0:00:05 > 0:00:08You hear that noise, you see that smoke?
0:00:08 > 0:00:11That's the sight of the earth actually coming alive.
0:00:11 > 0:00:15And we've travelled a long way to get here by plane, by boat,
0:00:15 > 0:00:19it's been a good four hours' hike up the mountain and we're here
0:00:19 > 0:00:23to get face-to-face with one of the awesome forces on our planet,
0:00:23 > 0:00:25an erupting volcano.
0:00:26 > 0:00:29On today's explosive Fierce Earth special,
0:00:29 > 0:00:32we're travelling to Italy to witness the awesome power
0:00:32 > 0:00:35of two of the world's most spectacular volcanoes,
0:00:35 > 0:00:37Etna and Stromboli.
0:00:41 > 0:00:43We're going inside secret lava tubes...
0:00:44 > 0:00:48..outside with children who live on a volcano...
0:00:48 > 0:00:51and climbing all the way to the red-hot top!
0:00:51 > 0:00:52That is fantastic!
0:00:56 > 0:00:58What happens when the ground shakes,
0:00:58 > 0:01:02the seas rise up and the air tears itself apart?
0:01:02 > 0:01:04The Fierce Earth team move in,
0:01:04 > 0:01:08taking on the most powerful forces on the planet.
0:01:23 > 0:01:28Get ready for Fierce Earth. The earth, and how to survive it.
0:01:30 > 0:01:33Volcanoes are planet earth's spectacular, and terrifying,
0:01:33 > 0:01:38fireworks display. Living mountains that erupt molten rocks
0:01:38 > 0:01:40from deep within the earth.
0:01:40 > 0:01:43There are more than 500 active volcanoes in the world today
0:01:43 > 0:01:47and right now about 20 will be erupting.
0:01:47 > 0:01:53Volcanoes can lie dormant for years, perhaps centuries, and then, boom!
0:01:53 > 0:01:56They explode, releasing seemingly endless rivers
0:01:56 > 0:02:02of super-hot molten rock that destroy everything in their path.
0:02:04 > 0:02:07I've travelled the world for many years,
0:02:07 > 0:02:10chasing and observing these natural wonders.
0:02:10 > 0:02:16I love volcanoes. I fear volcanoes. My mates call me Doctor Volcano.
0:02:18 > 0:02:22Volcanoes are a reminder that the very ground humans walk upon
0:02:22 > 0:02:26is ever-changing, and that the planet, not far below our feet,
0:02:26 > 0:02:29is a violent furnace.
0:02:29 > 0:02:33Today I'm on a mission to get right up close to an erupting volcano
0:02:33 > 0:02:36and discover just where they get their awesome power.
0:02:36 > 0:02:39So I'm heading straight for Europe's biggest,
0:02:39 > 0:02:43Mount Etna on the island of Sicily, in Italy.
0:02:45 > 0:02:48This cut-open peach is a great example of what the earth
0:02:48 > 0:02:51might look like if we cut it with a really big knife.
0:02:51 > 0:02:55On the outside is the thin, cold crust, that's where we live.
0:02:55 > 0:02:59But inside it's thousands of degrees centigrade right to the eye
0:02:59 > 0:03:01and core in the middle.
0:03:01 > 0:03:04Now, this area here is known as the mantle
0:03:04 > 0:03:07and that's where magma gets generated,
0:03:07 > 0:03:10and, if cracks can be made in the earth's crust,
0:03:10 > 0:03:13that magma can escape and form volcanoes.
0:03:13 > 0:03:16So why do those cracks appear?
0:03:16 > 0:03:20It's all down to plate tectonics. The earth's outer layer is made up
0:03:20 > 0:03:25of giant tectonic plates that lock together like a huge jigsaw puzzle.
0:03:25 > 0:03:27The plates float around on top of the sticky,
0:03:27 > 0:03:29toffee-like mantle beneath.
0:03:29 > 0:03:32The plates move very slowly, just centimetres a year,
0:03:32 > 0:03:35but as they pull apart or push together,
0:03:35 > 0:03:38the movement helps generate and release magma.
0:03:38 > 0:03:39A volcano is born.
0:03:44 > 0:03:47Etna is where the African Plate meets the European Plate,
0:03:47 > 0:03:51with volcanic consequences. Just look at this lava flow.
