Saviez-vous qu'il y a eu une éruption en 2022 si spectaculaire qu'elle a laissé les scientifiques perplexes ? 🌋 Elle s'est produite sous l'eau lorsque le volcan Hunga Tonga-Hunga Ha'apai dans l'océan Pacifique a éclaté avec une force si énorme qu'il a littéralement envoyé des ondes de choc autour du globe. L'éruption a créé un panache de cendres qui s'est élevé plus haut que tout ce que nous avions jamais vu, atteignant même l'espace, et a déclenché un tsunami qui s'est propagé à travers les océans. 🌊 Ce qui a laissé tout le monde stupéfait, c'est la quantité énorme de vapeur d'eau que le volcan a propulsée dans l'atmosphère, ce qui pourrait potentiellement affecter les schémas météorologiques pendant des années. Les experts disent que cette éruption a été l'une des plus puissantes depuis plus d'un siècle, et pourtant si peu de personnes en ont entendu parler ! Animation créée par Sympa.
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FunTranscript
00:00On January 14, 2022, the inhabitants of Anchorage, in Alaska, heard a series of strong detonations.
00:07They continued for nearly half an hour.
00:10As they discovered later, the source of the detonations was located 9,650 km away,
00:17in the Tonga archipelago, in the south of the Pacific Ocean.
00:20The Tonga volcano suddenly woke up from its deep sleep.
00:31Its last eruption was at the end of December 2021, after 7 years of inactivity.
00:37The Tonga volcano had projected a large ash panache into the stratosphere,
00:42visible even from the capital located 69 km from the volcano.
00:46The following days, it had emitted steam and gas at an altitude of 11 km.
00:52In addition, it had released ashes that had accumulated on its flanks,
00:56and which had even increased the size of its island.
01:00It then fell asleep, and the authorities had announced that it was asleep.
01:05But a few weeks later, it woke up again, with crazy strength.
01:10It projected ash clouds 19 km into the atmosphere.
01:15These clouds blocked the sun in some places, and fell from the sky in the form of rain.
01:20The sound waves of the eruption formed several times around the planet.
01:24The inhabitants of the Fiji Islands heard a sound that reminded them of thunder.
01:28Some thunder even reached Canada.
01:30The shock waves were felt four times in Japan and Utah,
01:34and at least twice in Massachusetts.
01:37The eruption caused tens of thousands of lightning bolts.
01:40It also triggered a mega-tsunami several hundred meters high.
01:44It damaged buildings and infrastructure, such as underwater cables.
01:49These extreme waves spread to the Californian coast,
01:53and an unusually high tide occurred along the Pacific coast of Canada.
01:58Scientists then studied the seismic data to understand the causes of such a massive eruption.
02:04Their research model showed that there was a big explosion,
02:07probably because gas was trapped in the rocks,
02:10like in a cockatoo minute left on fire for too long.
02:13This explosion released a huge amount of energy,
02:16equivalent to five of the largest underground nuclear tests.
02:20This incident occurred in a shallow area of the sea,
02:23where the rocks were filled with gas.
02:29Normally, when a volcano erupts,
02:32its smoke causes a temporary cooling on the surface of the earth.
02:36But the eruption of the Hunga Tonga was different.
02:38It did not produce a lot of smoke, but released a huge amount of water vapor.
02:43The equivalent of 60,000 Olympic swimming pools.
02:46The intense heat of the eruption transformed large amounts of sea water into vapor,
02:51which was then projected into the atmosphere.
02:54All this water vapor was found in the stratosphere,
02:57a layer of the atmosphere too dry to form clouds or rain.
03:01Scientists, having no observations of this type,
03:04are not able to tell us if this eruption will have long-term effects on our weather conditions.
03:11Indeed, the only way to measure stratospheric water vapor is to use special satellites.
03:16And these have only existed since 1979.
03:20And there has not been an eruption similar to that of the Hunga Tonga during this period.
03:24In fact, the incident of the Hunga Tonga is the best documented eruption of this type in recent history.
03:30Scientists had many tools to study it.
03:33Satellites that took pictures from space,
03:36as well as sensors that listened to the vibrations and movements of the earth.
03:39A similar eruption took place in 1991 on a volcano in the Philippines.
03:45But at the time, scientists did not have instruments as perfected as today.
03:50Experts from different countries examined the satellite data just after the eruption of the Hunga Tonga.
03:56They wanted to know how long the water vapor would remain in the stratosphere,
04:00where it would go and, of course, what it would mean for the planet and for all of us.
