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UPSC Geography Interior of the earth Short Notes - Rocks and Minerals

Short Notes - Rocks and Minerals

Category : UPSC

 

Rocks and Minerals

 

  • Rocks are naturally occuring hard substances made up of either single or multiple minerals compactly held together by cement like mineral matrix.
  • As many as 87% of the minerals in the Earth's crust are silicates.

 

Types of Rocks

  • On the basis of modes of formation there are three types of rocks.
  • Igneous Rocks: Igneous rock is formed through the cooling and solidification of magma or lava such as granite and diorite.
  • Sedimentary Rocks: Sedimentary rocks are derived from the process of deposition and  solidification of sediments after the process of
  • denudation. For instance; Sandstone, limestone and chalk rock salts, gypsum or calcium sulphate, etc.
  • Metamorphic Rocks: Metamorphic rocks arise from the transformation of existing rock types, in a process called metamorphism, which means
  • "change in form". Gneiss phyllite, slate, schist, marble, quartzite, etc belongs to the category ofmetamorphic rocks.

 

Basic rocks Metamorphosed

 

  1. Limestone to Marbles
  2. Sand stones to Quartzites
  3. Shales/ Clays to Slates / Schist
  4. Granite to Gneisses
  5. Gabro to Serpentine
  6. Coal to Graphite

 

Whole Earth's Composition

 

Elements

Percentage

Iron

35

Oxygen

30

Silicon

15

Magnesium

13

Nickel

2.4

Sulphur

1.9

Calcium

1.1

Aluminium

1.1

Others

1.0

 

Earth's Crust

 

Elements

Percentage

Oxygen

46

Silicon

28

Aluminium

8

Iron

6

Magnesium

2

Calcium

4

Potassium

2.3

Sodium

3.0

Others

1.0

 



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