Competitive Exams: Earth՚s Movement Endogenetic Forces

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The forces coming from within the earth are called as endogenetic forces which cause two types of movements in the earth, viz,

  • Horizontal movements, and
  • Vertical movements.

These movements motored by the endogenetic forces introduce various types of vertical irregularities which give birth to numerous varieties of relief features on the earth ′ s surface, eg. , mountains, plateaus, plains, lakes, faults, folds, etc. On an average, the origin of endogenetic forces is related to thermal conditions of the interior of earth. Generally, the endogenetic forces and related horizontal and vertical movements are caused due to contraction and expansion of rocks ′ because of varying thermal conditions and temperature changes inside the earth.

The endogenetic forces and movements are divided, on the basis of intensity, into two major categories:

  • Sudden forces are the result of long period preparation deep within the earth. Only their cumulative effects on the earth՚s surface are quick and sudden. Geologically, these sudden forces are termed as ‘constructive forces’ because these create certain relief features on the earth՚s surface.
  • Diastrophic forces include both vertical and horizontal movements which are caused due to forces deep within the earth. These diastrophic forces operate very slowly and their effects become discernable after thousands and millions of years. These forces also termed as constructive forces, affect larger areas of the globe and Produce meso-level reliefs, for example, mountains, plateau, plains, lakes, big faults, etc. These diastrophic forces are further subdivided into two groups, namely, epeirogenetic movements and orogenetic movements.
    • Epeirogenetic movements: Epeirogenetic word consists of two words, viz: ‘epiros’ (meaning thereby con-tinent) and ‘genesis’ (meaning thereby original) . Epeirogenetic movement causes upliftment and subsidence of continental masses through upward movements are, infact, vertical movements. These forces and resultant movements affect larger parts of the continents. These are further divided into two types: upward movement and downward movement.
    • Orogenetic movement: The word orogenetic has been derived from two Greek words, ‘pros’ (meaning thereby mountain) and ‘genesis’ (meaning thereby origin or formation) . Orogenetic movement is caused due to endogenetic forces working in horizontal movements. Horizontal forces and movements are also called as tangential forces. Orogenetic or horizontal forces work in two ways, namely,
      • in opposite direction
      • towards each other.

This is called ‘tensional force’ when it operates in opposite directions. Such type of force and movement are also called as divergent forces.

Thus, tensional forces create rupture, cracks, fracture, and faults in the crustal parts of the earth. The-force when operates face to face, is called compression force or convergent force. Compressional force causes crustal bending leading to the formation of fields or crustal warping leading to local rise or subsidence of crustal parts. Crustal bending: When horizontal forces work face to face, the crustal rocks are bent due to resistant compressional and tangential forces. It is in two ways:

  • warping
  • folding

The process of crustal warping affects larger areas of the crust wherein the crustal parts are either warped (raise) , upward or downward. The upward rise of the crustal part due to compressive force resulting from convergent horizontal movement is called up warping. While the bending of the crustal part downward in the form of a basin or depression is called down warping.

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