0:03:51 > 0:03:53This has come barrelling from the top of the mountain,
0:03:53 > 0:03:57Mount Etna in the cloud there, all the way down, burning trees,
0:03:57 > 0:04:00killing everything in its path.
0:04:00 > 0:04:03Now, this would have been red-hot molten rock, a lava flow,
0:04:03 > 0:04:07which people often fear the most. But sometimes it's the volcanoes,
0:04:07 > 0:04:12the active ones that don't erupt lava, which are the most dangerous.
0:04:12 > 0:04:13Let me show you why.
0:04:16 > 0:04:20Take two mini volcanoes, tins for magma chambers
0:04:20 > 0:04:23and coloured milk for the magma itself.
0:04:23 > 0:04:27Both identical, but for one crucial difference
0:04:27 > 0:04:29that will make one of them deadly.
0:04:34 > 0:04:39So we've created two very simple homemade volcanoes here, OK?
0:04:39 > 0:04:41We've put magma in both of them and I am just going to do
0:04:41 > 0:04:45two very simple eruptions to explain the point.
0:04:45 > 0:04:49I'm going to add these effervescent tablets to trigger the eruption.
0:04:49 > 0:04:53Let's start with volcano number one, see what happens.
0:04:53 > 0:04:56The fizzy tablets set off a reaction that simulates lava
0:04:56 > 0:04:59leaving a volcano when flowing freely.
0:04:59 > 0:05:01Beautiful, look at that.
0:05:01 > 0:05:04A great lava flow now, it's starting to flow down the side
0:05:04 > 0:05:07of our makeshift mountain, fantastic.
0:05:10 > 0:05:13Etna erupts like this every few years
0:05:13 > 0:05:16and the Sicilians are used to dealing with it.
0:05:16 > 0:05:19Roads and houses often have to be rebuilt.
0:05:19 > 0:05:21Although it's dangerous,
0:05:21 > 0:05:25lava on the slopes here tends to be relatively slow-moving.
0:05:25 > 0:05:27If it's heading in your direction,
0:05:27 > 0:05:29you usually have time to get out of the way.
0:05:31 > 0:05:34These lava flows will destroy everything in its wake,
0:05:34 > 0:05:36just like what you see behind me.
0:05:36 > 0:05:38But you will survive.
0:05:38 > 0:05:42What happens, though, if the magma can't escape so easily,
0:05:42 > 0:05:44if the gases can't release so easily?
0:05:44 > 0:05:47So what we're going to do with volcano number two,
0:05:47 > 0:05:49we've got the effervescent tablets,
0:05:49 > 0:05:52but this time we're going to put a lid on.
0:05:54 > 0:05:59Let's pile some rocks up. Look at that, a few rocks on top.
0:05:59 > 0:06:03Now then, I'll just get out the way a bit.
0:06:03 > 0:06:07We sit back and wait to see what happens.
0:06:07 > 0:06:09You can see the pressure building now,
0:06:09 > 0:06:13you see the rocks starting to move? There's real pressure building,
0:06:13 > 0:06:15I can feel it... Oh! Look at that!
0:06:15 > 0:06:20Wow! Now, you don't want to be around when that happens.
0:06:22 > 0:06:26Sadly, that's exactly what did happen in the north west of the USA
0:06:26 > 0:06:30in 1980. Sticky magma and tons of rock had combined
0:06:30 > 0:06:33to keep Mount St Helens quiet for centuries.
0:06:33 > 0:06:35But when it did finally erupt
0:06:35 > 0:06:38they were the very things that made it so deadly.
0:06:38 > 0:06:42The sudden release of pressure blew the entire top
0:06:42 > 0:06:45and side of the volcano completely off.
0:06:45 > 0:06:49A crater was left a kilometre and a half wide
0:06:49 > 0:06:52and 57 people lost their lives.
0:06:56 > 0:06:59Up on the slopes of Mount Etna, it's clear that there have been
0:06:59 > 0:07:02huge amounts of volcanic activity over the years.
0:07:02 > 0:07:06But, luckily, very few catastrophic explosions.
0:07:06 > 0:07:07Look at this.
0:07:07 > 0:07:10This ropey texture,
0:07:10 > 0:07:12that's typical of lava flows.
0:07:12 > 0:07:14Unlike explosive volcanoes,
0:07:14 > 0:07:17the magma here is less sticky
0:07:17 > 0:07:20and it flows down the side of the mountain.
