Soufrière : le réveil redouté du volcan le plus instable des Caraïbes – Documentaire Catastrophe- GD

La Soufrière est un volcan actif et imprévisible qui nécessite une surveillance constante. Les équipes de l’observatoire multiplient missions, mesures et analyses pour comprendre les signaux de la “vieille dame”, dont l’histoire est marquée par l’éruption de 1976 et des tensions scientifiques majeures.👉 Les meilleurs documentaires ? Ils sont ICI 👉 https://bit.ly/2zfgboK 👈 Abonnez-vous !

00:00 — Présentation de la Soufrière et du contexte géographique
03:03 — Premières techniques de surveillance volcanique
06:03 — Communications, stations et infrastructure scientifique
10:01 — Réunions, instruments et analyses des gaz
13:03 — Expédition au sommet et conditions extrêmes
17:39 — Gaz volcaniques et recherches biologiques
22:42 — Exploration interne et déformations du volcan
26:39 — Crise de 1976 et conflit scientifique
30:26 — Conséquences sociales, économiques et mémoire locale
34:45 — Biodiversité et parc national
38:34 — Cyclones et adaptation des écosystèmes
41:47 — Sources hydrothermales et géothermie
45:56 — Réflexion finale sur les risques volcaniques

La Guadeloupe se présente géographiquement sous la forme d’un papillon aux ailes déployées. Basse-Terre, l’aile gauche du papillon, en impose avec son relief les nombreuses rivières et ravines qui la traversent.
Basse-Terre compte six volcans. Soufrière, le plus jeune, montre une activité soutenue. Son sommet est interdit à la population, seuls les scientifiques ont un droit d’accès.
Le réveil du volcan, l’été 1976 a marqué tous les esprits. La population s’attend à une nouvelle éruption.

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Soufrière, la vieille dame indomptable
Réalisé par : Philippe Lespinasse
Tous Droits réservés

#Soufriere #VolcanSoufriere #VolcanGuadeloupe #EruptionVolcanique #VolcanCaraibes #Guadeloupe #DocumentaireVolcan #Volcanisme #DangerVolcanique #ObservatoireVolcanique #Eruption1976 #RisquesNaturels #CatastropheNaturelle #Caraibes #ScienceVolcanique

It’s an island in two parts. On one side, an arid plateau,
white sand beaches, a mangrove and large seaside resorts. On the other side, Basse-Terre is of
volcanic origin, covered with a tropical forest above which rises
the highest peak in the Lesser Antilles, La Soufrière. It’s a dangerous volcano. It is probably one of the
most dangerous volcanoes in the world. Do you think we’ll have
an eruption soon? If it’s just a sum of money
, I’m not going to leave. Battered by winds and storms,
shrouded in fog for most of the year, the summit is a
diabolical tangle of crevasses, craters and faults, from
which gases and burning mud constantly escape.
Sale. There is a lot of wind and therefore,
for some techniques, it is not possible to see. But that’s what a volcano is,
especially an active volcano. There are flank destabilizations
which cause suspended or embedded materials to fall and wash away. The
Guadeloupe Volcanological and Seismological Observatory is a hive where all the specialists
in modern volcanology, chemists, geologists, physicists,
are able to work in complete autonomy. Here in Guadeloupe, there are quite a few
climatic hazards, there are cyclones, etc. We need to be able to deal
with all of this. A complex and still unknown system,
volcanoes have not yet revealed all their secrets. The sulfur mine is about to become operational. But no one can predict when. It’s a mountain that you don’t
walk on like other mountains. Constant humidity,
vegetation that devours the paths, permanent landslides
and a colossal presence. What you can find right here,
on this ground, is ash. And here, it is a completely
altered ash which, if you look closely, was used to make the clay necessary for humus,
here, so that the plant kingdom could establish itself. And that was the case, for example,
on that entire collapsed section. And when you look closely, once
the small plants are established, the large plants can establish themselves. And as a result, the plant kingdom
takes on its full scope. Thierry Quitou and Tristan Didier, an
engineer at the Seismological and Volcanological Observatory of Guadeloupe,
regularly have to use the paths that run
along the slopes of the volcano. They know that the sulfur mine is alive
and requires constant attention. This is a leaf that we monitor,
for example in extension metry, because we know very well that in terms
of deformation, when magma or any other material wants to
rise to the surface, it deforms the volcano. And so, in ’76,
what happened on August 30th, precisely, everything that was in there came out
and rolled down the slope. And we think that this could play a role
in a future eruption or any future eruption. So we monitor this type
of place, which is characteristic of us. And in fact, we install what are called
measurement points between the two sides of the fault. It is an automatic acquisition system
