0:00:03 > 0:00:06This week on Fierce Earth we explore the power of ice.
0:00:08 > 0:00:10And where better to start than here.
0:00:11 > 0:00:13Welcome to Iceland.
0:00:13 > 0:00:17Iceland is one of the least populated countries in Europe.
0:00:17 > 0:00:19There may not be many people here
0:00:19 > 0:00:22but there are loads of mountains, volcanoes and glaciers.
0:00:25 > 0:00:27And it's those glaciers that have brought us here
0:00:27 > 0:00:29because on today's Fierce Earth...
0:00:29 > 0:00:32The big chill sets in, as we get to grips with ice.
0:00:34 > 0:00:37We're going to show you the awesome power of ice as carves its way
0:00:37 > 0:00:39through mountains.
0:00:39 > 0:00:43Mike will be there as a terrifying winter storm
0:00:43 > 0:00:45strikes North America.
0:00:45 > 0:00:47Just look at this! This is insane!
0:00:47 > 0:00:51And we'll see Leo shoot across ice at super-high speeds.
0:00:52 > 0:00:56And we're going to see how this seemingly innocent substance
0:00:56 > 0:00:58can be so destructive and dangerous.
0:01:01 > 0:01:05What happens when the ground shakes, the seas rise up
0:01:05 > 0:01:08and the air tears itself apart?
0:01:08 > 0:01:09The Fierce Earth team move in,
0:01:09 > 0:01:12taking on the most powerful forces on the planet.
0:01:30 > 0:01:34Get ready for Fierce Earth - the Earth and how to survive it.
0:01:38 > 0:01:41Ice makes up about 10% of our planet.
0:01:41 > 0:01:45There's enough of this frozen substance on Earth to cover
0:01:45 > 0:01:47the whole of Britain over 65 times.
0:01:52 > 0:01:54Ice takes all kinds of different forms.
0:01:55 > 0:01:59It can be glacial ice which forms on land.
0:01:59 > 0:02:02Ice sheets which float on the sea.
0:02:02 > 0:02:05Or polar ice which forms a frozen desert at the top
0:02:05 > 0:02:06and bottom of our planet.
0:02:07 > 0:02:10But where does this ice actually come from?
0:02:11 > 0:02:15We've travelled all the way to the country of Iceland to show you.
0:02:16 > 0:02:18To understand how ice forms,
0:02:18 > 0:02:23I'm coming face to face with a gigantic lump of the stuff.
0:02:23 > 0:02:26It's called the Svinafellsjokull glacier.
0:02:26 > 0:02:30When water gets to about zero degrees centigrade,
0:02:30 > 0:02:32it can freeze rapidly and turn to ice.
0:02:32 > 0:02:36But that isn't how most of the ice on Earth is created.
0:02:36 > 0:02:38Some of the most powerful ice on our planet
0:02:38 > 0:02:42starts off as the humble snowflake.
0:02:42 > 0:02:44Now it's hard to imagine how simple,
0:02:44 > 0:02:49fluffy snowflakes that fall from the sky, can actually become this.
0:02:49 > 0:02:53But if you collect enough of them, and you compact them over time,
0:02:53 > 0:02:57you can form some of the most powerful ice rivers on the planet.
0:02:58 > 0:03:01And the way that the snowflakes are crushed together,
0:03:01 > 0:03:04helps scientists like me actually study the ice.
0:03:06 > 0:03:09Iceland has some fantastic glacial formations.
0:03:09 > 0:03:12When you see them in cross-section,
0:03:12 > 0:03:16they tell you the age of the ice, step by step, year by year.
0:03:16 > 0:03:19You can pick out dark and light layers.
0:03:19 > 0:03:22The light layers represent snowfall in winter.
0:03:22 > 0:03:27The dark layers represent dust blown over the ice in the summer.
0:03:27 > 0:03:29It's like the rings of a tree.
0:03:29 > 0:03:32Winter after winter, new layers of snow fall
0:03:32 > 0:03:36and the weight from each layer weighs heavily on the previous one.
0:03:36 > 0:03:39The layers get thinner and thinner, making them more dense.
0:03:39 > 0:03:43The pretty snowflake shape we know is crushed
0:03:43 > 0:03:45and all of the air squeezed out,
0:03:45 > 0:03:49until you get to see the dark blue dense ice that we see around us.
