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  • Our planet is about 4.5 billion years old (give or take) and it has a history of doing

  • shadowy things, such as creating landmasses and then making them disappear. Around 1 billion

  • years ago, I wasn’t around then, a mysterious supercontinent was formed, and it swallowed

  • and flipped the mainland inside out. And that could happen again quite soon. In geological

  • time. The historical period when the land connected

  • to become the Rodinia supercontinent and the time frame it split are a big foggy. Geologists

  • believe that roughly every 600 million years we are met with the same fate. Our continents

  • connect to form a huge landmass; our oceans connect to form a super-ocean; and then they

  • split. The first supercontinent ever was Nuna. It

  • appeared about two billion years ago and broke apart roughly 1 billion years later. Then,

  • after some more million years, Rodinia (roughly translated asbirth-giver”) appeared.

  • It collected most of the Earth’s landmasses and then split around 750 million years ago.

  • Now, this is our mysterious supercontinent. So, from what you understand, this dance between

  • continents happens at a snail’s pace. Even the longest living animals on Earth that can

  • live up to 400 yearslike the Greenland sharkwon’t be able to experience this

  • re-organization. Would you like to see any of the supercontinents,

  • if you had such a chance, though? Let me know in the comments.

  • There isn’t much information about the position where Rodinia formed. But geologists are constantly

  • finding new clues on its original location around the globe.

  • As the time went on, Rodinia began to split, but that happened in stages. The breakup was

  • triggered by a superplumehuge rising jets of hot molten rock in the Earth’s mantle

  • began expanding. That caused enormous volcanic eruptions that were later found in every continent.

  • After the initial split, another sea appeared 200 million years later. It became the famous

  • Lapetus super ocean and it stuck around until 400 million years ago. It formed in the Southern

  • hemisphere of our globe around 3 ancient continents. These were Laurentia, Avalonia and Baltica.

  • But history was once again repeating itself; so, the ocean vanished, and the lands merged

  • again to form a new great supercontinent called Pannotia.

  • Now, Rodinia stood out for a ton of reasons. One of them was because the landmass was barren.

  • It couldn’t produce vegetation and it was overall lifeless. No trees or plants were

  • around. It appeared during a time when life on dry land didn’t even exist.

  • That’s when the ozone layer comes into play. The ozone shield started forming a little

  • after the Rodinia continent appeared. Sunlight hit the oxygen molecules and broke them into

  • smaller individual atoms. Interestingly, the ozone layer, unlike oxygen and oxygen gas,

  • consists of 3 oxygen atoms, and it appears as O3.

  • Since its appearance, it began absorbing higher levels of radiation from the sun, and that

  • allowed life on land to flourish. Before the ozone layer, the only living things could

  • be found in the ocean. They were blue-green algae. But after the protective shield formed,

  • small creatures appeared, life grew, and evolution thrived.

  • When Rodinia started welcoming new tiny beings, it also started to separate, and new oceans

  • were born. The seafloors started spreading and that resulted into warmer oceanic lithospheres.

  • Now those lithospheres had low density, and when they warmed up, they couldn’t dive

  • as deep as the cooler ones did. Here’s where it gets interesting. A study

  • led by Zheng-Xiang Li from Curtin University in Australia, found some unique patterns about

  • the supercontinent cycle and the Earth’s lithosphere. They found patterns in the mantle

  • that matched perfectly to a 600-million-year-long cycle.

  • According to one of the papers, Li and his team believe that the Earth has two alternating

  • cycles. The first one runs for 600 million years and it brings all the landmasses together.

  • The second cycle lasts for double the timearound 1.2 billion yearsand a new

  • super ocean is born. Each of these events has two shifting methods:

  • introversion and extroversion. No, I’m not talking about psychology, these are geological

  • terms. So, let’s start with the first oneintroversion. Now imagine a giant landmass

  • being surrounded by a super ocean. When the continent starts to separate and small rifts

  • form, water begins to slowly flow through them until a smaller inner ocean is formed.

  • That’s when subduction zones come into play. These are the boundaries that mark the collision

  • between tectonic plates. Dropping all the sciencey stuff, here’s what I mean. When

  • tectonic plates meet at a subduction zone, one bends and then slides under the other.

