INSIDE OUR EARTH

                                                               

                                                    INSIDE OUR EARTH

Layers of the Earth:

 

What is Crust?

 

Crust is the uppermost layer of the Earth's surface. It is the thinnest of all the layers.It is around 35 km thick in the landmass and just 5-10 km thick under the oceans.

                          The continental mass of the Earth formed by silica and aluminium. Therefore it is called Sial. Here 'Si' from 'silica' and 'Al' from 'aluminium'.

                                  Similarly, the  oceanic crust mainly constitutes of silica and magnesium. So it is called Sima. Here 'Si' from 'silica' and 'Ma' from 'magnesium'.

 

 

 

What is Mantle?

The mantle layer is about  2900 km thick. It is mainly composed of Ferro-magnesium silicates. This layer can be divided into two as the upper and lower mantle.

 

What is Core?

The core is the innermost layer of the Earth. It is about 3500 km radius. The core is divided as

a) Outer core: It is liquid and constitutes iron and nickel. Thus, it is called Nife.' Ni 'from 'nickel' and 'Fe' from 'ferrous' or 'iron'.

b) Inner core: The inner core is solid and mainly composed of iron.

 

What is rock?

Any natural mass of mineral matter that makes up the Earth's crust is called rock.

 

What are the basis of classification of rocks?

Rocks are generally classified by their composition, by their appearance or texture and by the processes of their formation.

 

What are the three types of rocks?

Rocks are classified into three types. They are-

a) Igneous Rocks:Igneous rocks are called primary rocks. The igneous rocks are formed when molten magma cools and turns into solid rock.

                     Further, this rock is classified into two types:

                      1) Extrusive or volcanic rocks: When any volcano erupts molten lava and it flows out,they rapidly cools down and solidifies into rocks. Such rocks are called volcanic or extrusive rocks.  Examples of extrusive rocks are pumice and basalt.

                       2) Intrusive or plutonic rocks: They are formed when magma cools and crystallizes slowly within the earth's crust. Example of intrusive rocks is granite. 

b) Sedimentary Rocks: Due to weathering action of water and wind, Sun, rain ,etc rocks keep breaking, cracking and disintegrating.These smaller pieces and particles get transported by winds and water and collect at places in the form of sediments. They gradually get compressed by their own weight and harden into rocks. These rocks are known as sedimentary rocks.Sandstone, mudstone, limestone etc are some examples of sedimentary rocks.

 c) Metamorphic Rocks: Metamorphic rocks are rocks which have changed their state from their earlier form.They are form by subjecting any rock type to different temperature and pressure conditions than those in which the original rock was formed. Some examples are limestone, changes to marble and clay into slate. 

 

What is Rock Cycle?

The rock cycle is a process of transformation of a rock from one rock form to another.  

                          Rocks changes from one type to another under certain conditions in a cyclic manner. This process of transformation of the rock from one another is known as the rock cycle.

             

 

          For example, we found that cooled molten magma become igneous by solidifying . These igneous rocks are broken down into small particles that are transported and deposited to form sedimentary rocks. When they are subjected to heat and pressure they change into metamorphic rocks. Under heat and pressure, metamorphic rocks melt down to form molten magma. This molten magma again can cool down and solidify into igneous rocks.

 

How are rocks useful to us?

Rocks are used by humans for various construction activities. They are used in making  roads, houses, buildings, etc. Rocks are crushed , grinded, cut and polished to change their shape and size to make them usable in different forms.

 

What are Minerals?

Minerals are naturally occurring substances which have distinct physical and chemical composition. Coal, iron, aluminium, petroleum, natural gas, silica, uranium, gold, silver are some examples of minerals.