The earth our home planet is a dynamic planet that undergoes lots of changes inside and

outside especially the deepest interiors. The earth is made up of several concentric

layers with one inside the other. The outer most layer is the crust, which is the thinnest

of all layers with a thickness of 35 km on the continental masses and 5 km on the oceanic

floors. The main consistent of the continental masses is the silica and aluminum which is

also referred as SILA where as the oceanic crust mainly consists of silica and magnesium

and is therefore called as SIMA. Beneath the crust there is a 2nd layer, the

mantle which extends up to a depth of about 2900 km and a radius of about 3500 km.

The minerals that are mostly found in this layer are Nickel and ferrous which account

for very high temperature in the interiors of the earth

Rocks and minerals A natural mass of mineral matter that constituents

the earth crust consists of rocks of different colours, sizes and textures.

There are three major types of rocks 1. Igneous

2. Sedimentary 3. Metamorphic

The formation of these igneous rocks or primary rock as they are also called occurs when the

molten magma cools and becomes solid. There are two types in these igneous rocks. They

are Intrusive and extrusive rocks. The lava which is fiery molten magma that comes out

of the volcanoes become hard when it touches the crust forming extrusive igneous rocks.

They have a very fine grained structure. One the example is Basalt. The deccan plateau

is primary made up of basalt rocks. when the magma cools down inside the crust,

really hard and solid rocks are formed which are called intrusive igneous rocks. An example

of this type of rock is granite which is used to make grinding stones.

Sedimentary rocks are formed by a process when rocks roll down and hit other and crack

forming sediments. These sediments are transported and deposited by wind, water etc. They are

in the form of layers of rock called the sedimentary rocks. Sandstone is formed by these grains

of sedimentary rocks. Under great heat and pressure the sedimentary

and igneous rocks are transformed into Metamorphic rocks just the way in which clay changes into

slate and slate into marble. Rocks as we all know are used to make roads, buildings and

houses. You can look around you and see the different types, shapes and sizes of rocks.

As we learnt before, rocks changes its types under external conditions and this process

of transformation is called the rock cycle. The first step of the cycle starts when molten

magma cools and solidifies into igneous rocks. Next when these igneous rocks are broken down

they transform into sedimentary rocks. The cycle continues till igneous and sedimentary

rocks that are subjected to heat and pressure change into metamorphic rocks. If these metamorphic

rock continue to be under heat and pressure, they melt to form molten magma thus completing

the rock cycle. Rocks also constitute minerals which are naturally occurring substances of

different physical properties and definite chemical structure. They are used as petroleum,

gas, aluminium, granite etc