Basic Concept of Mountains.

DEFINITION :-

A mountain may be defined as a huge landmass on the earth's surface,attending a great height above the surrounding with a series of oranges and loftly crests and peaks covered with snow.

DESCRIPTION :-

A mountain is a highland area with a series of ranges and peaks.It has many gorges and valleys.Between the high ranges,there are intermont plateaus.High mountains are regions of glacical activity.

FORMATION :-

Mountains are formed in various ways.They are formed by wrinkling up the earth,s surface.Giving away heat from its body,the earth wrinkles.As a result,compression and contraction take place and folds,fractures and faults are formed in the rock-beds which in time build up mountains and valleys.Volcanic eruption erects volcanic mountains.Erosional agents ( The sun,the rain,,the wind and the running water) wear away the soft rocks of the highlands ; the high resistant rocks are left there as erosional mountain.

An eminent German, Prof Alfred Wegner (1912) explained in his 'Continental Drift Theory ' how the mountains were formed .According to his theory,the lighter rocks-beds are in a floating state on the heavier rock-masses.In the primitive world there was a single landmass called 'Pangaea'.Natural forces broke it down into pieces ; the major pieces are know as continents.In time, they drifted apart. As they drifted away, the horizontal pressure pushed the rock-beds to form fold ; harder rock beds got fracture and faulting occurred. Thus the drifting of the continents caused the formation of the fold mountains and other landforms.

In the recent years, "Plate Tectonic Theory" has become popular. It has developed the idea on the former. This theory states that the continents and the oceanic beds consist of a series of plates; the continents plates are floating on the oceanic plates. The get motion when disturbances occur in the interior of the earth; sometimes intrusion takes place from the interior to the upper layer and the plates begin to move. As the plates move towards each other, friction sometimes occurs. It exerts pressure which forces the rock-beds to bend and thus (i) folds (ii) Faults and (iii) Eruption occur, resulting in the formation of mountains and different types of landform.

Classification of Mountain :-

Mountain can be classified into four major types, according to their mode of formation : (i) Fold mountain (ii) Block mountain (iii) Volcanic mountain and (iv) Relict mountain or Erosional mountain.

  

Basic Concept of Metamorphic Rock

DEFINITION AND FORMATION:-

 Metamorphic rock is formed by ( the change the greek word 'metamorphosis' means change of form ) in a rock from its original form by heat and by pressure beneath the surface of the earth. The igneous and sedimentary rocks undergo a great change in their physical appearance and chemical properties due to (1) Intense heat and (2) Great pressure. Thus internal changes take place within the rocks. The particles are rearranged and redistributed affecting the structure and character of the rocks. The crystal in the rocks are arranged in fine parallel layer.

Sometimes, the change is so thorough that the original characters are no longer present in the altered rock.

EXAMPLES :-

Gneiss, Marble, Quartzite, Graphite, Slate, Amphibolite etc.are the example of metamorphic rocks. Under the process of metamorphism (1) Granite changes into gneiss, (2) Basalt into Amphibolite, (3) Limestone into marble, (4) Shale into slate, (5) Sandstone into Quartzite and (6) Peat coal into graphite.

Fig : Gneiss

Fig :- Structure of Graphite 

Fig :- Structure of Graphite

Fig :- Quartizite

Fig :- Slate

Fig :- Amphibolite

Fig :- Granite into Gneiss

Fig :- Basalt into Amphibolite

Fig :- Limestone into Marble

Fig :- Shale into Slate

METAMORPHISM :-

The greek word metamorphosis means change of form.The changes which take place in rocks due to intense heat and pressure is known as metamorphism.It is of two types : (1) Contact Metamorphism or local Metamorphism and (2) Regional Metamorphism.

CONTACT OR LOCAL METAMORPHISM :-

 When hot magma enters the fissures, it bakes the adjoining rocks in the contact zone.It produces chemical replacement and recrystallisation. As it affects by means of contact,it is know as contact metamorphism.As it also affects a small area, it is called local metamorphism.In this metamorphism,limestone is changed into marble.

REGIONAL METAMORPHISM :-

 Generally, it associates with great mountain building movements.Thus change which occurs,takes a long period and affects a large area.Hence,this is known as regional metamorphism.The pressure of the overlying rocks recrystallizes the rocks below.In this way, shale is changed into slate; and again state is changed to schist.

CHARACTERISTICS AND USES OF METAMORPHIC ROCKS :-

Metamorphic rocks are massive,completely crystalline and hard.They are resistant to erosion. They are very rich in minerals.they attract huge mining population.Since they are hard ,they are used as building and road materials.No fossil is found in metamorphic rock.when sedimentary rock undergoes changes,the fossils are destroyed by heat and pressure.

Basic Concept of Sedimentary Rocks

Definition and Formation :-

 Sedimentary rocks are formed by the worn-out sediments of previous rocks. The primary rocks are worn down by the different natural agents such as sun,rain,running water, wind , moving ice etc. The fragment of rocks and sediments are brought down by the glacier, river, stream, wind and wave etc.and they are subsequently deposited in layers on the sea-bed.In time,owing to pressure of their own layers, heat of the interior and the chemical reaction of lime , these layers of sedimentary undergo solidification and cementation to form hard rocks.Thus the sedimentary rocks are formed in layers of sediments and they are also know as stratified rock.