0:07:20 > 0:07:22But it's the hidden treasures that lie beneath this
0:07:22 > 0:07:24is what I've come to see today.
0:07:24 > 0:07:27And that's what I'm going to need this for.
0:07:29 > 0:07:33Sometimes, rather than looking up at a volcano,
0:07:33 > 0:07:35it pays to look down.
0:07:35 > 0:07:39Under the slopes are secret tunnels built by the volcano itself.
0:07:45 > 0:07:49The walls, ceiling and floor are all made of lava.
0:07:49 > 0:07:52These lava tubes are all over Etna,
0:07:52 > 0:07:54sometimes miles from the crater
0:07:54 > 0:07:56where the lava first started flowing.
0:07:58 > 0:08:02Lava tubes are formed when the top layer of lava hardens.
0:08:02 > 0:08:05The rock roof keeps everything inside from cooling,
0:08:05 > 0:08:07a bit like the insulation on a hot-water pipe.
0:08:07 > 0:08:11The hot lava inside carries on flowing and, when the eruption ends,
0:08:11 > 0:08:15it leaves behind this amazing network of tubes.
0:08:15 > 0:08:20Tunnels like this are the real hidden wonder of the volcano.
0:08:20 > 0:08:22The magma would have started up at this level
0:08:22 > 0:08:25and it drained rapidly to start forming a lava tube.
0:08:25 > 0:08:29You can see the drips of lava it left behind as it drained.
0:08:29 > 0:08:32And just here you can see there's a tide mark.
0:08:32 > 0:08:34This is where the river of lava once was.
0:08:34 > 0:08:37If I was in this tunnel now when that lava was flowing,
0:08:37 > 0:08:40it would be around sort of waist high here, chest high.
0:08:40 > 0:08:42I'd be sort of wading against a river of lava
0:08:42 > 0:08:45which is cascading down the mountain
0:08:45 > 0:08:48and feeding lava flows maybe... maybe miles away from the vent.
0:08:48 > 0:08:50It drained even further.
0:08:50 > 0:08:53It cooled and formed the top crust of the final lava flow,
0:08:53 > 0:08:54the final resting place.
0:08:54 > 0:08:58Now, if I was in this tube when that lava was flowing,
0:08:58 > 0:08:59I'd be burnt alive.
0:09:02 > 0:09:07All volcanoes are named after Vulcan, the Roman god of fire.
0:09:07 > 0:09:10It was Vulcan's job to make weapons for the other gods
0:09:10 > 0:09:12and the Romans believed the glow of the lava
0:09:12 > 0:09:16was from Vulcan's furnaces as he worked away under the earth.
0:09:19 > 0:09:22Around three quarters of the world's volcanoes
0:09:22 > 0:09:25are found around the edge of the Pacific Ocean.
0:09:25 > 0:09:28Because of this, the area is known as the Ring of Fire.
0:09:31 > 0:09:32Volcanoes are always changing,
0:09:32 > 0:09:36and an active one may suddenly go quiet and become dormant.
0:09:37 > 0:09:40Others are very reliable and have been erupting for decades
0:09:40 > 0:09:42or even centuries.
0:09:43 > 0:09:46Here are three of the most active volcanoes on the planet.
0:09:48 > 0:09:49The US state of Hawaii
0:09:49 > 0:09:53is a chain of volcanic islands in the Pacific Ocean.
0:09:53 > 0:09:58The main volcano, Kilauea, has been erupting on its flank since 1983.
0:09:58 > 0:10:00It's generally not explosive
0:10:00 > 0:10:02but it's thought to release more lava
0:10:02 > 0:10:04than any other volcano in the world.
0:10:06 > 0:10:08At two is Stromboli,
0:10:08 > 0:10:10off the coast of Sicily in Italy.
0:10:10 > 0:10:13This tiny island is pretty much all volcano
0:10:13 > 0:10:17and has been providing amazing firework displays without a break
0:10:17 > 0:10:19for the last 2,000 years.
0:10:19 > 0:10:22Number-one most long-standing active volcano
0:10:22 > 0:10:24is Etna on Sicily in Italy.
0:10:24 > 0:10:28Estimated to have been erupting on and off
0:10:28 > 0:10:30for an incredible 3,500 years,
0:10:30 > 0:10:35it's the biggest volcano in Europe and, despite all this activity,
0:10:35 > 0:10:38over a million people, a quarter of all Sicilians,
0:10:38 > 0:10:40live on its slopes.
