00:00The scientists came to reconstitute one of the biggest volcanic eruptions in the history of the Earth.
00:07And the more they have creased the subject, the more it was alarmant.
00:11It is more than 350 000 years ago, the center of the island of the Nouvelle-Zélande had a very
00:17different face.
00:18The mountains that we see today didn't exist anymore.
00:22The climate was more cold and the region was in full air glaciers.
00:26The winter was rude and the temperatures remained low every year.
00:31Everything seemed calm and peaceful.
00:33Finally, on surface.
00:35Sous-Terre, something accumulated again and again,
00:39up to the point of rupture.
00:42A great eruption hit the volcanic zone of Topo,
00:47the eruption of Fokamaru,
00:49one of the most powerful ever recorded on Earth.
00:52It wasn't a single mountain that was produced.
00:54It was a whole volcanic system,
00:57extending from Wakahari, White Island, to Ruapu, to the south.
01:03A fragile zone of the terrestre was detached and fractured at the same time.
01:08A force pushed the magma to the top,
01:11one other pushed the ground.
01:14This combination still aliment the region today.
01:17But at the time, it reached the extreme.
01:20The eruption of the ocean had reached so much material,
01:23that the sand had spread out in large parts of the Nouvelle-Zélande.
01:27The surface was so thick that it had soiled the soil
01:31under the strates of volcanic rocks and debris.
01:33Like if we had to break a thousand kilometers of stone in all the country.
01:39Today, this same zone has been a cold source,
01:41and all that depends on the same system, a bit more calm, but still there.
01:51The volcanic zone of Toppo is active for about 2 millions of years
01:55and has produced at least 4 super eruptions.
01:59It was not a small event.
02:01On the number of volcanic explosions,
02:04they reach the level of 8, the maximum known to this day.
02:09On the number of dozens of eruptions of this type on Earth.
02:13The recent eruption of Doruanui,
02:17around 25300 years ago.
02:19It was even more luminous and created what is today the lake Toppo.
02:24Other than, Fouakamaru was not an isolated accident.
02:28It's what this volcanic system does from time to time.
02:34The super eruptions are one of the most big cases-têtes for scientists.
02:39How a huge mass of magma can accumulate under the air,
02:43monter in pressure,
02:44then explode almost from one single coup?
02:47To understand it, the researchers study the vestiges,
02:50of the ancient volcanoes.
02:52There are two types of.
02:54The first, the depots of decoudment,
02:56laid by the avalanches of roaches brulantes,
02:59of gases and of cendres,
03:01called pyroclastics.
03:03All this mass défaire the ground like a fire,
03:07then solidify.
03:10The other type of proof is the depots of retombées.
03:14These are the materials more light,
03:15like the cendres, the crystals and the ver volcanic.
03:19Projected very high in the atmosphere,
03:22they return to the ground.
03:24The problem is the time.
03:27Most of these depots do not survive.
03:29They are empty, empty, fragmented.
03:32What remains is often dispersed on huge distances.
03:37The super eruption of Fouakamaru
03:40has exactly this kind of chaos.
03:42An enormous pyroclastic
03:44formed of dense rocks
03:47in the regions of Fouakamaru
03:49and King Country.
03:51More deep,
03:52the cendres and pierre ponce
03:53have spread quite a bit more large,
03:56covering a large part of the North
03:58and reaching even the areas of the Pacific Ocean.
04:01To rebuild the puzzle,
04:04the researchers have first found
04:05the origin of each fragment.
04:09They have created a database
04:11of volcanoes and compared them
04:14with a chemical signature
04:15covered in small fragments
04:17of volcanic rocks.
04:19Each eruption
04:20lets a chemical mix
04:21slightly different.
04:23With this method,
04:25scientists have analyzed
04:26more than 30 sites in New Zealand
04:28and in the South Pacific.
04:30And despite the distance
04:31between the particles,
04:32all correspond to the same source,
04:35the super eruption of Fouakamaru.
04:38The researchers have finally
04:40reconfigured
04:41what happened
04:41during the most
04:43big eruptions
04:44of the history.
04:46At the start,
04:47the center of the
04:48island of the North
04:48was probably
04:49a large lake,
04:50similar to the lake Topo
04:52today.
04:53Then,
04:54the magma
04:54has perched the surface
04:55in the middle of this
04:56of the water.
04:57It's there
04:58that everything is
04:59emboldened.
05:00When the magma
05:01touches the water,
05:02it turns out
05:03instantaneously
05:04in vapor.
05:05It can make an eruption
05:06extremely destructive.
05:08And it's
05:09definitely
05:09what caused it
05:10to cause.
05:12At the beginning,
05:13a massive
05:14magma
05:14magma
05:15could probably
05:15make an eruption.
05:17But very quickly,
05:18the situation has changed.
05:20The eruption
05:21continued
05:21and the lake
05:22has been destroyed,
05:23combed by the volcanic materials.
05:26And once
05:26the water disappeared,
05:27the style of the eruption
05:28has changed.
05:30It's becoming
05:30more dry
05:31and more direct.
05:33And
05:33on the ground,
05:34something even more
05:35grave was happening.
05:37In lieu
05:37of a single
05:38magma
05:38magma
05:39slowly,
05:40the system
05:41divided into
05:42many active areas.
05:44At least 5
05:45reservoirs
05:46distincts
05:46could enter
05:47in eruption
05:47simultaneously.
05:50The production
05:51of sand
05:52became extreme.
