What do you imagine about the nature of the earth? Do you imagine it to be a solid ball like cricket ball or a hollow ball with a thick covers of rocks i.e. lithosphere? You have heard about the Earth forming materials have been distributed in the form of layers from the crust to the core. So, let’s know about these layers of earth in details:
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| Layers of earth |
The Crust
It is the
outermost solid part of the Earth. It is brittle in nature. The thickness of
the crust varies under the oceanic and continental areas. Oceanic crust is
thinner as compared to the continental crust. The mean thickness of oceanic
crust is 5 km whereas that of the continental is around 30 km. The continental
crust is thicker in the areas of major mountain systems. It is as much as 70 km
thick in the Himalayan region.
It is made
up of heavier rocks having density of 3g/cm3. This type of rock
found in the oceanic crust is basalt. The
mean density of material in oceanic crust is 2.7g/cm3.
The Mantle
The portion
of the interior beyond the crust is called the mantle. The mantle extends from
Moho’s discontinuity to a depth of 2,900 km. The upper portion of the mantle is
called asthenosphere. The word astheno means weak. It is considered to
be extending upto 400 km. It is the main source of magma that finds its way to
the surface during volcanic eruptions. It has a density higher than the crust’s
(3.4g/cm3). The crust and the uppermost layer of the mantle is
called lithosphere. Its thickness
ranges from 10 – 200 km. The lower mantle extends beyond the asthenosphere. It
is in solid state.
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| Crust, Mantle and Core |
The Core
The
earthquake wave velocities helped in understanding the existence of the core of
the earth. The core – mantle boundary is located at the depth of 2900 km. The
outer core is in liquid state while the inner core is in solid state. The
density of material at the mantle core boundary is around 5g/cm3 and
at the centre of the earth at 6,300 km,
the density value is around 13g/cm3. The core is made up of very
heavy material mostly constituted by nickel and iron. It is sometimes referred
to as the nife layer.
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Structure of the Earth
Reviewed by Deepworld
on
November 17, 2019
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Reviewed by Deepworld
on
November 17, 2019
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