The structure of Earth

Structure, Depth, Parts 

1)    The Crust : mainly SiAl (Silica + Aluminium)

·       Outermost solid part of the earth., brittle in nature

·       Thickness of crust more at continental areas (it is around 30 Kms) than at oceanic areas (where it is around 5 km).

·       At major mountains, thickness is as high as 70 Kms.

·       Rock density is around 3 g/cm³ in continent areas.

·       At oceanic area, rock is mainly basalt with density around 2.7 g/cm^3.

2)    Mantle: mainly SiMa (Silica + Magnesium)

·       Portion of interior beyond crust.

·       Extends from Moho’s discontinuity to depth of 2900 Kms.

·       Upper portion of Mantle is called asthenosphere (astheno means weak) – depth upto 400 Kms; main source of magma; density (3.4 g/cm³ ) more than crust.

·       Crust + upper mantle = lithosphere (its thickness ranges from 10-200 km).

·       Lower Mantle – beyond asthenosphere and is in solid state.

3)    The Core: mainly NiFe (Nickel + Iron)

·       Core-Mantle boundary located at 2900 km depth.

·       Outer core is in liquid state while inner in solid state.

·       Density at core mantle boundary is around 5g/cm³ & at centre is around 13g/cm³

^{There are zone of separation also known as discontinuities between above layers (i.e. Core, Mantle and Core) which are as under:}

 

All Discontinuity