Chapter – 5

Geomorphic Processes

In this post we have given the detailed notes of class 11 Geography Book 1 Chapter 5 (Geomorphic Processes) in English. These notes are useful for the students who are going to appear in class 11 board exams.

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Chapter 5: Geomorphic Processes

Introduction

• The Earth’s surface is constantly changing due to various processes.  
• These processes can be categorized into endogenic (internal) and exogenic (external) forces.  
• Geomorphic processes are the physical and chemical actions that shape the Earth’s surface.
• Geomorphic agents are the elements of nature (water, ice, wind) that cause these processes.  

Endogenic Processes

• Endogenic processes originate within the Earth and are driven by its internal heat.  
• This energy is generated by radioactivity, rotational and tidal friction, and primordial heat.  
• These processes include diastrophism and volcanism.  
• Diastrophism refers to the movements and deformation of the Earth’s crust, leading to the formation of mountains, continents, and other large-scale features.  
• Volcanism involves the movement of molten rock (magma) onto or toward the Earth’s surface, creating various volcanic landforms.  

Exogenic Processes

• Exogenic processes are driven by external forces, primarily solar energy and gravity.  
• These processes include weathering, mass wasting, erosion, and deposition.  
• Weathering is the breakdown of rocks, soil, and minerals through contact with the Earth’s atmosphere, water, and biological organisms.  
• Mass wasting is the movement of rock and soil down slopes under the force of gravity.  
• Erosion is the process of moving weathered material from one location to another by agents like wind, water, or ice.  
• Deposition is the laying down of eroded material.  

Weathering

• Weathering can be categorized into three types: chemical, physical, and biological.  
• Chemical weathering involves the decomposition of rocks through chemical reactions.
  • Solution: Dissolving of minerals in water.  
  • Carbonation: Reaction of minerals with carbonic acid.  
  • Hydration: Absorption of water by minerals.  
  • Oxidation: Reaction of minerals with oxygen.  
  • Reduction: Removal of oxygen from minerals.  
• Physical weathering is the breakdown of rocks into smaller pieces without changing their chemical composition.
  • Thermal expansion and contraction: Repeated heating and cooling causing rocks to break.  
  • Frost wedging: Water freezing in cracks and expanding, breaking the rock.  
  • Salt weathering: Salt crystals growing in cracks and pores, causing stress.  
  • Unloading: Removal of overlying pressure causing expansion and fracturing.  
• Biological weathering is the weakening and disintegration of rocks by plants, animals, and microbes.
  • Root wedging: Plant roots growing into cracks and breaking the rock.  
  • Burrowing animals: Animals digging and exposing new surfaces to weathering.  
  • Organic acids: Acids produced by decaying organisms aiding in decomposition.  

Mass Movements

• Mass movements are classified based on the speed and type of movement.  
• Slow movements:
  • Creep: Gradual downhill movement of soil and regolith.  
  • Solifluction: Slow flow of saturated soil over impermeable material.  
• Rapid movements:
  • Landslides: Rapid downslope movement of rock and debris.
    • Slump: Sliding of rock debris with backward rotation.  
    • Debris slide: Rapid rolling or sliding of earth debris.  
    • Debris fall: Free fall of earth debris from a vertical face.  
    • Rockslide: Sliding of rock masses down bedding planes or faults.  
    • Rockfall: Free falling of rock blocks over a steep slope. 
  • Debris avalanche: Extremely rapid flow of rock and debris.
• Factors influencing mass movements include slope angle, water content, and vegetation cover.

Erosion and Deposition

• Erosion is the process of transporting weathered material by geomorphic agents.  
• Deposition occurs when the transporting agent loses energy and the material settles.  
• Erosional agents:
  • Running water: Rivers and streams carve valleys and transport sediment.  
  • Glaciers: Erode and transport vast amounts of rock and debris.  
  • Wind: Picks up and carries loose particles, creating sand dunes and other features.  
  • Waves: Shape coastlines through erosion and deposition.  
  • Groundwater: Dissolves soluble rocks, creating caves and sinkholes.  
• These processes lead to the formation of various landforms, such as valleys, deltas, and beaches.  

Soil Formation

• Soil formation (pedogenesis) is the process of weathering and transporting materials to form soil.  
• Soil-forming factors include parent material, topography, climate, biological activity, and time.  
• Parent material refers to the original material from which the soil is formed.  
• Topography influences soil formation by affecting drainage and exposure to sunlight.  
• Climate plays a crucial role in soil formation through temperature and precipitation.  
• Biological activity contributes to soil formation by adding organic matter and nutrients.  
• Time is essential for soil development and profile formation.  

Conclusion

• Geomorphic processes are essential in shaping the Earth’s surface.  
• Understanding these processes is crucial for managing natural resources and mitigating natural hazards.  
• By studying geomorphic processes, we can better appreciate the dynamic nature of our planet and its diverse landscapes.  

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