Quick Revision Notes

Class 11 Geography: Geomorphic Processes

Madhya Pradesh Board of Secondary Education (MPBSE)

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1. Introduction to Geomorphic Processes

• Geomorphic Processes: The endogenic (internal) and exogenic (external) forces that cause physical stresses and chemical actions on earth materials and bring about changes in the configuration of the earth's surface are called geomorphic processes.
• Geomorphic Agents: Mobile mediums (like running water, groundwater, glaciers, wind, waves) that remove, transport, and deposit earth materials. Note: Gravity is the prime driving force behind all geomorphic processes.
• Diastrophism and Volcanism are endogenic processes.
• Weathering, Mass Wasting, Erosion, and Deposition are exogenic processes.

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2. Endogenic Processes (अंतर्जात प्रक्रियाएँ)

Forces originating from within the earth's crust, responsible for building up relief features (tectonic movements).

• Diastrophism (पटल विरूपण): All processes that move, elevate, or build portions of the earth's crust come under diastrophism. It includes:
  1. Orogenic Processes: Mountain-building processes through folding and faulting.
  2. Epeirogenic Processes: Uplift or warping of large parts of the earth's crust (continental building).
  3. Earthquakes: Sudden local movements causing vibrations.
  4. Plate Tectonics: Horizontal movements of crustal plates.
• Volcanism (ज्वालामुखीता): Movement of magma towards or onto the earth's surface, resulting in intrusive (inside) and extrusive (outside) volcanic landforms.

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3. Exogenic Processes & Weathering (बहिर्जात प्रक्रियाएँ एवं अपक्षय)

Exogenic processes derive their energy from the sun and atmospheric gradients. Weathering is the action of elements of weather and climate over earth materials. It is in-situ or on-site breakdown of rocks.

Types of Weathering:

1. Chemical Weathering (रासायनिक अपक्षय):
   • Solution: Minerals dissolve in water (e.g., limestone).
   • Carbonation: Reaction between carbonates/bicarbonates and carbon dioxide in water.
   • Hydration: Chemical addition of water to minerals (causes swelling and stress).
   • Oxidation and Reduction: Combination of minerals with oxygen (e.g., rusting of iron).
2. Physical / Mechanical Weathering (भौतिक अपक्षय):
   • Unloading and Expansion: Removal of overlying rock burden causes surface rocks to expand and fracture (Exfoliation).
   • Temperature Changes: Alternate heating and cooling of rocks cause differential expansion and contraction.
   • Freezing, Thawing, and Frost Wedging: Water freezes in cracks, expanding by ~9% and splitting rocks.
   • Salt Weathering: Expansion of salt crystals in rock pores due to thermal action or evaporation.
3. Biological Weathering (जैविक अपक्षय):
   • Caused by the growth of roots, burrowing animals (earthworms, rabbits, termites), and human activities.

• Significance of Weathering: Basis for soil formation, creates mineral resources (bauxite, laterite), and aids in erosion.

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4. Mass Movements / Mass Wasting (वृहत क्षरण)

• Definition: Movement of rock debris down a slope under the direct influence of gravity.
• Note: Unlike erosion, there is no transporting medium like running water or glaciers. Weathering is not a pre-requisite for mass movement, though it aids it.
• Types of Mass Movements:
  1. Heave: Slow downward progression (e.g., soil creep).
  2. Flow: Rapid movement where debris behaves like a fluid (e.g., earthflow, mudflow, debris avalanche).
  3. Slide: Rapid to slow movement along a defined plane or slip surface (e.g., slump, rockslide).
  4. Fall: Free fall of rock pieces over a steep cliff.
  • Landslide: A rapid and perceptible type of mass movement heavily active in young fold mountains like the Himalayas.

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5. Erosion and Deposition (अ अपरदन एवं निक्षेप)

• Erosion: Application of kinetic energy of running water, wind, glaciers, etc., to detach and remove rock particles.
• Deposition: The dropping of eroded materials when the velocity of the geomorphic agent decreases.
• Together, erosion and deposition shape the final landscape through the continuous work of geomorphic agents (Gradation).

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6. Soil Formation (pedogenesis) (मृदा निर्माण)

Soil is a dynamic medium formed by the interaction of five major factors over a long period:

1. Parent Material (पैतृक पदार्थ): The rocks from which soils are derived.
2. Topography (स्थलाकृति): Slope steepness dictates drainage and accumulation.
3. Climate (जलवायु): Temperature and rainfall control the rate of weathering and leaching.
4. Biological Activity (जैविक गतिविधियाँ): Vegetation and organisms add humus and assist in nutrient cycling.
5. Time (समय): Determines the maturity and depth of the soil profile.

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All the best for your MP Board Class 11 Geography exams!