0:10:42 > 0:10:47Around 500 million people live on or near volcanoes.
0:10:47 > 0:10:49Why would so many people choose to live
0:10:49 > 0:10:52so close to such dangerous mountains?
0:10:52 > 0:10:55Well, it's all down to our old friend lava.
0:10:55 > 0:10:58It's full of minerals that make the land around volcanoes
0:10:58 > 0:11:01incredibly fertile - great for growing food,
0:11:01 > 0:11:04and the reason why people first started living around volcanoes.
0:11:07 > 0:11:11To find out what that's like, I am off to number two in our chart,
0:11:11 > 0:11:14Etna's little brother, Stromboli.
0:11:17 > 0:11:19The Mediterranean Sea.
0:11:19 > 0:11:22The water here is full of fish
0:11:22 > 0:11:24and the coast is green and fertile.
0:11:24 > 0:11:26Because of this, the area has been home
0:11:26 > 0:11:29to generations of farmers and fishermen.
0:11:29 > 0:11:32But this particular home happens to be...
0:11:32 > 0:11:35a real volcano.
0:11:38 > 0:11:40Stromboli is the tiny volcanic island
0:11:40 > 0:11:43that makes a very big impression.
0:11:43 > 0:11:46It's been erupting so regularly, and for so long,
0:11:46 > 0:11:50that the Romans called it the Lighthouse of the Mediterranean.
0:11:54 > 0:11:57Around 800 people live on the island,
0:11:57 > 0:12:01in two villages clinging to the edge of the volcano.
0:12:03 > 0:12:06There's only one school, with less than 50 children.
0:12:07 > 0:12:12Instead of playing fields out the back, there's a live volcano.
0:12:13 > 0:12:17Playing in the shadow of Stromboli looks scary.
0:12:17 > 0:12:20So, what do the kids think of their volcano?
0:12:20 > 0:12:21CHILDREN SPEAK ITALIAN
0:12:21 > 0:12:25TRANSLATION: In reality, you ought to be scared of Stromboli
0:12:25 > 0:12:27but once you've got used to living here a while
0:12:27 > 0:12:30you no longer have all this fear.
0:12:32 > 0:12:34- TRANSLATION:- I have always liked the volcano
0:12:34 > 0:12:37because in the evening
0:12:37 > 0:12:39I hear it do things.
0:12:39 > 0:12:43"Voom, voom, voom!" is the noise it makes.
0:12:46 > 0:12:48- TRANSLATION: - We can see the theatre of fire.
0:12:48 > 0:12:50Also, if there are any flares
0:12:50 > 0:12:55they are beautiful because you can see real things close up.
0:12:55 > 0:12:57TRANSLATION: Even from my house.
0:13:02 > 0:13:04- TRANSLATION:- I'm never scared of the volcano
0:13:04 > 0:13:06because the lava has never come down this far,
0:13:06 > 0:13:08so we don't need to be scared.
0:13:08 > 0:13:10We can rest easy with no worries.
0:13:14 > 0:13:18The two villages on Stromboli are on the other side of the island
0:13:18 > 0:13:20from the main danger zone.
0:13:20 > 0:13:22But that doesn't mean there's no risk.
0:13:22 > 0:13:27In 2003, a series of major eruptions nearly caused Stromboli
0:13:27 > 0:13:29to be evacuated.
0:13:29 > 0:13:32There were no deaths, even though boulders ejected from the crater
0:13:32 > 0:13:33left houses in ruins.
0:13:33 > 0:13:37For this reason, emergency plans are in place.
0:13:39 > 0:13:41- TRANSLATION:- If there IS an enormous eruption,
0:13:41 > 0:13:44then we can evacuate the island by boat.
0:13:45 > 0:13:47Because of the 2003 eruption,
0:13:47 > 0:13:51a volcano monitoring station was put in place
0:13:51 > 0:13:54and is manned 24 hours a day, all year round,
0:13:54 > 0:13:58watching over the safety of the children below.
0:13:58 > 0:14:01TRANSLATION: There are explosions that are beautiful
0:14:01 > 0:14:04because they light up everything. I like it a lot.
0:14:06 > 0:14:10Far from being scared of the fire-breathing mountain
0:14:10 > 0:14:11in their own back yard,
0:14:11 > 0:14:14the children of Stromboli love the volcano
0:14:14 > 0:14:18they call simply "iddu" - "him".
