0:00:06 > 0:00:10Hidden in the heart of Africa,
0:00:10 > 0:00:12deep in the Congo,
0:00:12 > 0:00:15is one of the most spectacular volcanoes on Earth.
0:00:19 > 0:00:20Nyiragongo.
0:00:22 > 0:00:24It is also one of the most deadly.
0:00:25 > 0:00:26It's ferocious.
0:00:26 > 0:00:28It feels very alive.
0:00:29 > 0:00:31It last erupted in 2002...
0:00:34 > 0:00:36..devastating the nearby city of Goma.
0:00:38 > 0:00:42The Earth's molten core enveloping an African town.
0:00:44 > 0:00:46There are few places on Earth
0:00:46 > 0:00:50where an active volcano threatens so many people,
0:00:50 > 0:00:53in a country already shattered by decades of violence.
0:00:57 > 0:01:00Now there's an uneasy peace,
0:01:00 > 0:01:03so a team of international and local scientists are on a mission
0:01:03 > 0:01:05to explore this rarely visited volcano...
0:01:08 > 0:01:10..to try and predict when it will next erupt.
0:01:12 > 0:01:15This is some of this really fast moving lava.
0:01:15 > 0:01:1830, 40, even more miles per hour.
0:01:18 > 0:01:22The team are also investigating the surprising ways this volcano affects
0:01:22 > 0:01:24all aspects of life here.
0:01:32 > 0:01:36Their search for answers will take them deep inside the crater...
0:01:36 > 0:01:38I've just come over the edge.
0:01:38 > 0:01:41..and into great danger.
0:01:41 > 0:01:44If any of this rock goes here, that's it for both of us.
0:02:05 > 0:02:07On a remote jungle road,
0:02:07 > 0:02:10the team of scientists is heading towards a highly active volcano...
0:02:12 > 0:02:14..Nyiragongo.
0:02:16 > 0:02:19It lies on the Democratic Republic of Congo's
0:02:19 > 0:02:21eastern border with Rwanda.
0:02:21 > 0:02:25To the south, just seven miles away, is Goma,
0:02:25 > 0:02:27a city of almost a million people.
0:02:33 > 0:02:36Last time Nyiragongo erupted, Goma was taken by surprise.
0:02:38 > 0:02:42The expedition hopes to find new ways of predicting the next eruption
0:02:42 > 0:02:45so the city has enough warning to evacuate.
0:02:48 > 0:02:51The team have brought an array of equipment to investigate this
0:02:51 > 0:02:52volcano like never before.
0:02:56 > 0:02:59- Just take care that the men take the heavy bag.- Yes.
0:02:59 > 0:03:03Leading the science team is Belgian volcanologist Benoit Smets.
0:03:05 > 0:03:07Actually, that's the one I'm worried about.
0:03:07 > 0:03:10- The seismometer? - I don't want someone to drop it.
0:03:10 > 0:03:13Americans Professor Jeff Johnson and Dr Kayla Iacovino
0:03:13 > 0:03:15have brought specialist kit
0:03:15 > 0:03:19that can identify warning signs of an impending eruption.
0:03:19 > 0:03:21I think it'll be good.
0:03:21 > 0:03:23Is this like normal fieldwork?
0:03:23 > 0:03:25Is this what you always bring?
0:03:25 > 0:03:27I think, for me, this kind of
0:03:27 > 0:03:31highlights the range of things we do in geology, right?
0:03:31 > 0:03:34Joining them are two British scientists,
0:03:34 > 0:03:36humanitarian Dr Xand van Tulleken
0:03:36 > 0:03:39and geologist Professor Chris Jackson.
0:03:40 > 0:03:44For me, I'd literally have a notebook and a pencil, a compass.
0:03:44 > 0:03:46- A little hammer?- A little hammer!
0:03:52 > 0:03:55Sun's out down here. Did you have a good night last night?
0:03:55 > 0:03:57Absolutely hammered it down.
0:03:57 > 0:03:59Really come down. Big, big...
0:03:59 > 0:04:02Former Royal Marine Aldo Kane is in charge of getting everyone and
0:04:02 > 0:04:06everything to the top of the volcano,
0:04:06 > 0:04:10and he's hired in 140 local porters to help.
0:04:10 > 0:04:15So we've got science kit, expedition kit, rigging kit, food, water.
0:04:15 > 0:04:18Nearly four tonnes of kit that's going up the hill today.
0:04:29 > 0:04:34Nyiragongo's crater rim is 2,000 vertical metres above the jungle
0:04:34 > 0:04:36and only accessible on foot.
0:04:39 > 0:04:41But Chris and Xand both know
0:04:41 > 0:04:43how important getting the expedition to the top is...
0:04:46 > 0:04:48..because yesterday they travelled
0:04:48 > 0:04:51in through the city that lies at the foot of this volcano.
0:04:57 > 0:05:01Goma is little known outside the Congo,
0:05:01 > 0:05:03but it's an extraordinary city
0:05:03 > 0:05:05that owes its very existence to Nyiragongo.
0:05:12 > 0:05:14It's all made of lava, isn't it?
0:05:14 > 0:05:19Yeah, this is all lava rock directly from Nyiragongo,
0:05:19 > 0:05:21the volcano we're going to go and visit.
0:05:21 > 0:05:25It's amazing to think that there's such a threat posed by that volcano,
0:05:25 > 0:05:27yet because of that volcano
0:05:27 > 0:05:29you can build houses and some sort of infrastructure,
0:05:29 > 0:05:33so there's a gift and a curse, really, there with the volcano.
0:05:33 > 0:05:35I guess I was expecting one thing
0:05:35 > 0:05:39- and it's actually quite a lively town, isn't it?- Yeah.
0:05:40 > 0:05:43Today, Goma is growing rapidly,
0:05:43 > 0:05:47but it has been rebuilt, literally from ashes,
0:05:47 > 0:05:51because in 2002 it was shattered by the eruption of Nyiragongo.
0:05:56 > 0:05:58- NEWS CORRESPONDENT: - The red river keeps flowing,
0:05:58 > 0:06:01pouring out of the volcano and down towards Goma.
0:06:04 > 0:06:07With little warning, the city was overrun by lava.
0:06:07 > 0:06:12Daylight and some of the first pictures reveal a black blanket of
0:06:12 > 0:06:14lava covering entire neighbourhoods.
0:06:14 > 0:06:16SIREN
0:06:22 > 0:06:25Nyiragongo impacts life here in many unexpected ways...
0:06:28 > 0:06:30..and it's this that Xand will be investigating.
0:06:33 > 0:06:37I'm a doctor and I have a particular interest in humanitarian medicine.
0:06:37 > 0:06:40I'm fascinated by this relationship to the volcano,
0:06:40 > 0:06:44how the volcano affects every aspect of daily life here,
0:06:44 > 0:06:47how people here cope with the constant threat of eruption,
0:06:47 > 0:06:50and what another eruption would do to the people living here.
0:06:52 > 0:06:56Nyiragongo has erupted twice within the last 40 years.
0:06:58 > 0:07:01There's little doubt it will again,
0:07:01 > 0:07:03with the same catastrophic consequences.
0:07:05 > 0:07:09Chris has studied volcanic landscapes across the world.
0:07:09 > 0:07:12For him, predicting eruptions is
0:07:12 > 0:07:16both a scientific and humanitarian challenge.
0:07:16 > 0:07:18For a geologist, this is incredibly exciting,
0:07:18 > 0:07:22to be joining an expedition like this to do cutting-edge,
0:07:22 > 0:07:24critical science for the people
0:07:24 > 0:07:26living in the shadow of this giant volcano.
