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Class 11 Geography NCERT Solutions Chapter 6 Geomorphic Processes

1. Multiple choice questions.

(i) Which one of the following processes is a gradational process?
(a) Deposition
(c) Volcanism
(b) Diastrophism
(d) Erosion

Ans: (d) Erosion

Explanation: Erosion is a gradational process that involves the wearing away and removal of rock and soil by natural agents like water, wind, and ice. It gradually shapes and changes the Earth’s surface over time.

(ii) Which one of the following materials is affected by hydration process?
(a) Granite
(c) Quartz
(b) Clay
(d) Salts

Ans: (b) Clay

Explanation: Clay minerals are affected by the hydration process, which involves the absorption of water molecules into the crystal structure of the minerals, causing them to expand and sometimes altering their properties. This process plays a significant role in soil behavior and engineering.

Clay Class 11 Geography NCERT Solutions Chapter 6 Geomorphic Processes

(iii) Debris avalanche can be included in the category of:
(a) Landslides
(c) Rapid flow mass movements
(b) Slow flow mass movements
(d) Subsidence

Ans: (c) Rapid flow mass movements

Explanation: Debris avalanches are a type of rapid flow mass movement where a mixture of rock, soil, and other materials rapidly moves downslope due to the force of gravity. This movement can be very fast and destructive, making it a part of the category of rapid flow mass movements.

2. Answer the following questions in about 30 words.

(i) It is weathering that is responsible for bio-diversity on the earth. How?

Ans: Weathering contributes to biodiversity by breaking down rocks into smaller particles, creating soil. This soil provides a habitat for various plants and organisms, supporting complex ecosystems. Weathering’s role in soil formation and nutrient release enhances plant growth, which in turn sustains diverse animal life, thus fostering biodiversity on Earth.

(ii) What are mass movements that are real rapid and perceptible? List.

Ans: Rapid and perceptible mass movements include landslides, rockfalls, debris avalanches, mudflows, and snow avalanches. Triggered by factors like heavy rainfall, earthquakes, or snowpack instability, these movements have swift and significant impacts on landscapes, ecosystems, and human environments.

(iii) What are the various mobile and mighty exogenic geomorphic agents and what is the prime job they perform?

Ans: Various mobile and mighty exogenic geomorphic agents include rivers, glaciers, wind, and waves. Their prime job is to shape and modify the Earth’s surface through processes like erosion, transportation, and deposition of sediments. They sculpt landscapes, carve valleys, deposit sediments, and contribute to the ongoing changes in the Earth’s surface features.

(iv) Is weathering essential as a pre-requisite in the formation of soils? Why?

Ans: Yes, weathering is essential for soil formation. It breaks down rocks into smaller particles, releasing nutrients and minerals. These weathered materials mix with organic matter, forming the basis of soil. Soil texture, fertility, and drainage depend on weathering, supporting plant growth and ecosystems.

3. Answer the following questions in about 150 words.

(i) “Our earth is a playfield for two opposing groups of geomorphic processes.”

Ans: The Earth’s surface is constantly shaped by two opposing groups of geomorphic processes: exogenic and endogenic processes. These processes act in concert yet often exhibit conflicting effects, leading to the dynamic nature of the Earth’s landscape.

Exogenic processes, driven primarily by external forces such as weathering, erosion, and deposition, work to modify the Earth’s surface. For instance, rivers carve valleys, wind erodes rocks, and waves shape coastlines. These processes are vital for sculpting landscapes, redistributing materials, and creating various landforms.

In contrast, endogenic processes result from internal forces, including tectonic activities, volcanic eruptions, and earthquakes. These processes build and reshape the Earth’s crust. Mountains are uplifted due to tectonic collisions, and volcanic eruptions contribute to the formation of new landforms. These processes are responsible for creating geological features that significantly impact the surface.

The interplay between these opposing processes leads to a continuous transformation of the Earth’s surface. While exogenic processes modify and shape the terrain, endogenic processes create and deform landforms. This dynamic balance maintains the ever-changing nature of our planet’s topography, contributing to the diverse and intricate landscapes observed around the world.

(ii) Exogenic geomorphic processes derive their ultimate energy from the sun’s
heat. Explain.

Ans: Exogenic geomorphic processes are driven by the energy derived from the Sun’s heat, which sets in motion various natural phenomena that shape the Earth’s surface. This energy transfer and its effects can be explained as follows:

  1. Solar Radiation: The Sun emits solar radiation, which reaches the Earth’s surface in the form of sunlight. This energy heats the Earth’s atmosphere and surface.
  2. Temperature Differences: Solar radiation heats different parts of the Earth’s surface unevenly, creating temperature variations. Warmer air near the surface becomes less dense and rises, while cooler air sinks. This movement leads to the generation of winds.
  3. Wind Erosion: Winds generated by temperature variations transport loose particles like sand, silt, and dust. Wind erosion occurs as these particles are lifted and carried across the landscape, sculpting features like sand dunes.
  4. Water Cycle: Solar energy drives the water cycle by evaporating water from oceans, lakes, and rivers. The evaporated water rises, condenses into clouds, and precipitates as rainfall. This water flows over the land, causing erosion, forming river valleys, and shaping the landscape.
  5. Ocean Currents and Waves: Solar heating of the oceans creates temperature and density differences, which drive ocean currents and generate waves. Ocean currents transport water and influence coastal erosion and deposition.
  6. Glacial Melting: Solar energy contributes to the melting of glaciers and ice sheets, leading to glacial erosion and the formation of glacial landforms.
  7. Biological Processes: Sunlight is essential for photosynthesis in plants, which influences soil development and stability. Plant growth helps anchor soils, preventing erosion by wind and water.