0:14:19 > 0:14:22Stromboli can make life in a country with no volcano
0:14:22 > 0:14:24seem a little boring
0:14:24 > 0:14:27but there is volcanic action if you know where to look -
0:14:27 > 0:14:30as Leo is about to find out in Edinburgh.
0:14:34 > 0:14:37Edinburgh, in wet and windy Scotland.
0:14:37 > 0:14:41It seems about as far as a volcano as you can possibly get
0:14:41 > 0:14:44but even in the UK there is evidence of volcanic activity
0:14:44 > 0:14:45if you know where to look.
0:14:47 > 0:14:51Believe it or not, there are two here, but where are they hiding?
0:14:53 > 0:14:55For this slightly unusual challenge,
0:14:55 > 0:14:58I have chosen one of my favourite ways of getting around -
0:14:58 > 0:14:59a mountain bike.
0:14:59 > 0:15:02There is no better way to go urban-volcano hunting.
0:15:02 > 0:15:03You just need to know the clues.
0:15:05 > 0:15:07I have climbed enough mountains to know
0:15:07 > 0:15:10that you need to look for a certain sort of volcanic rock.
0:15:10 > 0:15:13It's the rock that will give away the location of volcanoes,
0:15:13 > 0:15:16even millions of years after they were active.
0:15:18 > 0:15:21My first sleeping giant is right under the noses
0:15:21 > 0:15:23of all the tourists at Edinburgh Castle.
0:15:23 > 0:15:25The castle is at the very heart of Edinburgh
0:15:25 > 0:15:27and it's famous throughout the world,
0:15:27 > 0:15:30but what I am interested in is what is underneath it - Castle Rock.
0:15:33 > 0:15:37The rock that creates the spectacular setting of the castle
0:15:37 > 0:15:40is actually the remains of an ancient volcano.
0:15:40 > 0:15:43Over the millennia the earth's tectonic plates shifted
0:15:43 > 0:15:46and the volcanoes became extinct.
0:15:46 > 0:15:48The mud around the extinct volcanoes eroded
0:15:48 > 0:15:51and all that was left of these once-fearsome mountains
0:15:51 > 0:15:53was their central cores of tough volcanic rock.
0:15:55 > 0:15:57So that's volcano number one,
0:15:57 > 0:15:59but I want to show you another in Edinburgh
0:15:59 > 0:16:01that is even more spectacular.
0:16:07 > 0:16:10If you want to go ancient-volcano spotting yourself,
0:16:10 > 0:16:13there are opportunities all over the UK -
0:16:13 > 0:16:15the Giant's Causeway in Northern Ireland
0:16:15 > 0:16:18and Fingal's Cave on the Isle of Staffa in Scotland
0:16:18 > 0:16:20were both built from cooling lava.
0:16:21 > 0:16:24And many of the peaks in Snowdonia in Wales
0:16:24 > 0:16:26were originally volcanoes.
0:16:26 > 0:16:28It's a shame we are a little too late to see them erupting -
0:16:28 > 0:16:31about 60 million years too late.
0:16:33 > 0:16:36With some hard pedalling, I make a two-mile loop of the city streets
0:16:36 > 0:16:37in under ten minutes.
0:16:37 > 0:16:39You can't miss what I have come for
0:16:39 > 0:16:41and there it is, brooding over the city -
0:16:41 > 0:16:45secret volcano number two, and it's a whopper.
0:16:45 > 0:16:47That's Arthur's Seat,
0:16:47 > 0:16:50the central core of a massive volcano
0:16:50 > 0:16:52right in the middle of the city.
0:16:53 > 0:16:56These are the clues that give the volcanic activity away.
0:16:56 > 0:17:00Even today, you can clearly see layers of ancient lava and ash -
0:17:00 > 0:17:04still visible despite millions of years of erosion -
0:17:04 > 0:17:06all that's left of a once-great volcano.
0:17:10 > 0:17:13There's no way I'm leaving Edinburgh without conquering
0:17:13 > 0:17:14this mini-mountain.
0:17:16 > 0:17:19I'm not going to scare Bradley Wiggins at this speed,
0:17:19 > 0:17:22but I need to pick up the pace if I am to get to the top.