0:07:38 > 0:07:40After six hours, the team are
0:07:40 > 0:07:42reaching the upper slopes of Nyiragongo.
0:07:49 > 0:07:52The weather's closed in and it's cold.
0:07:56 > 0:08:01But their reward is a view of one of Earth's great natural wonders.
0:08:06 > 0:08:09HE LAUGHS
0:08:11 > 0:08:13Oh, my goodness.
0:08:21 > 0:08:24So, this is the coolest thing I've ever seen, but you all seem pretty
0:08:24 > 0:08:27psyched as well and, like, this is for you another day in the office,
0:08:27 > 0:08:30isn't it? You're like, "Yeah, another day, another volcano."
0:08:30 > 0:08:31No?
0:08:31 > 0:08:34I think this might be the coolest thing I've ever seen.
0:08:34 > 0:08:36- Really?- There's literally
0:08:36 > 0:08:38nothing like this in the world.
0:08:44 > 0:08:47There are six lava lakes, permanent lava lakes, on Earth.
0:08:47 > 0:08:49You are standing looking into one of those six.
0:08:49 > 0:08:52Of those six lava lakes, they are all babies compared to...
0:08:52 > 0:08:53Yeah, they are.
0:08:53 > 0:08:57All other global lava lakes could fit into this lava lake
0:08:57 > 0:08:58with tons of room left over.
0:08:58 > 0:09:00This lava lake is enormous.
0:09:00 > 0:09:03The sheer size of it, I think, is just hard to even fathom.
0:09:09 > 0:09:10The crater rim is a vast
0:09:10 > 0:09:141.2 kilometres in diameter.
0:09:14 > 0:09:17Inside is a permanent cauldron of molten rock
0:09:17 > 0:09:20that is 260 metres across,
0:09:20 > 0:09:22more than twice the length of a football pitch...
0:09:27 > 0:09:31..and it constantly churns at over 1,000 degrees.
0:09:36 > 0:09:38It's ferocious.
0:09:38 > 0:09:39It feels very alive.
0:09:41 > 0:09:43And even when we're silent,
0:09:43 > 0:09:45there's that constant roar.
0:09:45 > 0:09:47It just doesn't let up at all.
0:09:48 > 0:09:50As a structural geologist, we're
0:09:50 > 0:09:52often left with what's at the Earth's surface, so we're looking at
0:09:52 > 0:09:55rocks, we're describing the rocks, we're measuring the rocks,
0:09:55 > 0:09:59we're mapping the rocks, and we may then use also some other geophysical
0:09:59 > 0:10:03techniques to look down into the Earth,
0:10:03 > 0:10:05but we don't need to kind of image it.
0:10:05 > 0:10:07We're actually seeing right down into the lava lake.
0:10:11 > 0:10:14But the team haven't come this far just to admire the view.
0:10:19 > 0:10:22Tomorrow, they plan to abseil into the crater
0:10:22 > 0:10:24to study the lava lake up close.
0:10:29 > 0:10:32From where we are here, to get down there is over 400 metres.
0:10:32 > 0:10:34So that's, what, four times Big Ben?
0:10:36 > 0:10:38That is full-on.
0:10:41 > 0:10:44That's where we hope to camp, down there on that second level.
0:10:47 > 0:10:49Are you all like, "Yeah, I can't wait,"
0:10:49 > 0:10:51first light, you're going to be down there?
0:10:51 > 0:10:52You are super-psyched to get down there?
0:10:52 > 0:10:55Well, I don't know. This is terrifying.
0:10:55 > 0:10:58That, to me... When I look at the lava lake, I don't see danger
0:10:58 > 0:11:01so much. It's an amazement. It's not a fear.
0:11:01 > 0:11:03I'm afraid of the getting down there.
0:11:03 > 0:11:06That's terrifying. That is absolutely terrifying.
0:11:17 > 0:11:21Understanding the lava lake's behaviour is crucial,
0:11:21 > 0:11:24because it could be linked to forces deep inside the volcano...
0:11:27 > 0:11:30..and may provide warning signs of an eruption.
0:11:34 > 0:11:37But as Chris and Xand bed down for the night,
0:11:37 > 0:11:40it's the descent into the crater, rather than volcano science,
0:11:40 > 0:11:43that's playing on their minds.
0:11:43 > 0:11:46Whether it's going to be the physical aspect or the mental aspect
0:11:46 > 0:11:49that's most challenging, that's probably what I'm going to have
0:11:49 > 0:11:52the most sleeplessness about tonight.
0:11:52 > 0:11:54There's a lot of risk there that you can't modify.
0:11:54 > 0:11:56- Yeah. - You can wear a helmet and stuff,
0:11:56 > 0:11:58but if you're going to get hit by a big rock,
0:11:58 > 0:12:00- it's going to be bad.- That's it.
0:12:00 > 0:12:02Hello. Sorry, were you doing a video diary?
0:12:02 > 0:12:04We're doing a big diary sesh. Now we've got the man himself.
0:12:04 > 0:12:07Now, we've been talking about risk, Aldo.
0:12:07 > 0:12:10When is something too risky to not do it?
0:12:10 > 0:12:11We've done as much as we can
0:12:11 > 0:12:15to mitigate all of the known risks that we can mitigate against,
0:12:15 > 0:12:18and then the rest of it is just risky.
0:12:18 > 0:12:20LAUGHTER
0:12:21 > 0:12:23You were really doing well there.
0:12:23 > 0:12:26It was really convincing until you said that.
0:12:26 > 0:12:28For Xand, this is only a brief visit to the crater.
0:12:31 > 0:12:33Now he's seen the volcano,
0:12:33 > 0:12:34he's heading back down
0:12:34 > 0:12:38to investigate the complex ways it impacts life in Goma.
0:12:43 > 0:12:45First light on the crater rim.
0:12:47 > 0:12:50The priority is to get down to the lava lake as soon as possible.
0:12:53 > 0:12:56Even though the current weather conditions are miserable,
0:12:56 > 0:12:59at this altitude it can get a lot worse.
0:12:59 > 0:13:01The temperature is slightly warmer in there,
0:13:01 > 0:13:03but it can change like that,
0:13:03 > 0:13:05and it can go down to freezing.
0:13:05 > 0:13:08My team were down there yesterday and were caught out in a hailstorm.
0:13:10 > 0:13:14OK, it's just started with the heaviest hail.
0:13:19 > 0:13:23Torrents streamed down the loose crater wall,
0:13:23 > 0:13:26creating the climber's enemy - rock fall.
0:13:26 > 0:13:32OK, there are waterfalls coming all down the side of the volcano.
0:13:32 > 0:13:35And the waterfalls are knocking massive rocks
0:13:35 > 0:13:37coming flying towards us.
0:13:38 > 0:13:42For Aldo, the risk of bad weather means a change of plan.
0:13:43 > 0:13:47What we want to do is cut the amount of people that are going down into
0:13:47 > 0:13:50the volcano to essentials only.
0:13:50 > 0:13:53And, Kayla, I was speaking to you earlier on and you mentioned you can
0:13:53 > 0:13:56do a lot of your stuff up on the top here,
0:13:56 > 0:13:58so I'm happy to keep you up here
0:13:58 > 0:14:00and not take you down there because of that.
0:14:00 > 0:14:04I can do all of the work that I need to do, basically, on the rim.
0:14:09 > 0:14:12There are definitely some mixed emotions behind
0:14:12 > 0:14:13me not being able to go down.
0:14:13 > 0:14:19There's a bit of relief because it is so dangerous to do
0:14:19 > 0:14:23and there's also a bit of disappointment because, you know,
0:14:23 > 0:14:24what an amazing experience
0:14:24 > 0:14:27to spend a couple of nights in the crater next to the lava lake.