0:03:50 > 0:03:55And that is how the ice that covers over 10% of our planet is formed.
0:03:55 > 0:03:58But as you can see from these speeded up pictures
0:03:58 > 0:03:59once it's been created,
0:03:59 > 0:04:02the ice in these glaciers doesn't just sit there.
0:04:02 > 0:04:03It moves,
0:04:03 > 0:04:08and that movement is responsible for the way the land around us looks.
0:04:08 > 0:04:12I'm fascinated by how ice has shaped our planet for thousands,
0:04:12 > 0:04:14if not millions, of years.
0:04:14 > 0:04:17Glaciers are ever-changing.
0:04:17 > 0:04:19These huge lumps of ice that move
0:04:19 > 0:04:23and gouge out the sides of the mountains to create the valleys.
0:04:23 > 0:04:25Glaciers move because of the huge weight
0:04:25 > 0:04:29pushing down from the snow and ice at the top of mountain.
0:04:29 > 0:04:33Slowly but surely, this huge beast moves forward,
0:04:33 > 0:04:36sweeping away everything in front of it.
0:04:36 > 0:04:40Thousands of years ago glaciers like this covered Britain too,
0:04:40 > 0:04:44and it's their movement, pushing rock and soil in front of them,
0:04:44 > 0:04:45that shaped our country as well.
0:04:46 > 0:04:50Glaciers are really fascinating powerhouses of our planet.
0:04:51 > 0:04:54They represent Mother Earth's bulldozer,
0:04:54 > 0:04:58carving the mountains and valleys that we see around us.
0:04:58 > 0:05:03From California in the USA to the Lake District in the UK,
0:05:03 > 0:05:06the power of ice has helped shape the whole planet.
0:05:07 > 0:05:10When it comes to rocks and ice there's only one winner.
0:05:10 > 0:05:12And that's ice.
0:05:15 > 0:05:19Up on mountains isn't the only place you'll find ice.
0:05:19 > 0:05:22You'll also find it floating in the water as icebergs.
0:05:24 > 0:05:29How do icebergs get into the sea and what could they mean for our planet?
0:05:30 > 0:05:34I've travelled to the south east coast of Iceland to find out.
0:05:34 > 0:05:37This is the Jokulsarlon lagoon.
0:05:37 > 0:05:39It is filled with icebergs.
0:05:39 > 0:05:42The glacier is just up there and that's where the icebergs come from.
0:05:42 > 0:05:46They break off or carve and float very slowly down towards the coast.
0:05:47 > 0:05:50The lagoon is a brilliant example of how
0:05:50 > 0:05:54icebergs are created from melting or retreating glaciers.
0:05:54 > 0:05:5680 years ago, this was solid ice
0:05:56 > 0:05:59but, since then, the glaciers have slowly retreated.
0:05:59 > 0:06:01In doing so, the sea has flowed in,
0:06:01 > 0:06:05but the glacier continues to feed the icebergs.
0:06:05 > 0:06:06It is an incredible sight.
0:06:08 > 0:06:11Icebergs cover the lagoon, there are hundreds of them.
0:06:11 > 0:06:15But there's a lot more to be seen under the surface.
0:06:15 > 0:06:17To investigate what's going on below the water line,
0:06:17 > 0:06:19I've got a little camera here.
0:06:21 > 0:06:22It shows me
0:06:22 > 0:06:26that almost 90% of the icebergs are actually below the water.
0:06:26 > 0:06:29And that means the more you can see of an iceberg above,
0:06:29 > 0:06:30the more there is below.
0:06:31 > 0:06:34Hence the phrase "tip of the iceberg".
0:06:34 > 0:06:38And that's the reason they can cause so many problems for ships.
0:06:39 > 0:06:44The largest icebergs could sink even the biggest and strongest of ships.
0:06:45 > 0:06:52The one that sank Titanic was over a mile long, now that's a lot of ice.
0:06:52 > 0:06:56But big chunks of ice don't just pose a danger to ships.
0:06:56 > 0:06:58Ice sheets, that can be as much as 100 miles across,
0:06:58 > 0:07:02could have a worldwide effect when they fall in to the oceans.
