Imaginez si tous les océans disparaissaient soudainement—pourriez-vous simplement marcher vers d'autres continents ? Eh bien, sans eau, vous verriez d'immenses vallées et des plaines rocheuses escarpées qui étaient autrefois le fond de l'océan, reliant des endroits comme l'Amérique du Nord à l'Asie ! Mais traverser ne serait pas une promenade de santé ; le fond océanique est rempli de fosses profondes, de crêtes imposantes et de boue sans fin qui rendraient le voyage presque impossible. De plus, sans océans, la température de la Terre monterait en flèche, transformant ces zones asséchées en déserts brûlants. Vous seriez confronté à des défis sauvages comme des tempêtes de sable, le manque de nourriture et à peine d'eau douce pour survivre. Donc, techniquement, les continents seraient connectés—mais ce serait un voyage extrême que seuls les explorateurs les plus endurcis pourraient entreprendre ! 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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00:00The distance between New York and Lisbon, across the Atlantic, is well over 5,000 km.
00:06At an average walking speed, such a journey could be accomplished in about a month and a half,
00:11not counting the stops to rest and the necessary sleep.
00:14Although buying a plane ticket or embarking on a ship is one of the more judicious options,
00:19these are, to this day, the only ways to cover this distance.
00:23But if such a crossing on foot became conceivable one day, would you be tempted to take up this challenge?
00:28The most obvious obstacle remains the vast expanse of water that is the Atlantic Ocean,
00:33which covers about a fifth of the Earth's surface.
00:36The oceans as a whole occupy nearly 70% of the planet.
00:41When you open the tap or buy a bottle of water, you only consume a tiny part of this drinkable resource.
00:47Indeed, 97% of the Earth's water is contained in the oceans, in the form of saltwater, unsuitable for consumption.
00:55If we add the 2% of water trapped in the calottes and glaciers, less than 1% of the Earth's water is actually drinkable.
01:05If you were to convert these percentages into figures, you would need a very long sheet of paper.
01:10According to the US Geological Survey estimates, the volume of water on Earth exceeds 138,600,000 cubic kilometers.
01:18This resource is essential for the maintenance of all forms of life, including human.
01:22The oceans also play a key role in the regulation of global air temperatures.
01:27Without them, the regions located around the equator would experience extreme heat.
01:32This imaginary line, separating our planet into two hemispheres, passes through 13 countries, such as Brazil, Kenya and Indonesia.
01:40The oceans of the globe are fundamental to the water cycle on Earth, a process that you have probably studied at school.
01:47The precipitation from the clouds ends up feeding the rivers, which are then thrown into the oceans.
01:53As a result of solar radiation, this vast mass of water evaporates, rises into the atmosphere and forms new clouds, thus perpetuating the cycle.
02:02This mechanism directly influences the global climate.
02:06This is why the Mediterranean is so popular during the summer holidays, because the region benefits from a pleasant and temperate climate.
02:15If we remove the oceans from the equation, the water cycle would stop.
02:20The vast area they occupied would transform into a gigantic surface of dust.
02:25The dried up soil would spread out at a loss of sight.
02:28Without evaporation, the clouds would no longer form, making the precipitation rare.
02:33Humanity would quickly be deprived of drinking water sources.
02:36The landscape of our planet would turn into a huge desert, similar to a Sahara spreading over its entire surface.
02:43The aridity would be such that fires would easily ignite, driven by the dry atmosphere.
02:49This would certainly not be ideal conditions to undertake a long walk between continents.
02:54But let's assume that you have survived this new environment.
02:57You then embark on a walk through this desert land, which used to be the Atlantic Ocean.
03:03What would this journey look like?
03:05You would be confronted with a landscape radically different from the one visible above the marine surface.
03:11What lies beneath the waves exceeds in height and depth the world we know.
03:16It is a kingdom of extremes.
03:18Take, for example, the highest mountain on our planet.
03:21If the Himalayas and its summit, Mount Everest, come to mind, you are partly right.
03:29This chain is the highest when measured from the level of the sea, reaching just over 8,848 meters.
03:36However, if we consider the height of a mountain from its base to its summit, the Himalayas loses its first place.
03:43In reality, the highest summit on Earth is Mount Mauna Kea, located in Hawaii.
