Fig 8: The Discontinuities

It extends from 2900 Km depth upto the centre of the earth (6378 km). It is the interior most part of the earth. It begins from Gutenberg Discontinuity. The mantle is demarcated from the core by Gutenberg Discontinuity. The core is divided into two parts: (i) The Outer Core, (ii) The Inner Core.

The outer core is possibly in wholly liquid or semi-liquid state. The transverse or S-waves of earthquakes, seem to disappear at the Gutenberg Discontinuity. The outer core extends from the depth of 2900 km, upto 5150 km. It has an average density of 10. The inner core is believed to be solid. It extends from the depth of 5150 km upto the centre of the earth (6378 km). The velocity of P waves increases at the boundary of outer and inner core. Its density is between 12-

13. To volume of the entire core is 16% of earth as a whole. The mass of the core is 32% of the earth’s mass. The major part of the core is made up of heavy metals like iron and nickel. This zone is therefore known as Nife (Ni = Nickel, Fe = Ferrous). It is also known as Barysphere (which means heavy metallic rocks).