0:07:04 > 0:07:06When water freezes, it expands.
0:07:06 > 0:07:09Ice takes up more space than water,
0:07:09 > 0:07:13so when a big chunk breaks off an ice shelf the sea level rises.
0:07:13 > 0:07:17Although we're only talking about a small rise in levels,
0:07:17 > 0:07:20when you combine melting ice with other factors that lead to
0:07:20 > 0:07:23an increase in sea levels, it could be serious.
0:07:24 > 0:07:26If the sea rises by just 7m,
0:07:26 > 0:07:29both London and Los Angeles would be under water.
0:07:30 > 0:07:33We don't need to panic...yet.
0:07:33 > 0:07:37Melting polar ice and rising sea levels happens over decades
0:07:37 > 0:07:42and, by fighting global warming, we can still help to reduce it.
0:07:44 > 0:07:47But here in Iceland, something very unusual can happen
0:07:47 > 0:07:50that the Icelanders DO need to worry about.
0:07:54 > 0:07:58There are fierce volcanoes here that can make huge amounts of ice
0:07:58 > 0:08:00melt in a matter of seconds.
0:08:02 > 0:08:06To show you what happens when ice meets fire,
0:08:06 > 0:08:08I need to get right on top of the ice cap.
0:08:08 > 0:08:11Now, that's several miles in that direction,
0:08:11 > 0:08:12but I'm going to go in style.
0:08:12 > 0:08:14I'm travelling in one of these babies
0:08:14 > 0:08:17This bad boy is fully loaded with...
0:08:17 > 0:08:20Massive tyres to get us over the snow and ice.
0:08:21 > 0:08:24A whopping great engine to get us up the steep slopes.
0:08:24 > 0:08:29And a driver that knows the terrain like the back of his hand.
0:08:29 > 0:08:30I think we're good to go.
0:08:40 > 0:08:44Here we go. You can't really see it outside but on the GPS
0:08:44 > 0:08:46You can see this blue line
0:08:46 > 0:08:51and that marks the point that we're actually going onto the ice cap.
0:08:51 > 0:08:54So although it's a whiteout outside,
0:08:54 > 0:08:57the car is now driving on ice. Below us.
0:09:02 > 0:09:04This is one of the biggest single chunks of ice
0:09:04 > 0:09:05in the whole of Europe.
0:09:06 > 0:09:09It's fierce, cold, and a blizzard is blowing.
0:09:10 > 0:09:14So we've driven up on top of the ice cap now.
0:09:14 > 0:09:15I'm standing on snow
0:09:15 > 0:09:18and there's a blizzard around me
0:09:18 > 0:09:21but beneath the snow is hundreds of metres of ice
0:09:21 > 0:09:25and beneath that is a volcano, Katla. A live active volcano.
0:09:25 > 0:09:29And when that volcano erupts it brings hot magma,
0:09:29 > 0:09:34hundreds of degrees centigrade, almost 1,000 degrees centigrade,
0:09:34 > 0:09:38in contact with that cold ice and it starts to melt,
0:09:38 > 0:09:41producing millions and millions of tonnes of meltwater
0:09:41 > 0:09:45and when that meltwater is released it is called a jokulhlaup.
0:09:45 > 0:09:47And that is what we're here to find out about.
0:09:47 > 0:09:50Time to get out of the blizzard.
0:09:52 > 0:09:55I've travelled into the heart of the glacier to create
0:09:55 > 0:09:59an experiment that will show you what happens when fire meets ice.
0:10:01 > 0:10:05So here we are, we've actually come under the ice.
0:10:05 > 0:10:08You can see the blue light shining through the ice.
0:10:08 > 0:10:11We're actually in an ice cave.
0:10:11 > 0:10:13So we're going to do a little experiment.
0:10:13 > 0:10:16What we've got here is a couple of holes that we've drilled
0:10:16 > 0:10:20into the ice and we've put a little water reservoir in there
0:10:20 > 0:10:24and I'm going to start up my volcano here. There we go.
0:10:24 > 0:10:27So my little meltwater pocket is trapped.
0:10:30 > 0:10:34There we go. There. It's all flooding out now.
0:10:34 > 0:10:37This is a very small-scale operation.
