Les scientifiques gardent un œil attentif sur les supervolcans, car si l'un d'eux entre en éruption, cela pourrait signifier la fin de l'humanité ! Ces volcans massifs, comme celui sous Yellowstone, ont le pouvoir de projeter tellement de cendres dans le ciel qu'elles pourraient occulter le soleil pendant des années. Cela signifie refroidissement global, récoltes ratées et chaos total. Bien que des éruptions de cette ampleur soient rares, les experts disent que ce n'est pas une question de si, mais de quand. La bonne nouvelle ? Les scientifiques travaillent sur des moyens de prédire et de se préparer à une telle catastrophe. Mais si un supervolcan décide de se manifester, nous n'aurons peut-être d'autre choix que de croiser les doigts ! 😬🔥 Animation créée par Sympa.
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FunTranscript
00:00Scientists predict a volcanic eruption likely to be among the most devastating in human history.
00:08The probability that such an event will occur during this century is one in six,
00:13and these repercussions could not only further alter the climate, but also threaten millions of lives.
00:20In January 2022, the Hunga Tonga Hunga Haapai volcano erupted in the South Pacific Ocean,
00:27generating an explosion of considerable magnitude.
00:30This eruption triggered tsunamis that reached the coasts of Japan and America.
00:35The Tonga, on the other hand, suffered damage of such a magnitude
00:38that they represented nearly 20% of the country's gross domestic product.
00:42Researchers at the Niels Bohr Institute in Copenhagen
00:45analyzed ice carcasses taken from Greenland and Antarctica,
00:49and their conclusions are alarming.
00:51A world-scale volcanic disaster could occur.
00:55According to them, the probability of an eruption of an intensity 10 to 100 times higher than that of the Tonga is real.
01:02In the past, cataclysms of this magnitude have profoundly disrupted the climate,
01:07and have even led to the collapse of certain civilizations.
01:10Although the threat of a major volcanic eruption is evident,
01:13specialists believe that the world is not prepared at all.
01:17Michael Cassidy, a volcanologist at the University of Birmingham,
01:21warns against the lack of significant effort to anticipate such a disaster.
01:26He underlines that NASA and other space agencies
01:29are devoting billions of dollars to protection against asteroids,
01:34while a supervolcanic eruption remains a much more likely scenario.
01:38However, to date, no global plan has been developed to face an event of this magnitude,
01:44despite the devastation it could cause.
01:47The last magnitude-7 eruption occurred in 1815 on Mount Tambora, Indonesia.
01:53In the space of a few days, thousands of people lost their lives.
01:57This event also disrupted the climate and caused shortages worldwide,
02:01affecting millions of people.
02:03This is the most powerful eruption ever recorded.
02:06It projected a colossal amount of particles into the atmosphere,
02:10which obscured the sunlight, causing a cooling and plunging the world into chaos.
02:15The following year, the eruption was nicknamed the year without summer.
02:19Temperatures fell, crops were destroyed, famine spread,
02:24and a cholera epidemic killed tens of thousands of people.
02:28A striking detail?
02:29The eruption would have even inspired Mary Shelley to write Frankenstein
02:33when she was forced to stay locked up during this unusually cold summer of 1816 in Switzerland.
02:40Since then, many volcanoes have erupted,
02:43but none equaled Tambora in intensity.
02:46More than two centuries later, scientists warned of a new volcanic threat.
02:51A super-eruption could be imminent, and the world could not be prepared for it.
02:56While researchers seriously evaluate this probability,
02:59experts call for urgent measures before it is too late.
03:04A large-scale volcanic eruption today could prove even more devastating than the year without summer.
03:10Contrary to the time, we are already facing climatic upheavals
03:14and an increased fragility of global systems, which would amplify the consequences.
03:19Dr. Michel Rampinot, a specialist in geology,
03:22warned that the current instability of the world would make a modern mega-eruption even more catastrophic.
03:28Paradoxically, greenhouse gases from fossil fuels
03:31could accentuate post-eruption cooling instead of mitigating it.
03:35In other words, volcanic activity could be a direct threat to humanity.
03:41Dr. Thomas Aubry, a volcanologist,
03:44pointed out that with a warmer and more unstable atmosphere,
03:47sulfur dioxide released by an eruption would spread faster and further than before.
03:52This gas generates sulfate aerosols, which reflect sunlight
03:57and thus contribute to global climate cooling.
04:01These tiny particles, by dispersing more uniformly,
04:05would have a cooling effect even more pronounced than in 1815.
04:09Another Cambridge-based atmosphere specialist
04:11emphasized that their size played a crucial role in the absorption of sunlight.
04:16In a warmer future climate, an eruption could thus accentuate 15% surface cooling.
04:23Many unknowns still exist.
04:25The researchers at the University of Geneva
04:27estimate that we are just beginning to measure the magnitude of the effects of such a phenomenon.
04:31In addition, the estimation of the risks of future eruptions remains difficult,
04:35due to the lack of precise data on ancient volcanic events.
