*Earth's movements

   The surface of the earth is not stable,it is changing day by day, month by month, year by year, decade by decade and century by century.Behind this transformation, there are many forces responsible for it.Due to these forces , mountains , hills , plateau ,plains ,rivers ,rift valleys are formed. Basically we can classify these forces into two groups :- 
   
 (A).Endogenic forces 
      (B).Exogenic forces
                   

          
     There are many factors that are responsible for these movements are given below:-
(1). Rotation of the earth
(2). Various climatic factors that contribute to these movements like pressure belts, winds ,precipitation etc.
(3). Movement in the tectonic plate due to movement of lava in the mantle or tectogenesis.
(4) Isostacy:-It is the process in which big blocks of earth crust, because of variations in density would rise to different levels and appear on surface as plateau, mountains, plains etc.



  *Classification of these forces:-
          #Endogenic movements#
   (A).Diastrophism
     (a).Epeirogenic or continent forming
        (1).Upward
        (2).Downward
     (b).Orogenic or mountain building
        (1).Tension
        (2).Compression
   (B).Sudden movements
     (a).Earthquakes
     (b).Volcanoes

          *Endogenic movements:-These are the movements which are taking place inside the earth's crust.Many factors are responsible for these movements like rotation of earth, earth's internal radioactivity and heat from the core of the earth.These movements are mainly of two types :-
            
            (A).Diastrophism :- It is the term that defines slow bending ,folding of the earth crust. All the processes that elevate , move or build the earth crust are called Diastrophism.

           (a).Epeirogenic or vertical Movements :- These movements are basically associated with upliftment and subsidence of the continent. These movements are generated from the centre or core of the earth. In the formation of continents and plateau , these movements play a vital role . The central parts of continents are called Cratons .The horizontal layers of crust does not change due to these movements.

           (1).Upliftment of landmass :- Due to these movements ,some parts of the landmass are uplifted.The evidences of this movements are raised beaches , sea caves , elevated wave cut terraces and fossiliferous beds. There are some islands which have uplifted due to these forces like Korkai on the coast of Thirunelveli , Coringa near the mouth of the Godavari.


     Source :-Upliftment         
   
             (2).Subsidence of landmass :- Various submerged forests and valleys are evidence of this type of movement. In India ,the lignite and peat beds are formed due to Subsidence of forests.The lower region of Rann of Kachh was also a submerged area and filled with salty water.

            (b).Orogenic or Mountain building :- In these types of movements , either compression or tension occurred because of that folds or fissures are generated.Orogenic movements basically effect the crust horizontally. A large extent of disruptions in the crust is generated by these forces.

            (1).Tension :- Tension forces work horizontally but the direction of the forces is totally opposite or at 180° to each other.Under these conditions of forces ,large amount of rock strata is disrupted or damaged and cracks or fracture ,faulting is occured. It is basically the process of displacement of rock along a crack or fracture .Fault line is generated which is basically the line along which displacement is occured.Due to faulting , some places undergo subsidence while other remains as it as.Because of it , these remaining parts look higher and another look lower. Because of it ,rift valleys and block mountains (Vindhya and Satpura) are formed.
  Source:-Rift cross section
      
•Graben :- Rift valley base
•Horst :- Block mountain base
•Escarpment :- Steep slope in a continuous line along a fault

             (2).Compression :- When forces push Christ's rocks against a hard plane from one side or from both the sides ,then bending or folding of rocks happened and due to this bending and folding , fold mountains are formed. The upper top of the mountains is called Anticline and lower valley is called Syncline. All the great mountains of the worlds are fold mountains ,like Himalayas in India ,Andes in South America , Alps in Europe etc.


            (B).Sudden Movements :-
                
              (a). Earthquakes :- When the earth's crust is disrupted and due to release of energy ,there happened a couldn't shaking of the ground . These disruptions result in the release of energy along a fault and cause the earth to shake . The point at which an earthquake originates is called as Focus or Hypocenter .The point exactly above the Hypocenter on the earth's surface is called as the Epicenter .All major earthquakes take place in the Lithosphere from where earthquake waves are generated.




               (b).Volcanoes :- When lava or magma comes out of hill type structure from the mantle then it is termed as volcanoes .The pressure in the mantle or in the interior of the earth pushes lava out with large force ,then it outbursts in the form of volcanoes .According to plate tectonics theory ,large plate subducted under the small plate .Volcanic activity is included in endogenic process .
   Source :-Volcanic Eruptions         

 *Types of Volcanoes :-
              (1).Shield Volcanoes
              (2).Composite Volcanoes
              (3).Fissure Volcanoes
              (4).Caldera