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1º ESO/PANGAEA - Contenido educativo
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Once upon a time, South America lived harmoniously alongside Africa
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until a crack in the earth drove the two continents apart.
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This breakup began about 200 million years ago
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during the separation of the supercontinent known as Pangea.
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Their proximity back then explains why the same plant fossils
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and reptile fossils like the Mesosaurus
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can be found on the South American east coast and African west coast.
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However, this evidence does not account for how the continents moved apart.
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For that, we'll need to take a close look at the Earth below our feet.
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Though you may not realize it,
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the ground below you is traveling across the Earth
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at a rate of about 10 centimeters per year,
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or the speed at which your fingernails grow.
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This is due to plate tectonics,
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or the large-scale movement of Earth's continents.
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The motion occurs within the top two layers of the Earth's mantle,
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the lithosphere and asthenosphere.
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The lithosphere, which includes the crust and uppermost mantle,
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comprises the land around you.
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Beneath the lithosphere is the asthenosphere,
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the highly viscous but solid rock portion of the upper mantle.
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It's between 80 and 200 kilometers below the Earth's surface.
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While the asthenosphere wraps around the Earth's core as one connected region,
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the lithosphere is separated on top into tectonic plates.
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There are seven primary tectonic plates
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that compose the shape of the planet we know today.
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Like the other smaller tectonic plates,
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the primary plates are about 100 kilometers thick
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and are composed of one or two layers,
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continental crust and oceanic crust.
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Continental crust forms the continents
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and areas of shallow water close to their shores,
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whereas oceanic crust forms the ocean basins.
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The transition from the granitic continental crust
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to the basaltic oceanic crust
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occurs beyond the continental shelf,
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in which the shore suddenly slopes down
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towards the ocean floor.
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The South American plate is an example
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of a tectonic plate made of two crusts,
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the continent we know from today's map
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and a large region of the Atlantic Ocean around it.
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Collectively comprising the lithosphere,
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these plates are brittler and stiffer
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than the heated, malleable layer
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of the asthenosphere below.
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Because of this, the tectonic plates
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Floats float on top of this layer independently of one another.
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The speed and direction in which these tectonic plates move
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depends on the temperature and pressure of the asthenosphere below.
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Scientists are still trying to nail down the driving forces behind this movement,
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with some theories pointing towards mantle convection,
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while others are examining the influence of the Earth's rotation and gravitational pull.
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Though the mechanics have not been sorted out,
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the scientific community agrees that our tectonic plates are moving,
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than they have been for billions of years.
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Because these plates move independently,
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a fair amount of pushing and pulling between the plates occurs.
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The first type of interaction is a divergent boundary
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in which two plates move away from one another.
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We see this in the Mid-Atlantic Ridge between South America and Africa.
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The next interaction is when two plates collide,
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known as a convergent boundary.
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In this instance, the land is pushed upward
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to form large mountain ranges like the Himalayas.
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In fact, the Indian plate is still colliding with the Eurasian plate,
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which is why Mount Everest grows one centimeter per year.
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Finally, there's the transform boundaries,
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where two plates scrape past one another.
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The grinding of the transform boundary leads to many earthquakes,
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which is what happens in the 810-mile-long San Andreas Fault.
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The moving Earth is unstoppable,
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and while a shift of 10 centimeters per year may not seem like a lot,
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over millions of years, our planet will continue to dramatically change.
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Mountains will rise, shorelines will recede, islands will pop up.
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In fact, one projected map shows the cities of Los Angeles and San Francisco
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on top of each other.
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Maybe South America and Africa will come together again, too.
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Only time will tell.
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- Subido por:
- Alicia M.
- Licencia:
- Dominio público
- Visualizaciones:
- 152
- Fecha:
- 7 de marzo de 2021 - 21:02
- Visibilidad:
- Público
- Centro:
- IES LA SENDA
- Duración:
- 04′ 26″
- Relación de aspecto:
- 1.78:1
- Resolución:
- 1280x720 píxeles
- Tamaño:
- 34.88 MBytes
