00:00While you're watching this video, pieces of continents are slowly breaking off from below
00:05and are pulled down into the oceanic mantle, a hot, mostly solid layer that moves slowly
00:11under the seafloor. As soon as these fragments reach the mantle, they can trigger volcanic
00:16eruptions in parts of the ocean where there are no volcanoes. Plus, when continents break apart,
00:22it happens not only at the surface, but also deep down. But more on that later.
00:27This process can continue for tens of millions of years. The new study shows that Earth's insides
00:34are even more dynamic than we thought. It also explains why many volcanic islands,
00:39including Christmas Island in the Northeast Indian Ocean, contain unusually high levels of
00:45certain chemical elements. The thing is, these elements are normally only found in continental
00:51crust. Well, scientists did suspect that these elements showed up because some powerful
00:57forces deep inside the Earth took old, recycled pieces of rock and mixed them into the mantle.
01:03This process works a bit like when you mix together ingredients for cake batter.
01:09But before, researchers believed those elements came from two main sources, sediment that sank into
01:15the mantle as oceanic plates got pushed down, or from mantle plumes. Those are columns of hot rock
01:23rising up from deep inside Earth. However, these explanations don't fit all observations.
01:30In some volcanic areas, there's almost no sign that the crust has been recycled. In other places,
01:36the mantle seems to cool and too close to the surface to be affected by the rising hot rock.
01:42Scientists used to wonder how this could happen. Now we know that some of the material in those regions
01:47come from pieces of continents that sink deep into the mantle. And these pieces affect the volcanoes that
01:54form above. The new study also suggests a curious idea. Continents don't just break apart at the surface,
02:02they peel away from below too. And this can happen over much greater distances than scientists thought
02:09before. Researchers used simulations to figure out how continents and the mantle behaved when stretched
02:16by tectonic forces. Their work is built on earlier research showing that when continents split,
02:23deep, powerful forces inside our planet create a mantle wave. This wave moves along the base of the
02:31continent at depths of about 90 to 125 miles. The wave moves extremely slowly, about a millionth of the speed
02:41of a snail, and gradually strips material from the roots of the continents. These peeled off fragments are
02:48then carried sideways, sometimes more than 620 miles, into the oceanic mantle. Once there, they can trigger
02:57volcanic eruptions in the ocean for tens of millions of years.
03:03The research also shows that the mantle continues to feel effects of continental breakup long after the
03:10continents themselves have separated. Even after a new ocean basin forms, the mantle keeps moving, reorganizing
03:18and transporting enriched material far from where it originally came. To make this conclusion, researchers
03:25studied geochemical data from different parts of the Earth, including the Indian Ocean Seamount province.
03:31That's a chain of volcanic formations that appeared after the supercontinent Gondwana had broken apart
03:38over 100 million years ago. Their computer models and chemical tests showed that right after the
03:45supercontinent Gondwana broke apart, a lot of magma with unusual chemicals pushed up to the surface.
03:53Over millions of years, this chemical signature slowly faded as less material came up from under the
03:59continent. The most unexpected discovery is that this happened without any help from those deep,
04:06hot columns of rock scientists used to think were needed. Now, to get an even clearer picture,
04:13let's sneak a peek into our planet's insides. Earth is about 4.6 billion years old. It was born from a huge
04:22cloud of dust and gas that slowly cooled, shrank and hardened into the planet we know today. As it cooled,
04:31heavy metals like iron and nickel sank to the center, and lighter, rocky materials floated upward. This
04:38created the Earth's layered structure, with each layer having its own unique properties. The crust is
04:45like Earth's skin. It's our planet's outermost layer made of solid rock. It's broken into huge pieces
04:53called tectonic plates that slowly drift over time. There are two kinds of crust, oceanic crust and
05:01continental crust. The oceanic crust is about 4 to 6 miles thick. It's covered with a thin layer of
05:08sediments like sand, clay and shells. Below that are dense rocks like basalt, rich in magnesium. As for
05:17the continental crust, it's thicker than oceanic crust and is located under continents. It's made of lighter
05:24rocks than oceanic crust. Beneath the crust is the mantle. It makes up more than 75% of Earth's volume.
05:33The top of the mantle is pretty rigid, but deeper down, it becomes soft and partially molten, which
05:39allows it to flow slowly. This flow is what moves the tectonic plates. At the center of the Earth lies the
05:48core. It's made mostly of iron and nickel and has two distinct layers, the outer core and the inner
05:55core. The outer core is a liquid layer of iron and nickel. It's insanely hot, up to 10,800 degrees
06:03Fahrenheit, as hot as the surface of the Sun. The outer core also generates Earth's magnetic field,
06:10which protects us from harmful solar radiation. The inner core is solid because of the crushing
06:16pressure inside the planet. It's also made of iron and nickel. Now, the Earth's outer shell, called the
06:23lithosphere, is made up of the crust and the uppermost part of the mantle. It's broken into large pieces,
06:31called tectonic plates. There are a few super large plates and many smaller ones. Six of the major plates
06:38are named after the continents they carry, like the North American, African and Antarctic plates. But even
06:44those smaller plates play an important role. For example, the tiny Juan de Fuca plate is responsible
06:51for many of the volcanoes in the Pacific Northwest of the United States. The plates are moving like a jumble
06:58of old conveyor belts. They move very slowly, about one to two inches per year. But over millions of years, this
07:05movement shapes the face of our planet. Most earthquakes, volcanoes, and mountain building happen
07:11where plates meet, pull apart, or slide past each other. There are three main types of plate boundaries.
07:19Convergent, when plates move toward each other. Divergent, when plates move apart. And transform,
07:26that's when plates slide sideways past each other. When tectonic plates collide,
07:32the crust crumples and buckles, forming mountain ranges. About 55 million years ago, India crashed
07:38into Asia, slowly creating the Himalayas, the tallest mountains on Earth. The collision continues today,
07:46so the mountains are still rising. Mount Everest, the highest point on Earth, may even grow a tiny bit
07:52taller over time. At some convergent boundaries, an oceanic plate dives under a land plate in a process
08:00called subduction. The land above lifts up, forming mountains, and the sinking plate melts and triggers
08:07volcanic eruptions. This is how some mountains in the Andes of South America were formed. When two
08:14oceanic plates collide, one usually slides beneath the other, creating deep ocean trenches, like the
08:20Mariana Trench in the North Pacific, the deepest point on Earth. These collisions can also form underwater
08:28volcanoes that eventually rise above the ocean and turn into island chains, such as Japan. At divergent
08:37boundaries, tectonic plates move away from each other. In the oceans, magma from deep in the mantle rises
08:43to fill the gap. This creates underwater mountains and volcanoes along the seam. This process renews the
08:51ocean floor and slowly widens the ocean basins. By the way, a single mid-ocean ridge system
08:58connects all the world's oceans, making it the longest mountain range on Earth. On land, when plates pull
09:05apart, they form giant valleys, such as the Great Rift Valley in Africa. If this stretching continues over
09:13millions of years, East Africa could split off to become a new landmass. One famous example of
09:21transform boundaries is the San Andreas Fault in California. Unlike convergent or divergent boundaries,
09:27transform boundaries usually don't create mountains or oceans, but the grinding motion can cause
09:33powerful earthquakes, such as the 1906 earthquake that destroyed much of San Francisco.
09:40That's it for today. So, hey, if you pacified your curiosity, then give the video a like and share it with
09:46your friends. Or if you want more, just click on these videos and stay on the Bright Side!
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