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Four layers of the Earth

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Four layers of the Earth

Why in news:

  • Recently scientists found that there is an inner core with in the inner core itself.

The layers of Earth are:

  • Crust – 5 to 70 km thick
  • Mantle – 2,900 km thick
  • Outer Core – 2,200 km thick
  • Inner Core – 1,230 to 1,530 km thick

1.  Crust:

  • It is the thin (relatively) outermost layer that wraps around the Earth and ranges in temperature from 500 to 1,000°C.
  • The crust is split into two types, continental and oceanic. Earth’s crust is 5 to 70 km thick.
  • Continental crust makes up the land on Earth, it is thicker (35 – 70 km), less dense and mostly made up of the rock granite.
  • Oceanic crust makes up most of the ocean, it is thinner (5 – 7 km), denser and mostly made up of the rock basalt.
  • The crust makes up only 1% of the volume of Earth.

2.   Mantle:

  • Just below the crust lies the mantle.
  • The mantle is semi-liquid, sort of like a malleable plastic and makes up 84% of Earth’s volume.
  • Earth’s mantle is 2,900 km thick and is broken down into 3 main zones, the lithosphere, asthenosphere, and mesosphere.
    • The lithosphere is a bit confusing since it makes up both the lower part of the crust and upper part of the mantle.
    • It is about 100 km thick and consists of the 15 major tectonic plates on Earth.
    • The asthenosphere is where the mantle turns much more fluid and flows, allowing the above lying tectonic plates to drift across Earth.
    • The deepest part of the mantle is the mesosphere where temperatures and pressures get so high that the rock becomes more rigid and doesn’t flow as easily.
  • The most common mineral in the mantle is olivine, which is also known as peridot when the mineral is gem quality.

3.   Outer Core:

  • The outer core lies beneath the mantle.
  • This liquid iron and nickel layer spins as the planet rotates and creates Earth’s magnetic field.
  • This magnetic field helps to protect us from the Sun’s solar radiation.
  • The outer core is 2,200 km thick and very hot at up to 6,100°C.

4.   Inner Core:

  • The inner core is the deepest layer on Earth.
  • It is also made up of iron and nickel but the pressure is so high that it is no longer liquid.
  • The temperatures in the inner core are as hot as the surface of the sun, about 5505 °C. Earth’s inner core is 1,230 to 1,530 km thick.

Syllabus: Prelims; Geography

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