The interior structure of the earth is also layered like its outer structure. The structure of earth can be defined in two ways: mechanically or chemically. Mechanically it can be divided into lithosphere, asthenosphere, mesosphere, outer core and inner core. Chemically, the earth’s surface can be divided into crust, upper mantle, lower mantle, outer core and inner core.
Inner core
The solid inner core has the radius of nearly 1220 km, suspended in the molten outer core. It is believed to be composed of iron and nickel. It is solidified due to decrease in temperature or increase in pressure.
Outer core
The liquid outer core extends beyond the radius of 3400 km. The liquid outer core surrounds the inner core and is believed to be composed of iron mixed with nickel and trace amounts of lighter elements. This layer is hot and electrically conductive within which convective motion occurs. This layer combines with Earth’s rotation to form Earth’s magnetic field.
Lower mantle
This layer is 400 to 650 km deep. The lower mantle is composed of silicon, magnesium and oxygen and traces of iron, calcium and aluminum.
Upper mantle
The upper mantle is 10 to 400 km deep. Olivine and pyroxene are the primary minerals found in this layer. Part of the upper mantle called the asthenosphere might be partially molten.
Crust
This is the outermost layer and ranges from 5 to 70 km in depth. The this parts are the oceanic crust, which underlie the ocean basins (5–10 km) and are composed of dense iron magnesium silicate rocks, like basalt.The thicker crust is continental crust, which is less dense and composed of (felsic) sodium potassium aluminium silicate rocks, like granite. Silica and aluminum are the main constituents of continental mass and silica and magnesium composes oceanic crust. The crust-mantle boundary occurs as two physically different events. First, there is a discontinuity in the seismic velocity, which is known as the Mohorovicic discontinuity or Moho.
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