KERALA PSC / PHYSICAL GEOGRAPHY / STRUCTURE OF EARTH / NOTES

 

KERALA PSC / PHYSICAL GEOGRAPHY / STRUCTURE OF EARTH / NOTES

KERALA PSC / PHYSICAL GEOGRAPHY / STRUCTURE OF EARTH / NOTES

 

·       The earth is made up of a number of concentric layers of materials as in the bulb of an onion

·       Earth can be divided into different layers such as Crust, Mantle and Core

·       Crust: This is the outer layer of the Earth varying between 5 to 50 km in depth under the surface of the earth

Ø It is the outermost and thinnest layer of the earth’s surface

Ø The crust comprises about 5% of the earth body

Ø Thickness of the crust is more under the continents and lesser under oceans

Ø The outermost layer of the crust is composed of lighter silicates termed as sial (Silica + Aluminium)

Ø Moho or Mohorovicic discontinuity separates crust from mantle.

Ø The average density of this layer is 2.7

·       Mantle: a layer between crust and the core

Ø Mantle contains 83% of the total volume and 68% of the total mass of the earth. Average density of this layer is 5.68.

Ø Mantle is separated from the core by Gutenberg discontinuity

Ø It is largely composed of silicon and magnesium called sima

Ø The rocks in this layer may be in the glassy state.

Ø The temperature of this layer ranges up to 1600ºC and extends downwards to a depth of about 1000 km. The thickness of the lower mantle is about 1900 km.

·       Core: is the central region of the earth

Ø It is 3475 km in radius

Ø By volume, it is 16% of the earth body

Ø By mass, it constitutes 32% of the mass of the earth. The outer core, approximately 2100km thick, consists of molten iron and nickel with temperatures ranging between 2000ºC and 5000ºC. Below this is the solid inner core which has diameter of 2740 km.

Ø The temperature of the inner core is 6000ºC-7000ºC.

Ø The inner core is composed of NiFe (Ni for Nickel Fe for Iron)

Ø Density of this part is 17.2

Ø Average density of earth is 5.53

 

KERALA PSC / PHYSICAL GEOGRAPHY / STRUCTURE OF EARTH / NOTES