00:00A gigantic volcano that everyone thought was gone,
00:04woke up one day and projected a cloud of black ash
00:08rising 80 km high,
00:10about 9 times the height of Mount Everest.
00:13Located in present-day Indonesia,
00:15the powerful Krakatoa caused huge tsunamis
00:18that affected ships up to South Africa.
00:20It also altered world temperatures for several years.
00:24The volcanic island of Krakatoa, in the detroit of the probe,
00:27was probably born thanks to another major eruption
00:30that occurred several centuries earlier.
00:32The volcano had not erupted for nearly 200 years
00:35before 1883.
00:36Also, the first earthquakes and explosions in May of that year
00:40took the rivers by surprise.
00:43The ships, taking this very common maritime passage,
00:46began to signal the clouds of ash
00:49rising above the volcano.
00:51Even when it became calm again,
00:53ashes continued to swirl above.
00:56The eruption culminated at the end of August
00:58and was so violent that it literally pulverized the island.
01:02The sound of the explosion was heard all the way to Australia,
01:05almost 5,000 km away,
01:07and was described as a terrible rumble of artillery.
01:10Some say it was the loudest sound ever heard in human memory.
01:14Over the next 5 days,
01:16the shock wave of the eruption,
01:18detected by barometers on various continents,
01:20circled the Earth three and a half times.
01:23Pyroclastic flows
01:25swallowed the slopes of the volcano at dizzying speeds,
01:28covering up to 40 km away.
01:30They destroyed the neighboring islands
01:33and killed 36,000 people.
01:35Tens of thousands more
01:36perished in the tsunamis triggered by the volcano's collapse
01:40in its own caldera.
01:41More than a hundred coastal villages in Java and Sumatra
01:44were completely razed.
01:47The Krakatoa eruption
01:49has thus become one of the most devastating volcanic events
01:52in the history of mankind.
01:56Earth's crust looks like a huge puzzle
01:58made up of large pieces called tectonic plates.
02:01These plates constantly slide against each other along the mantle,
02:04a layer of fused rocks just below.
02:07However, Indonesia is precisely at the heart of a subduction zone,
02:11where the Indo-Australian plate collides with part of the Asian plate
02:15as it moves north.
02:17When the oceanic plate plunges down,
02:19it warms up,
02:21creating ideal conditions for a volcanic hot spot.
02:24The Krakatoa had three summits,
02:26each used as an evacuation for the huge magmatic chamber below.
02:30During a previous eruption, debris had obstructed one of its exits,
02:34causing an accumulation of pressure.
02:36When the Krakatoa finally exploded,
02:39the detonation deeply cracked the magmatic chamber.
02:43This eruption triggered what is called a volcanic winter.
02:47The Krakatoa projected 25 km3 of rocks,
02:50ashes, dust and debris into the atmosphere,
02:53forming a thick veil around the Earth.
02:56These particles dispersed the sunlight,
02:58cooling the troposphere upside down.
03:01This effect lasted for several years.
03:04The northern hemisphere experienced temperatures lower than average.
03:07And in some regions,
03:09the summer temperatures could no longer reach their usual levels.
03:12Southern California also recorded record rainfall
03:16in the months following the eruption.
03:19The sky remained dark in various parts of the globe
03:21for years after the eruption.
03:23Sunsets became real spectacles,
03:26sparkling with red and orange for many months.
03:30An astronomer even assumed that this could have inspired
03:33the cry of Edvard Munch,
03:34whose painting perfectly illustrates the Norwegian sky
03:37the day after the eruption.
03:40The Krakatoa also produced a rare type of halo called Bishop's Ring,
03:44as well as a violet volcanic glow at dusk.
03:48Several years after the eruption,
03:50the moon appeared blue, and sometimes green.
03:52Because some ash clouds contained large enough particles
03:55to disperse the red light, leaving everything but other colors.
03:59Some even observed a lavender blue sun,
04:01and bright clouds at night.
04:04The Krakatoa became the first volcanic eruption
04:08to be studied and documented so extensively.
04:11Between the first ash emissions detected by a ship
04:14and the catastrophic eruption,
04:15scientists managed to organize geological expeditions
04:19to study the volcano and collect samples of its rocks.