0:10:37 > 0:10:41You imagine millions and millions of tonnes of water
0:10:41 > 0:10:45filling up in a cave just like what we've got around us now.
0:10:45 > 0:10:49And then all of a sudden the volcano comes knocking at the door
0:10:49 > 0:10:53and - whoosh! - the whole lot comes rushing out in one go,
0:10:53 > 0:10:56rocks, ice and debris, all in one big massive flood.
0:10:56 > 0:10:58You've got yourself a massive jokulhlaup.
0:11:01 > 0:11:04This is a jokulhlaup that hit Iceland recently
0:11:04 > 0:11:06and, believe it or not, this is just a small one.
0:11:08 > 0:11:12Luckily no-one lived in the area the water flowed through and I'm
0:11:12 > 0:11:16now standing right in the middle of where all that melted ice travelled.
0:11:17 > 0:11:20This devastated land that you can see all around me
0:11:20 > 0:11:23is the result of one of these flooding events
0:11:23 > 0:11:25that hit here two years ago.
0:11:25 > 0:11:28It's covered an area the size of a small city.
0:11:28 > 0:11:30There is no vegetation for miles.
0:11:30 > 0:11:35A flash flood, cutting through everything, bringing in debris
0:11:35 > 0:11:37and creating, essentially, a moonscape.
0:11:37 > 0:11:39There's absolutely nothing left.
0:11:39 > 0:11:42If you're here when this jokulhlaup hits,
0:11:42 > 0:11:44there's no surviving it.
0:11:45 > 0:11:48Like weather forecasters, volcano experts like me
0:11:48 > 0:11:52can roughly predict when a volcano is likely to erupt.
0:11:52 > 0:11:56And the bad news for the people of Iceland is that the one underneath
0:11:56 > 0:12:00the huge glacier I travelled across is expected to blow.
0:12:00 > 0:12:01Soon.
0:12:01 > 0:12:03When it does, the ice will melt
0:12:03 > 0:12:07and unleash a flood with more water than there is in all of Britain's
0:12:07 > 0:12:12rivers combined with the Amazon, the Nile and the mighty Mississippi.
0:12:12 > 0:12:13But there is hope.
0:12:15 > 0:12:17Now the key to survival in one of these flooding events,
0:12:17 > 0:12:19is prediction and warning.
0:12:20 > 0:12:22If Katla starts erupting,
0:12:22 > 0:12:25signals from this station will get sent to Reykjavik.
0:12:25 > 0:12:27They can understand those signals
0:12:27 > 0:12:33and tell people in surrounding areas that the volcano is becoming alive.
0:12:33 > 0:12:35It's that chain of connection
0:12:35 > 0:12:38and those chains of events that will help save lives
0:12:38 > 0:12:39and allow people to prepare,
0:12:39 > 0:12:42ultimately, for a massive flooding event.
0:12:45 > 0:12:46The place most at risk
0:12:46 > 0:12:49from the flood of icy water is a small town called Vik.
0:12:51 > 0:12:54When the warning is sent out, every person who lives here has to
0:12:54 > 0:12:55get ready to evacuate.
0:12:58 > 0:13:01This is Throan, he's the man in charge of making sure
0:13:01 > 0:13:05the town of Vik is empty when Katla erupts and the ice melts.
0:13:05 > 0:13:08He'll receive the signal that the volcano is coming to life
0:13:08 > 0:13:10and sound the alarm.
0:13:11 > 0:13:14When Katla erupts, the amount of water comes down from the glacier.
0:13:14 > 0:13:19The flooding, it would take out most of the houses in the lower village
0:13:19 > 0:13:23so we have to evacuate the lower part of the village.
0:13:23 > 0:13:28We sent directly text messages to all phones in that area to tell
0:13:28 > 0:13:32people where to go, what is happening and to try to find a safe place.
0:13:32 > 0:13:35After the text message is sent we have to
0:13:35 > 0:13:37make sure that everyone has left.
0:13:37 > 0:13:41When the alarm rings out across Vik, the clock will be ticking
0:13:41 > 0:13:44because the villagers now have just 45 minutes to get out.
0:13:46 > 0:13:49This satellite image shows the huge section of land
0:13:49 > 0:13:52the glacial flood would threaten.
