Endogenic Movements
Endogenic Movements - These are the movements originated from the Earth's interior and they give rise to land upliftment, subsidence, folding, faulting, etc.
- Source of energy - Primordial heat and Radioactivity
- Responsible for major structural features on Earth's surface
It can be classified into Diastrophic and Sudden movement.
Sudden Movement - These are the movements of shorter duration which are unpredictable in nature and can be observed by human being. They may result in Catastrophic effect (disasterous).
Example - Earthquake, volcanic eruption, etc
Diastrophic Movement - These are the movements that operates very slowly but continuously and lead to formation of primary landforms. These movements elevates or moves or builds up the portion of Earth's crust.
The diastrophic movements are of three types -
- Tectonic movement
- Isostatic movement
- Eustatic movement
Tectonic Movement - The word tectonic is derived from the word 'Tekton' which means building or to build. These are continents and mountain building movements affecting the Earth's surface.
It includes Epeirogenic and Orogenic Movements.
Epeirogenic movements - these are the vertical movements caused by the radial forces acting from Earth's interior. They are characterised by large scale upliftment or emergence and subsidence or submergence of land areas.
They are very-very slow and widespread in a large area. They lead to continent building.
Example - Upliftment of Deccan Plateau and Subsidence of Northern coast of Gulf of Mexico.
Orogenic movements - These are the mountain building movements caused by the tangential forces which include compressional and tensional forces.
It includes folding, thrusting and faulting of narrow belts. Orogenic movements are classified into folding and faulting.
Folding - Folding are formed when the compressional forces cause the Earth's layer to push and squeeze against each other.
Folds are the structure in which the layers are bend or distorted without the loss of continuity.
- Limbs - Size of folds is called limbs.
- Anticline - When the strata is bent upward, it results in upfold known as anticline.
- Syncline - When the strata is bent downward, it results in downfold known as syncline.
- Symmetrical fold - If both the limbs of fold are inclined at same angle, it is called symmetrical fold.
- Asymmetrical fold - If one of the limb is inclined more than the other, it is called asymmetrical fold.
- Overfold - When the strata in one end is folded beyond the vertical axis, it is called overfold.
- Recumbent fold - The recumbent fold is a fold which is literally lying down resulting from continuation of pressure on one of the limbs.
- Nappe - When pressure exerted upon the recumbent force is sufficiently great to cause it to be torn from its root and thrust forward, it is known as nappe. Nappe discontinued the continuity.
Folds are well developed in Himalayas and Alps.
Faulting - The tensional forces pull the rocks apart resulting in the formation of fractures by which the primary surface areas are broken and displaced with the loss of continuity.
Example - Satpura and Vindhya fault.
Types of Faulting
Normal fault - When one of the block moves downward in relation to the other one due to tensional force, it is called Normal fault or Dip-Slip fault.
Example - Vindhya and Narmada Valley, Black forest and Rhine valley, etc
The downward block in a fault is called Graben and the valley is called Rift valley. The upper most fault is called as Horst.
Reverse fault - When one block moves up in relation to the other one due to compressional force, it is called Reverse fault or Thrust fault.
Strike-Slip fault - When both the blocks moves across each other involving no other vertical movement with only lateral movement, it is called Strike-Slip fault or Transform fault.
Difference between Fold mountain & Fault (Block) mountain
Fold mountains -
- result of folding
- have continuity
- created because of compressional force
- greater in length (spread upto 100 of KM)
Fault (Block) mountains -
- result of faulting
- have no continuity
- created because of compressional as well as tensional force
- wider than fold mountain but not very lengthier.
Previous Article - Earth's Movement: An introduction
Next Article - Isostatic and Eustatic movements
Notes on other subjects
Optional Notes
Note - This is my Vision IAS Notes (Vision IAS Class Notes) and Ashutosh Pandey Sir's Public Administration Class notes. I've also added some of the information on my own.
Hope! It will help you to achieve your dream of getting selected in Civil Services Examination 👍
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