Structure of the Earths Interior

The knowledge of the structure of the interior of the Earth is obviously important for understanding the origin of most igneous rocks and minerals but it is also f ascinating from a fundamental point of view regarding the behavior of materials under ultrahigh pressures and temperatures and hence it is briefly described here. 

The sharp boundary existing between the bottom of the Earth s crust and the upper mantle that was first identified in 1909 by the Croatian seismologist Andriaja Mohorovicic by a clear change in the velocity of P seismic waves is called the Mohorovicic discontinuity or simply Moho. 

The core formerly called the pyrosphere is mostly composed of iron and nickel and was first called NiFe and remains very hot with an estimated temperature of ca. 7000K even after 4.5 Ga of cooling. Its average density is 14,000 kg.m The core is structurally divided into two layers  

The Lehmann discontinuity that was predicted by the Danish seismologist Inge Lehmann in 1936, separates the outer core from the inner core. 

Lithosphere - the lithosphere, named from the Greek, lithos, stone, is the rigid outermost layer of the geosphere including the Earth crust and the uppermost rigid layer of the mantle. It averages about 100 kilometers in thickness, but may be 250 kilometers or more thick beneath the older portions of the continents (i.e., cratons). 

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