GEOGRAPHY- CLASS-11: FUNDAMENTALS OF PHYSICAL GEOGRAPHY
CHAPTER-5
Geomorphic Processes
1. Multiple Choice Questions
(i) Which one of the following processes is a gradational process?
Answer: (d) Erosion
Explanation: Gradational processes include weathering, erosion, transportation and deposition, which continuously modify the Earth's surface.
(ii) Which one of the following materials is affected by hydration process?
Answer: (d) Salts
Explanation: Hydration is a chemical weathering process in which minerals absorb water. Salts are commonly affected by hydration.
(iii) Debris avalanche can be included in the category of:
Answer: (c) Rapid flow mass movements
Explanation: A debris avalanche is a very fast movement of loose rock, soil and debris down a steep slope.
2. Answer the following questions in about 30 words.
(i) It is weathering that is responsible for bio-diversity on the Earth. How?
Answer:
Weathering breaks rocks into smaller particles and forms soil. The soil provides nutrients, water and support for plants. Plants, in turn, support animals and microorganisms, thereby increasing biodiversity on the Earth.
(ii) What are mass movements that are real rapid and perceptible? List.
Answer:
The rapid and easily noticeable mass movements are landslides, rockfalls, debris falls, debris avalanches, mudflows, earthflows and slumps. These movements occur suddenly, especially on steep slopes.
(iii) What are the various mobile and mighty exogenic geomorphic agents and what is the prime job they perform?
Answer:
The major exogenic geomorphic agents are running water, glaciers, wind, sea waves and groundwater. Their main work is to erode, transport and deposit rock materials, thereby shaping the Earth's surface.
(iv) Is weathering essential as a pre-requisite in the formation of soils? Why?
Answer:
Yes, weathering is essential because it breaks rocks into fine particles and releases minerals. These weathered materials, along with organic matter, form soil suitable for plant growth.
3. Answer the following questions in about 150 words.
(i) "Our Earth is a playfield for two opposing groups of geomorphic processes." Discuss.
Answer:
The Earth's surface is continuously shaped by two opposing groups of geomorphic processes: endogenic and exogenic processes. Endogenic processes originate inside the Earth and are powered by internal heat. They include volcanic eruptions, earthquakes, folding and faulting, which create mountains, plateaus and other landforms. These processes build up and uplift the Earth's surface. In contrast, exogenic processes operate on the Earth's surface and derive their energy mainly from the Sun and gravity. They include weathering, erosion, transportation and deposition carried out by rivers, glaciers, wind, sea waves and groundwater. These processes wear down elevated landforms and deposit sediments in lower areas. Thus, while endogenic forces build and uplift the Earth's surface, exogenic forces gradually level and reshape it. The continuous interaction between these two groups of processes is responsible for the formation and evolution of various landforms on the Earth.
(ii) Exogenic geomorphic processes derive their ultimate energy from the sun's heat. Explain.
Answer:
Exogenic geomorphic processes operate on the Earth's surface and obtain their ultimate source of energy from the Sun. Solar heat causes differences in atmospheric temperature and pressure, leading to the movement of winds. It also drives the hydrological cycle by causing evaporation, cloud formation and rainfall. Rivers, glaciers, sea waves and winds act as agents of erosion, transportation and deposition because of this solar energy. Gravity assists these agents by moving weathered materials from higher to lower elevations. Together, solar energy and gravity enable weathering, mass movement and erosion to take place continuously. These processes gradually wear down mountains, transport sediments and form new landforms such as valleys, floodplains, deltas and sand dunes. Therefore, the Sun provides the primary energy that powers almost all exogenic geomorphic processes.
(iii) Are physical and chemical weathering processes independent of each other? If not, why? Explain with examples.
Answer:
No, physical and chemical weathering are not independent of each other. They often work together and support one another. Physical weathering breaks large rocks into smaller fragments, increasing the surface area exposed to air and water. This makes chemical weathering more effective. Similarly, chemical weathering weakens rocks by altering their minerals, making them more likely to break apart through physical weathering. For example, repeated heating and cooling cause rocks to crack, allowing water to enter. The water reacts chemically with minerals through hydration or oxidation, further weakening the rock. In cold regions, water freezes inside these cracks, expands and breaks the rocks into smaller pieces. Thus, physical and chemical weathering are closely related processes that together contribute to soil formation and landscape development.
(iv) How do you distinguish between the process of soil formation and soil-forming factors? What is the role of climate and biological activity as two important control factors in the formation of soils?
Answer:
Soil formation is the process through which rocks are gradually converted into soil by weathering, decomposition of organic matter and the movement of minerals. Soil-forming factors are the conditions that influence this process. These factors include climate, organisms, parent material, relief and time. Climate is one of the most important factors because temperature and rainfall control the rate of weathering, leaching and decomposition of organic matter. Warm and humid climates promote rapid soil formation, while cold or dry climates slow the process. Biological activity is equally important because plants, animals and microorganisms add organic matter to the soil. Plant roots break rocks, earthworms mix the soil and microorganisms decompose dead plants and animals to form humus. Together, climate and biological activity determine the fertility, texture, structure and overall quality of soils.