Internal Structure and Composition of the Earth

Scientists believe that there are three main layers in the earth: the core, the mantle and the crust.

The core, which is the innermost part of the earth, is about 2900 kilometers from the earth's surface. The center of the earth is about 6390 kilometers from the surface. There are very dense rocks in the core. The core is made up of iron and nickel. The extreme temperatures range form about 4000°C to 5000°C. The inner core, which has a density of about 15g/cm³, is solid under immense pressure while the outer core, which has a density of about 12g/cm³, is in a semi-molten state under less pressure.

The mantle extends from the base of the crust to the top of the outer core. The density of the rocks, which ranges from about 3.3g/cm³ to 5.5g/cm³, increases at depth increases. The temperatures are at an average of 2000°C. The rocks in the mantle mainly consist of iron and magnesium. The uppermost mantle, the asthenosphere and the rest of the upper mantle form the upper mantle. The lithosphere consists of the crust and the uppermost solid zone. The semi-molten asthenosphere, which is below the lithosphere, extends from about 100 kilometers to about 250 kilometers below the earth's surface.

The crust, which is a thin layer, consists of the continental crust and the oceanic crust. The continental crust has an average density of about 2.7g/cm³ and is made up of granite rocks. It has an average thickness of about 35 kilometers to 70 kilometers. The oceanic crust, which has an average density of about 3g/cm³, is mainly made up of basaltic rocks, which are relatively denser. It has an average thickness of about 5 kilometers to 10 kilometers.

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