0:14:27 > 0:14:30It's something I could never have dreamed of being able to ever do.
0:14:32 > 0:14:34Later, the weather clears,
0:14:34 > 0:14:36and Aldo decides to get the team down.
0:14:38 > 0:14:41I can feel my heart rate going up just putting the harness on.
0:14:41 > 0:14:44- Wait till you look over the edge. - Yeah.
0:14:44 > 0:14:46Last bit before we go down, kicking rocks off,
0:14:46 > 0:14:49if you do kick a rock off, big shout, "Rock!"
0:14:49 > 0:14:52- OK.- If one of these rocks hits someone on the head,
0:14:52 > 0:14:54it'll kill them, even with these helmets on.
0:14:54 > 0:14:56OK. I think I'm ready.
0:14:56 > 0:14:58You should enjoy the view first before we go over,
0:14:58 > 0:15:01- because after that you're going to be fairly busy.- OK.
0:15:04 > 0:15:07Nyiragongo's crater has three levels.
0:15:09 > 0:15:13Tier one is a small outcrop around 250 metres below the rim.
0:15:15 > 0:15:18A sheer 80-metre drop below is tier two,
0:15:18 > 0:15:21where the team will be camping.
0:15:21 > 0:15:25And finally, tier three, the bottom level that surrounds the lava lake.
0:15:25 > 0:15:28- How are you feeling? - A blend of excitement and nerves,
0:15:28 > 0:15:30I'll be honest with you, yeah.
0:15:33 > 0:15:36Climbing down is the most dangerous part of the expedition.
0:15:39 > 0:15:41Doubly so for Chris...
0:15:41 > 0:15:43Nice and gently, Chris.
0:15:43 > 0:15:45..because he's not an experienced climber.
0:15:49 > 0:15:51How does it feel?
0:15:51 > 0:15:53Better now. I've just come over the edge.
0:15:53 > 0:15:58And in such a remote location, if anything goes wrong,
0:15:58 > 0:15:59there are no rescue teams.
0:16:03 > 0:16:06- Sorry.- Try not to do that because there are sections, if you do that,
0:16:06 > 0:16:08that the whole slope will go.
0:16:08 > 0:16:11- Yeah.- All of this is just waiting to fall.
0:16:15 > 0:16:17That wind's just picked up.
0:16:17 > 0:16:18Yeah, yeah, I can feel it.
0:16:22 > 0:16:23Be careful not to kick anything.
0:16:23 > 0:16:26If you kick anything, it's coming down on my head.
0:16:31 > 0:16:34Yeah, OK.
0:16:34 > 0:16:35Everything's moving.
0:16:37 > 0:16:38Nothing is stable.
0:16:41 > 0:16:43Rock!
0:16:46 > 0:16:48Oh, Jesus.
0:16:50 > 0:16:52Sorry.
0:16:52 > 0:16:54Have a look back up.
0:16:54 > 0:16:56Oh, yeah.
0:16:56 > 0:16:57Yeah.
0:17:01 > 0:17:03Yeah, that's good, that's good.
0:17:06 > 0:17:07- Ow.- You OK?- Yeah.
0:17:11 > 0:17:15As the weather holds, the rest of the team also start the descent.
0:17:17 > 0:17:19Just watch your feet coming down.
0:17:20 > 0:17:24Halfway down, Aldo spots a small but potentially deadly problem.
0:17:26 > 0:17:28Super sharp rock.
0:17:29 > 0:17:31- You see that?- Wow.
0:17:31 > 0:17:32What's happened there?
0:17:32 > 0:17:36That's where the rock fall has come down and chopped this rope.
0:17:36 > 0:17:38Has it gone through the fabric to the core?
0:17:38 > 0:17:40It's not chopped it completely.
0:17:40 > 0:17:43The inner core still looks like it's usable,
0:17:43 > 0:17:45but it will have lost a lot of its strength.
0:17:45 > 0:17:47I'm going to change over onto this,
0:17:47 > 0:17:49and then we'll put a backup on this.
0:17:52 > 0:17:54After three hours on the ropes,
0:17:54 > 0:17:56Chris has almost reached tier one.
0:17:56 > 0:17:59That's where we are heading to, to the base camp down there.
0:17:59 > 0:18:00- OK.- OK?
0:18:05 > 0:18:07But he needs to get to tier two
0:18:07 > 0:18:09if he's going to have a bed for the night.
0:18:19 > 0:18:22Goma isn't totally unprepared for Nyiragongo's next eruption.
0:18:24 > 0:18:27The city does have a volcano observatory.
0:18:29 > 0:18:32Its job is to keep an eye on volcanic activity...
0:18:34 > 0:18:37..and warn people about the dangers of living in this landscape.
0:18:41 > 0:18:46Xand is on his way to a small village just outside the city
0:18:46 > 0:18:48to meet with two scientists...
0:18:50 > 0:18:54..Dario Tedesco and Mathieu Yalire,
0:18:54 > 0:18:55who work there.
0:18:57 > 0:19:00This region comes with its own unique threats,
0:19:00 > 0:19:03and the scientists are warning the villagers about one of them.
0:19:08 > 0:19:11We've assembled the whole village around an area that, to me,
0:19:11 > 0:19:13looks completely normal, but is apparently extremely dangerous,
0:19:13 > 0:19:16and then we're going to do a demonstration.
0:19:16 > 0:19:18EQUIPMENT BEEPS
0:19:18 > 0:19:22Seeping from the ground is an invisible but lethal gas,
0:19:22 > 0:19:25so the observatory scientists use goats to warn local people,
0:19:25 > 0:19:28especially children, about its presence.
0:19:31 > 0:19:35The animal is led into an innocuous-looking patch of ground.
0:19:38 > 0:19:40At first, nothing happens,
0:19:40 > 0:19:42and the goat appears fine.
0:19:47 > 0:19:49But then, it collapses.
0:19:52 > 0:19:54Bring him up.
0:19:54 > 0:19:57- Bring him up. - With bottled oxygen to hand,
0:19:57 > 0:20:00it's a simple job to bring the animal round.
0:20:01 > 0:20:04There we go.
0:20:04 > 0:20:06OK, OK. There we go.
0:20:06 > 0:20:08How's he doing? Oh, he's good, he's back.
0:20:08 > 0:20:11Good job. Good job, young man.
0:20:11 > 0:20:13There you go.
0:20:13 > 0:20:15Well, my first goat resus.
0:20:15 > 0:20:18That is a very happy ending. Lovely.
0:20:18 > 0:20:22Although it looks traumatic, the goat makes a full recovery.
0:20:22 > 0:20:23It collapsed because it was
0:20:23 > 0:20:27suffocated by the invisible, odourless gas, carbon dioxide.
0:20:30 > 0:20:34This gas seeps up slowly through cracks in the rocks.
0:20:34 > 0:20:37It comes from the volcanic system that underlies this whole area.
0:20:39 > 0:20:42Because carbon dioxide is heavier than air,
0:20:42 > 0:20:43it forms deadly pools in thousands
0:20:43 > 0:20:46of shallow depressions that litter this region...
0:20:48 > 0:20:51..making them a particular hazard for children.
0:21:06 > 0:21:10This seems like an incredibly dangerous thing
0:21:10 > 0:21:11to have near a village.
0:21:11 > 0:21:15We call these areas mazuku.
0:21:15 > 0:21:16Mazuku?
0:21:16 > 0:21:19Mazuku means
0:21:19 > 0:21:21- evil wind.- Evil wind?
0:21:21 > 0:21:23Evil wind, yeah.
