Ncert class 11 geography chapter 3 || Different layers of the earth.

These is all about easy explanation of ncert class 11 geography chapter 3.  Here I will discuss different layers of the earth.

 

Majorly, earth is divided into 3 layers: 1) The crust, 2) The mantle, 3) The core

   Crust –

·        Outermost part.

·        Crust thickness is not the same everywhere. The oceanic crust is less thick compare to the continental crust. The thickness of the oceanic crust is around 5 km, and that of the continental crust is around 30 km. In mountain regions, for example Himalayas, the thickness can be as much as 70 km.

·        Crust made of heavier rocks. It has a density of 3g/cm³.

·        Basalt rock is found in the oceanic crust. The mean density of oceanic crust is 2.7g/cm³.

                          

  Mantle-

·        Mantle starts beyond the crust up to 2,900 Km.

·        The boundary line between the crust and the mantle is called the Mohorovicic Discontinuity.

·        Asthenosphere is upper part of the mantle. It is semi-solid (Astheno means weak). It is the main source of magma.

·        Crust and the uppermost part of the mantle, together called Lithosphere (Asthenosphere not included). It is extended from 10 km to 200 Km.

·        Beyond the Asthenosphere starts the lower mantle. It is solid.

·        Silicon and Magnesium are the primary elements in this mantle part. That’s why the mantle part is called SIMA.

·        Density higher than crust, around 3.4g/cm³.

·        The boundary line divides the upper mantle and lower mantle, called the Repetti Discontinuity.

 

 Core-

·        The line between mantle and core is called the Gutenberg Discontinuity.

·        It starts from 2,900 Km. The outer core is liquid form, and the inner core is solid.

·        The density of the mantle and core boundary zone is 5g/cm³. At a depth of 6,300 Km, its density becomes 13g/cm³.

·        Presence of heavy metal, primarily nickel and iron. That’s why this part is called as NIFE layer.