GEOGRAPHY – CLASS 11 (COURSE A)

CHAPTER 5: LANDFORMS & GEOMORPHIC PROCESSES

1. INTRODUCTION

The Earth’s surface is not uniform; it shows mountains, plateaus, plains, valleys, canyons, dunes, beaches, deltas etc.
These physical features are called landforms.
Landforms are continuously shaped and reshaped by geomorphic processes.
Geomorphic processes operate due to energy transfers within and outside the Earth.
Broadly, they are divided into:
- Endogenic processes → originate inside the Earth.
- Exogenic processes → operate on the surface of the Earth.
The balance and interaction between these processes create the dynamic nature of the Earth’s crust.

2. LANDFORMS & GEOMORPHIC PROCESSES

2.1 Landforms

Landforms are large natural features found on the Earth’s surface.
They are produced by:
- Tectonic forces
- Volcanic activities
- Weathering
- Erosion
- Transportation
- Deposition
Landforms are classified as:
- Primary landforms = created by internal forces (mountain ranges, rift valleys).
- Secondary landforms = created by external forces (valleys, floodplains, deltas).
- Tertiary landforms = modified forms of older landforms.

2.2 Geomorphic Processes

Geomorphic processes refer to natural forces that shape the Earth’s crust.
They involve the movement of matter (soil, rock, water, ice) through energy.
Energy sources include:
- Earth’s interior heat
- Sun’s radiation
- Gravity
- Atmospheric forces
Processes occur either through:
- Degradation → wearing down of the surface.
- Aggradation → building up of material on the surface.

3. ENDOGENIC PROCESSES

Endogenic processes originate from within the Earth, driven by internal heat, pressure, and mantle convection.

3.1 Characteristics

Responsible for broad, large-scale landforms.
Energy source: radioactive decay, mantle convection, gravitational pressure.
Effects are sudden (earthquakes, volcanic eruptions) or slow (folding, faulting).
They create mountains, plateaus, rift systems, volcanoes and uplifted crust.

3.2 Types of Endogenic Processes

Diastrophism (Crustal deformation)
Volcanism

4. DIASTROPHISM

Diastrophism includes all processes that cause the Earth’s crust to bend, fold, fracture or uplift.

4.1 Components of Diastrophism

A. Orogenic Processes (Mountain-building)

Involves intense compression.
Creates:
- Fold mountains (Himalayas, Rockies)
- Fault-block mountains
- Thrust belts

B. Epeirogenic Processes (Continent-building)

Slow uplift or subsidence of large crustal areas.
Form broad warping, plateaus, coastal submergence and uplifted peneplains.

C. Folding

Rocks bend due to compressional forces.
Produces:
- Anticlines (upfolds)
- Synclines (downfolds)
- Fold mountain chains

D. Faulting

Rocks crack due to tension/compression.
Produces:
- Rift valleys
- Block mountains
- Fault scarps
Important faults:
- East African Rift
- San Andreas Fault

4.2 Effects of Diastrophism

Formation of mountain arcs
Uplift of plateaus
Creation of basins
Earthquakes
Volcanic pathways

5. VOLCANISM

Volcanism includes all processes through which magma rises to the Earth’s surface.

5.1 Types of Volcanic Materials

Lava → molten rock
Pyroclasts → ash, cinders, bombs
Gases → CO₂, SO₂, water vapor

5.2 Intrusive Volcanic Forms

When magma cools inside the crust:

Batholith
Laccolith
Lopolith
Dykes
Sills

5.3 Extrusive Volcanic Forms

When magma reaches the surface:

Lava plateaus
Shield volcanoes
Composite cones
Caldera
Flood basalts

5.4 Importance of Volcanism

Fertile soils
Mineral deposits
Creation of new land (Hawaii)
Formation of volcanic mountains
Geothermal energy

6. EXOGENIC PROCESSES

Exogenic processes originate at the Earth’s surface, driven by:

Solar radiation
Atmospheric motion
Gravity
Hydrological cycle

6.1 Main Exogenic Processes

Weathering
Mass movement
Erosion
Deposition

These processes work together to sculpt the Earth’s surface.

7. MASS MOVEMENTS

Mass movement involves downslope movement of rock, soil and debris under gravity.

7.1 Characteristics

No external agent (river, glacier, wind) is involved.
Operates on slopes due to gravitational pull.
Influenced by weathering, water content, slope angle, and vegetation.

7.2 Types of Mass Movements

A. Rapid Mass Movements

Landslides
Rockfalls
Debris avalanches

B. Slow Mass Movements

Soil creep
Solifluction (in permafrost zones)

8. LANDSLIDES

8.1 Causes

Steep slopes
Heavy rainfall
Earthquakes
Deforestation
Construction activities
Weathering of rocks

8.2 Types

Translational slides
Rotational slides
Debris flows
Rock avalanches

8.3 Effects

Destruction of life and property
Blocking of rivers
Soil loss
Slope instability

8.4 Prevention and Control

Afforestation
Drainage management
Slope terracing
Retaining walls
Land-use planning

9. EROSION AND DEPOSITION

Erosion is the removal of soil and rock by natural agents; deposition is the laying down of sediments.

9.1 Agents of Erosion

Rivers
Winds
Glaciers
Waves & currents

9.2 River Erosion Landforms

V-shaped valleys
Waterfalls
Gorges
Meanders
Floodplains
Deltas

9.3 Wind Erosion Landforms

Deflation hollows
Yardangs
Mushroom rocks

9.4 Glacial Erosion Landforms

U-shaped valleys
Cirques
Aretes
Moraines

9.5 Marine Erosion Landforms

Cliffs
Sea arches
Stacks
Beaches

9.6 Deposition Landforms

River → levees, deltas
Wind → dunes, loess
Glacier → moraine deposits
Sea → beaches, spits, bars

10. SOIL-FORMING FACTORS

Soil formation is influenced by five major factors:

10.1 Climate

Temperature and rainfall regulate weathering and organic activity.

10.2 Organisms

Plants, animals, micro-organisms help in humus formation.

10.3 Parent Material

Determines soil’s mineral composition, texture and color.

10.4 Topography

Steep slopes → thin soil
Gentle slopes → thick soil

10.5 Time

Soil formation is slow; mature soils require thousands of years.

11. SOIL FORMATION (Pedogenesis)

Soil formation involves a combination of weathering, organic matter addition, and chemical processes.

11.1 Key Processes of Soil Formation

A. Weathering

Breaks parent rock into small particles.

B. Humification

Formation of humus from organic matter.

C. Leaching

Washing away of nutrients downward by water.

D. Illuviation

Deposition of materials in lower layers.

E. Eluviation

Removal of materials from upper layers.

11.2 Soil Profile

Typical soil horizons:

O-horizon → organic layer
A-horizon (Topsoil) → minerals + humus
B-horizon (Subsoil) → accumulation zone
C-horizon → weathered parent rock
R-horizon → hard bedrock

11.3 Types of Soils (General Classification)

Alluvial soil
Black soil
Red soil
Laterite soil
Desert soil
Mountain soil

12. CONCLUSION

Earth’s landscape is continuously shaped by internal (endogenic) and external (exogenic) forces.
Endogenic processes create large-scale structural features like mountains, rift valleys and plateaus.
Exogenic processes such as weathering, mass movement, erosion and deposition constantly modify these features.
Soil formation is also the result of long-term geomorphic processes combined with climatic and biological factors.
The interaction of these processes makes the Earth’s surface dynamic, ever-changing and diverse.
Understanding geomorphic processes helps in managing natural hazards (landslides, erosion), conserving soil, and planning sustainable development.