0:21:23 > 0:21:25I mean, it's one thing to have your parents say,
0:21:25 > 0:21:27"Don't go and play in the hole,"
0:21:27 > 0:21:29but it's another thing to see the goat pass out in the hole
0:21:29 > 0:21:32and realise how dangerous it is, I think.
0:21:33 > 0:21:36I started with a very clear idea that volcanoes are dangerous
0:21:36 > 0:21:39because they're boiling hot and they throw out rocks and lava,
0:21:39 > 0:21:41and actually this is a much more dangerous threat.
0:21:41 > 0:21:43It's not evident. It's secret.
0:21:43 > 0:21:45And because it's so un-obvious,
0:21:45 > 0:21:47it gets the most vulnerable people in the community.
0:22:04 > 0:22:08Back on the rock face, Chris is still descending.
0:22:08 > 0:22:11Just ready for first. It's going to be Chris, over.
0:22:13 > 0:22:15Make yourself comfy.
0:22:17 > 0:22:20He's about to be lowered by Aldo and his team
0:22:20 > 0:22:24down a final 80-metre free-hanging drop to the campsite below.
0:22:29 > 0:22:30Clear now.
0:22:32 > 0:22:34- Thank you.- Rock!
0:22:53 > 0:22:54Steady.
0:22:54 > 0:22:56- OK.- Chris is down.
0:22:56 > 0:22:58- Thanks. Cheers, man.- Spot on.
0:22:58 > 0:23:01- That is very good.- Oh, too intense.
0:23:01 > 0:23:03- Don't look back.- Don't look back.
0:23:03 > 0:23:04Don't look back.
0:23:20 > 0:23:22So, I've made it down to tier two.
0:23:22 > 0:23:27Daz is just sorting out the ropes to be sent back up for the next victim.
0:23:27 > 0:23:30The first thing I noticed as soon as I come down to this level,
0:23:30 > 0:23:32these giant chasms,
0:23:32 > 0:23:35maybe a metre, maybe two metres wide.
0:23:37 > 0:23:40You can see in the distance the campsite that's been set up.
0:23:41 > 0:23:45The tents are pitched between two potentially fatal hazards.
0:23:47 > 0:23:50The vertical drop down to the lava lake is less than 30 metres away.
0:23:52 > 0:23:53Just behind the tents
0:23:53 > 0:23:56lies a field of fallen rocks from the crater wall.
0:24:00 > 0:24:04Despite the danger, for Chris, it is out of this world.
0:24:05 > 0:24:10If I was to compare this environment anywhere else, I'd say Mars.
0:24:10 > 0:24:12There's just blacks and whites and reds -
0:24:12 > 0:24:14very simple colours everywhere.
0:24:18 > 0:24:20There is no vegetation whatsoever.
0:24:20 > 0:24:23There doesn't seem to be anything living down here.
0:24:23 > 0:24:27One of the reasons is actually what I'm smelling. It's sulphur.
0:24:27 > 0:24:28And all around us
0:24:28 > 0:24:32there's these vents which are spewing out sulphur into the air.
0:24:46 > 0:24:49As evening falls, the rest of the team descend...
0:24:58 > 0:24:59..with Aldo the last...
0:25:03 > 0:25:06..chancing his luck in complete darkness.
0:25:09 > 0:25:11Tomorrow, the science can begin.
0:25:18 > 0:25:20The next morning, down on tier two...
0:25:22 > 0:25:25..Benoit is up first, sorting out his experiment.
0:25:28 > 0:25:30Nyiragongo is very important for me
0:25:30 > 0:25:32because this volcano is very dangerous.
0:25:32 > 0:25:34It threatens a lot of people.
0:25:34 > 0:25:39Everything we do to understand this volcano is very important to avoid
0:25:39 > 0:25:42another disaster like in 2002.
0:25:45 > 0:25:48Benoit wants to monitor the lava lake level
0:25:48 > 0:25:50throughout the time in the crater.
0:25:50 > 0:25:53He wants to work out what's going on inside Nyiragongo.
0:25:55 > 0:25:59Unlike most volcanoes, Nyiragongo erupts from fissures in its flanks.
0:26:01 > 0:26:02But like all volcanoes,
0:26:02 > 0:26:05it erupts when pressure builds in its magma chamber.
0:26:09 > 0:26:11If the team could measure that pressure,
0:26:11 > 0:26:14it would provide a warning signal of an eruption.
0:26:14 > 0:26:19The problem is the magma chamber is over a kilometre underground,
0:26:19 > 0:26:21so it's impossible to measure pressure changes directly.
0:26:24 > 0:26:26But Benoit suspects
0:26:26 > 0:26:30those pressure changes may affect the behaviour of the lava lake.
0:26:31 > 0:26:35Here, we have the chance to have this big lava lake,
0:26:35 > 0:26:38and you can see the lava lake as a magmatic chamber at ground surface.
0:26:41 > 0:26:44The plan is to use time-lapse photography
0:26:44 > 0:26:47to record any changes in the lake level.
0:26:47 > 0:26:50But when it spends half its time hidden by clouds of gas,
0:26:50 > 0:26:53it's tricky to see,
0:26:53 > 0:26:56so Benoit has built his own infrared cameras to overcome this problem.
0:27:01 > 0:27:04I made these boxes myself.
0:27:04 > 0:27:07My box is made of a microcomputer
0:27:07 > 0:27:09that will control everything,
0:27:09 > 0:27:10a real-time clock
0:27:10 > 0:27:12to have an accurate time,
0:27:12 > 0:27:14and a camera.
0:27:14 > 0:27:18It's a small camera like you have in your smartphone.
0:27:18 > 0:27:20And it'll take every ten seconds,
0:27:20 > 0:27:22and by comparing these pictures
0:27:22 > 0:27:25I will be able to see the variations of the lava lake level.
0:27:31 > 0:27:36The next day, Benoit returns to his cameras to see if they've worked,
0:27:36 > 0:27:37and, more importantly,
0:27:37 > 0:27:41whether they can reveal anything about pressure in the magma chamber.
0:27:41 > 0:27:43Whoa.
0:27:43 > 0:27:47We've got a beautiful lava lake level drop compared to yesterday
0:27:47 > 0:27:49at the same time. It's great.
0:27:49 > 0:27:51So we recorded something special.
0:27:53 > 0:27:55The home-made technology works.
0:27:55 > 0:27:57Over the last 24 hours,
0:27:57 > 0:28:00the cameras recorded a small drop in the lake level.
0:28:00 > 0:28:05This suggests pressure in the magma chamber does affect the lava lake.
0:28:05 > 0:28:08It's not about having the lava lake level high or low,
0:28:08 > 0:28:12it's understanding these movements to predict
0:28:12 > 0:28:16big events like a flank eruption.
0:28:16 > 0:28:19We have the opportunity to measure the pressure change
0:28:19 > 0:28:20by looking at the lava lake level.
0:28:23 > 0:28:26At the moment, the volcano is stable,
0:28:26 > 0:28:29so there are only small changes in pressure.
0:28:29 > 0:28:32If the volcano was building towards an eruption,
0:28:32 > 0:28:35Benoit would expect to see huge variations in level,
0:28:35 > 0:28:3640 metres or more.
0:28:39 > 0:28:42His cameras can spot these changes,
0:28:42 > 0:28:44but they're not designed to be left in the crater...
0:28:46 > 0:28:50..so the team need to find a way to permanently monitor the lake level
0:28:50 > 0:28:52to provide Goma with a warning.
0:29:00 > 0:29:05Despite the threat of a volcanic eruption, Goma is a growing city.
0:29:06 > 0:29:09Each new house is built on old lava flows.
0:29:09 > 0:29:12This brings with it a potentially fatal health problem.