0:17:23 > 0:17:25It's not my toughest challenge,
0:17:25 > 0:17:27but it's made slightly harder by the fact
0:17:27 > 0:17:31there's no cycling allowed on the ancient volcanic rocks.
0:17:31 > 0:17:35There's nothing for it but for me to carry my bike.
0:17:35 > 0:17:36But it's worth it.
0:17:39 > 0:17:42It is incredible to think that this was once the centre
0:17:42 > 0:17:45of a giant volcano that created this entire landscape.
0:17:45 > 0:17:47Awesome.
0:17:48 > 0:17:51360 million years of history.
0:17:51 > 0:17:5340 km/h top speed.
0:17:53 > 0:17:56Two ancient volcanoes.
0:17:56 > 0:17:57Sorted.
0:18:00 > 0:18:03The ancient volcanoes of Scotland are long extinct
0:18:03 > 0:18:06but there are many around the world that are still very much alive.
0:18:06 > 0:18:11Back in Italy, Dougal is preparing for a close encounter
0:18:11 > 0:18:12with one of the most awe-inspiring.
0:18:14 > 0:18:15Stromboli -
0:18:15 > 0:18:19the tip of a massive volcano emerging from under the sea,
0:18:19 > 0:18:23erupting pretty much continuously for the last 2,000 years.
0:18:23 > 0:18:26Every year it gets a little bit bigger
0:18:26 > 0:18:31as yet more layers of ash and lava are launched out of its crater.
0:18:31 > 0:18:33If you want to get face to face with a volcano
0:18:33 > 0:18:35this is my particular favourite one,
0:18:35 > 0:18:39and today I'm going to go right to the top.
0:18:39 > 0:18:44Even from sea level it's clear that Stromboli is very much alive.
0:18:44 > 0:18:48They call this scree slope built from rocks ejected from the crater
0:18:48 > 0:18:52the Sciara del Fuoco - the Stream of Fire.
0:18:53 > 0:18:56Those rocks have bounced over 900 metres
0:18:56 > 0:18:58from the top of the volcano
0:18:58 > 0:18:59all the way down to the sea
0:18:59 > 0:19:01and that's how far we've got to go to get up to the top.
0:19:01 > 0:19:03It is going to be fantastic.
0:19:03 > 0:19:07900 metres is over twice the height of the Empire State Building
0:19:07 > 0:19:09in New York,
0:19:09 > 0:19:12and all of it built from volcanic rock.
0:19:12 > 0:19:15It's clear Stromboli is not to be messed with,
0:19:15 > 0:19:18so before my climb I drop in on the monitoring station
0:19:18 > 0:19:23that helps the islanders live safely side by side with their volcano.
0:19:23 > 0:19:28So, here we're at the main monitoring hub of Stromboli volcano,
0:19:28 > 0:19:31and these little diagrams here that have been
0:19:31 > 0:19:33almost virtually printed out on the screen,
0:19:33 > 0:19:35these record how the volcano shakes.
0:19:35 > 0:19:40Devices on the slopes measure minute changes in the volcano -
0:19:40 > 0:19:44rumblings that can predict when Stromboli may erupt dangerously.
0:19:44 > 0:19:46This is a lovely graphic here.
0:19:46 > 0:19:49You can see this is the April 2003 eruption.
0:19:49 > 0:19:53You can get a real feel for the small normal background eruptions
0:19:53 > 0:19:55and the big one.
0:19:56 > 0:19:58Let's hope that doesn't go off when we're up there.
0:20:01 > 0:20:03So, am I going to get what I came here for?
0:20:03 > 0:20:07A face-to-face encounter with an erupting volcano?
0:20:09 > 0:20:14It's time to head for the top of Stromboli and find out.
0:20:14 > 0:20:16Climbing an active volcano can be dangerous,
0:20:16 > 0:20:20so I'm travelling with local guide Antonio.
0:20:20 > 0:20:24I ask him how many times he's climbed Stromboli.
0:20:24 > 0:20:25Mille volte.
0:20:26 > 0:20:30- A thousand times?- Yes. - A thousand times. That's incredible.
0:20:41 > 0:20:44We are just about halfway up the volcano now
0:20:44 > 0:20:48and you get this fantastic view over what we saw from the boat -
0:20:48 > 0:20:51this scree slope of ejected bombs and debris.