03:48This dormant volcano, whose name means White Mountain in the local language, is partially submerged under the Pacific Ocean.
03:56Its total height exceeds Mount Everest by nearly 1.6 kilometers, culminating at 10,211 meters.
04:04Currently, it is difficult to appreciate its magnitude.
04:07But if the Pacific dried up, we could admire the base of this giant in full light.
04:12The bottom of the Atlantic Ocean also houses a comparable mountain range, which constitutes the largest geological structure on our planet.
04:20This formation, the Medio-Atlantic Dorsal, is almost entirely submerged under the waters.
04:25It rises from the ocean floor to an altitude that reaches about half that of Mount Kilimanjaro, in Tanzania.
04:34The width of this massive submarine chain is one tenth of the Earth's diameter.
04:39The only visible portions of the Medio-Atlantic Dorsal manifest themselves in the form of islands, such as Iceland and the Azores.
04:47The island inhabited by the most remote in the world, Tristan da Cunha, is also part of the rare elements of this geological formation that emerges from the sea.
04:55What is perhaps even more impressive than its size is the date of the discovery of this dorsal.
05:01It was only in the 1950s that scientists established cartography.
05:05Considering that our civilization dates back several millennia, this seems recent.
05:10And reveals how much our knowledge of ocean depths remains limited.
05:14According to UNESCO, humanity has explored only barely 5% of the Earth's oceans.
05:19As surprising as it may seem, more people have set foot on the Moon than on the seabed.
05:25And the deepest point of our planet is located in the Marianas Gorge of the Pacific Ocean.
05:32The discovery of the Medio-Atlantic Dorsal has raised the veil on the mystery of the formation of continents and oceans.
05:38By understanding the origins of these structures, you can better anticipate what awaits you during an imaginary crossing of the Atlantic.
05:45The Dorsal is located directly between North America and Europe.
05:49But it is convenient not to consider these terrestrial masses only as continents, but rather as tectonic plates.
05:56These represent huge segments of the lithosphere, the external layer of the Earth, mainly made up of rocks.
06:04Our planet has between 15 and 20 of these massive plates, which rest on a partially melted rock layer.
06:10Although they do not float, scientists use this term to best describe their instability.
06:19The tectonic plates are in perpetual motion and can collide.
06:24In these cases, one of the plates plunges, while the other is pushed up, releasing immense amounts of energy.
06:31On the surface, this is manifested by earthquakes and eruptions.
06:35These tectonic forces shaped our planet as we know it, and this is how the Himalayan mountains were formed about 40 to 50 million years ago.
06:45During this period, the Indian plate moved north, hitting the southern edge of the Eurasian plate.
06:52Since these two plates are made up of similar rocks, none of them plunged under the other.
06:57The only option was a push up.
06:59This process is still underway, and each year the Himalayan chain continues to rise by a centimeter.
07:07A comparable phenomenon occurs at the level of the Medio-Atlantic Dorsal, which widens by about 4 cm each year.
07:14This process has an intriguing side effect.
07:17If you remember the time when you built sand castles, you had to dig all around to raise the dungeon.
07:23Thus, the hole grew as the castle grew in size.
07:28In the Atlantic, a similar process is underway, but on a colossal scale.
07:33As the Medio-Atlantic Dorsal expands, the opposite coasts, carried by the North American and Eurasian plates, move away from each other.
07:41This could extend your hypothetical crossing of a world without oceans.
07:45Each year, this imaginary journey would extend by 2 to 3 cm.
07:50Although it seems insignificant today, in the distant future, you could even see the continents drift to you, making your journey useless.
08:01Evaporation is not the only mechanism that can cause an ocean to dry up.
08:06The opposite coasts could simply close on it.
08:10And scientists believe that this scenario will occur in the Pacific.
08:14In nearly 50 million years, the largest ocean on Earth will be unrecognizable.
08:19By performing computer simulations, experts have studied the future trajectory of the North and South American plates, which are heading towards the North Pole.
08:28In the long run, they will merge with Asia to form a new supercontinent.
08:33Which will profoundly change the appearance and size of the Pacific Ocean.
08:37This new set of emerged lands already bears a name.
08:41Amazigh.