0:29:24 > 0:29:27I didn't... I didn't bring any safety goggles,
0:29:27 > 0:29:29so I've got my sun specs instead.
0:29:30 > 0:29:33Every house starts with a stonemason
0:29:33 > 0:29:37like Heritier, chiselling out a long drop toilet.
0:29:37 > 0:29:41Problem is, cooled lava is an incredibly hard rock.
0:29:41 > 0:29:45I've been doing this for about 30 seconds and I'm winded.
0:29:52 > 0:29:55Heritier's job is tough but necessary,
0:29:55 > 0:29:57because without toilets,
0:29:57 > 0:29:59there's a deadly side-effect of living on lava.
0:30:00 > 0:30:04Long drop toilets work really well if you have a long drop toilet.
0:30:04 > 0:30:07And the problem here is that there have been loads and loads of things
0:30:07 > 0:30:09in Goma that have moved people out of Goma or moved people into them
0:30:09 > 0:30:11where they don't have toilets.
0:30:11 > 0:30:15We have refugee movement, violent conflict, and volcanic eruptions.
0:30:15 > 0:30:18And so if you have people without access to toilets,
0:30:18 > 0:30:23what you have is massive spread of infectious diarrhoeal illness,
0:30:23 > 0:30:24particularly cholera.
0:30:24 > 0:30:27This is one of the world hotspots for cholera.
0:30:29 > 0:30:33An estimated 13,000 refugees have died in the last week,
0:30:33 > 0:30:37mostly from cholera, and the bodies line the streets.
0:30:37 > 0:30:41In 1994, more than a million people crossed the border,
0:30:41 > 0:30:43which is just a few miles in that direction,
0:30:43 > 0:30:45from Rwanda, Rwandan refugees,
0:30:45 > 0:30:49and they stopped in Goma and in the surrounding countryside.
0:30:50 > 0:30:54A team of nurses are desperately trying to save the dying.
0:30:54 > 0:30:57There's a scramble to set up drips of rehydration fluids and salts.
0:30:59 > 0:31:00I've worked in cholera epidemics,
0:31:00 > 0:31:02and it's almost impossible to
0:31:02 > 0:31:05describe the amount of diarrhoea that's produced.
0:31:05 > 0:31:06So in a cholera treatment centre,
0:31:06 > 0:31:09you have sloping floors and you have beds with holes in them,
0:31:09 > 0:31:11so people go to the toilet directly onto the floor
0:31:11 > 0:31:14and you're just washing it into a central gutter.
0:31:14 > 0:31:18It's unbelievable, the quantities of fluid that you need to replace.
0:31:18 > 0:31:20We are talking about 20 litres,
0:31:20 > 0:31:23sometimes more, per day, of diarrhoea.
0:31:23 > 0:31:25So it can kill you within hours.
0:31:27 > 0:31:31The added layer of tragedy on top of that number of deaths
0:31:31 > 0:31:34is that, in this region, digging graves is virtually impossible,
0:31:34 > 0:31:37as you can see. Very, very hard to do.
0:31:38 > 0:31:40The cholera outbreak in 1994
0:31:40 > 0:31:43was caused by a mass movement of people
0:31:43 > 0:31:46with no access to decent sanitation,
0:31:46 > 0:31:49so human waste polluted Goma's main water source.
0:32:15 > 0:32:19Goma's population has now grown to almost a million people,
0:32:19 > 0:32:21so when Nyiragongo next erupts
0:32:21 > 0:32:23there will be a mass evacuation
0:32:23 > 0:32:26in numbers that haven't been seen since 1994.
0:32:27 > 0:32:29SIREN
0:32:33 > 0:32:37Practice drills have recently been introduced to test the response of
0:32:37 > 0:32:40police, charities, and medical aid to an eruption.
0:32:47 > 0:32:50But the danger is that hundreds of thousands of people
0:32:50 > 0:32:52fleeing their homes
0:32:52 > 0:32:54will find themselves without access to a toilet,
0:32:54 > 0:32:56leading to another epidemic.
0:32:57 > 0:32:59This town, Goma,
0:32:59 > 0:33:02is one of the first places I ever heard about when I started studying
0:33:02 > 0:33:06tropical medicine. I guess I thought that I knew a fair bit,
0:33:06 > 0:33:11and what I really love, and what's been very interesting and amazing,
0:33:11 > 0:33:14is that I really didn't understand anything at all.
0:33:14 > 0:33:17I guess you wouldn't think that
0:33:17 > 0:33:19a bacteria getting inside you and giving you diarrhoea
0:33:19 > 0:33:21would be determined by a volcano.
0:33:26 > 0:33:29Up on the volcano rim, Kayla is starting her investigation.
0:33:31 > 0:33:32She's studying the gases
0:33:32 > 0:33:35that constantly vent from the lake's surface...
0:33:38 > 0:33:39..because they can provide another way
0:33:39 > 0:33:42to tell what's happening in the magma chamber.
0:33:44 > 0:33:47The real power in gas measurements is that it can tell us about
0:33:47 > 0:33:49the entire system miles and miles beneath your feet.
0:33:49 > 0:33:53So that's where the action is. That is the driving force of volcanism.
0:33:53 > 0:33:57It's controlled deep down in the guts of the volcano.
0:33:59 > 0:34:02All lava contains gases,
0:34:02 > 0:34:05but when an eruption is building, those gases change.
0:34:07 > 0:34:11The one that alarms volcanologists is sulphur dioxide,
0:34:11 > 0:34:15because it often signals that lava is moving up towards the surface.
0:34:18 > 0:34:23With a simple device called a gas box, Kayla can detect its presence.
0:34:23 > 0:34:26Sulphur dioxide is the kind of gas that bubbles out of the magma
0:34:26 > 0:34:28in the really shallow part of the system,
0:34:28 > 0:34:30so just beneath the lava lake.
0:34:30 > 0:34:31If we see, all of a sudden,
0:34:31 > 0:34:34a huge spike in the amount of sulphur dioxide
0:34:34 > 0:34:35that's coming out of the crater,
0:34:35 > 0:34:38that could be something that happens before an eruption.
0:34:42 > 0:34:46After 12 hours, Kayla returns to find out what's been recorded.
0:34:52 > 0:34:54So, I'm just looking at the data now, and I'm pretty happy.
0:34:54 > 0:34:58So, these are sulphur dioxide. We're getting some readings there.
0:34:58 > 0:35:01Less than one part per million, but there is some reading there.
0:35:01 > 0:35:03So maybe not an immediate eruption.
0:35:04 > 0:35:06This low sulphur dioxide reading
0:35:06 > 0:35:09means no new magma is rising up through the volcano.
0:35:10 > 0:35:13For the moment, Goma is safe.
0:35:15 > 0:35:19The problem is, gases on their own are an unreliable warning indicator.
0:35:19 > 0:35:23Sampling them depends on weather conditions and wind direction.
0:35:23 > 0:35:26But the team are hoping to test another piece of technology
0:35:26 > 0:35:29that could provide a better way to warn of an eruption.
0:35:40 > 0:35:46When Nyiragongo erupted in 2002, lava flows split the city in three,
0:35:46 > 0:35:47killing around 100 people
0:35:47 > 0:35:50as the rest of the city fled for their lives.
0:35:53 > 0:35:55So is that where the lava got to?
0:35:55 > 0:35:58Yeah, exactly. The lava came and stopped...
0:35:58 > 0:36:01Xand's meeting local journalist Caleb Kabanda
0:36:01 > 0:36:03to find out what it was like
0:36:03 > 0:36:05and if there are any lessons to be learned.
0:36:08 > 0:36:11You couldn't get to, like, the top of a big building?