that transmits data directly to the Observatory and we will be able to process it
automatically to understand what happens when the volcano
is calm, that is, at the moment, that is, when there is no
eruption, when there is nothing. And when the volcano
erupts, for example. A little further on,
it’s practically a jungle. Overgrown by vegetation, the trails
can disappear in a few days. Only those who have already come
several times can find their way back. The equipment here
is put to the test. What you see there is a
geophysical station, a seismic station. And this seismic station
simply measures ground movement. So every time the ground
makes any vibration, this station is able
to transcribe that into a signal, the movements of that ground. So what we’re going to do is
connect to the antenna up there ,
and we’re going to try to get the maximum signal with that antenna,
because from time to time, we don’t know why, there are
interruptions related to the radio link. I think that otherwise, what we can do
is, we take this piece there,
we reattach this piece there with the two tabs, and we put the collar
directly onto this piece there. Without the tube. All right. Okay, I see what you mean. As high as possible. Do you need something to loosen it with,
or will you loosen it by hand? I think you’re serving by hand. In the team,
Thierry is in charge of instrument maintenance and Tristan tinkers,
fiddles, invents systems that cannot be found commercially. Yeah, it’s Tristan and Thierry.
Here, we’re on the ground. Because, Michael, you’re receiving us too? The two engineers are essentially left
to their own devices in the wilderness. We have a small problem with the wifi antenna. We have a small problem with
the orientation or azimuth with the scale and we would like to know if
you can give us an angle relative to our point. There’s no network here. Only the good old Toki Woki
allow you to call the Observatory. 155 degrees, your turn. 155, I confirm. Do you want a bomb in the geographical area
for North Manitoba, please? Confirm for us, it is
indeed the North Magnetic. Geographic North. Geographic North, very good, thank you. The station was reopened for a few months
before being swallowed up again by vegetation or disrupted by a cyclist. Just as we were about to leave, the sulfur mine
finally revealed itself. Then, on the right side,
an enigmatic figure appears. Do you see the man lying there? Or the woman to sleep with? With your mouth open?
Yes. Perhaps it’s her, Mrs. Souffrières. She screams towards the sky.
There. Perched on a dormant volcano and
facing Soufrière, the
Guadeloupe Volcanological and Seismological Observatory is the headquarters of scientists. From here, we monitor the volcano 24 hours a day
, as well as the seismology of the entire Lesser Antilles region. Whether in the field or in the offices,
a team of 15 people works in shifts around the clock. Sébastien de Roussy, who arrived more than 10 years ago, is an engineer. Today, he is one of the oldest members
of the Observatory. So here we are on the north terrace
of the Observatory, the one facing the Guadeloupe volcano. As is often the case,
we don’t see her today because she has her head in the clouds. Most of our field stations
are energy self-sufficient. There are
solar panels and batteries. And also equipped with telemetry,
they automatically send the data to the Observatory. It happens via the desert route. Once we get there, the data
arrives, it passes through the wires. And so, by following the cables,
we arrive at the computing room, the heart of the Observatory, where all
the data is processed and archived. That’s the general operating principle, let’s say
. It frequently happens that when
the sulfur mine is clear, particularly if, for example,
there are a few days which are quite rare, where it is very calm and sunny,
there is no wind, the sulfur mine is clear, and the fumaroles rise vertically. Well, there you go, everyone’s putting down their
computers to go and take a look at me. That’s something we never get tired of
. So here we arrive in the
archives room where seismicity has been recorded since
the beginning of the Observatory. At the time, seismologists worked
with soot paper, which is called… So in fact, it was a kind of
Kraft paper that had passed over some smoke. There was a potion to prepare before
lighting it, which produced a lot of smoke. And so, the seismometer came and
scratched the leaf here. It was by scraping away the soot that
the seismic traces were revealed. So, we can see that at the Observatory,
here, it was in 1968 that we switched from
soot rollers to rollers with ink. So, an ingrained technique. What’s the result of that? And so, here are a few signals. Those ones date from April 12, 1960. And so, there’s a little bit of a
comeback here. And we really went completely
digital in 2004 at the Observatory. At the Observatory, every Monday morning,
the week begins with a meeting. The goal is to coordinate
