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In this article we are discussing the Earth’s crust. The average radius of Earth is 6379 km.
The principle layers in the Earth’s interior are:
1) Core (barysphere):
a) The core of the earth is the innermost layer of the Earth. It is the densest layer on Earth.
b) It contains 2.18% volume & 2.72% mass of Earth.
c) The Earth’s core is made up of two distinct parts- a 2,200 km-thick liquid outer core and a 1,250 km-thick solid inner core.
d) The outer core is made up of iron & nickel which is also called as Nife layer. The temperature of this layer is about 4400 – 5000 degrees. This core is in liquid state.
e) This core creates a magnetic field, which in turn creates a protective barrier around Earth by deflecting Sun’s damaging solar wind.
f) The density of the core is 10gm/cm3 – 13.6gm/cm3
g) Due to high pressure in the inner core, the melting point of iron and nickel is higher than that of the prevailing temperature in the inner core. So, even with extremely high temperature, the inner core is solid in nature.
2) Mantle (mesosphere):
a) The mantle of the Earth extends from 40km to 2900km into the Earth’s interior.
b) This layer is in solid state.
c) It is formed mainly of iron & magnesium.
d) The density of this layer is 5gm/cm3
e) The temperature in the mantle is about 1600 – 2204 degrees.
f) The mantle makes up about 49.5% of Earth’s volume & 68.4% of its mass.
g) The asthenosphere is the highly viscous & mechanically weak region of the upper mantle of the Earth.
Gutenberg Discontinuity: The core-mantle boundary lies between the Earth’s silicate mantle and its liquid iron-nickel outer core. This boundary is located at approximately 2880 km depth beneath the Earth’s surface.
This discontinuity can be observed by the sudden disappearance of S waves and also by a sudden drop in the speed of P waves.
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