0:36:40 > 0:36:43The lava has been flowing for two days now.
0:36:43 > 0:36:45It shows no sign of stopping.
0:36:48 > 0:36:51So you come back that morning, and what does the city look like?
0:37:22 > 0:37:25As if the people of Goma had not suffered enough,
0:37:25 > 0:37:29this was a day that brought them more death, more tragedy.
0:37:29 > 0:37:33Fireballs filled the sky after a petrol station here exploded.
0:37:33 > 0:37:36Fuel cans leapt into the air.
0:37:45 > 0:37:48Walking through Goma, having heard Caleb's story,
0:37:48 > 0:37:52it's hard to think back to 2002 and imagine lava flowing through these
0:37:52 > 0:37:56streets, knocking buildings down, destroying everything.
0:37:57 > 0:38:01But what's even harder to imagine is how little time it took for the city
0:38:01 > 0:38:05to be inundated, how it seemed to be caught unawares.
0:38:09 > 0:38:12No matter how much warning the science team can provide,
0:38:12 > 0:38:17Goma's residents still need to know how much time they have to evacuate
0:38:17 > 0:38:19once the lava starts flowing from the volcano.
0:38:27 > 0:38:29Back in the crater, the team are now focusing on how quickly
0:38:29 > 0:38:32the lava could reach Goma.
0:38:32 > 0:38:35That's down to how fast it will flow during the next eruption.
0:38:41 > 0:38:43To find out, they'd ideally study
0:38:43 > 0:38:46the chemical composition of lava from the lake.
0:38:46 > 0:38:50But collecting samples is simply too dangerous.
0:38:50 > 0:38:52There is, though, another possibility.
0:38:55 > 0:38:57During preparations for filming,
0:38:57 > 0:38:59Aldo witnessed a new vent opening up
0:38:59 > 0:39:02that sent rivers of lava running across tier three,
0:39:02 > 0:39:05the crater floor.
0:39:05 > 0:39:07We were supposed to be heading down,
0:39:07 > 0:39:11but this aggressive vent here is
0:39:11 > 0:39:14constantly boiling and the, er...
0:39:15 > 0:39:18You can see there the lava bombs that are getting blown out of there
0:39:18 > 0:39:20are probably 40, 50 metres into the air.
0:39:23 > 0:39:25For Aldo, it was terrifying.
0:39:31 > 0:39:33Just so many...
0:39:42 > 0:39:43Now the vent is simply smoking.
0:39:45 > 0:39:49But the lava flows it left are just a few months old.
0:39:49 > 0:39:52They could be what the scientists need.
0:39:52 > 0:39:55So the plan is to descend to tier three.
0:39:56 > 0:39:59First, they need to check if the lava is cool enough to walk on.
0:40:01 > 0:40:07We're about to launch a thermal camera fitted to a drone
0:40:07 > 0:40:10that the Belgian science team have brought along, and it's going to be
0:40:10 > 0:40:15flown over T3, the lowermost level next to the lava lake,
0:40:15 > 0:40:20specifically to look at where there may be hot rocks or magma
0:40:20 > 0:40:22underneath a thin crust.
0:40:22 > 0:40:25So if we go over the fumaroles, we know they are about 60 degrees.
0:40:25 > 0:40:27So this would be, like, something we can use for...
0:40:27 > 0:40:29What's its max?
0:40:29 > 0:40:31- 500.- 500.- Yeah.
0:40:31 > 0:40:32- Don't go over the lake!- No!
0:40:38 > 0:40:41It's flying back this way.
0:40:42 > 0:40:45Yeah, there's something really hot there.
0:40:45 > 0:40:46It could be this vent.
0:40:46 > 0:40:48I have a problem with the drone.
0:40:48 > 0:40:49I cannot control it.
0:40:49 > 0:40:51Is the drone... Have you got control?
0:40:51 > 0:40:54- No.- Maybe you can move, try to keep the signal.
0:40:54 > 0:40:56Yeah, I think here.
0:40:56 > 0:40:58Just watch the...
0:40:58 > 0:41:00So we're, kind of, almost over
0:41:00 > 0:41:03the area that we'll be running the ropes in and abseiling down.
0:41:03 > 0:41:05Was that safe enough for tomorrow?
0:41:05 > 0:41:08I think that's fine as long as we don't go too close to the vent,
0:41:08 > 0:41:10which was really hot, but everything else was OK.
0:41:10 > 0:41:13I'm coming back, because I cannot control the drone.
0:41:13 > 0:41:15The wind is too strong.
0:41:15 > 0:41:16I've got visual.
0:41:23 > 0:41:26The crater floor is just about safe enough to walk on.
0:41:30 > 0:41:32But, by chance, Chris has discovered
0:41:32 > 0:41:36that it's not just the bottom of the crater that's warm beneath the feet.
0:41:37 > 0:41:40I've walked only ten metres away from the camp to take a pee,
0:41:40 > 0:41:43which is the minimum distance we have all agreed we should go
0:41:43 > 0:41:46before we actually use the toilet, and I've found out
0:41:46 > 0:41:48something remarkable about the rocks just around us.
0:41:48 > 0:41:51I'm going to pour some water on here in a live experiment
0:41:51 > 0:41:54to show you just how changeable and hostile this environment is.
0:41:59 > 0:42:02The water boils straightaway
0:42:02 > 0:42:04as it hits the rocks here,
0:42:04 > 0:42:09produces this horrible sulphuric acid smell or sulphur smell which
0:42:09 > 0:42:10has gone straight in my nostrils,
0:42:10 > 0:42:13so I think this isn't going to be my toilet place of choice any more.
0:42:15 > 0:42:18While Chris heads off to find a new location,
0:42:18 > 0:42:19at the edge of the cliff face
0:42:19 > 0:42:22Aldo is preparing the climb down to tier three
0:42:22 > 0:42:25for petrologist Olivier Namur.
0:42:25 > 0:42:28He thinks samples from the recent lava flow will reveal
0:42:28 > 0:42:32if the next eruption will be fast flowing or slow moving lava.
0:42:34 > 0:42:36I'm interested in the composition of the lavas
0:42:36 > 0:42:38and the evolution through time,
0:42:38 > 0:42:41so I've been sampling old lavas in the last couple of days
0:42:41 > 0:42:43and I will be sampling this very young lava
0:42:43 > 0:42:46that erupted last year on tier three.
0:42:46 > 0:42:48I think it's about 100 metres, so, that's...
0:42:48 > 0:42:51I think where we are now is about the height
0:42:51 > 0:42:52of the white cliffs of Dover.
0:42:52 > 0:42:54Yeah, thereabouts.
0:42:54 > 0:42:56I've never been down here before.
0:42:57 > 0:42:59This is going to be my first time.
0:43:03 > 0:43:05The descent isn't straightforward.
0:43:05 > 0:43:07There's an initial short abseil,
0:43:07 > 0:43:11then a sloping field of fallen boulders where the crater wall has
0:43:11 > 0:43:13collapsed, followed by a final
0:43:13 > 0:43:16vertical drop down to the crater floor.
0:43:16 > 0:43:19It all has to be rigged safely,
0:43:19 > 0:43:21so Aldo goes first.
0:43:21 > 0:43:23So brittle.
0:43:25 > 0:43:26- RADIO:- Go ahead.
0:43:26 > 0:43:28That's both Daz and I on boulder field, over.
0:43:35 > 0:43:40Whoa, there's some big chunks of rock there, mate.
0:43:40 > 0:43:43About 150 metres away from the lava lake at the minute, but...
0:43:44 > 0:43:47I reckon, Daz, about 80 metres?
0:43:47 > 0:43:49So it's about 80 metres straight down there.