0:13:52 > 0:13:53When they receive the alert,
0:13:53 > 0:13:56everyone in Vik must get out of that danger zone.
0:13:57 > 0:14:01The risk of Katla erupting and the ice melting is so high that
0:14:01 > 0:14:06even the youngest of villagers has to be educated about the dangers.
0:14:06 > 0:14:09If we stay here, it could be very dangerous
0:14:09 > 0:14:15because the volcano is going to...explode.
0:14:18 > 0:14:23Then we have to go high up because there is more safe.
0:14:23 > 0:14:27Knowing what to do when Katla erupts could be a matter of life and death.
0:14:27 > 0:14:31That's why every few months the kids practise this evacuation drill.
0:14:33 > 0:14:37First they're taken to an evacuation centre at the top of a hill,
0:14:37 > 0:14:42And from there they are taken even further out of the danger zone.
0:14:42 > 0:14:44Only when they have travelled 45 minutes
0:14:44 > 0:14:47out of town are the children safe.
0:14:47 > 0:14:51I know what to do then. That's why I'm not worried.
0:14:51 > 0:14:53It's good to know there's a plan like this in place
0:14:53 > 0:14:55and that the kids are ready
0:14:55 > 0:14:59because, when fire meets ice here, it spells trouble.
0:15:02 > 0:15:05Get ready to buckle up, because later on Fierce Earth,
0:15:05 > 0:15:08Leo is shooting across the ice at super-high speed.
0:15:11 > 0:15:16But first, you've seen the destructive power of ice on water,
0:15:16 > 0:15:20on the ground, as it carves its way through mountains...
0:15:23 > 0:15:28..and now it's time to see the power of ice when it forms in the air.
0:15:29 > 0:15:31I witnessed its awesome power
0:15:31 > 0:15:35when I travelled to Boston in the northeast United States
0:15:35 > 0:15:39and found myself in one of the biggest winter storms ever.
0:15:41 > 0:15:44Man, we're getting nailed by this blizzard right now.
0:15:44 > 0:15:46Just look at this! This is insane!
0:15:46 > 0:15:48'It was a scary night.'
0:15:48 > 0:15:50You need things like this just to hold on to
0:15:50 > 0:15:52because you'll get blown down the road.
0:15:52 > 0:15:55'And the heavy snowfall was one part of a winter storm
0:15:55 > 0:15:57'I never want to see again,
0:15:57 > 0:16:01'but it's what I saw the next morning that really blew me away...
0:16:04 > 0:16:05'..cars wrapped in ice...
0:16:08 > 0:16:11'..entire rows of houses covered with a layer
0:16:11 > 0:16:13'of thick, frozen water.'
0:16:14 > 0:16:17Just look at this ice. It's rock-solid.
0:16:18 > 0:16:21'I couldn't believe the damage the storm had done to trees,
0:16:21 > 0:16:25'houses, and even electrical cables.'
0:16:25 > 0:16:28The weight of the ice has taken these power lines
0:16:28 > 0:16:30and pulled them down to the ground.
0:16:30 > 0:16:34'What were the conditions that made this different to just snowfall?'
0:16:38 > 0:16:42To find out, Leo is visiting a special testing facility
0:16:42 > 0:16:47in the UK, where normally they run cold-weather tests on cars.
0:16:47 > 0:16:50But there's no cars today, just me,
0:16:50 > 0:16:52a cold chamber and a couple of bottles of water.
0:16:55 > 0:16:59This cold room is about minus ten, similar to a nasty winter storm.
0:17:01 > 0:17:04Watch this. Looks like an ordinary bottle of water, right?
0:17:04 > 0:17:07Wrong. I'm going to show you a trick. Check this out.
0:17:09 > 0:17:11Bang. Turns to rock-hard ice.
0:17:14 > 0:17:17In very special circumstances, water like this
0:17:17 > 0:17:20can exist as a liquid below zero degrees centigrade.
0:17:20 > 0:17:22It's called supercooled water.
0:17:22 > 0:17:26And when that water is given something to crystallise around,
0:17:26 > 0:17:29like air bubbles when the bottle is slapped,
0:17:29 > 0:17:32the ice crystals quickly spread and form solid ice.
0:17:32 > 0:17:35I'm about to show you how water like this
0:17:35 > 0:17:38can be responsible for devastating ice storms like the one Mike saw.