and centralize all information. Around the table, Roberto Moretti, the director, one of the world’s leading specialists in volcanic gases. Séverine Moud, the deputy director, is
also a volcanologist. Sébastien, Thierry and Tristan,
whom we have already met, as well as the other members of the team. One of the characteristics
of the Observatory is not only to bring together different
skills and specialties , computer scientists,
volcanologists, chemists and geologists,
but above all to be able to repair, invent its own tools, and
program software. In the field as well as in the offices,
you have to be autonomous with the feeling that everything you do is
of almost vital importance. So that’s called a multi-gas system. This is to measure different
chemical species in fumaroles. So, we have some at the top
that continuously measure the chemical composition, and it is
the variability of these chemical compositions that can give us
information about what is happening deeper down. And we have one, so this one,
which is portable, which allows us to take measurements pretty much
anywhere in the country. Are you capable of tinkering and
inventing systems? No, I’m not capable. That’s precisely why I called on my colleagues,
because I’m not capable of doing that myself. So, that’s why,
especially in an observatory, I would say that in a research lab,
we are perhaps more isolated, we may work more,
precisely, via emails, there are Skype calls with other researchers
abroad, but we are a little more isolated. But here at the Observatory, we
really need to all work together. So, we are all really complementary
and that’s what makes things move forward. They both had messages there, that’s it. Can’t
you leave it? That’s good. Bring us back. The observatory has just received
a new wind turbine which will supply energy to one of the stations in the field. The previous one was
destroyed by a hurricane. I’ll look at the documentation,
we’ll find a tube that has good… It says so, it’s… We want an observatory
that works no matter what. Here in Guadeloupe, there are quite a few
climatic hazards, there are cyclones, etc. We need to be able to deal
with all of this. Whatever happens, let’s call it a risk,
we can overcome it and continue to function. If there had been an eruptive crisis, we would have had to
adapt. Everyone is Jean-Christophe Komorowski, is a volcanologist, is in charge of all French observatories. Former director of the
Guadeloupe Observatory himself, he constantly returns
to La Soufrière, conducts missions there, and brings students there. He has already climbed the volcano hundreds
of times, and will lead us to the summit, in an area closed to the public,
too dangerous. But I’ll only know that
after a tour. For the students,
this will be an exceptional outing. We’re going up there via a trail that is
closed quite quickly to tourists except those accompanied by guides wearing masks.
All right. So, as soon as we reach the summit
near the Fumeroles, we need to put on the masks. Okay, let’s go. A little courage. After a few minutes of walking,
a driving rain and a strong wind caught the under-equipped group,
who were clearly unprepared to brave the elements. The teachers are not very happy. You had too good weather
the first time you went up there. You were seeing real conditions. It was very good. The thing is, every time we
explain, nobody believes us. People need to
take a good shower. Those are our conditions. They say: No, you’re exaggerating. That’s
it. And then he left the fault line. What’s going on ?
It’s raining. The weather is like La Soufrière,
so it’s raining heavily. There is a lot of wind and therefore,
for some techniques, it is not possible to see it. There are techniques, multigas,
with electrochemical sensors, there is electronics involved. When we want, one,
the gas is not representative of what we are studying because there will be rain
which will catch some gas, which will cause the pannage to fall. So it’s not representative
of what we want to study. And secondly,
there’s a risk of damaging the instrument. So, as a result, we can’t. We go back down . Jean-Christophe continues with the students and with David
to take temperature measurements. In a mixture of thick fog,
icy wind, burning and corrosive
fumaroles, the rest of the group finally reached the Dome of La Soufrière,
where Roberto, the chemist, was to take gas samples. What do you do
with this recipe? I’m getting cold. The water needs to be applied
to the bulb to cool it down, so that the winter doesn’t explode after a while. Is that right ? That’s because it’s
water vapor that comes out each time. That’s the most important thing. And the goal is to prevent
our system from overheating. So. So, we try to reduce the temperature
and therefore the pressure inside the nozzle. You’re still using your
tools, you told me. Absolutely. The problem is that psychologically,
when you’re in the Caribbean, you think: It’s going to be hot.
