Crust: or the lithosphere, is the outer part of the earth is where the life exist. The average thickness of crust beneath continents is about 40km where as it decreases to as much as 5km beneath oceans. The oceanic crust is constituted by basaltic rocks and continental part by granitic rocks overlying the basaltic rocks. Compared to the layers below, this layer has high rigidity and anisotropy.

Mantle: is a 2900 km thick layer. The mantle consists of 1) Upper Mantle reaching a depth of about 400 km made of olivine and pyroxene and 2) Lower Mantle made of more homogeneous mass of magnesium and iron oxide and quartz. No earthquakes are recorded in the lower mantle. The specific gravity of mantle is about 5. The mantle has an average temperature of about 2200degree Celsius and the material is in a viscous semi molten state. The mantle act like fluid in response to slowly acting stresses and creeps under slow loads. But it behaves like as solid in presence of rapidly acting stresses, e.g. that caused by earthquake waves.

Core: has a radius of 3470 km and consists of an inner core of radius 1370 km and an outer core (1370 km < R<3470 km). The core is composed of molten iron, probably mixed with small quantities of other elements such as nickel and sulphur or silicon. The inner solid core is very dense nickel-iron material and is subjected to very high pressures. The maximum temperature in the core is estimated to be about 3000 degree Celsius. The specific gravity of outer core is about 9-12 where as that of inner core is 15.