A layer of sedimentary rock rest upon another layer . The plane or the surface which separates one layer of sedimentary rock from another is know as bedding plane.

Fossil :-

Fig :- Fossil

Fig :- Fossil

  With the sediments,remains of animals and plants are also carried down and these undergo solidification to from rock.Thus organic rocks are formed ; they are also know as fossils.Thus fossils are the recognizable parts trace or imprint of a particular pre-historic animal or planet once buried in sediment and subsequently hardened like of rocks.

Example :-

sandstone, mud stone, limestone, conglomerate and shale are the examples of sedimentary rocks. These rocks and some fossils are found in the layers of the sedimentary rocks of the Himalayas.

Fig :- Sandstone

Fig :- Conglomerate

Fig- Lime stone

Fig :- Shale

Classification of sedimentary rock according to its mode of formation :  

 According to its mode of formation,sedimentary rocks can be divided into the following three types: (1) mechanically formed rocks, (2) organically formed rocks and (3) chemically formed rocks.

Mechanically formed rocks :-

These rocks are consolidated in a mechanical manner. They are coarse grained.

Example :- 

 Conglomerate, Mudstone and Breccia are of this type of sedimentary rock. Large rounded boulders, sand and fragments of rock together from conglomerate. Breccia is formed by triangular from of rock-particles. Minute particles of sedimentary constitute the Mud stone.

Fig-Breccia

Fig :- Mudstone

Organically formed rock   :-

Hard particles of once living organism may accumulate to from the organically formed rocks.

Example :- 

Limestone and Coal are the example of organically formed rocks.Calcareous Limestone are composed of shells and skeletons of animals largely consisting of calcium carbonate.Coal is carbonaceous rock.It is formed from plant accumulation beneath the surface of the earth .

Fig-Limestone and Coal

Chemically formed rocks :-

These rocks are mostly precipitated from solution of certain salts and other chemical compounds.

Example-

Rocks salt , Dolomite, Calcite, Gypsum borax etc. are the examples of chemically formed rocks.

Fig :- Dolomite

Fig :- Calcite

Characteristics and uses of sedimentary rocks :-

(1) The sedimentary rocks are formed by sediments and remains of the primary rocks. (2) They are formed mainly by the action of water and are, therefore, called aquatic rocks. (3) They are formed in states of horizontal layers and are,therefore, know as stratified rocks. (4) They contain particles of various sizes and shape. (5) They are less hard than igneous and metamorphic rocks. (6) They cover nearly 70% of the total surface of the earth.(8) They contain several kinds of fossil. (9) They are not resistant to erosion.Sedimentary rocks are very useful.Sandstone and limestone are of great economic value. Sandstone are useful as building and road materials. They are used to raw materials in the glass factory. Limestone are used in cement industry. The fossils are very useful to trace out the past history of the earth.

Basic Concept of Igneous Rock

Definition of Rocks :-

A rock may be difined as an aggregate of minerals of different kinds in varying proporation, occurring in natural condition. All meterials  that make the earth's crust are called rocks. They may be soft like clay or hard like granite . clay , sand , slate and basalt are all rocks in the widest term of the world.

Classification of rocks :-

 Rocks can be classified into three main types according to their mode of origin : (1) Igneous rocks , (2) Sedimentary rocks, (3) Metamorphic rocks.

IGNEOUS ROCK :-

The igneous rocks are formed by cooling and solidification of hot molten lava and magma poured out on the earth's surface or poured in below the solid rock of the earth's crust by volcanic activity  at the beginning when the earth born ,it was just a glowing ball of gas. Gradually, it cooled down and its molten volatile surface solidified. In this way the igneous rock formed at first on the earth's crust . Hence it is called primary rock. It has no layer and that is why it is called unstratified rock . 

Classification of igneous rock according to its mode of formation :

The igneous rock originates from the hot molten lava and magma under various circumstance. According to the mode of formation , it can be classified into the following types : (1) Extrusive rock and (2) Intrusive rock.

                                                                                                                                                         

Extrusive rocks :-

Extrusive rock is formed , when hot moltem lava pours out on the earth's surface and cools there. As its cools very rapidly , its forms very fine crystal. Thus extrusive rock is a fine-grained rock.

Example :-

Basalt contains extremely fine crystal . Basalt is a very common rock in Chotanagpur plateau. It is also found in some parts of the lava plateau of Maharastra.

Fig :- Bassalt

Fig :- Bassalt 

Intrusive rocks :-

Intrusive rock is formed when magma intrudes into the earth's crust. As it cools there slowly,it forms large crystal. Thus intrusive rock is a coarse - grained rock.