Warm temperatures are expected. It’s 16 degrees here. With the wind at 70 km/h,
it must be maybe 10 degrees. But we’ve already been deceived. It can get approximately 7 to 9 meters
of rain per day on the blowhole. The people in the operating room are doing an
extraordinary job because it is very difficult to maintain equipment
in these conditions of 100% humidity all the time. Even when it’s sunny,
there’s humidity. There may be slightly fewer, 80,
but there is still humidity. And in the whole area that is affected
by the winds, there are acidic gases coming out of this material. These are hydrogen sulfide gases, H2s,
sulfur dioxide, CO₂, a very small amount, mainly
water vapor and CO₂ and HCl. That’s why I also enjoy doing this. I’m going to do my business in there because
you can’t bite there, I’m going to do my business in there. Under the supervision
of Jean-Christophe Komorowski, a doctoral student is also taking
samples, with the aim of finding bacteria
capable of living and developing in extreme environments. Today, it is believed that life did
not appear in the oceans, but on Earth,
in the form of soups of bacteria and amino acids, in
volcanic lagoons 3.5 billion years ago. It is perhaps in an environment as hostile as this one that the first living matter was received. The research is not finished,
but the students are frozen, a little terrified, and do not have the strength
to feel sentimental about the origins of the world. The defining characteristic of La Soufrière
is its chronic instability due to very rich and sustained hydrothermal activity
over time. Which causes the volcano to collapse. But obviously, if it collapses,
it rebuilds itself. And so, there is
also classic magmatic activity for this volcano, with explosive eruptions
marking its history. It’s a dangerous volcano. It is probably one of the
most dangerous volcanoes in the world. Not the most dangerous,
but it is one of the most dangerous volcanoes, also because there is a form
of forgetting and a form of perception of its nature that does not match reality. La Soufrière is showing
signs of activity. Volcanologists must
therefore constantly conduct observation missions. An eruption does not necessarily start
from the summit, but sometimes explodes the flanks of the volcano. Recruitment.
That’s the only thing… Apparently, there has been a recruitment drive.
Yes, yes, yes, there you go. Retained? That’s
it. Detained. That’s what
I told him. OK, agreed. The Observatory team is
like the crew of a ship facing storms, far from any help. This is the case for research
and missions, but also for more prosaic tasks
like meals that everyone eats together. No one is obliged,
but the Observatory is far from the city and this fosters team spirit. The observatory also has a
chemistry laboratory where samples can be analyzed
without having to send them to mainland France. And the laboratory
is Vincent’s kingdom. Here are the light bulbs that Roberto
and Arnaud have. I raised it this morning. As you may have noticed,
gas sampling is something extremely complicated. And gas analysis is
extremely complicated as well. Because while analyzing water is
extremely simple, analyzing a gas is just something
that is supposed to be quite fast in leaving the atmosphere
and being mixed with the atmosphere. So , there you have it. So, we’re going to analyze these light bulbs
on a machine we have here called a mass spectrometer. So, the analysis
will be quite quick. We will be able to shut off the pump here,
the suction, and release
the volcanic gas trapped this morning on the ground by opening the tap here. And this gas will travel all the way
to the mass spectrometer. When we combine this data with
that of the multi-gas, for example, we will be able to get an
instant idea of ​​the activity at the summit. And by looking at this data over
time and its evolution, we will get an idea if there are
significant changes at the summit of the volcano, if, for example,
magma is rising, there will be a composition,
a direct signature at the summit that will indicate these major changes. Then afterwards, when you get used to it,
you can see right away, even if you don’t have the figures in front of
you, whether the collection worked well. And in that respect, we can say that they did a
good job on the ground. So, we’ll have some great data
for this month. That’s great.
Hi Vincent. SO ? How are you ?
It’s good and you ? I have just finished analyzing the
ampoules you collected this morning. The three soda ampoules
from this morning worked well. So, we’ll have good figures
for this month, no problem. Okay, that’s perfect.
