Chapter 5: Landforms
Source: NCERT Official Textbook
Endogenic processes, driven by Earth’s internal energy, include diastrophism (mountain and continent building) and volcanism. Exogenic processes, powered primarily by solar energy, encompass weathering, mass wasting, erosion, and deposition, collectively known as denudation.
The chapter provides a detailed examination of weathering, the in-situ breakdown of rocks through chemical, physical, and biological means, highlighting its crucial role in preparing material for erosion and soil formation. It then explores mass movements, the downslope movement of debris under gravity, explaining various types like slump, landslides, and rock falls, and their triggers. Finally, the chapter outlines the fundamentals of soil formation (pedogenesis), identifying five key control factors: parent material, topography, climate, biological activity, and time.
It explains how climate and biological activity act as active agents, influencing the rate of chemical reactions and humus content, ultimately determining the character and maturity of the soil profile. The entire discussion underscores the dynamic and interconnected nature of the systems that sculpt our physical environment.
Topics Covered:
Section A: Descriptive Questions
- Why is the surface of the earth uneven? Explain the roles of endogenic and exogenic forces. (Pg. 2) Page 37
- What is the difference between a geomorphic process and a geomorphic agent? (Pg. 3) Page 38
- Differentiate between orogenic and epeirogenic processes. (Pg. 3) Page 38
- How do climatic factors influence the intensity of exogenic geomorphic processes? (Pg. 4) Page 39
- What are the three major groups of weathering processes? Briefly define each. (Pg. 5) Page 40
- What is exfoliation and how does it occur? (Pg. 6) Page 41
- What are the activating causes that precede mass movements? List any five. (Pg. 7) Page 42
- Why are the Himalayas particularly susceptible to debris avalanches and landslides? (Pg. 8) Page 43
- Describe the process of soil formation, starting from the weathering mantle. (Pg. 9) Page 44
- Explain how climate acts as an active factor in soil formation, giving examples of wet and dry climates. (Pg. 10) Page 45
Section B1: Objective MCQs
Which of the following are classified as endogenic geomorphic processes? (Pg. 3)
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Reference: NCERT Page 38
What is the prime source of energy behind endogenic geomorphic processes? (Pg. 3)
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Reference: NCERT Page 38
Which of the following is a general term that covers all exogenic processes? (Pg. 4)
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Reference: NCERT Page 39
What is the sole driving force behind all exogenic processes? (Pg. 4)
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Reference: NCERT Page 39
Which type of weathering involves processes like solution, carbonation, and oxidation? (Pg. 5)
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Reference: NCERT Page 40
How does weathering contribute to the national economy? (Pg. 6)
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Reference: NCERT Page 41
What is the term for a rapid mass movement where rock debris slips with a backward rotation? (Pg. 7)
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Reference: NCERT Page 42
Which of the following is NOT considered a climatically controlled agent of erosion? (Pg. 8)
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Reference: NCERT Page 43
Which of the following is considered a passive control factor in soil formation? (Pg. 9)
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Reference: NCERT Page 44
In which climatic region would you expect soils with very low humus content due to rapid bacterial action? (Pg. 10)
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Reference: NCERT Page 45
(Exercise) Which one of the following processes is a gradational process? (Pg. 11)
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Reference: NCERT Page 46
(Exercise) Which one of the following materials is affected by hydration process? (Pg. 11)
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Reference: NCERT Page 46
(Exercise) Debris avalanche can be included in the category of: (Pg. 11)
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Reference: NCERT Page 46
Section B2: Factual One-Liners
The actions of exogenic forces result in the wearing down of relief, which is known as ______. (Pg. 2) Page 37
Reveal Answer
All processes that move, elevate or build up portions of the earth’s crust are collectively called ______. (Pg. 3) Page 38
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The force applied per unit area on earth materials is called ______. (Pg. 4) Page 39
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Weathering is an ______ process, meaning very little or no motion of materials takes place. (Pg. 5) Page 40
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______ weathering involves contributions from or removal by organisms like earthworms and plant roots. (Pg. 6) Page 41
Reveal Answer
The transfer of rock debris down slopes under the direct influence of gravity is called ______. (Pg. 6) Page 41
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The nearly free fall of earth debris from a vertical face is called ______. (Pg. 7) Page 42
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______ is a consequence of erosion, occurring when erosional agents lose their velocity. (Pg. 8) Page 43
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The science of soil is called ______. (Pg. 9) Page 44
Reveal Answer
The process by which bacteria convert gaseous nitrogen from the air into a usable chemical form for plants is called ______. (Pg. 10) Page 45
Reveal Answer
(Exercise) List examples of mass movements that are real rapid and perceptible. (Pg. 11) Page 46