58:45 “It’s destructive and yet it also protects us.”
00:58:49 “Now, it’s changing fast”
00:58:51 “with potentially devastating consequences.”
00:58:57 “Woo hoo! Whoa!”