That works. Working on a volcano is
not like an architect working on a building. We do not know the initial drawings,
the initial projects, the initial plans, so we cannot calculate
the distribution of forces, tension, etc. We know some things here, but not much. We try to take information from the outside,
especially, of course, from the top,
to invert it and understand what is happening inside. It would be much better if we had
a nice image, a nice implant of how it’s made
inside, but sorry, nature did n’t give us those files. We are working with an object whose
internal workings we don’t fully understand. It is a partial image which, of course,
determines a certain ambiguity in any interpretation
of the measurements that are taken. We just need to move forward
and try to reduce this ambiguity. But we are making progress more and more. On the ground, we find Sébastien
and an intern heading out on a mission that will take them
almost into the bowels of the volcano. Here, she moves
very, very, very little. No, yeah. Yeah
. It was said that it would close
from the bottom. And today, you’re coming down, right? So, we’re going to go and measure it down there. Simply, at the bottom of the fault line, right there. Do you have a ladder to
go down or up? No, you have to do a bit of scrambling like that. Because right now, you’re… It’s not going to happen
quickly, is it? You managed to get down anyway. There’s a small hole you need to know about. And so, if there is
carbon dioxide, we leave. We have no way,
if you will, to breathe. And if the values ​​are too important… They cross paths with
hikers who are not allowed to go where they are going. Now, this is a slippery slope. I’ll go through that hole first. You will pass your bag.
Okay, let’s go. Okay, I have… There you go, and no, you can follow. It is the extraordinary variety
of situations between laboratory work and field trips to unique environments that makes the work
of volcanologists so fascinating. The fault is like a crypt at the center
of the Earth where no one ever goes. And we’re going in here. The time is 11:52. There is no wind. We will set the temperature at the end of the experiment. I’m giving you the value of the ribbon,
so it’s 2.20 meters. 2.20 meters. So. So here there are two cliffs,
we can say that they are two blocks of rock. So, there you have two blocks of rock. These two blocks
are located in the fault, there, and so they will move
relative to each other. They can move by sliding,
either horizontally or vertically, and possibly by spreading apart. Here, we are down below, at the foot of the volcano. The variations are truly minimal. We can see that the closer we get to the top
of the dome, the more we have an opening onto the faults. So, it’s really the dome that
tends to see it open up a bit like that.
Over the last few years, we’ve had… Over the last few years,
we’ve had about 7 millimeters of deformation per year,
over the last two years. There we go, things are moving. 30.72.
Okay, great. Well, there you have it . There’s a hole there.
We mustn’t fall into that trap. The fact that a volcano moves is normal,
there is no need to worry, but you should never stop monitoring it. Below, masses of magma weighing several
billion tons are just waiting to come out, as has already happened. In Guadeloupe, the situation
has suddenly worsened. At the La Soufrière volcano,
Professor Bruce’s team informed the regional prefect that a
magma chamber had suddenly increased its pressure. The pressure reached would become equivalent to the
power of several atomic bombs. In August 1976, after several weeks
of activity that destabilized the flanks of Soufrière, the prefect decided to
evacuate the entire Baster region. The episode has remained
in memory as much because the economy of Guadeloupe was permanently
altered as because dissensions within the scientific community, involving
two strong personalities,
were brought to light. On one side, Haroun Taziev,
the man who tamed volcanoes, a superstar of the era, an
unparalleled popularizer, whom Jean Cocteau had called a poet of fire. To consider that the sulfur mine
posed no danger and that there was no need to evacuate. On the other hand, Claude Allègre,
director of the Institute of Earth Physics, is therefore the
hierarchical superior of Haroun Taziev, an outstanding researcher with a
more technical, more rational profile, who thought it was necessary to distance himself. The volcanologist Georges Boudon was
director of the Guadeloupe Observatory, just after what was
called the war of the volcanoes. Looking back , we realized that we
knew absolutely nothing about this volcano, so we had no idea what
could happen since it had not been studied, or very little. So, we didn’t have knowledge,
precisely, of the importance of reconstructing the entire volcanological history, the
entire eruptive history, which is to know well the types
of eruptions that can occur. So, we didn’t have… Then, indeed, there was
