00:00At the end of December 2021, an underwater volcano with a rather exotic name, the Unga Tonga, woke up after several years of sleep.
00:09He did it with so much energy and strength that people heard the eruption over 180 km away.
00:15He then fell asleep, but a few weeks later, he woke up again with a strength seven times greater.
00:22He cut the island above him in half.
00:25The lightning storm that broke out following the eruption was the most intense ever recorded in history.
00:31The sound waves of the eruption went around the planet several times.
00:35Someone even heard a loud explosion in Alaska, 10,000 km away.
00:40The eruption triggered the first megatsunami known since antiquity.
00:44This tsunami cost the lives of two people in Peru and even caused trouble for two Californian fishermen.
00:51But that's not all. This eruption could have changed the weather conditions of our planet for several years.
00:58You may have seen the first signs of it in the summer of 2024, which were said to be abnormally humid.
01:07Scientists believe that the eruption was caused by an immense accumulation of gas.
01:12Different minerals, including anhydrite, quartz, and sulphur, would have accumulated for several months
01:18until the flowways were blocked and the gas trapped inside the Hunga Tonga.
01:23Normally, when a volcano erupts, its smoke causes a temporary cooling on the surface of the earth.
01:30But the eruption of the Hunga Tonga was different.
01:33It did not produce a lot of smoke, but released a huge amount of water vapor equivalent to 60,000 Olympic swimming pools.
01:40The intense heat of the eruption transformed huge amounts of seawater into vapor, which it then projected into the atmosphere.
01:47All this water vapor ended up in the stratosphere, a layer of the atmosphere far too dry for clouds to appear.
01:55Scientists have no data on this type of volcanic eruption,
01:59and are therefore unable to predict the effects it will have on weather conditions.
02:05They do not know exactly how long these effects could last.
02:09Indeed, the only way to measure stratospheric water vapor is to use satellites,
02:13and they have only existed since 1979, a period during which there was no eruption similar to that of the Hunga Tonga.
02:23Experts from different countries began to analyze satellite data just after the eruption of the Hunga Tonga.
02:29They wanted to know how long the water vapor would remain in the stratosphere, where it would go, and, above all, what it would mean for the planet.
02:38The first major consequence of the eruption was a huge hole in the stratosphere, which remained for several months in 2023.
02:46When it appeared, the water vapor had reached the polar stratosphere above Antarctica.
02:51But as a result, there will no longer be enough vapor to enlarge this hole.
02:56The Hunga Tonga will ultimately seem to have only a minimal effect on global temperatures.
03:01But some lasting and surprising regional effects are to be feared.
03:05One of our scientific models predicts colder and drier winters in northern Australia until around 2029.
03:12In North America, warmer winters are expected, and Scandinavia could experience even more rigorous winters.
03:19However, this is only a study and a way to understand how the eruption of the Hunga Tonga could change our climate.
03:28We have in history at least one example of a volcanic eruption that has shaken the planet.
03:33More than two centuries ago, in 1815, the Tambora erupted and caused a year without summer.
03:40The following year, the winter was exceptionally cold and humid in Europe and North America.
03:46A recent study has confirmed that the year 1816 would not have been as cold without this volcanic eruption.
03:54The immediate effects of the eruption were catastrophic.
03:58Tsunamis destroyed houses, 10,000 people lost their lives, and 80,000 others fell ill.
04:04The Tambora eruption was one of the most powerful in the last millennium.
04:08It ejected a huge amount of sulfur dioxide, which then quickly spread throughout the world.
04:14The result is that it had not been so cold for at least 250 years on Earth.
04:20In May, the frost destroyed most crops in the states of New York, Massachusetts, New Hampshire, and Vermont.
04:28In June, abundant snow fell on Albany, New York State, and Dennisville, Maine.
04:33New Jersey experienced five consecutive nights of frost.
04:36The cold continued until the end of the summer, which should have been the harvest season.
04:40But in July, lakes and rivers were still frozen to the northwest of Pennsylvania.
04:46And the frost persisted in Virginia until the end of August.
04:49Temperatures went from a maximum summer higher than normal to a temperature close to freezing point in just a few hours.
04:57The weather was totally unpredictable.
05:00Food prices went up sharply.
05:03The cost of oats for horses, which was the main means of transport, also increased significantly.
05:11Some think that this situation prompted Carl Drais to invent the bicycle in 1817.
05:20The Tambora completely changed the weather conditions, not for a year, but for three years.
05:26The entire planet cooled down, and the crops, which were bad, at least a million people died of hunger.
05:32Scientists know no volcanic eruptions, having caused more victims than the Tambora.
05:38But the Krakatoa eruption, in Indonesia, in 1883, is more famous than the Tambora,
05:45because the information about it spread all over the world via telegrams and photos.
05:51Its final explosion was the loudest sound ever recorded in history.
05:56People were able to hear it over 10% of the planet's total surface.
06:00The eruption caused a tsunami whose waves reached half the height of the Statue of Liberty, or 42 meters.
06:07However, it was less powerful than the Tambora eruption.
06:10The island that housed the Krakatoa disappeared during this event,
06:14but new eruptions, about 50 years later, created the cone known as the Krakatao Child
06:20in the center of the caldera of the old eruption.
06:23The new volcano is still rising from time to time.
06:27The Vesuvius eruption, which destroyed Pompeii, is one of the most famous volcanic disasters in history.
06:33It cost the lives of about 2,000 people, much less than the Tambora.
06:37According to a famous Roman author of the time, the eruption lasted 18 hours.
06:41Pompeii was covered with a layer of ashes and sandstone twice the size of a human being.
06:48The neighboring coast also changed spectacularly.
06:55In today's world, the consequences of volcanic eruptions are often more dangerous than the eruptions themselves.
07:02Thanks to technological advances, we can now predict eruptions with precision
07:07and implement safety measures such as evacuations and flight cancels.
07:12But the risks remain significant due to climate change and drought,
07:17especially in regions such as India, East Asia and East Africa, which are subject to fog.
07:26Volcanic eruptions can also have unexpected effects.
07:29Among them, we can cite the evolution of dinosaurs, which were initially big like cats
07:34and patiently awaited their hour of glory.
07:37This moment happened about 230 million years ago.
07:40This period was known as the Pluvial episode of the Carnian.
07:44Before that, the Earth had only one dry and arid supercontinent, the Pangaea.
07:48It was then that four major volcanic events projected huge amounts of carbon dioxide into the atmosphere.
07:56The temperatures and humidity of the planet then rose sharply.
07:59These massive eruptions were most likely caused by the eruption of the great province of Vrangelia,
08:05in what is now British Columbia and Alaska.
08:09This prolonged volcanic activity created the conditions conducive to the evolution and diversification of dinosaurs,
08:15as well as the appearance of other groups such as modern conifers,
08:19ferns, crocodiles, turtles, insects and the first mammals.
08:24With higher temperatures and more precipitation,
08:28terrestrial plants have evolved and the brightest in humidity have become dominant.
08:33Without these changes, our natural history could have been completely different.
08:38We have evidence that volcanic activity has really changed the weather conditions of the time.
08:44In the core of the Earth, scientists have discovered layers containing different types of carbon.
08:50This tells us that there were four massive emissions of carbon dioxide in the atmosphere.
08:55The data we have also shows us that high concentrations of mercury
09:00were caused by a major volcanic event that affected the global carbon cycle.
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