Saturday, 10 January 2015

Geography - Inside our Earth

                            Inside our Earth

                                The Earth is a dynamic planet

what is the crust ?
  • The uppermost layer cover the earth surface is called the crust.
  • It is thinnest of all the layer 
  • It is about 35 km on the continental masses and only 5 km on the ocean floors.
  • The main minerals constituents of the continental mass are silica(Si) and alumina(Al).it is thus called SIAL.
  • The oceanic crust mainly consists of silica(Si) and magnesium(Ma). It is therefore called SIMA

What is the Mantle ?
  • Just beneath the crust is the mantle which extents up to a depth of 2900 km.
What is the Core ?
  • The innermost layer is the core with a radius of about 3500 km. 
  • It is the mainly made up of nickel(Ni) and iron(Fe), hence it is called NIFE. The central core has very high temperature and pressure.

What is Rock ?
  • The earth's crust is made up of various type of rocks. any naturals mass of mineral matter that makes up the earth's crust is called rock.
  • Rocks can be of different colour, size and texture.
How many types of rocks?
  • There are three types of Rocks

  1. Igneous rocks.
  2. Sedimentary rocks.
  3. Metamorphic rocks.
What is Igneous Rocks ?
When the molten magma cools, it becomes solid rocks. The rocks thus formed are called igneous rock. They are also called primary rocks.

How many types of Igneous rocks? 
  1. Extrusive igneous rocks.
  2. Intrusive igneous rocks.
What is Extrusive igneous rocks ?
  • Lava is actually fiery red molten magma coming out from the interior of the earth to its surface. When this molten lava comes on the earth surfaces, it rapidly cools down and become solid, rocks formed in such a way on the crust are called extrusive Igneous rocks. 
  • They have a very fine grain structure.
  • For example- Basalt .The Deccan plateau is made up of basalt rocks.
What is Intrusive igneous rocks?
  • The molten magma cools down deep inside the earth's crust.solid rocks so formed are called intrusive igneous rocks.
  • Granite is an example of such rock.
  • Grinding stones used to prepare paste/powder of spices and grains are made of granite.
What is Sediments?
Rocks roll down, crack and hit each other and are broken down into small fragments. These small particles are called sediments.

What is Sedimentary rocks?
Sediments are transported and deposited by wind, water, etc. these loose sediments are compressed and hardened to form layers of rocks, these types of rocks are called sedimentary rocks.
For example- Sandstone, this rock contain fossils of plant, animals and micro-organism that once lived on them.

What is fossils ?
The remains of the dead plants and animals trapped in the layers of rocks are called fossils.

What is metamorphic rock?
  • Igneous and sedimentary rocks can change into metamorphic rocks under great heat and pressure
  • Clay changes into slate and limestone into marble.
  • The Red Fort is made of Red sandstone.
  • The Taj Mahal is made of white marble.
What is rock cycle?
One type of rocks changes to another type under certain conditions in a cyclic manner . This process of transformation of the rock from one to another is known as the rock cycle.


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