Haroun Taziev, who was rather in favor of the interpretation
of a small phreatic activity without great magnitude. Others were like Claude Allègre,
others were rather saying: There may be a significant magmatic phenomenon
, a major eruption. And so, when you don’t know… And then we had the opposition between two
strong characters, Arun Taziev and Claude Allègre,
which meant that they quickly came into conflict. Claude Allègre dismisses
Haroum Taziev for serious misconduct. The sulfur mine does not explode. The Institute of Earth Physics is
still traumatized by the episode. There is a good guy and a bad guy,
but we shouldn’t fool ourselves. In any
case, between 15,000 and 30,000 people would have had to be evacuated in 1976. Because of the environmental pollution
that was generated by the eruption, even though it had remained,
as was the case, a non-magnetic eruption, let’s
say, of small magnitude. Haroun Taziev was right,
but he was wrong a few years later, on the occasion of the eruption of Mount
Saint Helens in the United States, which presented the same symptoms
that the volcanologist minimized and which he himself described as mini-sulfur volcanoes. The eruption caused
the death of 57 people. An overwhelming responsibility
constantly rests on the shoulders of volcanologists. At the Saint-Claude market,
everyone remembers the eruption of ’76. Me, I experienced the
art events just yesterday. I was young and it amused me. When the wind started blowing hard
, I was completely covered, completely noisy. It made me swoon because
I didn’t realize it. And then, a few hours later,
they announced that everyone had to be evacuated. So, everyone
in Basse-Terre left. We’ve made it to good land. The debate was because we
found ourselves without a home, without anything. We abandoned everything in Basqueterre,
we had left. As a result, Basqueterre
has suffered greatly ever since. While all the shops,
Basqueterre, the ports, all of that, everything is dead. So, we can’t just go back
and leave everything like this again. He told me: Look up there,
the suffering has exploded. I said: I’m going to get my children. I went to get them,
everyone was leaving. We left everything we had
at home and we left. When I stayed there
three months ago, I already came down on myself. I have returned to my homeland. The best thing was that there was
water, there was electricity. The children were at school
in Port-à-Prince, I took them away, I homeschooled my children. When they went to school in Wepuy,
they even swapped classes. When people returned, we
already had plenty of vegetables that I would go and sell on foot at the market. Because ash
was like fertilizer. The vegetables grew well,
it made a bouill. We grew a lot
of vegetables in Saint-Robel. Do you think we’ll have
an eruption soon? If it’s just ashes,
I’m not going to leave. I’m going to stay home. I am from Basse-derre,
I live at the foot of the volcano. Are the people here used to it? We don’t think about it. It’s you
scientists who are thinking about it. We know, you scientists, that we don’t think about it
. She makes her sobs and sounds. I can’t hear my heart down there,
and then, in my heart down there. The volcano is the same. The old lady has the right to live. She needs to show that she’s there. And for us too, to
help us say: Beware, they are thinking neither of Psynami,
nor of deceiving my heart, nor of cyclone. They are coming, they are coming to capture us. It comes as it comes, it’s as best we can. The
people of Guadeloupe are attached to La Soufrière, the old lady,
and they take life as it comes. The town of Saint-Claude never
recovered from the 1976 episode, because the evacuation order was maintained for five months. In 2004, the access road to the volcano was
cut off by an earthquake, and from 400,000 tourists,
there are now fewer than 100,000. This is the disheartening observation made by
a group of investors who decided to revive tourism with
the construction of a museum and an amusement park dedicated to the volcano. So here we are on the three
hectares of land on which the reception park is planned. So, the Volcano Museum, in reality,
has 300 square meters of museum space, roughly 300 square meters of 4D cinema. There will be two 4D cinemas. There will be a lava tunnel. In other words ,
we go down and there is a simulation of a lava flow and a pyroclastic flow,
to get a visual idea of ​​what it looks like. And we will also try to teach
people the reactions they should have in the event of an
earthquake, the possibility of a tsunami, and the actions to take. Inspired by Vulcania in Auvergne,
the Volcano Park project is not without controversy,
because after the first phase of the amusement park,
a cable car is being rebuilt which would allow people to get close to the summit. Our idea is to build a cable
car that would pass over the canopy. That is to say, the desire to avoid cutting down even a