Example :- 

Granite, Gabbro, Dolerite are example of intrusive rock may be further into two more types are (1) Plutonic rock and  (2) Hypabyssal Rock

Fig :- Granite

Fig :- Gabbro

Fig :- Gabbro

Fig :- Dolerite

Plutonic rock :-

The magma which cools down very slowly in the deep underground of the earth's crust is called plutonic rock after pluto, the god of the under grounded. As it cools down very slowly , large crystals are formed in it . Thus plutonic rock is characterized by large crysalled, compactness and coarse texture.

Example :-

 Granite and Gabbro are plutonic rocks. these rocks are found in the Deccan plateau of India .

Fig :- Granite and Gabbro

Fig :- Deccan Plateau of india

Fig :- Granite and Gabbro

Hypabyssal rock :-

It is formed when intrusion of magma occurs in the cracks or along the lines of weakness in the earth's crust. As it cools down more rapidly  than the plutonic rock but slower than the extrusive rock, smaller crystals than the plutonic rock , but larger than the extrusive rock , are formed.

Examples :-

Dolerite and Prophyrie are typical examples of  hypabyssal rock. Dolerite and prophyrie are typical examples of Hypabyssal rock. Dolerite is commonly found in Jharia and Raniganj coalfields.

Characteristics and uses of igneous rocks :-

(1) Igneous rocks are formed by cooling and solidification of hot molten lava and magma. (2) They are compact , massive and crystalline. (3) They contain several kinds of minerals ,though they are not rich in mineral resources. (4) They do not contain any fossil. (5) They are very usefull as building and road materials.

Basic Concept of Plateau

DEFINITION  :-

A plateau is an extensive unpland area with almost flat topped surface and broad summit. Plateaus are extensively flat upland areas with altitudes of above 300 meters from the sea-level. They have steep sides and deep edges. They often look tables standing above the surroundings and for this, they are, sometimes, called tablelands. The plateaus are of different heights.Some plateaus are very high : some of them higher than mountains. The tibetan plateau is about 4,500 meters high. There are also many low plateaus with a height of a few hundred meters. The plateaus along the western margin of West Bengal are only 300 meters. The Pamirs in Asia is the highest plateau 4,873 meter in the world and that is why it is called "The roof of the world". The Ladakh plateau 3,500 meters of Kashmir is the plateau in India.

FORMATION :-

Plateaus are formed in various ways :

 (1) The accumulation of lave erupted from the volcanoes, sometimes, build up plateaus ;

Example :-

Maharrashtra plateau. 

Fig :- Maharrashtra Plateau

(2) Tectonic movements sometimes lift the land up and this upliftment of the lowland often forms plateau ;

Example  :-

The Tibetan plateau

Fig :- Tibetan Plateau

(3) sometimes extensive uplands and mountain areas are worn down by natural agents  (the sun,the rain and the running water etc.) and low dissected plateaus are formed .

CLASSIFICATION OF PLATEAUS   :-

Plateaus are mainly of three major types : (1) DISSECTED PLATEAU (2) INTERMONTANE PLATEAU and (3) LAVA PLATEAU

DISSECTED PLATEAU :-

The plateaus which are formed owing to weathering,erosion,and denudation of the former upland areas and are cut by innumerable rivers and rivulets with small vales and dales,are popularly know as dissected plateaus.

FORMATION :-

The natural agents, such as, the sun, the rain, the wind, the running water and the glacier wear away the soft rocks of the upland areas.The resistant rock masses are left there standing on the ground above the surroundings. The sometimes from almost level surface, cut by rivers and streams. These upland areas together form dissected plateau.

EXAMPLE :-

(1) The chotanagpur plateaus of jhrkhand, (2) Malnad regions of karnataka, (3) The malwa plateau of central india and (4) The plateaus of wales in great Britain are some of the important examples of the dissected plateau.

Fig :- Chotanagapur Plateaus

Fig :- Malanad regions of karnataka

INTERMONTANE PLATEAU  :-

The plateaus which have mountain rim round their surroundings are know as intermontane plateaus. These plateaus are, in fact, encircled by high mountain chains. The intermontane plateaus are some of the high plateaus of the world.

FORMATION :-

During mountain building movement when fold mountains rise up due to the horizontal pressure on the layers of rock,the lands in between the mountains also lift up.Thus the upliftment of fold mountains often builds up the intermontane plateau in between their ranges.

EXAMPLE :-

(i) The Tibetan plateau in between the Himalayas and the Kunlun, (2) Iranian plateau in between the Zagros and Elburz mountain, (3) The Anatolian plateau in between the pontics and Taurus mountain are the most suitable examples of the intermontane plateau.

LAVA PLATEAU :-

The plateaus which are formed by volcanic lava, are called lava plateaus.

FORMATION  :-

These  plateaus are formed as a result of lava flow in volcanic regions. Lava spreads over the earth's surface and solidifies to form a lava plateau.These plateaus cover large areas on the earth's surface.

EXAMPLE :-

 (1) The plateau of Maharashtra, situated in the north-west of the decan plateau in India, is formed by lava. (2) The snake-Columbia basin in U.S.A. (3) The plateau of Somalia and Ethiopia in east Africa, (4) The plateau of Bolivia in south america and (5) The plateau of Maxico (Sierra madre) are the distinctive examples of lava plateau in the world.