0:43:52 > 0:43:53At the foot of the cliff,
0:43:53 > 0:43:57recent rock fall is clear evidence of its fragility.
0:43:57 > 0:44:00Oh, man, look at these rocks.
0:44:00 > 0:44:02Just precariously balanced.
0:44:02 > 0:44:04If any of these rocks decide to go...
0:44:09 > 0:44:10..then that's it.
0:44:15 > 0:44:17As Aldo drops over the edge,
0:44:17 > 0:44:20Daz, his climbing buddy, keeps an eye on him.
0:44:32 > 0:44:35Any false move could create a lethal rock fall.
0:44:45 > 0:44:50Even up on the camping level, Benoit can see the risk Aldo is taking.
0:45:01 > 0:45:03Mate, right here.
0:45:05 > 0:45:07So, I've just arrived on tier three.
0:45:09 > 0:45:12The lava lake is about 100 meters that way
0:45:12 > 0:45:16and that is the route I've just abseiled down.
0:45:16 > 0:45:17It is...
0:45:18 > 0:45:20..without doubt,
0:45:20 > 0:45:23one of the most dangerous things I've ever done.
0:45:24 > 0:45:26My mouth is dry...
0:45:28 > 0:45:29..and my heart rate is up.
0:45:32 > 0:45:34All the classic signs of...
0:45:37 > 0:45:40..100% pure, unadulterated fear.
0:45:49 > 0:45:50Time to get out.
0:46:01 > 0:46:03It is super sketchy.
0:46:03 > 0:46:06I think it's the most sketchiest thing that
0:46:06 > 0:46:09I've seen since being in here.
0:46:09 > 0:46:11I don't know what you're used to, but...
0:46:13 > 0:46:16..not entirely sure I would go back down there.
0:46:16 > 0:46:20If you think it's not a good idea, we'll not take the risk.
0:46:20 > 0:46:22I mean, we are here to do good science
0:46:22 > 0:46:27and collect exceptional data, but not taking stupid risks.
0:46:27 > 0:46:30I know you well enough to know
0:46:30 > 0:46:34that if that situation down there is...
0:46:34 > 0:46:37..you're fearful of that, then...
0:46:37 > 0:46:39No, it's too dangerous.
0:46:39 > 0:46:41Let's forget about going to tier three.
0:46:45 > 0:46:49The team abandon the planned descent to the crater floor,
0:46:49 > 0:46:51but there is still a possible source of fresh lava.
0:46:53 > 0:46:57During the recent eruption, the vent threw out lava bombs,
0:46:57 > 0:47:00and some may have landed on the boulder field
0:47:00 > 0:47:02halfway down to tier three.
0:47:02 > 0:47:05If they can find any, Olivier will have his sample of lava.
0:47:08 > 0:47:11For the rock samples, we can have some spatters.
0:47:11 > 0:47:14- Yeah, but only...- ..coming from the vent in the boulder field.
0:47:14 > 0:47:16It's not ideal.
0:47:16 > 0:47:19It's not ideal but it's better than nothing.
0:47:24 > 0:47:27The team quickly get to work.
0:47:27 > 0:47:29No-one wants to hang around here too long.
0:47:33 > 0:47:36I mean, you're standing hammering a cliff
0:47:36 > 0:47:39which is clearly already unstable.
0:47:39 > 0:47:44Yeah, this is true but this is the only way to get these samples.
0:47:44 > 0:47:48Olivier soon finds what he was looking for - new lava bombs.
0:47:49 > 0:47:50What have you got?
0:47:50 > 0:47:53It's a very fine grained lava.
0:47:53 > 0:47:55This should be enough.
0:47:55 > 0:47:58It's quite fresh. I think that will tell us quite a lot about
0:47:58 > 0:48:00the recent activity of the volcano.
0:48:02 > 0:48:03They are quite nice.
0:48:05 > 0:48:08After one happily uneventful hour,
0:48:08 > 0:48:10he has enough samples
0:48:10 > 0:48:12and, for an experienced geologist,
0:48:12 > 0:48:14they contain an unmistakable message,
0:48:14 > 0:48:16but it's not good news.
0:48:16 > 0:48:19Let me show you one of the samples that I collected
0:48:19 > 0:48:20from the active vent.
0:48:23 > 0:48:27We can see that these samples are a glassy black matrix.
0:48:27 > 0:48:30We can see a lot of bubbles here around,
0:48:30 > 0:48:32and a few tiny white crystals.
0:48:32 > 0:48:36We know that the composition of these volcanoes are low in silica,
0:48:36 > 0:48:38very low, below 40%.
0:48:38 > 0:48:42This makes this lava very fluid, so they have low viscosity,
0:48:42 > 0:48:43they will be flowing like water
0:48:43 > 0:48:47along the flanks of the volcano, rather than mud.
0:48:47 > 0:48:49And on top of that, because they have only a few crystals,
0:48:49 > 0:48:52that decreases again the viscosity of this lava.
0:48:52 > 0:48:56Because they have only a few crystals, they are very fluid.
0:48:56 > 0:48:59So I suspect that if there is a new eruption, with this composition,
0:48:59 > 0:49:02it might be flowing even faster than during 2002.
0:49:07 > 0:49:10In 2002, lava flowed into Goma
0:49:10 > 0:49:14at reported speeds of up to 40 kilometres per hour,
0:49:14 > 0:49:17reaching its centre in fewer than ten hours.
0:49:18 > 0:49:22Olivier's samples have revealed that next time, it could be even faster,
0:49:22 > 0:49:25so the city may have even less time to evacuate.
0:49:26 > 0:49:29That makes the need for an effective warning system more pressing.
0:49:31 > 0:49:35Tomorrow, the team have the last piece of kit to test.
0:49:44 > 0:49:47Nyiragongo creates a unique set of problems for
0:49:47 > 0:49:49the people who live in its shadow.
0:49:49 > 0:49:52But there's another side to this city -
0:49:52 > 0:49:54the character that's defined by the volcano.
0:49:56 > 0:49:58It's symbolised by a local invention
0:49:58 > 0:50:01that is found nowhere else in Africa -
0:50:01 > 0:50:06a deceptively simple wooden scooter called a chukudu.
0:50:06 > 0:50:08Xand wants to find out the story behind them.
0:50:12 > 0:50:15Since I arrived in Goma, I've seen hundreds of these things.
0:50:15 > 0:50:16They're all over the place.
0:50:16 > 0:50:19They're usually carrying massive, massive loads.
0:50:19 > 0:50:22They're real feature of the landscape here.
0:50:25 > 0:50:27But seeing them up close, I mean,
0:50:27 > 0:50:33carving a perfectly circular wheel out of hardwood with a machete is...
0:50:35 > 0:50:38I don't think it looks easy, but it's a lot harder than it looks.
0:50:41 > 0:50:44Can I try? OK.
0:50:44 > 0:50:46Like that? OK.
0:50:46 > 0:50:48I'm not very good at this.
0:50:49 > 0:50:51You made it look... You made it look very easy.
0:50:57 > 0:50:58I got a little bit off there.
0:51:00 > 0:51:02How did you learn to do this?
0:51:09 > 0:51:11How much weight could this chukudu carry?
0:51:15 > 0:51:16You don't have a tape measure.
0:51:27 > 0:51:30What colour can I get it in?
0:51:30 > 0:51:32The chukudus tell...
0:51:32 > 0:51:34..almost tell the story of the whole region
0:51:34 > 0:51:35just captured in this one thing.
0:51:37 > 0:51:41You have people doing a kind of extraordinary job
0:51:41 > 0:51:44under unbelievably difficult circumstances.
