The earth is made up of several layers of material arranged on top of each other. The outermost layer is the thinnest layer, called the solid crust, further classified into oceanic crust and continental crust. The oceanic crust, the crust beneath the oceans, is only 5 kilometres thick while the continental crust is around 35 kilometres thick.
The oceanic crust, is made up of silica and magnesium, and is called sima while the continental crust is composed of two minerals: silica and alumina and called sial. The next layer is a highly viscous layer called the mantle. The mantle is 2,900 kilometres deep and is thickest among all the layers forming 83% of the earth’s volume. The material inside the mantle is known as magma.
When the earth’s crust gets ruptured, hot molten magma, ash and gases come out from the core to the surface of the earth. This results in the formation of a volcano and the magma released on the surface of the earth is called lava.
Below the mantle is the core of the earth divided into outer core and inner core. The outer core is mainly made up of nickel and iron, called as nife. The materials in the outer core are in a liquid state. The temperatures in the inner core range from 5000 to 6000 degree Celsius. The core as a structural element of the earth was discovered in 1906 by R.D. Oldham.