0:17:42 > 0:17:46Now, remember, this is just cold water, supercooled water.
0:17:46 > 0:17:49Watch what happens when I pour it on these freezing surfaces.
0:17:49 > 0:17:50Here you can see my house,
0:17:50 > 0:17:53my dumper truck, just like the one I drive at home,
0:17:53 > 0:17:56and I'm going to show you what happens in an ice storm.
0:17:56 > 0:17:58Look at that. It turns to ice
0:17:58 > 0:18:02immediately, and it stays as ice. And you can see it's layering up
0:18:02 > 0:18:05and getting heavier and heavier.
0:18:06 > 0:18:10When the supercooled water hits an object like a tree, car
0:18:10 > 0:18:13or house that's already cold, it turns to ice.
0:18:13 > 0:18:16Imagine if that's the roof of your house, there.
0:18:16 > 0:18:19It's starting to get a massive amount of weight on it.
0:18:19 > 0:18:23When this happens for real, it can have devastating consequences.
0:18:23 > 0:18:27And that build-up of frozen water is exactly what happens
0:18:27 > 0:18:30during an ice storm - supercooled water falls through the air
0:18:30 > 0:18:34and hits cold objects on the ground, like tree branches.
0:18:34 > 0:18:38Layers of heavy ice build up and cause devastating damage.
0:18:39 > 0:18:42Some of the most damaging and expensive storms
0:18:42 > 0:18:44in North America have been ice storms.
0:18:44 > 0:18:47This ice storm that hit Canada in 1998
0:18:47 > 0:18:51caused over 1 billion worth of damage, destroyed trees and houses,
0:18:51 > 0:18:55and left some people living without power for a whole month.
0:18:56 > 0:19:00All that devastation from something as simple as cold water.
0:19:00 > 0:19:02That is the power of ice.
0:19:05 > 0:19:08CLARE: We're back in the land of fire and ice, Iceland.
0:19:08 > 0:19:11As you've seen, ice can be dangerous stuff,
0:19:11 > 0:19:15and that's especially true of these things - glaciers.
0:19:15 > 0:19:17You can understand why people would want to come here
0:19:17 > 0:19:21and experience this most amazing sight, but when an adventurer's hike
0:19:21 > 0:19:24becomes the stuff of nightmares, who do you call?
0:19:27 > 0:19:30The answer is Iceland's rescue service - ICESAR.
0:19:33 > 0:19:36Ice is such a big deal here that these guys specialise
0:19:36 > 0:19:40in saving people when they get into trouble on its frozen surface.
0:19:40 > 0:19:43There are 18,000 volunteer members of ICESAR,
0:19:43 > 0:19:46and they are highly skilled in ice rescue.
0:19:48 > 0:19:50They can move like lightning across ice,
0:19:50 > 0:19:55using crampons that give them extra grip, ice axes that allow them
0:19:55 > 0:19:56to safely climb up and down,
0:19:56 > 0:20:00and special rope and ice anchor systems that allow them
0:20:00 > 0:20:04to pull people to safety on this treacherous surface.
0:20:05 > 0:20:09Today, they're on a training exercise for something they're called out to
0:20:09 > 0:20:11most often - crevasse rescue.
0:20:12 > 0:20:15Glaciers move on a daily basis,
0:20:15 > 0:20:18and as they move, deep cracks in the ice appear.
0:20:18 > 0:20:21These cracks are called crevasses,
0:20:21 > 0:20:25and its when people fall into them that ICESAR are called out.
0:20:25 > 0:20:28So the training that you're doing today
0:20:28 > 0:20:30is so essential for saving lives?
0:20:30 > 0:20:31Yes, it is.
0:20:31 > 0:20:35We have accidents on glaciers and we have to keep updated -
0:20:35 > 0:20:40we have to do this over and over again, to increase our efficiency.
0:20:40 > 0:20:42Living in Iceland, you... Well, you have to love ice.
0:20:42 > 0:20:45OK. Put me into a crevasse. Let's go.
0:20:47 > 0:20:50The team are going to do a simple rescue exercise where they lower me
0:20:50 > 0:20:53into and out of a crevasse.
0:20:53 > 0:20:57It's one of the first lessons they give to new team members.
