The earth rock and soil

Introduction
We know that earth is one of eight planet. Although it appears round in the space, it is not completely round . the equatorial diameter is the boarder than the polar diameter. The surface of the earth is no uniform and smooth. There are many structures like plain, mountains, plateaus, hills,valleys etc. the surface of the earth where we live is cool and favourable for life. The inner surface of the earth is not similar. The temperature and the density of the material goes on increasing in the inner part of the earth. Scientist has divided the internal part of the earth. They are crust, mantle outer core and inner core.
The outermost layer of the earth is crust. The crust is made up of rocks. The rocks are hard materials found on the surface of the earth. Rocks are also found in the inner depth of crust. Soil is formed by weathering of rocks. Most part of the surface contain soil which is covering the hard rockbeneath it. The bottom layer is bed rock. This is why the soil contains many rocks mixed in it.
Rocks
Rocks make the earth’s surface. Rocks are found on the surface as well as in the inner part of the earth.in the regions where plant is growing, the rock is covered by soil. The hard materials which make the earth’s crust are called rocks. The branch of science which deals with rocks is called geology. The scientist who are engaged in the study of rocks is called geologist.

Composition of rock
There are rocks of different shape, sizes ,color texture, hardness and chemical nature.the chemical nature or composition means different proportions of elements on the rocks. Different types of rocks have different proportions of different elements in them. The rocks on disintegration provide different elements to the soil which is utilized by plants and animals. The increase indifferent elements in the soil like calcium, potassium, sodium, magnesium etc . make soil fertile. In this way rocks support life.

Types of rocks
On the basis of origin and formation of, rocks are catagorised I nto three types.
1. Igneous rock
We have already study that the inner part of the earth has substances in a molten state. the molten mass, mixture of liquid and gas at high temperature is called magma. The magma sometimes due to some reasons comes out to the surface of the earth. The magma on the surface of the earth is called lava. The magma comes out through narrow channels or a passage searching for the weak parts on the earth’s crust. The points or regions on the surface through which lava comes out is called crater. The lava on reaching the earth surface get coole, solified and change into rocj. This type of rocks is called igneous rock.they are found in volcanic zones.some of them are granite, pumice, obsidian, basalt.


2. Sedimentary rocks
The weathering of rocks is continuous process on the earth’s surface.the continuous breaking changes rocks into small particles. Sedimentary rocks are formed by this tiny particles.wind, river ,air deposit materials. The deposited layer is called sediments. Many layer of sediments are formed continuously by this process. After a long period the layer underneath into hard rocks. This type of rock is called sedimentary rocks. Some of them are conglomerate, sandstone, shale, limestone etc.




3.metamorphic rock
The types of ricks which are formed by the change in sedimentary or igneous are called metamorphic rocks. They are found in the inner part. Some of them are quartzite, graphite, marble, schist, diamond slate etc.