Ce n'est pas un Astéroïde qui a Fait Disparaître les Dinosaures

Sympa

Saviez-vous qu'il se pourrait que ce ne soit pas un astéroïde qui ait exterminé les dinosaures ? Des recherches récentes suggèrent que l'activité volcanique et le changement climatique auraient pu jouer un rôle important dans leur extinction. L'impact de l'astéroïde a certainement causé le chaos, mais l'environnement changeant de la Terre mettait déjà à l'épreuve la population des dinosaures. Imaginez ces pauvres dinos faisant face à des éruptions volcaniques et à des changements climatiques drastiques en plus de l'impact de l'astéroïde ! C'est un revirement fascinant dans l'histoire de la disparition de ces créatures incroyables.  Animation créée par Sympa. ---------------------------------------------------------------------------------------- Musique par Epidemic Sound https://www.epidemicsound.com   Pour ne rien perdre de Sympa, abonnez-vous!: https://goo.gl/6E4Xna​ ---------------------------------------------------------------------------------------- Nos réseaux sociaux : Facebook: https://www.facebook.com/sympasympacom/ Instagram: https://www.instagram.com/sympa.officiel/  Stock de fichiers (photos, vidéos et autres): https://www.depositphotos.com https://www.shutterstock.com https://www.eastnews.ru ----------------------------------------------------------------------------------------  Si tu en veux encore plus, fais un tour ici:  http://sympa-sympa.com

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00:00Are you sure that an asteroid is really responsible for the extinction of dinosaurs?

00:05The mystery surrounding the disappearance of these terrifying creatures

00:08arouses many debates, both in the scientific field and on the big screen.

00:12But what really happened?

00:14How did scientists elucidate this enigma?

00:17And why is it so important?

00:19Let's explore this question together.

00:21Let's go back to England in 1842,

00:24when a scientist named Sir Richard Owen

00:27devoted himself to the study of fossils of gigantic reptiles.

00:30He noticed that three of these creatures,

00:32the Megalosaurus, the Iguanodon and the Hilaeosaurus,

00:36had common characteristics.

00:38Seized by a brilliant intuition,

00:41he decided to group them under a new term,

00:44Dinosauria, meaning terrible, lizard in Greek.

00:50At that time, scientists were content to classify dinosaurs

00:54according to their appearance.

00:56Then, Charles Darwin came up with a revolutionary theory,

01:00species evolve over time.

01:03This idea shook up pre-existing conceptions

01:06and forced researchers to rethink the classification of dinosaurs.

01:10They introduced a new method called

01:13phylogenetic classification.

01:16Imagine a huge genealogical tree

01:19encompassing all the creatures that never existed.

01:22At the top of this tree,

01:24we find the Megalosaurus and the Iguanodon.

01:27And we say that all the descendants of these dinosaurs

01:30share a common ancestor.

01:32It's a bit like tracing your own genealogical tree

01:35to the original ancestor of dinosaurs.

01:38All this seemed to be an excellent plan

01:41until things got complicated.

01:44By studying dinosaurs,

01:46we discovered species with feathers,

01:49beaks and other blood.

01:51This is how we realized that birds were cousins of some dinosaurs,

01:56or even their direct descendants.

02:02After understanding this,

02:04scientists had to reexamine the genealogical tree of birds

02:08and redefine the very notion of dinosaurs.

02:11In the end, they concluded that birds were, in a way, dinosaurs.

02:16But not exactly.

02:18Disconcerting, isn't it?

02:20Anyway, we now have two distinct groups.

02:23The first is made up of birds.

02:25The second group is made up of non-avian dinosaurs,

02:28which are now extinct.

02:30Therefore, instead of asking ourselves

02:32what caused the extinction of dinosaurs,

02:35we should rather ask ourselves

02:37what caused the extinction of non-avian dinosaurs.

02:41The answer seems obvious.

02:43We often think that a gigantic asteroid

02:45is the cause of the extinction of dinosaurs,

02:48and this is probably the first idea that comes to mind.

02:51Even Google and other search engines agree on this point,

02:55like classmates copying their homework from each other.

03:02History teaches us that about 66 million years ago,

03:06dinosaurs practically all disappeared,

03:09except for those that evolved into birds.

03:12Of course, reality is more complex.

03:14All dinosaurs did not suddenly disappear.

03:17Some naturally disappeared,

03:19and minor extinctions occurred

03:21throughout their terrestrial existence.

03:23But the major event we are talking about

03:26looks like a change of scenery in a movie,

03:29as if a TV channel was suddenly turned on.

03:32And the Earth went from the era of dinosaurs to that of mammals.

03:36Scientists call these periods the Cretaceous and the Paleogene.

03:40We even have a name for this particular event,

03:43the K-Pg or K-T extinction.

03:46Some also refer to it as the event of 65 million years ago,

03:50although the most precise date is rather 66 million years.

03:54Two main theories predominate,

03:57the brutal impact of a repeated asteroid or volcanic eruptions.

04:01Let's talk about the hypothesis of the asteroid.

04:04Imagine, about 66 million years ago,

04:07a colossal asteroid hitting the Earth.

04:10This object was about 10 km in diameter,

04:13that is, a little bigger than Mount Everest.