0:51:44 > 0:51:46You don't find these anywhere else
0:51:46 > 0:51:48and that's because this is a totally unique place.
0:51:48 > 0:51:51There isn't really another landscape like it.
0:51:53 > 0:51:56It's very difficult to farm. It's very difficult to move stuff around.
0:51:58 > 0:52:00You do see this extraordinary
0:52:00 > 0:52:05level of work and resilience and willingness to try and imagine
0:52:05 > 0:52:07a better future and work towards it.
0:52:08 > 0:52:10This is almost a symbol of resistance
0:52:10 > 0:52:13and a very, very big part of people's identity here.
0:52:20 > 0:52:24Back inside the crater, the team return to their main challenge...
0:52:25 > 0:52:29..detecting signs of an impending eruption.
0:52:29 > 0:52:31Earlier, Benoit established
0:52:31 > 0:52:34that sudden, erratic changes in the lava lake level
0:52:34 > 0:52:37usually happen before an eruption,
0:52:37 > 0:52:40so the key to an early warning system is monitoring that level.
0:52:43 > 0:52:48American volcanologist Jeff Johnson thinks he can do this by listening
0:52:48 > 0:52:50to the sounds Nyiragongo produces.
0:52:51 > 0:52:52But not just any sounds.
0:52:55 > 0:52:57This is a custom-built microphone,
0:52:57 > 0:52:59and it's capable of recording sounds
0:52:59 > 0:53:03beyond the threshold of human hearing.
0:53:03 > 0:53:07Jeff's microphone is designed to pick up very low-frequency sound,
0:53:07 > 0:53:09what's known as infrasound.
0:53:09 > 0:53:12Volcanoes speak at low frequencies.
0:53:12 > 0:53:14They generate sound that we can hear,
0:53:14 > 0:53:17but they also generate this world of infrasound...
0:53:19 > 0:53:24..a unique voice print that we want to recognise and understand
0:53:24 > 0:53:26so that when that tone changes in the future,
0:53:26 > 0:53:29we will be able to understand what's going on.
0:53:32 > 0:53:36The theory is that, like a sliding trombone,
0:53:36 > 0:53:39as the level of the lava lake rises and falls,
0:53:39 > 0:53:40the infrasound tone changes.
0:53:44 > 0:53:48Using infrasound is at the cutting edge of volcano science,
0:53:48 > 0:53:50and Chris is keen to see how it works.
0:53:57 > 0:54:01So we're listening to sounds coming from the lava lake, is that right?
0:54:01 > 0:54:03We're trying to hear the lava lake with these sensors?
0:54:03 > 0:54:05The infrasound is detecting motions
0:54:05 > 0:54:07that occur both at the lava lake surface
0:54:07 > 0:54:10and also inside this bowl, that can be vibrating.
0:54:13 > 0:54:16You don't think of a caldera this big as being an air mass
0:54:16 > 0:54:18- that may be going up and down.- No.
0:54:18 > 0:54:20But that's what we have discovered,
0:54:20 > 0:54:23the crater actually acts as a musical instrument.
0:54:24 > 0:54:27First, the microphones need to be installed.
0:54:28 > 0:54:30To detect the infra sound tone,
0:54:30 > 0:54:32Jeff and Chris place groups of them
0:54:32 > 0:54:35at several locations around the crater,
0:54:35 > 0:54:37as close to the edge as they dare.
0:54:37 > 0:54:39Go from here to there.
0:54:39 > 0:54:41- Yeah.- And from here to there.
0:54:41 > 0:54:42OK.
0:54:49 > 0:54:52It's not long before they are producing results.
0:54:53 > 0:54:55So we've collected some data.
0:54:55 > 0:54:57It looks like a bunch of wiggles on a screen to me.
0:54:57 > 0:55:00What noise is the volcano making?
0:55:00 > 0:55:02Right, so, we can't hear infrasound,
0:55:02 > 0:55:04but we can speed it up and we can make it audible.
0:55:04 > 0:55:06Here's an example of the infrasound being sped up...
0:55:06 > 0:55:10- RATTLING - ..by a factor of 40.
0:55:10 > 0:55:11This, to me, is exciting.
0:55:11 > 0:55:15I see the data, it's good, good quality, and I am happy.
0:55:16 > 0:55:18Different infrasound tones
0:55:18 > 0:55:21correlate with different levels of the lava lake.
0:55:21 > 0:55:24Installing a network of microphones within the crater would mean
0:55:24 > 0:55:26the level can be monitored remotely,
0:55:26 > 0:55:30and any dramatic changes in the lake level used as a warning.
0:55:30 > 0:55:33So it would be fair to say that infrasound could help better
0:55:33 > 0:55:35protect the people of Goma from a volcanic eruption?
0:55:35 > 0:55:38So, I'm a scientist and I'm naturally cagey about
0:55:38 > 0:55:40answering a question like that but, yes, I do believe
0:55:40 > 0:55:44that infrasound is a fundamental tool for volcano monitoring
0:55:44 > 0:55:47and, not too far down the road, we will be able to use
0:55:47 > 0:55:51infrasound monitoring here to better forecast Nyiragongo's next eruption.
0:55:56 > 0:55:59The science team are packing up, ready to head out of the crater.
0:56:03 > 0:56:06It's a time to reflect on what's been achieved.
0:56:12 > 0:56:15The volcanoes can live for millions of years and we're here for a couple
0:56:15 > 0:56:18of weeks, but we're getting the beginnings of an idea of what
0:56:18 > 0:56:20this volcano is capable of doing.
0:56:24 > 0:56:29Their work has revealed that, for the moment, Nyiragongo is quiet,
0:56:29 > 0:56:30but when it does next erupt,
0:56:30 > 0:56:33the lava is likely to reach Goma faster than ever.
0:56:36 > 0:56:39They've also established that infrasound could be a way
0:56:39 > 0:56:42to remotely monitor the lake level,
0:56:42 > 0:56:44a key warning sign of an eruption.
0:56:48 > 0:56:50Nyiragongo is not an easy volcano to study.
0:56:50 > 0:56:54It is a massive headache in terms of getting people and equipment here.
0:56:54 > 0:56:56The motivation for it is very clear.
0:56:56 > 0:56:59There are a million people living very close to this volcano
0:56:59 > 0:57:01so, despite all the problems, it's worth it.
0:57:04 > 0:57:07The expedition has also worked with a local volcano observatory
0:57:07 > 0:57:11to help prepare the people of Goma for the dangers of living
0:57:11 > 0:57:13in this highly volcanic landscape.
0:57:15 > 0:57:16I've been thinking more and more
0:57:16 > 0:57:20about how people here can manage to do the impossible thing
0:57:20 > 0:57:24of living with this volcano that is such a constant threat to this city.
0:57:24 > 0:57:26On the one hand, the volcano
0:57:26 > 0:57:29is deeply connected to deadly epidemics,
0:57:29 > 0:57:32to the destruction of houses, the destruction of communities.
0:57:32 > 0:57:36And, of course, you can't quite live with that idea.
0:57:36 > 0:57:38It's hard to hold it in your head.
0:57:38 > 0:57:41But the work the scientists are doing in predicting the eruption
0:57:41 > 0:57:44will give people time, maybe to not save their property or their houses,
0:57:44 > 0:57:48maybe not to save their land, but at least to save themselves,
0:57:48 > 0:57:50and that does give you a hope of rebuilding.
0:57:56 > 0:57:58Next time, the team move on
0:57:58 > 0:58:01to an even bigger and more violent volcano...
0:58:03 > 0:58:07..and discover how these volcanoes affect every aspect of life here,
0:58:07 > 0:58:12from endangered wildlife to the conflicts this region has suffered.