Answer: (d) Erosion

Explanation:
Gradational processes work to level the Earth's surface. They include both wearing down high areas (degradation) and filling up low areas (aggradation).
- Erosion is a process of degradation.
- Deposition is a process of aggradation.
- Diastrophism and Volcanism are endogenic forces that create relief, which gradational processes then act upon. Since erosion is a key part of this leveling process, it is considered a gradational process.

Answer: (d) Salts

Explanation:
Hydration is a chemical weathering process where water molecules are added to a mineral, causing it to expand and become unstable. While clay minerals can expand with water, salts (like rock salt) are particularly susceptible to hydration. For instance, anhydrite takes up water to become gypsum, a process involving hydration.

Answer: (c) Rapid flow mass movements

Explanation:
A debris avalanche is an extremely rapid and destructive flow of rock, soil, and debris, often saturated with water. Its high speed places it squarely in the category of rapid flow mass movements, which is distinct from the slower movement of landslides or soil creep.

Answer:

Exogenic and endogenic processes are the two primary forces shaping the Earth's surface.

Feature	Endogenic Processes	Exogenic Processes
Origin	Originate from within the Earth.	Originate from the Earth's atmosphere.
Function	Land building, creating relief.	Land wearing, levelling the surface.
Examples	Volcanism, earthquakes, diastrophism.	Weathering, erosion, deposition.

Answer:

Weathering is the in-situ (in one place) breakdown and decomposition of rocks at or near the Earth's surface. It prepares material for erosion. The three major groups of weathering processes are:

1. Chemical Weathering: Decomposition through chemical reactions (e.g., oxidation, carbonation).
2. Physical (or Mechanical) Weathering: Disintegration without chemical change (e.g., frost wedging, thermal expansion).
3. Biological Weathering: Breakdown caused by living organisms (e.g., plant roots, burrowing animals).

Answer:

A geomorphic process is a physical or chemical action that creates or modifies landforms on the Earth's surface. These processes get their energy from two main sources:

• Endogenic processes are powered by the Earth's internal heat.
• Exogenic processes are driven by solar energy (insolation) and gravitational forces.

Answer:

A geomorphic agent is a mobile medium (like running water, moving ice, wind, waves) that removes, transports, and deposits earth materials. The main geomorphic agents and their roles are:

• Running Water: This is the most dominant geomorphic agent. In hilly areas, rivers with high velocity erode their valleys, forming V-shaped valleys and gorges. In plains, their velocity decreases, leading to the deposition of sediment and the formation of floodplains, deltas, and meanders.
• Groundwater: In areas with soluble rocks like limestone, seeping groundwater causes chemical weathering (solution). This leads to the formation of unique landforms like caves, stalactites, and stalagmites (karst topography).
• Glaciers (Moving Ice): In cold, high-altitude regions, glaciers act like giant bulldozers. They erode the landscape by plucking and abrasion, creating U-shaped valleys, cirques, and aretes. When they melt, they deposit the debris as moraines.
• Wind: In arid and semi-arid regions (deserts), wind is a powerful agent. It erodes by lifting and carrying sand (deflation and abrasion), creating features like mushroom rocks. It deposits sand to form sand dunes.
• Waves and Currents: Along coastlines, waves constantly erode cliffs and headlands, forming sea caves and stacks. They also deposit sand and shingle to create beaches and bars.

The basic role of these exogenic agents is denudation—the overall process of wearing down the land surface, which involves weathering, erosion, and transportation.

Answer:

Yes, it is absolutely necessary to distinguish between weathering and erosion, although they are closely related and often work together. Confusing them can lead to a misunderstanding of how landscapes evolve.

The fundamental difference lies in movement:

• Weathering is an in-situ or "on-site" process. It is the static breakdown of rocks into smaller fragments or their chemical alteration without any transportation of the resulting material. Imagine a rock slowly crumbling in one spot due to temperature changes or acid rain. This is weathering. It prepares the material, making it loose and ready to be moved.
• Erosion is a dynamic process that involves movement. It is the acquisition (picking up) and transportation of weathered material by a geomorphic agent like wind, water, or ice. For example, after a rock has been weathered into sand, the wind picking up that sand and carrying it away is erosion.

