Denudational Process Lesson Note
Learning Objectives
This SS3 Geography lesson note covers Denudational Process for First Term, Week 3.
Lesson Note
Learning Objectives
At the end of the lesson, students should be able to:
i. Define denudation.
ii. State the factors affecting denudation.
iii. Identify the major denudational processes.
iv. Explain the sequence of denudation.
v. Appraise the impact of denudation on man and the environment.
A. Meaning of Denudation
Denudation is the overall process by which the Earth's surface is worn away, lowered, and reshaped through the combined actions of weathering, erosion, transportation, and deposition. It gradually reduces highlands and fills lowlands.
Factors Affecting Denudation
1. Climate: Heavy rainfall, temperature changes, and wind influence the rate of denudation.
2. Nature of Rocks: Hard rocks resist denudation, while soft rocks wear away easily.
3. Relief (Slope): Steep slopes encourage rapid erosion, while gentle slopes slow it down.
4. Vegetation Cover: Dense vegetation protects the soil from erosion.
5. Human Activities: Farming, mining, bush burning, deforestation, and construction can accelerate denudation.
6. Running Water: Rivers and streams increase erosion and transportation of sediments.
7. Wind and Ice: In deserts and cold regions, wind and glaciers contribute significantly to denudation.
Denudational Processes
The major processes of denudation include:
1. Weathering
The breakdown of rocks into smaller particles at or near the Earth's surface without movement.
2. Erosion
The wearing away and removal of weathered materials by agents such as rivers, wind, glaciers, and sea waves.
3. Transportation
The movement of eroded materials from one place to another by water, wind, ice, or gravity.
4. Deposition
The laying down of transported materials when the transporting agents lose energy.
Sequence of Denudation
The sequence of denudation follows these stages:
1. Weathering – Rocks are broken down into smaller particles.
2. Erosion – The weathered materials are removed by natural agents.
3. Transportation – The eroded materials are carried away.
4. Deposition – The transported materials are deposited in low-lying areas.
Impact of Denudation on Man and the Environment
Positive Impacts
1. Formation of fertile floodplains for agriculture.
2. Creation of beautiful landforms that attract tourists.
3. Provision of sand, gravel, and other building materials.
4. Formation of river valleys suitable for transport and settlement.
5. Exposure of valuable mineral resources for mining.
Negative Impacts
1. Soil erosion reduces soil fertility.
2. Destruction of farmlands and crops.
3.Damage to roads, bridges, and buildings.
4. Flooding due to excessive erosion and sediment deposition.
5. Desertification and land degradation in vulnerable areas.
6. Loss of vegetation and wildlife habitats.
Evaluation
OBJECTIVE QUESTIONS
1. Denudation is the process by which the Earth’s surface is
A. Built up by volcanic activities
B. Worn away and lowered
C. Covered by vegetation
D. Heated by the sun
2. Which of the following is the first stage in the sequence of denudation?
A. Transportation
B. Deposition
C. Weathering
D. Erosion
3. Which of the following is not a denudational process?
A. Weathering
B. Erosion
C. Transportation
D. Folding
4. The movement of weathered materials from one place to another is known as
A. Weathering
B. Transportation
C. Deposition
D. Evaporation
5. Which of the following agents is responsible for erosion?
A. Wind
B. Running water
C. Glaciers
D. All of the above
6. The laying down of eroded materials is called
A. Weathering
B. Transportation
C. Deposition
D. Solution
7. Which of the following factors affects the rate of denudation?
A. Climate
B. Rock type
C. Vegetation cover
D. All of the above
8. Which of the following human activities can accelerate denudation?
A. Afforestation
B. Deforestation
C. Irrigation
D. Crop rotation
9. One positive impact of denudation is the
A. Formation of fertile floodplains
B. Destruction of roads
C. Loss of soil fertility
D. Increase in desertification
10. Which of the following is the correct sequence of the denudational process?
A. Erosion → Weathering → Transportation → Deposition
B. Weathering → Erosion → Transportation → Deposition
C. Transportation → Deposition → Weathering → Erosion
D. Deposition → Transportation → Weathering → Erosion
Theory Questions
1a. Define denudation
1b. State 5 factors affecting denudation
2a. Mention the major denudational process
2b. Explain the sequence of denudation
2c. State 5 positive and 5 negative impacts of denudation