0:20:51 > 0:20:54Now, this stuff is ejecting out of the volcano
0:20:54 > 0:20:56and just dropping to the ground
0:20:56 > 0:20:58and the volcano builds
0:20:58 > 0:21:02piece by piece, bit by bit, relentlessly out.
0:21:05 > 0:21:08We're a good two hours into the climb now
0:21:08 > 0:21:10and we spot something I'm not expecting.
0:21:10 > 0:21:12Turns out humans aren't the only creatures
0:21:12 > 0:21:15to make their home on the steep slopes of Stromboli.
0:21:16 > 0:21:18As we get towards the rim of the volcano here
0:21:18 > 0:21:21we are seeing more and more of this metalwork.
0:21:21 > 0:21:26These solar panels and aerials and so on are housing seismographs,
0:21:26 > 0:21:29there's a thermal camera there constantly monitoring the volcano
0:21:29 > 0:21:33and they send this as messages, radio messages,
0:21:33 > 0:21:36down from here all the way down to the observatory
0:21:36 > 0:21:37where we were this morning.
0:21:37 > 0:21:40And that's really how we can sort of listen
0:21:40 > 0:21:41to the heartbeat of the volcano.
0:21:46 > 0:21:50We're nearing the climax of our four-hour climb.
0:21:50 > 0:21:52As we get closer to the crater,
0:21:52 > 0:21:56the danger of approaching a live volcano becomes very clear.
0:21:58 > 0:21:59Wow.
0:21:59 > 0:22:03Things are starting to get a little interesting.
0:22:03 > 0:22:07Believe it or not, this is a bomb.
0:22:07 > 0:22:09This is a ballistic that's been thrown from the volcano
0:22:09 > 0:22:13during one of its slightly more... aggressive phases, let's say.
0:22:13 > 0:22:15There's lots of them, actually.
0:22:15 > 0:22:18These small ones are the usual size of things that might fall.
0:22:18 > 0:22:21So I think it's a good time we probably put our hard hats on.
0:22:23 > 0:22:25Now, I'm not sure how a hard hat like this
0:22:25 > 0:22:29is going help me when a rock like this falls out the sky,
0:22:29 > 0:22:31but we've got to wear them from now on in anyway.
0:22:35 > 0:22:38The last couple of hundred metres is tough going
0:22:38 > 0:22:41with a loose surface that's difficult to walk on.
0:22:41 > 0:22:42The rocks are called scoria.
0:22:42 > 0:22:46Every single bit was once a chunk of hot lava,
0:22:46 > 0:22:50rocks thrown out from the depths of the earth by this awesome volcano
0:22:50 > 0:22:54as it built itself up, piece by piece, out of the sea.
0:22:58 > 0:22:59Wow.
0:22:59 > 0:23:03This... This is an incredible vantage point
0:23:03 > 0:23:08We have got all four, five craters of the volcano at eye level.
0:23:08 > 0:23:10- HE SNIFFS - There is sulphur in the air.
0:23:10 > 0:23:14You can see an eerie gas and fog drifting over the mountain.
0:23:14 > 0:23:17We are right now close to the heart of Stromboli.
0:23:17 > 0:23:19All we've got to do is wait here
0:23:19 > 0:23:22and see if Stromboli is going to talk to us.
0:23:25 > 0:23:27Turns out our timing is perfect,
0:23:27 > 0:23:32and the view, just 150 metres from the live crater, is awesome.
0:23:32 > 0:23:37Look, you can see the red blocks of lava now, drifting down.
0:23:37 > 0:23:40It didn't take long for Stromboli to say hello.
0:23:40 > 0:23:43It's so exciting to see a live volcano erupt.
0:23:43 > 0:23:46Stromboli doesn't let us down.
0:23:46 > 0:23:51But we haven't yet seen just how red hot the rocks really are.
0:23:51 > 0:23:53I wait for it to get dark -
0:23:53 > 0:23:56my favourite time to view an erupting volcano.
0:23:56 > 0:23:59Between eruptions, it almost looks like
0:23:59 > 0:24:02some of the land over there is quite safe.
0:24:02 > 0:24:05You can only just see a little bit of the volcano
0:24:05 > 0:24:07glowing in the background,
0:24:07 > 0:24:10but when you bring a heat camera up and have a look,
0:24:10 > 0:24:12you can actually see
0:24:12 > 0:24:15every one of those craters over there
0:24:15 > 0:24:17is glowing hot.
0:24:17 > 0:24:20And you're getting spot heights
0:24:20 > 0:24:23in excess of 100 degrees centigrade.