04:05The first significant result of the eruption, at least in part,
04:08was a huge hole in the stratosphere, which remained for several months in 2023.
04:14When it appeared, the water vapor had reached the polar stratosphere above Antarctica.
04:20But the eruption of the Hunga Tonga
04:22finally had only a minimal effect on global average temperatures, at least for now.
04:27Let's hope it will not repeat the history of the Tambora, in present-day Indonesia.
04:31More than two centuries ago, in 1815, this evil volcano erupted
04:36and caused a year without summer.
04:38The following year, winter was exceptionally cold and humid in Europe and North America.
04:44There were also catastrophic tsunamis,
04:47which destroyed houses and cost the lives of 10,000 people,
04:51and 80,000 others fell ill as a result of these events.
04:55It is impossible to miss an event like the eruption of the Hunga Tonga or Tambora,
04:59but some underwater volcanoes are discovered by accident.
05:02A passenger on a commercial flight, who was looking through the window above the Pacific Ocean,
05:07saw a stain of a strange color on the water.
05:10She thought it could be an oil stain,
05:13or floating sandstone,
05:15an indicator of a recent volcanic eruption.
05:19She decided to send a photo of this area to a geologist.
05:22And that's how scientists discovered one of the largest volcanoes in the world,
05:27the Havre.
05:28It is hidden about 900 meters below the surface.
05:31In 2012, this volcano experienced a massive eruption,
05:35which lasted about 90 days a day.
05:38Burning lava flowed from 14 different chimneys around its crater in the shape of a semicircle.
05:44The Havre is one of the many volcanic systems covered by thousands of meters of water.
05:48These volcanoes, the most active on the planet,
05:51are part of a gigantic system called the Medio-Oceanic Dorsal System,
05:55which extends all around the world.
05:57This system produces about 75% of all the magma that comes out of the Earth's volcanoes each year.
06:03It releases more than 2 cubic kilometers of lava.
06:06When the magma cools down, it forms the edges of new oceanic plates,
06:11which are like giant puzzle pieces that make up the earth's crust.
06:15A team of scientists studied the materials left at the bottom of the ocean
06:19by the volcanic eruptions of the Bronze Age.
06:21About 3,600 years ago, a partially submerged volcano in the south of the Aegean Sea
06:27erupted.
06:29This eruption destroyed the island of Santorin
06:31and projected huge amounts of ash, rocks and gas into the air.
06:36It left behind thick layers of ashes and rocks
06:40that piled up at the bottom of the ocean.
06:43Scientists have been studying the ancient eruption of Santorin for several years
06:47in order to understand what happens during eruptions of such magnitude.
06:52Their research allows us to explain how future volcanic eruptions
06:55could affect the climate of our planet.
06:58This study also helps scientists understand the force of eruptions,
07:03the height of eruptive columns,
07:05and the size of the waves that form when all the ashes and rocks
07:09settle at the bottom of the ocean.
07:11This information will help predict the dangers of future eruptions.
07:15When a volcano erupts,
07:17no one should be inside.
07:19But scientists have tried the experiment.
07:22In a way, they have developed a new intelligent imaging technique
07:27that uses the best methods of medical imaging and optical microscopes.
07:32Matrix imaging, as this technique is called,
07:35makes it possible to better understand what is happening underground,
07:38even when there are not many sensors available.
07:41These sensors, called geophones,
07:43detect and record the movement of seismic waves,
07:47i.e. vibrations that propagate through the earth.
07:50The study of these waves allows scientists to know the different types of rocks
07:54and their arrangement under the surface.
07:56Researchers tested their method on a volcano in Guadeloupe, in the Caribbean.
08:01There are not many geophones on this site,
08:03but scientists were able to combine the data of several geophones
08:07thanks to their new technology.
08:09They used a trick called memory effect
08:11to reverse the distortions that occur
08:14when seismic waves ricochet on different subterranean materials
08:18and find the appearance of the original signals.
08:20They were thus able to clearly see the interior structure of the volcano
08:24up to a depth of about 10 km,
08:26with incredibly detailed images of extremely high resolution.
08:31They discovered that there are many layers of magma stored underground.
08:35These layers are related to other deep parts of the planet.
08:38The knowledge of these layers and their behavior
08:41could allow scientists to better predict the moment of eruption of a volcano.
08:45If they succeed, they may be able to warn people earlier
08:49and protect them from the most destructive events.