0:20:57 > 0:21:02It's a great chance for me to safely see what it's like inside a glacier,
0:21:02 > 0:21:03but I'm still a bit nervous.
0:21:05 > 0:21:06That's it, yeah. OK.
0:21:06 > 0:21:09On ice, anything can happen.
0:21:09 > 0:21:11Oh. Hang on. Hold it tight. That's it.
0:21:13 > 0:21:16This is putting science really into action.
0:21:17 > 0:21:21I'm going down to a part of the glacier that probably no-one's ever
0:21:21 > 0:21:25seen before, and may never see again, because the thing about glaciers -
0:21:25 > 0:21:27they're for ever moving.
0:21:27 > 0:21:29Oh, it's really deep down there!
0:21:29 > 0:21:32The thing is now, it's getting very narrow down here.
0:21:32 > 0:21:36- Um... Hang on a sec.- Stop.
0:21:38 > 0:21:41Even though I'm safely attached to a rope,
0:21:41 > 0:21:44it's an eerie feeling, being surrounded by ice,
0:21:44 > 0:21:48and looking down, I can see how dangerous a crevasse is.
0:21:48 > 0:21:51So if you were ever to find yourself on a glacier,
0:21:51 > 0:21:53here is the ICESAR survival guide.
0:21:55 > 0:21:59First up, never go onto a glacier without a professional guide.
0:21:59 > 0:22:03Glaciers change all the time, and crevasses can be hidden
0:22:03 > 0:22:05and even covered with snow.
0:22:05 > 0:22:08The second survival tip is not to fall into a crevasse
0:22:08 > 0:22:10in the first place!
0:22:10 > 0:22:11Travel slowly, carefully,
0:22:11 > 0:22:15and experienced mountaineers even travel linked together by a rope.
0:22:15 > 0:22:18Crevasses can be up to 50m deep.
0:22:19 > 0:22:23That's enough of a fall to cause serious injury.
0:22:23 > 0:22:26If you are lucky enough to fall onto a flat ledge, stay calm,
0:22:26 > 0:22:30stay still and wait for rescue.
0:22:30 > 0:22:32You don't want to fall any further.
0:22:36 > 0:22:38'Back to my crevasse,
0:22:38 > 0:22:41'and I've reached the bottom, and being surrounded by this dark ice
0:22:41 > 0:22:46'is enough to make anyone nervous, so I'm not hanging around.'
0:22:46 > 0:22:48OK, I think I'm ready to come up now!
0:22:51 > 0:22:55I'd be very scared indeed, fearful for my life,
0:22:55 > 0:22:57if I fell down one of these crevasses,
0:22:57 > 0:23:00but that's why these sort of practice runs are so essential.
0:23:01 > 0:23:04Nice and slowly. Hand over hand.
0:23:06 > 0:23:09'With one last heave, I'm out. Safety at last.'
0:23:15 > 0:23:17Thank you. Thank you.
0:23:17 > 0:23:20That's good. On the top of the ice again.
0:23:23 > 0:23:26It's the movement of ice that creates crevasses
0:23:26 > 0:23:28and the need for many ICESAR rescues,
0:23:28 > 0:23:32so, next, Leo's travelled to Switzerland in the European Alps
0:23:32 > 0:23:37to find out what it is about ice that makes this slippery customer move,
0:23:37 > 0:23:40and how we humans have used the slippery properties of ice
0:23:40 > 0:23:43to create super-speed winter sports.
0:23:44 > 0:23:47But how do you reach these speeds travelling on ice?
0:23:47 > 0:23:49Well, I'm here in Switzerland to show you.
0:23:53 > 0:23:55Hidden in a peaceful forest near the town of St Moritz,
0:23:55 > 0:23:59this is one of the most famous and feared sports venues in the world.
0:24:02 > 0:24:05We're at the famous Olympia bobsleigh track.
0:24:09 > 0:24:12This is where the sport of bobsleighing was born.
0:24:15 > 0:24:17It's the only track like it on the planet,
0:24:17 > 0:24:20and it's only here for a few icy months of the year.
0:24:22 > 0:24:25It is the perfect place to demonstrate why ice can appear
0:24:25 > 0:24:28to be so slippery when, in fact, it isn't. I'll show you why.