single tree. We will have a magnificent view of the whole of
Basse-Terre and of La Soufrière volcano, whether going up or down. Today, the people of Saint-Claud
no longer go up to the sulfur mine. I used to go up with my parents. Every Sunday or one Sunday, one day,
two, we would go up, we would spend an hour at the sulfur mine. I rarely went up to the summit with them,
but I would go for a walk to the cistern. It was a walk
that got us back in shape. My parents were happy. It was a short walk before
Sunday lunch. And it was a habit,
but one that many Saint-Claudiens had. Today, a large part
of the population does not go up there. Young people in Saint-Claude today do
not know about La Soufrière. The elected officials are generally in favor of it. Environmental groups
are strongly opposed to it. This is a societal issue. Should we leave the volcano alone
or try to take advantage of it in some way? La Soufrière is part
of the Guadeloupe National Park. Do we need a sanctuary
or development zones? And a simple question, a
very simple question indeed: why do we live at the foot of volcanoes? Volcanoes are one of the
most extraordinary environments on Earth when the volcano is not active. It creates topography,
therefore it creates rain, the sulfur volcano and the water tower of Guadeloupe. This is indeed one of the problems
since 90% of the population in Guadeloupe drinks water that comes from the lowlands
and in particular from the Guadeloupe sulfur mine. This obviously creates very rich soils. Volcanic ash brings
minerals that mix with the soil. At first, the vegetation dies, but afterwards
it enriches the soil and we have very high productivity. In Indonesia, it is possible to have up to
three rice harvests per year. Volcanoes have always been valued by
human civilization, by ecosystems, plants, and animals. But you have to know how to manage it,
you have to know how to distance yourself from them when they become very active. There are already many species there.
Everything looks the same. Nothing looks more like one tree than
another tree, except perhaps that tree fern there, which we see,
which is not very widespread. These are very old ferns. They were there
during the time of the dinosaurs. And this, this climbing vine,
which is firmly attached, which produces a fruit. And the fruit, it’s perfectly round
and it’s called brocouille. Professor Félix Lurel teaches
botany at the University of Pointe-à-Pitre. His specialty
is species endemic to volcanic soil,
because just as humans enjoy living near volcanoes,
a specific flora has made its home there. There’s too much stuff here. You don’t know where to look
, I tell you. Walking with Félix in the forest
is like navigating a living encyclopedia of natural poetry. It’s amazing how good it feels. Beautiful red flower. No dry areas. Then, there are little flowers there. Minor psychotria. Wow, that’s magnificent.
Look at this. Look at this.
Look at. So. Suspended like that, like a garden, there. It’s suspended. And then that too,
all of that, is endemic. And that’s rainforest,
tropical rainforest. That’s a treasure for the planet. That’s a treasure for the planet. We have a duty
of responsibility for this. There, there was no human settlement
that brought small seeds, small fruits.
That’s indigenous. It’s the forests, it’s the cyclones,
it’s the vegetation with all the local heritage. Because we have this because of
cyclones and volcanoes. It is because of these
geological and climatic conditions that we have this forest. So it was once this system was put
in place with all these phenomena, all these
atmospheric disturbances and others. How do these
trees survive cyclone season? How are they still standing? Species have strategies,
different strategies. Many species will drop
their branches to let the wind pass through. Others will break. Others have a power of germination, of
regeneration, a very important power. Even with anastomoses
between the trees. There are trees that will
form welds. Welding and exchanges. They give themselves a little strength,
a little sap here and there. You were more affected than I was. I still have a few leaves. They send him a little flow,
a little energy. Yes, that’s how it works. So, a great deal of solidarity,
a great deal of interdependence. It’s a system that works. The species have
complementary strategies that are perfectly adapted to these climatic and other conditions. This entire forest massif
acts as a water tower. And the volcano, due to the mountainous topography, has an altitude of 1460 meters. For the Lesser Antilles, that’s a lot. So, that stops the clouds. In order to cross this
mountain barrier, the clouds are forced to lighten. They must rise, rise. And as they become lighter going up, they
also lose water through condensation, since it gets colder and colder at the
top. That means that in total, on the peaks here,
of this forest massif in Guadeloupe, 10 meters, 12 meters of water are falling.
