Explanation: STRUCTURE OF THE 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.
• 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.
• The Core As indicated earlier, 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 2,900 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 5 g/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.

Source: NCERT Class 11