Question.
What are the three layers of the earth?
( Chapter - 2 Inside Our Earth, Class 7 NCERT, Our Environment( Geography) )
Answer.
Our earth is made up of mainly three concentric layers with one inside another. The name of the three layers of the earth are-
- Crust
- Mantle
- Core
About crust:
The crust is the uppermost layer of the earth and it is the thinnest of all the three layers, it is about 35 km deep on the continent and 5 km deep on the ocean floor. There are two types of crust namely continental crust and oceanic crust. The mineral composition of the Continental crust is silica and alumina, which is why is it also known as sial( silica and alumina). The mineral composition of the oceanic crust is silica and magnesium, that is it is also known as sima( silica and magnesium). By volume, the crust is comprised of only one percent of the total volume of the earth.
About Mantle:
Just beneath of crust is called the mantle layer of the earth. It extends up to 2900 km below the crust. The mantle layer is comprised 84 percent of the total volume of the earth.
About Core:
Just beneath of mantle is called the core layer of the earth. The radius of the core is about 3500 km. It is mainly made up of nickel and iron, which is why it is known as the nife layer. The central core has very high pressure and temperature, which is why it is found in solid form. By volume, the core makes up 15 percent of the total volume of the earth.
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