04:16Breaking through the sky at a staggering speed,

04:19it moved at a hundred times the speed of sound.

04:22During its impact, it released an immense amount of energy.

04:26This cataclysm was called the K-Pg.

04:29This cataclysm occurred in what is now southern Mexico,

04:33near the famous crater of Chicxulub,

04:36linked to the extinction of dinosaurs.

04:39Everything that was near the impact was instantly vaporized.

04:43Imagine the most massive explosion that the Earth has experienced in several billion years.

04:47Nothing survived in this area.

04:50Then, the repercussions were felt.

04:53As the fireball dissipated, the surface of the Earth sank into chaos.

04:57The ground trembled and distorted,

05:00triggering earthquakes of unimaginable magnitude.

05:03The continents looked like huge inflatable castles in full delirium.

05:11Then, the debris projected into the atmosphere by the impact

05:14began to fall back into a dense rain.

05:17Even if you were not near the huge fragments falling in Mexico,

05:21you would have been hit by these tiny burning particles

05:25that were flying in the air.

05:27The atmosphere became so hot that entire forests

05:30spontaneously caught fire all over the world.

05:33And that's not all.

05:35Prepare for a gigantic tsunami.

05:37The bottom of the ocean was totally shaken,

05:40pushing gigantic waves into the land around the Gulf of Mexico.

05:45But even that was not enough to eradicate all the dinosaurs.

05:49Those of New Zealand, for example, seemed relatively spared.

05:53So what happened to make them all disappear?

05:56They first felt a slight shake,

05:59then the sky began to darken and become gloomy,

06:02as if it was night.

06:04And suddenly, a thick mantle of ash began to slowly envelop the entire planet.

06:13Now, this is where the real drama begins.

06:16The major problem with the impact of this asteroid

06:19does not lie in the explosion.

06:21As one might imagine, but rather in its long-term effects.

06:25Imagine the debris thrown into the sky,

06:27masking the light of the sun.

06:29The days turning into nights,

06:31and the temperatures falling abruptly.

06:33The herbivorous dinosaurs quickly periclited,

06:36leaving the carnivores feasting.

06:38But not for long.

06:40Without the light of the sun, the food chain collapsed very quickly.

06:44Then the ashes fell back on the ground,

06:47aggravating the situation again.

06:49Harmful elements, such as carbon dioxide,

06:52began to float in the air.

06:54This carbon dioxide, combined with fragments of the seabed,

06:57caused extreme temperature variations.

07:00The earth alternated between intense heat and ice cold.

07:04It was then that 50 to 80% of the dinosaur species disappeared forever.

07:09What is even more tragic,

07:11is that this figure only accounts for the species themselves.

07:14This figure is much higher,

07:16if we consider the number of affected individuals.

07:20We might think that the mammals

07:22finally had their chance after the disappearance of the dinosaurs.

07:25But even they had to go through difficult times.

07:28We are very lucky that some mammals,

07:30among the most resilient,

07:32survived this chaos.

07:34Those who survived were real little champions.

07:38Endowed with rapid metabolism,

07:40flexible food regimes,

07:42or perfectly sheltered terriers.

07:47But this story is just a hypothesis.

07:49There is another theory,

07:51that of volcanism.

07:53Volcanoes, these mountains of fire,

07:55are used to vomit lava,

07:57and to cause incomparable ravages.

08:00Surprisingly, this theory does not concern explosive eruptions,

08:04but something slower and more pernicious.

08:07About a million years before the disaster of the dinosaurs,

08:10a great upheaval occurred under the surface of the Earth.

08:14Deeply buried under what is now India,

08:17a river of magma began to form,

08:20gradually warming the region.

08:22Then, India was violently hit,

08:25turning into a sea of lava,

08:27similar to a burning ocean.

08:30As if a multitude of Ben trucks

08:32were slowly pouring out their lava content.

08:35These solidified residues are known as the Deccan Trap,

08:39a deep layer of solidified lava

08:41covering an area the size of France.

08:47Just like in our history of asteroids,

08:49the real problem with volcanism lies in the air.

08:53For hundreds of thousands of years,

08:55sulfur dioxide spread like an unstoppable shadow,

08:59darkening the sky and causing acid rains.

09:03Food sources turned into poison,

09:06and the oceans became acid baths.

09:08Then, carbon dioxide took over.

09:11It was like playing with a thermostat,

09:13completely disrupting the Earth's climate.

09:16This led to a real chaos.

09:19Ecosystems were disrupted,

09:22food chains were broken,

09:24and species were extinguished one after the other.

09:28These two theories seem quite credible.

09:31Experts engaged in great debates

09:33to determine which was correct

09:35and explain why dinosaurs disappeared.

09:38So, what is the real answer?

09:41Unfortunately, we still don't know.

09:43Some scientists defend a theory,

09:46while others prefer the latter,

09:48leaving us all perplexed.

09:51But don't be too harsh on the media or scientists.

09:55They do their best to elucidate the mystery

09:57of the disappearance of dinosaurs,

09:59and maybe one day we'll finally discover the real answer.

10:02So, stay tuned.

10:05NASA Jet Propulsion Laboratory, California Institute of Technology

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