  • Then, they both slowly curve down into the mantle. Wow, that’s some subduction going

  • on all right. Now, tectonic plates can either be both oceanic

  • and continental, or they can be one of each type. For example, the oceanic crust is denser

  • than the continental. So, at a subduction zone, the oceanic crust will be the one to

  • sink below the lighter continental crust. Sometimes, there could be a collision between

  • two continents, so the plates crash together without a subduction zone forming. That’s

  • exactly what happened when India slammed into Asia millions of years ago, and the Himalayan

  • chains formed. Now that we got the gist of what subduction

  • zones are, let’s get back into the juicy methods the Earth uses to make things disappear.

  • During the introversion method, the oceanic crust dives back into the Earth’s hot mantle.

  • The inner ocean sinks back into the Earth’s interior and then the continents re-connect

  • again. So, a new supercontinent gets formed with the same old water that existed before.

  • But extroversion is quite different. That method creates a new super ocean and a fresh

  • landmass. Let me show you. At first, the supercontinent starts to separate,

  • so water begins to flow through it and an internal ocean is formed. But the subduction

  • zone doesn’t appear there. It shows up in the super ocean around the separating landmass.

  • Then, the earth swallows the super ocean while also pulling apart the rifting continental

  • crust, which begins to sink at the bottom. So, the landmass literally flips inside out.

  • The coastlines collide again to form new centers, and the middle of the old continent becomes

  • the new coast. Li and his research team created a simulation

  • to study that pattern, and they found that in the last hundred million years both extroversion

  • and introversion changed. If the pattern continued, we’d be due to a new extroversion method

  • in a few hundred million years, yet we are due to another introversion.

  • Let’s go back to the Nuna supercontinent that I told you about at the beginning. When

  • that happened, it occurred through introversion. Both Nuna and Rodinia had the same super-ocean

  • surrounding them. That ocean was called the Mirovoi.

  • When the Oceanic crust started to subduct, Rodinia began separating and the sea disappeared.

  • Interestingly, that super ocean re-appeared as the Panthalassa in the formation of Pangea.

  • After Pangea broke apart, Panthalassa appearedwhich means the whole sea survived in

  • the Pacific’s ocean crust. Since the patterns have changed, it’s estimated that the next

  • supercontinent will be created through introversion again. The Indian, Southern Oceans and possibly

  • the Atlantic will disappear, the Pacific will expand again, and a super ocean will be born.

  • This future hypothetical supercontinent is given the name of Amasia. It got the title

  • from the idea that Asia will merge with North America. The theory relied on the fact that

  • the Pacific Crust is subducting under Eurasia and North America.

  • Another clue is that the western part of the Pacific Plate is subducting under the Philippine

  • Sea, which created the Mariana Trenchthe deepest part of the Pacific Ocean. But this

  • is just a theory. Some models tried to follow the movements of our continents to see if

  • an extroversion or introversion is possible. Li and his colleagues researched the molecular

  • variation patterns in ancient rocks and found that introversion is most likely to happen.

  • Everything comes down to plate tectonics. The problem is, nobody knows what causes the

  • beginning of a subduction. There is even disagreement among geologists on when the Earth’s plates

  • started moving around. Some of them say it started a few million years after the Earth

  • was formed, while others claim it started 2-3 billion years later.

  • But at least now we were able to understand how the Earth can flip its continents inside

  • out and that it won’t probably happen when a new landmass forms.

  • Right now, the tectonic plates are moving North, which includes Australia and Africa.

  • It is estimated that in a few hundred million years—I won’t be around then -- all the

  • landmasses excluding Antarctica will connect in the North Pole to form the Amasia. That

  • makes everyone wonder how we will evolve, what the climate of the supercontinent will

  • be like and how life will adapt. But I’ll leave that to scientists. Or my fortune teller.

  • Hey, if you learned something new today, then give the video a like and share it with a

  • friend! And here are some other cool videos I think you'll enjoy. Just click to the left

  • or right and stay on the Bright Side of life!

Our planet is about 4.5 billion years old (give or take) and it has a history of doing

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かつて地球はどのようにして海を飲み込んだのか (How the Earth Once Swallowed Its Ocean)

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    林宜悉 に公開 2021 年 01 月 14 日
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