Back to: GEOGRAPHY SS3
Welcome to class!
In today’s class, we will be talking about denudational processes/weathering. Enjoy the class!
Denudational Processes/Weathering
Denudation is a process of lowering and levelling of the earth surface by gradual breaking and wearing away of the surface of the earth or soil. The agents or forces which promote these breaking and lowering of the earth’s surfaces are called the agents of denudation. Examples of agents of denudation are wind, running water, ice and waves.
Factors affecting denudation
The rate of denudation depends on the following factors:
- Nature of relief: The higher the relief, the higher the rate of denudation.
- The structure of the earth: The softer the rocks, the greater the rate of denudation and vice versa.
- The local climate of the area: Wet climate tends to increase the rate of denudation more than dry climate.
- Influence of man: The higher the level of man’s activities on the earth surface, the greater the rate of denudation.
Sequences of denudation
Denudation involves four sequences or stages which include:
- Weathering: This is the gradual disintegration of rocks by physical, biological and chemical processes.
- Erosion: This is the active wearing away of the earth’s surface by agents of denudation such as running water, wind, ice and waves.
- Transportation: This is the active removal of eroded materials to new positions or areas.
- Deposition: This is the dumping of the debris carried by the process of transportation in certain parts of the earth where it accumulates to form soils.
Evaluation
- What is denudation?
- State the processes of denudation.
Weathering
Weathering is defined as the gradual breaking down or disintegration of rocks by either physical (mechanical) or chemical processes.
Factors affecting weathering
The following factors affect the weathering of rocks:
- Climate: Climatic elements like temperature and rainfall are the major factors affecting weathering. While physical (mechanical) weathering is aided by temperature and water to break down rocks, chemical weathering is aided by water and other gases in the atmosphere. Generally, chemical weathering is common in hot and wet climate (i.e humid regions with high temperature) while mechanical weathering is common in arid and cool temperate climates.
- Types of rock: Rocks are made up of different minerals, while some are resistant to weathering, others are not, simply because of their differences in structure, texture, composition and size of the rocks.
- Relief: Steep slopes like high mountains encourage weathering especially frost action while gentle and even slopes favour chemical weathering.
- Living organisms: Plants and animals have a great influence on weathering. Roots of plants promote physical weathering as the root penetrates into rocks and breaks them. Chemical weathering occurs due to vegetative cover which conserves water to produce weak acid in the soil. Animals bore holes into it and break them, besides, to allow other agents of chemical weathering to take place.
Weekend assignment
- An extensive area of level or gentle undulating land which is usually a few meters above the sea level is known as (a) Plain (b) Mountain (c) Valley (d) Plateau
- Which of these plain is associated with glacier (a) Deltaic plain (b) Flood plain (c) Outwash plains (d) Lacustrine plains
- Plains formed by agents of denudation are known as (a) Dissected plain (b) Residual plain (c) Erosional plains (d) Structural plain
- Which of the following is not a depositional plain (a) Outwash plain (b) Pedi plain (c) Deltaic plain (d) Flood plain
- Great plains of USA is a good example of (a) Volcanic plains (b) Structural plains (c) Erosional Plains (d) Depositional plains
Theory
- Explain briefly the difference between chemical weathering and physical weathering.
- State three effects of weathering.
In our next class, we will be talking more about Denudational Processes/Weathering. We hope you enjoyed the class.
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