04:39To trace past volcanic activity,
04:41scientists study the ice caps of Greenland and Antarctica,
04:45as well as the cones of ancient trees,
04:48real archives of climatic variations.
04:51These analyses reveal that several eruptions
04:54that occurred over the last millennia
04:56have temporarily cooled the planet from 1 to 1.5 degrees.
05:01One of the most devastating eruptions was that of Samalas in 1257, in Indonesia,
05:07whose power would have triggered the Ice Age,
05:10a period of global cooling that lasted several centuries.
05:13More recently, the eruption of Mount Pinatubo in 1991 in the Philippines
05:18caused a slight terrestrial cooling for a few years.
05:22Thanks to satellites, scientists were able to accurately measure
05:25the amount of sulfur dioxide released and its atmospheric impact.
05:30Despite modern technologies, satellites and seismic instruments,
05:34predicting the next major eruption remains a challenge.
05:37However, even without being able to determine the exact moment,
05:41it is possible to study extreme scenarios
05:43to help authorities anticipate the crisis.
05:46This involves, in particular, the development of evacuation plans
05:49and the formation of food reserves
05:51to deal with the possible loss of crops caused by global cooling.
05:56The alteration of meteorological regimes could increase volcanic activity.
06:01The melting of glaciers eases the pressure exerted on the underground magma,
06:05thus increasing the risk of eruptions.
06:07In addition, the recrudescence of violent precipitation
06:10promotes the infiltration of water into volcanic faults,
06:14which can lead to violent explosions caused by steam.
06:17This phenomenon affects both active volcanoes and those in sleep.
06:21Faced with these dangers,
06:22scientists have established a map of the volcanoes
06:25most prone to climate change.
06:28Their analysis reveals that the most threatening supervolcanoes
06:31are located in Iceland, Chile and Indonesia,
06:35regions where glaciers melt rapidly
06:37or where precipitation increases spectacularly.
06:41A 2022 study identified 716 volcanoes around the world,
06:45i.e. about 58% of known active and emerging volcanoes,
06:49likely to be agitated by extreme precipitation,
06:52which could increase the risk of a new small ice age.
06:56Now let's go back to the eruption of the Hunga Tonga-Hunga Haapai,
07:00which occurred on January 15, 2022.
07:03Scientists have confirmed that it generated the highest volcanic panache
07:06ever recorded.
07:09This underwater volcano in the South Pacific
07:11projected a cinder cloud at an altitude of 57,000 meters,
07:15surpassing all the eruptions previously documented.
07:18What makes this event even more exceptional
07:21is that it is the first volcanic panache to reach the mesosphere,
07:25the third layer of the Earth's atmosphere.
07:28This zone, located at an altitude of 50,000 meters,
07:31is where meteors consume and give birth to shooting stars.
07:36To determine the height of the panache,
07:38researchers at the University of Oxford and RAL Space
07:41used data from three geostationary weather satellites.
07:45Until then, the record was held by the eruption of Mount Pinatubo
07:49in 1991 in the Philippines,
07:51whose panache had culminated at 40,000 meters.
07:54It is interesting to note that this type of measurement
07:57is only possible thanks to recent advances in satellite data,
08:01and that 10 years ago such an analysis would have been impossible.
08:05Another volcano to be closely monitored
08:07due to its destructive potential
08:09is located on the Icelandic peninsula of Reykjanes.
08:12Its last eruption, which occurred in November 2024,
08:16led to the evacuation of the surrounding areas.
08:18Volcanic activity began shortly after 11 p.m.,
08:21without major signs of precursors,
08:23releasing a stream of orange lava
08:25from a 3-kilometer-long crack.
08:27Authorities ordered the evacuation of about 50 houses
08:30as well as the thermal complex of Blue Lagoon,
08:32a tourist destination located southwest of Reykjavik.
08:36Although air traffic has not been disturbed,
08:39authorities have nevertheless warned
08:41about the potentially toxic gas dispersion
08:44in certain areas of the peninsula,
08:46notably on the outskirts of the city of Grindavik.
08:49This locality of 3,800 inhabitants
08:51has been faced with volcanic activity many times
08:54and has undergone eruptions in the past
08:56that damaged its infrastructure
08:58and forced its inhabitants to evacuate.
09:01Thus, in August 2024,
09:03a crack of 3,800 meters
09:05opened at the level of the Sundnukskigar crater,
09:08near Grindavik,
09:09forcing authorities to decree an emergency
09:12while the lava was spreading in several directions.
09:15Fortunately, Icelandic meteorological services
09:18have indicated that this last eruption
09:20was significantly less important
09:22than the one that occurred in August.
09:24Geophysicists performed aerial surveys
09:27and found that the intensity of the event
09:29was less compared to previous eruptions.
09:32For now, Grindavik is not in immediate danger,
09:35but a resumption of activity cannot be ruled out.
09:38Researchers indeed estimate
09:40that new volcanic eruptions are to be foreseen.