Introduction to Interior Of The Earth Video Lecture - Social Studies (SST) Class 7

in this module you'll learn about the
internal structure of the earth to
understand the structure of the earth
first let's get a background on how the
earth was formed it happened 4.5 billion
years ago the earth then was nothing
like what it is today the earth started
off as a round ball of homogeneous
molten material revolving around the Sun
as the liquid slowly cooled down the
denser materials that form the earth
solidified and sank to the center of the
earth where they formed a metallic core
at the same time the lighter less dense
elements were pushed out toward the
surface where they formed the earth's
crust this led to the formation of the
earth with several different layers of
material very much like an onion these
layers are arranged one on top of the
other the outermost layer is the solid
crust next is the highly viscous layer
called the mantle below the mantle is
the liquid outer core of the earth a
solid inner core forms the earth's
innermost layer the topmost layer the
crust is the thinnest layer this layer
can be classified into oceanic crust and
continental crust the oceanic crust that
is the crust beneath the oceans is only
about five kilometers thick
on the other hand the continental crust
can be as thick as 35 kilometers however
considering the Earth's size the crust
is quite thin suppose the earth was
scaled down to the size of a football
can you guess how big the crust would be
it would be about half a millimetre
thick the Earth's crust is at its
thinnest in places such as the Rift
Valley in East Africa and thickest under
mountain ranges the continental crust is
composed of two minerals silica and
alumina the combination of these two
elements gives it the name SIA the
oceanic crust on the other hand is
mostly made up of silica and magnesium
and is called cyma did you know when the
Earth's crust gets ruptured the hot
molten magma ash and gases come out from
the core to the surface of the earth
this results in the formation of a
volcano the magma that is released on
the surface of the earth is called lava
the Hawaiian Islands are said to have
formed due to undersea volcanic
activities the crust however makes up
only 0.5 to 1% of the Earth's volume so
what about the other components that
make up the earth well 83% of the earth
is made up of the mantle and the
remaining 16% consists of the inner and
the outer
cause the mantle lies just below the
Earth's crust and is 2,900 kilometers
deep that makes it the thickest among
all the layers that comprise the earth
it is made up of viscous material the
temperature and the pressure within the
mantle are high as it is located below
the crust that makes the material of the
mantle very viscous
which means although it is in liquid
form it does not flow freely this
material inside the mantle is more
viscous than tar and is known as magma
it is semi solid and can flow magma is
contained within the magma chamber
finally as you go deeper inside the
earth you come to the core the core
consists of an outer core and an inner
core the outer core lies just below the
mantle and is mainly made up of nickel
and iron this combination gives it the
name knife the materials within the
outer core are in a liquid state
considering how high the temperatures in
the outer core are can you guess what
the conditions in the inner core would
be like it would be even hotter the
temperatures in the inner core range
from five thousand to six thousand
degrees Celsius you may be wondering why
the inner core is solid despite such
high temperatures the pressure in the
inner core is so high
the material gets solidified did you
know the core as a structural element of
the earth was discovered in 1996 by Rd
Oldham during his study of earthquake
records it was the first such internal
structural element of the earth to be
identified in this module you learned
that the earth is made up of several
different layers of material the
outermost layer is the crust the crust
is classified into oceanic crust that
consists of cyma continental crust that
consists of soil the next layer is
highly viscous and is called the mantle
the mantle is the thickest layer and
forms 83% of the earth's volume the
outer core is made of nickel and iron
and is called knife the material in this
layer is in a liquid state the inner
core is solid and has very high
temperature and pressure