In essence, the Sun’s heat sets in motion a chain of events that drive winds, precipitation, ocean currents, and other exogenic processes. These processes, fueled by solar energy, continuously shape and modify the Earth’s surface features, creating diverse landscapes and influencing the overall geomorphic evolution of the planet.

(iii) Are physical and chemical weathering processes independent of each other? If not, why? Explain with examples.

Ans: Physical and chemical weathering processes are not entirely independent of each other; they often interact and complement each other in breaking down rocks and altering landscapes. The interactions between these two types of weathering can be seen through various examples:

  1. Frost Wedging (Physical) and Hydrolysis (Chemical):
    • Frost wedging occurs when water seeps into cracks in rocks, freezes, and expands, causing the rock to break apart.
    • Hydrolysis is a chemical process where water chemically reacts with minerals in the rock, weakening and decomposing them.
    • Interaction: Frost wedging can create openings in rocks, allowing water to penetrate deeper and facilitating hydrolysis, which further breaks down the minerals.
  2. Root Wedging (Physical) and Carbonation (Chemical):
    • Plant roots can grow into cracks and crevices in rocks, exerting physical pressure and breaking the rock.
    • Carbonation is a chemical process where carbon dioxide dissolves in water to form carbonic acid, which reacts with minerals in rocks like limestone, leading to their dissolution.
    • Interaction: Root wedging can create openings in rocks, enabling carbonic acid to penetrate deeper and accelerate the chemical breakdown.
  3. Abrasion (Physical) and Oxidation (Chemical):
    • Abrasion occurs when rocks and particles are transported by wind, water, or ice and collide with other surfaces, wearing them down.
    • Oxidation is a chemical process where minerals in rocks react with oxygen, leading to the breakdown and weakening of the rock.
    • Interaction: Abrasion exposes fresh surfaces of rocks, providing more area for oxidation to occur and speeding up the chemical weathering process.

These examples illustrate how physical and chemical weathering processes often work together to accelerate the breakdown of rocks. Physical weathering can create openings, increase surface area, and facilitate the penetration of water and chemicals, thereby enhancing the effects of chemical weathering. Similarly, the products of chemical weathering can weaken the rock and make it more susceptible to physical weathering processes. As a result, the interactions between physical and chemical weathering contribute to the overall degradation and transformation of rocks and landscapes over time.

(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?

Ans: The distinction between soil formation and soil-forming factors lies in their nature and relationship:

  1. Soil Formation (Pedogenesis): Soil formation refers to the process by which raw materials, derived from weathering of rocks and organic matter, undergo various transformations over time to develop into a mature soil profile. It involves physical, chemical, and biological processes that result in the creation of distinct soil horizons with unique properties.
  2. Soil-Forming Factors (CLORPT): Soil-forming factors are the key elements that influence and control the process of soil formation. The acronym CLORPT represents the five main factors:
    • Climate: Influences weathering rates, organic matter decomposition, and leaching, affecting soil characteristics.
    • Organisms (Biological Activity): Plants, animals, microorganisms, and their interactions contribute to organic matter input, nutrient cycling, and soil structure development.
    • Relief (Topography): Slope, aspect, and elevation affect water movement, drainage, and erosion, which influence soil properties.
    • Parent Material: The source of mineral and organic material that undergoes weathering to form soil. Different parent materials result in varying soil compositions.
    • Time: The period during which soil-forming processes occur. Longer exposure to weathering and other factors leads to more developed soils.

Role of Climate and Biological Activity:

  • Climate: Climate has a significant impact on soil formation. Temperature and moisture regimes influence rates of weathering, organic matter decomposition, and leaching. Wet climates may lead to more leaching, resulting in nutrient-poor soils, while arid climates can lead to accumulation of salts.
  • Biological Activity: Biological activity, including plant growth, root penetration, and microbial decomposition, contributes to the formation of organic matter-rich horizons. The decay of organic matter provides nutrients, enhances soil structure, and influences soil color and texture.

In summary, soil formation is the process by which materials transform into mature soil, while soil-forming factors are the elements influencing this process. Climate and biological activity play crucial roles in determining the rate and extent of soil formation by affecting weathering, organic matter input, nutrient cycling, and overall soil characteristics.

NCERT Geography Class 11