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Exogenetic and Endogenetic Forces
Landform, whether large or small result from the interaction of certain forces, they
accomplish their work by various means of processes, which may be described as geologic,
Climatic and biologic and these processes bring about the changes in the Earth’s surface
which may be Classified as
(I)
Long Period Changes (Man is unable to notice this change) and
(II)
Short period Changes.
The forces which affect the crust of the earth are broadly classified in two types


ENDOGENETIC FORCE (ORIGINATES FROM WITHIN THE EARTH)
EXOGENETIC FORCE (ORGINATES FROM WITHOUT, OR BEYOND THE
EARTH)
1. ENDOGENETIC FORCES: The forces coming from within the earth are called as
Endogenetic forces which causes two types of movement in the earth viz Horizontal
movements and Vertical movements.
These forces derive their energy from changes such as radioactivity, chemical recombination,
expansion or contraction or displacement of molten materials which occurs in the interior of
the earth. This group of forces may be called as Tectonic forces which manifests through
Processes Called Diastrophism and Volcanism. The origin of Endogenetic forces and related
horizontal and vertical movements are caused due to contraction and expansion of rocks
because of varying thermal conditions and temperatures inside the earth. Volcanic eruptions
and seismic events are also expressions of Endogenetic forces. The displacement and
readjustment of geomaterials sometimes take place so rapidly that earth’s movements are
caused below the crust. On the basis of intensity the Endogenetic forces and movements are
divided in to two major Categories
 SUDDEN FORCES
 DIASTROPHIC FORCES
 SUDDEN FORCES AND MOVEMENT: Sudden and become disastrous When they
occur in densely populated localities. These forces work very quickly and their results are
seen within minutes. Movements, caused by sudden-Endogenetic forces coming from
deep within the earth cause sudden and rapid events that cause massive destructions at
and below the earth’s surfaces. Such events like volcanic eruptions and earthquakes, are
called ‘EXTREME EVENTS’ and become disastrous hazards when they occur in
densely populated localities. These forces work very quickly and their results are seen
within minutes. ‘It is important to note that these forces are the result of long period
Preparation. 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. For example, volcanic eruptions
result in the formation of volcanic cones and mountains while fissure flows of lavas form
extensive lava plateau and lava plains Earthquakes create faults, fractures, lakes etc.
Lecture Delivered by: Prof. Khurshid Anwar
Exogenetic and Endogenetic Forces
 Diastrophic Forces and Movements: 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 discernible after
thousands and millions of years. These forces are also termed as constructive forces,
affect large areas of earth and produce meso-level reliefs such as mountains, Plains,
Plateaus, lakes, big faults etc. These diastrophic forces and movements further subdivided
in to
 EPEIROGENETIC MOVEMENTS
 OROGENETIC MOVEMENTS
 EPEIROGENETIC MOVEMENTS: Epeirogenetic movement causes upliftment
and subsidence of continents masses through upward and downward movements
respectively. Both, the movements are in fact vertical movements. These are further
divided in to
 Upward Movement
 Downward Movement
 Upward Movement: Upward movement causes upliftment of continental masses in two
ways
 The upliftment of whole continent or part there of
 The upliftment of Coastal land of the continents and such type of upliftment is
called EMERGENCE
 Downward Movement: Downward movement causes subsidence of continent in
two ways
 The subsidence of the land area
 Alternatively, the land area near the sea coast is moved downwards or subsided
below sea level and is thus submerged under seawater and such type of downward
movement is called SUBMERGENCE
 OROGENETIC MOVEMENTS: Orogenetic movements results in the formation of
mountains which are caused due to the Endogenetic forces working in a horizontal
manner. The horizontal forces and the resultant movements are also called as ‘tangential
forces’. These forces work in two ways and they are
 Tensional Force: These forces operate in opposite direction and thus create ruptures,
cracks, fractures and faults in the crustal parts of the earth. Such type of forces and
movements are also Called as DIVERGENT forces and movements.
 Compressional Force: These forces operate towards each other or face to face and they
cause crustal bending leading to the formation of folds or crustal warping leading to
the local rise or subsidence of crustal Parts. They are also called
as CONVERGENT forces.
2. EXOGENETIC FORCES
The exogenetic forces or Processes, also called as denudational processes, or ‘destructional
forces or processes’ are originated from the atmosphere. These forces are continuously
engaged in the destruction of the relief features created by Endogenetic forces through their
weathering, erosional, depositional activities. Denudation includes both weathering and
Lecture Delivered by: Prof. Khurshid Anwar
Exogenetic and Endogenetic Forces
erosion where weathering being a static process includes the disintegration and
decomposition of rocks in situ whereas erosion is dynamic process which includes both,
removal of materials and their transportation to different destinations.

WEATHERING: Weathering is basically of three types
1. Physical or Mechanical weathering
2. Chemical weathering
3. Biological weathering
These processes are very important for the biosphere ecosystem because weathering of parent
rocks results in the formation of soils which are very essential for the sustenance of the biotic
lives in the biosphere.

EROSION
The erosional processes include running water or river, ground water, sea –waves, glaciers,
periglacial processes and wind. These erosional processes erode the rocks, transport the
eroded materials and deposit them in suitable places and thus form several types of erosional
and depositional landforms of different magnitudes and dimensions.
Lecture Delivered by: Prof. Khurshid Anwar