Geomorphic Processes 11 Geography Chapter 5 CBSE Notes 2025-26

The surface of the earth is shaped by a constant balance between opposing forces. Endogenic (internal) forces such as diastrophism and volcanism help in building up landforms by causing uplift, folding, and faulting, which result in features like mountains and plateaus. On the other hand, exogenic (external) forces such as weathering, mass wasting, erosion, and deposition act to wear down these elevated surfaces, gradually transforming landscapes.

The earth’s crust keeps moving, both horizontally and vertically, but the rate and style of movement can vary depending on factors like crust thickness and internal energy. While internal (endogenic) forces create relief, external (exogenic) forces, powered mainly by the sun and gravity, work to even out these variations by breaking, wearing down, and transporting materials from higher to lower areas.

Endogenic geomorphic processes originate from heat within the earth. The energy comes from radioactivity, rotational and tidal friction, and primordial heat. These processes include diastrophism—responsible for large-scale movements, folds, faults, and continental uplift (orogeny and epeirogeny)—and volcanism, which results in magma erupting onto or near the surface. Earthquakes and plate tectonics are also endogenic, causing both sudden and gradual changes in the crust.

• Orogenic processes—form mountains by intense folding and faulting along narrow belts.
• Epeirogenic processes—cause broad uplift or depression of large crust areas.
• Volcanism—involves magma movement and the creation of volcanic landforms.
• Earthquakes and crustal plate movement—cause sudden or gradual changes in surface relief.

These internal forces create uneven land, giving rise to mountains, plateaus, and basins, which are later modified by external forces.

Exogenic processes get their energy from the sun (driving atmospheric processes) and from the gravitational force that moves materials downslope. These processes include weathering, mass movements, erosion, and deposition—together known as denudation, which strips and lowers the earth’s surface. The intensity of these actions depends heavily on climate (temperature, rainfall), slope, and rock type and structure.

• Weathering—breaks down rocks in place by physical, chemical, or biological means.
• Mass wasting—moves weathered materials downslope due to gravity, with no external transporting agent.
• Erosion—removes and carries rock debris through agents like water, wind, ice, and waves.
• Deposition—occurs when transporting agents lose energy and drop their load, often forming new features.

The balance between endogenic uplift and exogenic degradation shapes earth’s landforms, producing the variety of mountains, valleys, plains, and soils present today.

Weathering refers to the breakdown of rocks at or near the earth’s surface into smaller fragments by physical (mechanical), chemical, and biological processes. Mechanical weathering includes freeze-thaw action, heating and cooling, and pressure release, while chemical weathering involves processes like solution, hydration, carbonation, and oxidation. Biological weathering is caused by plant roots, burrowing animals, and microbial activities.

• Physical weathering: Involves breaking rocks without changing their composition. Occurs due to temperature changes, water freeze-thaw cycles, unloading (release of overburden), or crystal growth.
• Chemical weathering: Alters the mineral composition of rocks by exposure to water, oxygen, acids, etc., leading to reactions like dissolution, oxidation, and hydration.
• Biological weathering: Animals burrow and plants grow roots, breaking rocks physically and aiding chemical changes.

Exfoliation is a notable weathering process where curved sheets of rock peel off due to expansion and contraction or removal of overburden. Weathering produces regolith, influences soil formation, and supports biodiversity by helping plants take root and thrive.

Mass movements involve the downward movement of rock debris and soil under the direct influence of gravity. They differ from erosion as they do not require moving agents like water or wind. The basic types include creep (slow movement), flow (mixing and movement, as in mudflows), slide (material moves along a plane), and fall (materials drop freely).

• Slump—mass slides downslope with backward rotation.
• Debris flow and slides—rapid movement of saturated or dry debris.
• Rockslide and rockfall—sudden, often vertical movement of rocks.

Such movements are common where slopes are steep, rocks are weakly consolidated, or vegetation is absent. In India, the Himalayas, Nilgiris, and Western Ghats frequently experience landslides due to active tectonics, rainfall, and unstable terrain.

Erosion is the removal and transportation of weathered rocks by natural agents like water, wind, ice, or waves. The ability of these agents to erode depends on their energy, which is supplied by gravity and the sun. Running water erodes valleys, wind shapes deserts, glaciers carve mountains and valleys, and ocean waves erode coastlines. Erosion, mass wasting, and weathering together reduce land elevations.

Deposition occurs when these agents lose their kinetic energy and drop their load, often forming features like alluvial fans, deltas, sand dunes, and moraines. Erosional and depositional activities work together to continually reshape the face of the earth’s surface.

Soil is a dynamic, layered mixture of mineral particles, organic matter, water, and air formed by the weathering of rocks and the activity of living organisms. Soil development (pedogenesis) begins when weathered rock is colonized by bacteria, fungi, lichens, and mosses, whose remains add humus. With time, grasses, trees, roots, animals, and insects further break down and mix the material, gradually building up soil layers or horizons.

• Parent material: The original rock or sediment influences soil’s mineral content, structure, and properties, especially in young soils.
• Topography: Slope controls soil thickness and drainage. Steep slopes often have thin soils; flat uplands have thicker soils.
• Climate: Rainfall and temperature control weathering rates and organic activity. Excess rainfall leads to leaching and removal of nutrients; dry climates favor salt accumulation.
• Biological activity: Plants, animals, and microbes add organic matter, mix the soil, and influence its porosity and fertility. Rhizobium bacteria are important for nitrogen fixation.
• Time: The longer the period, the more developed the soil profile becomes, with distinct layers.

Climate and living organisms (biological activity) are considered active factors because they directly drive soil formation, while parent material, topography, and time are passive, providing the basic setting for soil formation but not controlling processes themselves.

Understanding geomorphic processes helps students appreciate the evolution and diversity of landforms, the importance of conserving soil and land resources, and the natural hazards like landslides and soil erosion that occur in different regions. The NCERT chapter concludes with practice questions on weathering, mass movement, agent roles, and differences between major geomorphic processes to strengthen learning outcomes.

Revision activities may include identifying local geomorphic processes, analyzing soil properties, and answering MCQs and descriptive questions to help reinforce key concepts from the chapter.

Class 11 Geography Chapter 5 Notes – Fundamentals of Physical Geography: Geomorphic Processes & Landforms

These concise revision notes for Class 11 Geography Chapter 5 explain key ideas such as geomorphic processes, weathering, erosion, and soil formation. You'll find clear explanations on how internal and external forces shape landforms, making it easier to grasp difficult concepts before exams. Use these notes to quickly review the NCERT Geomorphic Processes chapter for scoring better in Geography.

By summarizing the causes and effects of weathering and erosion, these notes save your time during last-minute revision. Structured bullet points and short explanations help you remember the differences between various landform-building agents and the factors affecting soil formation. Accessing these notes supports efficient exam preparation and concept clarity for CBSE Geography.