05:53Most of the
05:54island
05:55and even
05:56the distant island
05:56Tchattam
05:57were found
05:58with about 30 cm
06:00of volcanic material.
06:02More close
06:02of the source,
06:03up to 4,5 mètres
06:04of depots
06:05cover the soil
06:06in some regions.
06:08Then,
06:08came to
06:09the pyroclastic
06:10currents
06:10of gas
06:12and of
06:12rocks
06:13at great speed.
06:14Close
06:15of the eruption
06:15they left
06:16of several
06:17tens of
06:18meters
06:18of
06:18many
06:19earth.
06:19When we add
06:20everything,
06:21the numbers
06:22are over
06:22the imagination.
06:24The eruption
06:25has
06:25expulsed
06:26about 2300
06:27kilometers
06:28of
06:28material.
06:29If
06:30the entire
06:32country
06:34would
06:34fall
06:34down
06:35to 9 mètres
06:37of
06:37volcanic debris.
06:38But the most
06:39terrifying
06:40is that the
06:41volcanic zone
06:41of Topo
06:42is the most powerful
06:45of the planet.
06:46The super
06:48eruptions
06:48such as the
06:49Wakamaru
06:50are rare.
06:50But the system
06:51has also produced
06:52numerous
06:53eruptions
06:53more modest
06:54they also
06:56to remodel
06:57of vast regions.
06:58That's why
06:59these research
07:00are not only
07:01geologists.
07:02It must
07:03understand how
07:04these eruptions
07:05pass from a unique
07:06source
07:06of magma
07:07to a multi-chamber catastrophe.
07:10Thus,
07:11we can anticipate
07:12what such a system
07:14capable of
07:14the future.
07:17And the New
07:18Zealand is not
07:19the only place
07:19where scientists
07:20are worried about
07:21volcanoes.
07:23One of the most famous
07:25examples
07:25is Yellowstone
07:26in Wyoming,
07:27Montana
07:28and Lidao.
07:29Some experts
07:30think
07:31a massive eruption
07:32would be in
07:33retard.
07:34The last eruption
07:35had been around
07:3670.000 years
07:37according to the
07:38Institute
07:38Geological
07:39America.
07:40And the last
07:41super eruption
07:42rise to
07:43about 640.000
07:45years.
07:46And yes,
07:47the volcano is still
07:48active,
07:49even if it is not
07:50the imminent catastrophe
07:51that most people
07:52imagine.
07:54We can see
07:55this activity
07:55in the surface.
07:57The Great
07:58Prismatic Spring
07:59is the biggest
08:00hot source
08:01of the United States
08:02and the third
08:02in the world.
08:04Its famous
08:05colors
08:05are living
08:06in different
08:08temperatures
08:09around the source.
08:11L'eau
08:12atteint
08:12environ 70
08:13degrés Celsius.
08:14Cette source
08:14est bouillante
08:15et c'est l'activité
08:17volcanique
08:17qui en est la cause.
08:21Le système
08:22magmatique
08:23sous Yellowstone
08:24est colossal.
08:25Il pourrait même
08:26être plus vaste
08:27qu'on ne le pensait.
08:28S'il entrait
08:29un jour
08:30en éruption totale,
08:31il pourrait libérer
08:32environ 2500 fois
08:33l'énergie
08:34du mont Saint-Hélens.
08:35Et cette éruption-là
08:37était déjà dévastatrice.
08:40En 1980,
08:42un séisme
08:42de magnitude
08:435,1
08:44a provoqué
08:45l'effondrement
08:46du flanc nord
08:46de la montagne,
08:47créant la plus grande
08:48avalanche de débris
08:49jamais enregistrée.
08:51L'explosion
08:52a rasé environ
08:53600 km²
08:54de forêts
08:55et coûté la vie
08:56à 57 personnes.
08:58Quoi qu'il en soit,
09:00toute cette activité
09:01souterraine
09:01ne signifie pas
09:02que Yellowstone
09:03va exploser demain ?
09:05En fait,
09:06on y enregistre
09:07entre 700
09:07et 3000
09:08petits séismes
09:09chaque année.
09:10Et la plupart
09:11sont si faibles
09:12que personne
09:12ne les ressent.
09:14C'est juste
09:15le sol qui bouge
09:16et s'ajuste
09:16en permanence.
09:18Mais si
09:19une super éruption
09:20se produisait
09:21un jour
09:21dans cette région,
09:22ce serait
09:23une catastrophe totale.
09:25D'abord,
09:26des coulées pyroclastiques
09:28ravageraient
09:28des parties
09:28du Montana,
09:29de l'Idaho
09:30et du Wyoming.
09:33recommenceraient à tomber,
09:34se répandant
09:35sur l'ensemble
09:36des Etats-Unis.
09:37Par endroits,
09:39les toits pourraient
09:39s'effondrer
09:40sous le poids
09:41de ces cendres lourdes.
09:42La qualité de l'air
09:44chuterait
09:44et les réseaux d'eau
09:45seraient contaminés.
09:47Cette réaction
09:48en chaîne
09:48pourrait déclencher
09:49une crise alimentaire mondiale.
09:51Mais ce n'est qu'un scénario
09:53hypothétique
09:53pour l'instant.
09:56N'oublions pas
09:57que même
09:57si les super volcans
09:58sont terrifiants,
10:00ils sont rares.
10:01Ce sont souvent
10:02les volcans
10:03plus modestes
10:03qu'il faut surveiller.
10:04et...
10:04pour l'instant.
10:05...
10:05pour l'instant.
10:05pour l'instant.
10:06...
10:06pour l'instant.
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