0:24:28 > 0:24:32If I take these two chunks of ice and rub them together,
0:24:32 > 0:24:35they stick and grate and slide. Look at that.
0:24:35 > 0:24:38Nothing slippery about that at all. They're totally stuck together.
0:24:38 > 0:24:39But watch what happens now,
0:24:39 > 0:24:41when I move this knife blade
0:24:41 > 0:24:42over the surface of the ice.
0:24:42 > 0:24:47You can see it slides easily. The ice has become a slippery surface.
0:24:47 > 0:24:51That's because the thin edge of the blade puts a lot of pressure on it.
0:24:51 > 0:24:55Pressure creates heat, melts the ice, and the blade slides over
0:24:55 > 0:24:58the water, just like when you slip on a wet floor.
0:24:58 > 0:25:01Think about it - that's why the things that move fastest on ice
0:25:01 > 0:25:04have really sharp blades, like ice skates or bobsleds.
0:25:06 > 0:25:09The sharper the blades, the more heat is created
0:25:09 > 0:25:10and the quicker the object moves.
0:25:12 > 0:25:16'And today I'm getting to grips with this shiny beauty.
0:25:16 > 0:25:19'But first, I need to get some expert advice.'
0:25:20 > 0:25:23So what do you think is the top speed I can get out of this thing,
0:25:23 > 0:25:28- on this run?- When you start from the top, then you reach about 125,
0:25:28 > 0:25:30226, top-speed.
0:25:30 > 0:25:31It feels like a rocket.
0:25:33 > 0:25:38Wow - speed into three figures. I'd better get my racing threads on.
0:25:38 > 0:25:42Skintight Lycra, nice and aerodynamic so I can go even faster.
0:25:42 > 0:25:46This is one of the fastest tracks in the world.
0:25:46 > 0:25:48And that horseshoe corner looks terrifying.
0:25:49 > 0:25:53And all this in the name of showing you the slippery properties of ice.
0:25:53 > 0:25:56- I'm ready!- OK. Let's go.- Wahey!
0:25:58 > 0:26:02It's a slow start before gravity and the ice start to do their work,
0:26:02 > 0:26:03increasing my speed.
0:26:06 > 0:26:08And here comes that horseshoe corner.
0:26:11 > 0:26:14At this speed, it's difficult to keep control.
0:26:14 > 0:26:16And then there's a disaster.
0:26:20 > 0:26:22MAN SPEAKS IN GERMAN
0:26:26 > 0:26:28Don't worry - it was just one of the cameras!
0:26:30 > 0:26:33I've covered 800m in just 15 seconds.
0:26:33 > 0:26:35I'm just centimetres off the ground,
0:26:35 > 0:26:38and travelling faster than your parents' car on the motorway.
0:26:40 > 0:26:42The blades are cutting into the ice, generating heat
0:26:42 > 0:26:46and shooting me down this track at over 100km an hour!
0:26:47 > 0:26:49This is ice at its most slippery!
0:26:57 > 0:27:01That was brilliant. My goodness. You come down so quick,
0:27:01 > 0:27:05flying round the corners. there's so little friction on the ice, you're
0:27:05 > 0:27:08just whizzing down. Zoom, zoom, zoom. Absolutely amazing.
0:27:08 > 0:27:11It's not as violent as I thought it was going to be. You're actually
0:27:11 > 0:27:13quite smooth when you're in the bottom, but...
0:27:13 > 0:27:15That's so much fun. Can we do it again?
0:27:15 > 0:27:17Afraid not, Leo, because our expedition
0:27:17 > 0:27:19through the land of ice is over.
0:27:19 > 0:27:21On this journey,
0:27:21 > 0:27:26we've seen how tiny snowflakes can create mighty glaciers,
0:27:26 > 0:27:30how ice storms can bring whole cities to a standstill,
0:27:30 > 0:27:34and we've found out what it's like to fall into a crevasse.
0:27:35 > 0:27:41Next time on Fierce Earth, get ready for the heavens to open...
0:27:41 > 0:27:42It's pouring it down!
0:27:44 > 0:27:48..because we're on a soaking journey to the rainiest place on the planet.
0:27:48 > 0:27:51- It's going to be wet..- ..and wild!