0:24:23 > 0:24:25Now, water is going to flash to steam
0:24:25 > 0:24:27at over 100 degrees centigrade,
0:24:27 > 0:24:28so this is really, really hot stuff.
0:24:28 > 0:24:31Imagine boiling your kettle and sticking your hand in it,
0:24:31 > 0:24:32it's not a good idea at all.
0:24:32 > 0:24:34So you wouldn't be able to walk over there -
0:24:34 > 0:24:36it would start to melt your boots.
0:24:38 > 0:24:41Stromboli often erupts like this several times an hour.
0:24:41 > 0:24:43The explosions are so distinctive
0:24:43 > 0:24:47that the mountain lends its name to the classic volcanic sight -
0:24:47 > 0:24:49the Strombolian eruption.
0:24:49 > 0:24:51Whoa, whoa! Look.
0:24:51 > 0:24:54That is fantastic. Are you seeing that?
0:24:54 > 0:24:56I am getting that on the thermal camera.
0:24:56 > 0:24:59Wow. That is just what we've been waiting for.
0:25:00 > 0:25:03150... It went up very quickly.
0:25:03 > 0:25:05You can imagine.... Look at the scoria
0:25:05 > 0:25:08just falling down the scree slope there.
0:25:09 > 0:25:11Can you imagine tons and tons of that material
0:25:11 > 0:25:14every day gets erupted from this volcano?
0:25:14 > 0:25:18The road of fire is literally on fire now
0:25:18 > 0:25:21and all of that is falling down to the sea.
0:25:21 > 0:25:22Wow.
0:25:25 > 0:25:27That's fantastic.
0:25:27 > 0:25:30So. I've got exactly what I came for -
0:25:30 > 0:25:32a close-up encounter with the planet's
0:25:32 > 0:25:35most spectacular natural force.
0:25:35 > 0:25:37When you have witnessed something
0:25:37 > 0:25:39like Stromboli erupting in the flesh,
0:25:39 > 0:25:41it is something that just keeps giving -
0:25:41 > 0:25:43you want to keep coming back and seeing more and more.
0:25:44 > 0:25:46Whoa, here we go!
0:25:46 > 0:25:47Look at that!
0:25:49 > 0:25:50Oh, beautiful!
0:25:52 > 0:25:54Earth, raging earth!
0:25:55 > 0:25:58This is the earth at its most active and its most violent...
0:25:59 > 0:26:02..and yet it's so beautiful, you just can't stop watching.
0:26:13 > 0:26:15Where there are volcanoes,
0:26:15 > 0:26:17there will always be humans.
0:26:17 > 0:26:21And, being humans, we've developed ways to survive alongside volcanoes.
0:26:21 > 0:26:26Seismographs and other monitoring devices are used by scientists
0:26:26 > 0:26:28to predict large eruptions.
0:26:28 > 0:26:32Evacuation alerts are only issued in a real emergency, so act on them.
0:26:34 > 0:26:38Remember, when it comes to danger, all volcanoes are not equal.
0:26:38 > 0:26:40Extinct or dominant is your best bet.
0:26:40 > 0:26:44When volcanoes are active, a shield shape is safer -
0:26:44 > 0:26:47it means the lava can flow freely.
0:26:47 > 0:26:48Domes are more dangerous -
0:26:48 > 0:26:50pressure could be building deep beneath the earth
0:26:50 > 0:26:51with lethal consequences.
0:26:51 > 0:26:54If you are lucky enough to visit an active volcano,
0:26:54 > 0:26:58you should only ever approach it with a professional guide,
0:26:58 > 0:27:00check volcanic activity before your trip
0:27:00 > 0:27:02and always travel with communication,
0:27:02 > 0:27:05supplies and full safety gear.
0:27:05 > 0:27:08This is how you maximise your chances of surviving...
0:27:08 > 0:27:10the Fierce Earth.
0:27:12 > 0:27:14Coming up next time...
0:27:14 > 0:27:17The destructive force of the world's fastest winds...
0:27:20 > 0:27:25..winds that tear buildings apart and leave destruction in their wake.
0:27:25 > 0:27:29Join Fierce Earth for a spin inside the fury of the tornado.
0:27:29 > 0:27:31HE LAUGHS
0:27:50 > 0:27:53Subtitles by Red Bee Media Ltd