THE INTERIOR STRUCTURE OF THE EARTH

THE INTERIOR STRUCTURE OF THE EARTH

INTRODUCTION.

Knowledge of the structure of the Earth is necessary in order to understand the surface features of the earth. The surface of the earth consists of mountains, plateaus, plains, valleys and other features. These different types of Landforms vary in size and distribution. While some of these landforms are formed by the external denudation processes which take place on the surface of the Earth. Other owes their origin to the internal forces, which operate in the interior of the Earth. There, it is necessary to learn about the interior layers of the Earth. An idea of the interior structure of the Earth has been obtained from a study of earthquake waves. These are called the crust, the mantle and the core of the Earth. The density, temperature and pressure of these layers increase with depth.

The Chemical composition and Physical State of matter inside the Earth is of great concern for study of landforms on the surface of the Earth.

Crust of the Earth or Lithosphere.

The surface of the Earth consists of rocks of various types. The layer of rocks forms a relatively thin layer and is called the lithosphere of crust of the Earth. The crust has an acreage thickness of about 60 km. This forms less than 1 % of the radius of the Earth. The crust is subdivided into two parts according to their composition. The top most layer is lighter having an average density of 2.7 gm/cu.cm. This layer consists of silicates and aluminum and other higher metals. This layer is called the sial (silicate+aluminnium). The sial layer is thick over the continents but is thin ocean floors.

Below the sial layer is a denser layer, which consists predominantly of silicates os magnesium and other denser metals. This is called the sima (silicate+magnesium) layer. The sima layer has an average density of about 3.0gm/cu.cm. The sima layer forms the ocean floors.

The composition of the crust layer is of great interest because we get most of our minerals from the crust of the Earth. The physical features of the Earth's crust influence land use and other human activities. The density of human population also depends on the nature of the relief features in an area.

Mantle or Pyrosphere

The mantle of the Earth lies below the crust of the Earth. The mantle has an average thickness of about 2840 km. It consists of mixed silicates between 3.0 and 5.5 gm/cu.c. Though the temperature of the layer is quite high, the high pressure of the overing layers keeps this layer in a solid state.

Core of the Earth or Baryshere

The core of Earth has a radius of about 3500 km. It consists mostly of metala. As mickel and iron are the two most abundant metals, the core is called Nife (nickel + ferom). The density of the core is between 12 to 15gm/cu.cm. This dense layer is also called the Barysphere. The core of the Earth is estimated to have a temperature of about 5500^oc. The metallic core and the abubdance o iron also explain the earth's magnetism.