04:23These efforts were crucial to better understand volcanic activity.
04:28This volcano remained dormant until the 1920s,
04:31when inhabitants noticed a column of vapor and debris
04:34spilling out of the collapsed caldera.
04:37In a few weeks,
04:38the edges of a new cone emerged above sea level.
04:42After a year, it formed a small island called Anak Krakatoa.
04:46It continues to erupt, but fortunately, without serious consequences.
04:51At least for now.
04:52In April 1815, Mount Tambora caused a massive eruption
04:56that devastated the Indonesian island of Sumbawa.
04:59This disaster destroyed the habitats and killed 10,000 people.
05:04Subsequently, 80,000 others died as a result of respiratory diseases
05:08spread by the eruption.
05:09The following year would be recorded in history as the year without summer.
05:14Cold and humid conditions seized Europe and North America,
05:18causing unexpected cooling.
05:20This was the coldest summer period in nearly 250 years.
05:24Temperatures dropped significantly,
05:27preventing crops from growing,
05:29decimating livestock,
05:30and provoking famine in the West.
05:32In New England, strong frosts were even observed during the summer.
05:36Food prices skyrocketed,
05:39drilling for horses was a real luxury.
05:42Some even claim that all this would have led to the invention of the bicycle in 1817.
05:48Scientists used preliminary data and climate models
05:52to determine if the eruption of Tambora was the cause of these phenomena.
05:56They compared the data of that year with that of similar years,
06:00and found that the rainfall was about the same,
06:03but that the temperatures were much higher.
06:06By integrating the effects of the volcano in their simulations,
06:09they obtained results corresponding to those of the year without summer.
06:13According to them, such a powerful volcanic eruption
06:16would increase the probability of extreme cooling by up to 100 times.
06:22The explosion of the Toba supervolcano on the island of Sumatra,
06:25which occurred about 74,000 years ago,
06:28represents the largest terrestrial volcanic eruption in the last 28 million years.
06:32Regions of Indonesia, India and the Indian Ocean
06:35were covered by a thick layer of volcanic debris about 15 cm thick.
06:40The eruption caused a volume of rock equivalent to nearly 3 million Empire State Buildings,
06:45and the crater left by this explosion is still visible from space.
06:49The volcanic ashes and gases ejected into the atmosphere partially masked the light of the sun,
06:55triggering a rough volcanic winter that lasted 6 to 10 years.
07:00Some anthropologists establish a link between the eruption of the Toba
07:04and the limited genetic diversity of modern humans.
07:07At this precise time, we can observe a notable demographic decline,
07:11which explains why all modern humans can trace their origins
07:15down to a small group of survivors.
07:17The theory of the Toba disaster suggests that most of the first humans in Europe and Asia
07:23did not survive the climatic upheaval following the eruption.
07:27On the other hand, a more fortunate and genetically identifiable group found refuge in Africa.
07:33However, archaeological and paleoclimatic archives cannot confirm this theory.
07:40Dr. Benjamin Black of Rutgers University and his team
07:44have tried to clarify this paradox
07:46and discovered that we may have studied the climate under the wrong prism.
07:50They carried out 42 simulations of different climatic models,
07:54varying the magnitude of volcanic emissions, the season of the eruption,
07:58the ambient climatic state and the height of the eruption column
08:01in order to determine possible climatic disturbances caused by the eruption of the Toba.
08:06The results showed a significant decrease in temperatures in the northern hemisphere
08:10during the first year following the event, which could reach 10 degrees.
08:14However, the southern hemisphere, where the first humans settled,
08:18did not experience severe cooling, likely to affect them.
08:23The most significant eruptions, capable of seriously altering global climatic models,
08:28come from supervolcanoes such as Yellowstone or Mount Toba.
08:33Fortunately, these eruptions are extremely rare
08:36and only occur once every 100,000 years or more.
08:40However, climatologists study these eruptions to understand
08:44and explain the short cooling periods in the history of our planet.
08:49Every few decades, a volcanic eruption releases a substantial amount of particles and gas.
08:55Some of these eruptions block the light enough
08:58to cause a brief period of global cooling,
09:01felt around the world,
09:03even if this phenomenon does not reach the intensity of a true volcanic winter.
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