Sometimes, they are world records. It is one of the
rainiest places on the planet. Yeah, you really need to stabilize yourself so
that each step can support your body. Hey, you mean? Yeah, it’s intense. Like all his colleagues at the
Volcanology Observatory, Vincent, the chemist, carries out field missions,
but what he is looking for is not easily accessible. After gas or gap measurements,
water samples will provide indications about the evolution of the volcano. Wait. I’m listening. Regarding conductivity,
could you please give me the values? And could you please tell us the values
of the other parameters? Conductivity, it’s at 1085.
Yes. So. Ph, we’re at 6.59. Thank you, great. So today, to follow
the activity of the sulfur mine. There are obviously different disciplines. So today we’re going to study
hydrothermal vents. So, the springs at the level
of the sulfur mine, there are about ten that are monitored monthly. And these sources have been monitored
for several decades. These are sources that we know
and that we follow over the long term. And that is of paramount importance. The thing is, from one month to the next, the
source isn’t going to vary enormously. It is by monitoring
over a very long period of time that we will be able to see
fluctuations in the signal. All right ? Because we are dealing with
volcanic systems that generally evolve slowly. And so, if the temperature is going to increase,
it will increase over a very long period of time , taking on a few tenths
of a degree, a few degrees in a few years, decades. Volcanic water can be used
as an indicator, but also as an energy source. In Abouillante, on the slopes of the volcano,
a geothermal power plant has been producing electricity
for Guadeloupe since 1984. Because the relatively recent geological configuration
of Soufrière and its sustained activity mean that at a
depth of only 350 meters, boreholes allow fluids to be brought up
at 250 degrees and thus heat water. Unique in France,
the electricity produced covers 5% of the island’s energy needs. And right opposite the power plant,
the surplus heated water is discharged into the sea, creating a small
natural open-air jacuzzi for the inhabitants. The future of geothermal energy
probably lies at sea, as new thermal springs have just been
discovered offshore. Unlike other
energy sources, geothermal energy cannot be exhausted. Tristan, check if you have any rope. We find Vincent and Tristan
on the slopes of the volcano, who, after passing under waterfalls,
now have to use ropes to reach their sampling site. The water from this spring that we are going to
collect was at about 80 degrees in 76. And gradually,
the monthly or regular monitoring of this spring shows
a decrease in temperature. And today, we’re pretty much
at room temperature. The river we have next to us
is the Carbet River, which originates on the slopes of La Soufrière. It is mostly meteoric water,
that is to say, rainwater. On the other hand, laterally,
as we have here, we have hydrothermal sources,
so waters that seep in and interact with
the heat flows and volcanic gases that rise from the bowels of the earth. These sources are extremely charged
with ions and dissolved gases, and generally have a very acidic pH. Is this surface water
that enters the volcano and then flows out very quickly? Or is it water
that stagnates for several months, or even years, in the volcanic edifice
and therefore interacts strongly with heat flows
and volcanic gases? So that’s a question we’re still asking ourselves
today. And research is working
to answer these kinds of questions. Volcanoes retain their mysteries and care little for humans. The geological agenda and the
human agenda do not align. It is the goal and the heroic mission
of scientists to make them coincide in order to avoid catastrophes. The population has
a different perception of time. And this notion of time and space
is difficult to convey. So, we remember
the last eruptions. 1976 was traumatic,
but ultimately, it wasn’t 1902. 1956, the previous non-magnetic eruption
, was very small. We no longer have any perception of the
1812 eruption, much less that of 1836, much less that of 1797. These are all the known,
historical eruptions of La Soufrière, non-magnetic. But they all produced deposits,
phenomena that reached between one kilometer and 2.5 km in distance. And we have populations living
two kilometers apart. But this volcano, it has been producing lava for
about 400,000 years, the volcano of the great discovery Soufrière. That’s why we’re at an
altitude of 1,500 meters. But these were enormous eruptions
that lasted for a very long time. So these things happen. We must accept adapting and
living with our volcano, but consciously, that is,
not hoping that nothing will happen. We hope that nothing will happen, or we don’t hope that anything will happen
. In short, it is difficult to formulate what one
expects from a volcano or what one does not expect. Volcanologists strive
to understand, want to avoid human tragedies at all costs
, but deep down they dream that volcanoes will explode. In any case, the old lady will do
as she pleases.