Justification for the distinction:

1. Conceptual Clarity: Understanding that weathering happens first and prepares material for erosion clarifies the sequence of landscape degradation. Weathering weakens the rock; erosion carries the weakened debris away.
2. Process-Landform Relationship: Different landforms are created by each process. Weathering leads to the formation of soil (regolith). Erosion, combined with deposition, creates features like canyons, valleys, deltas, and sand dunes.
3. Practical Applications: In fields like agriculture and civil engineering, this distinction is vital. Farmers are concerned with soil formation (a product of weathering) and soil erosion (the loss of that soil). Engineers must account for both the on-site weakening of rock (weathering) and the potential for material removal by water or gravity (erosion and mass wasting) when building structures like dams or roads on hillsides.

Therefore, while they are partners in the denudation process, weathering is the breakdown, and erosion is the takeaway.

Answer: (c) Deposition. Difficulty: Easy.

Answer: (c) Carbonation. Difficulty: Easy.

Answer: (c) Glacier. Difficulty: Medium.

Answer: Soil creep is the very slow, almost imperceptible downward movement of soil on a slope, often indicated by tilted trees or fences. Mudflow is a rapid movement of water-saturated soil and debris, flowing like a liquid river of mud, common in areas with heavy rainfall and sparse vegetation. Difficulty: Medium.

Answer: Oxidation is a chemical reaction where minerals in a rock react with oxygen, often in the presence of water. This process weakens the rock. A common example is the rusting of iron. Rocks rich in iron-bearing minerals (like biotite or pyrite) turn brownish or reddish when oxidized, making them crumble easily. Difficulty: Medium.

Answer: Weathering weakens the internal cohesion of rock and soil particles. This makes the material loose and unstable. On a weathered slope, the pull of gravity can easily overcome the frictional forces holding the loose debris, triggering mass movements like landslides or slumps. Unweathered rock is more solid and resistant to gravity. Difficulty: Hard.

Answer: Physical (or mechanical) weathering breaks rocks into smaller pieces without changing their chemical composition. The main types are:

• Unloading and Exfoliation: Removal of overlying rock pressure causes underlying rocks to expand and fracture parallel to the surface, leading to peeling layers (exfoliation domes).
• Thermal Expansion and Contraction: In deserts, extreme daily temperature changes cause minerals in rocks to expand (day) and contract (night) at different rates, leading to stress and eventual fragmentation.
• Frost Wedging: In cold climates, water seeps into rock cracks, freezes, expands by about 9%, and exerts immense pressure, widening the crack. Repeated freezing and thawing breaks the rock apart.
• Salt Weathering: In coastal or arid areas, salt crystals grow in rock pores from evaporating water. These crystals exert pressure, causing the rock to disintegrate.

Difficulty: Medium.

Answer: Mass movement is the downslope transfer of rock and soil due to gravity. It can be classified as slow or rapid.

• Slow Movements:
  • Creep: The slowest form, involving the gradual movement of soil or rock.
  • Solifluction: Common in permafrost areas, where the saturated surface layer slowly flows over the frozen ground.
• Rapid Movements:
  • Flows: Material moves like a viscous fluid. Examples include earthflow, mudflow, and debris avalanche (the fastest).
  • Slides: Material moves as a coherent block along a planar or curved surface. Examples include rockslides and slumps (rotational slide).
  • Falls: Abrupt movement of rocks falling freely from a cliff face (e.g., rockfall).

Difficulty: Medium.

Answer: The event is a debris flow or mudflow, which is a type of rapid mass movement.

Answer:

• Natural Factor: Heavy monsoon rains, which saturated the soil and increased its weight, reducing friction.
• Human-made Factor: Deforestation, which removed the tree roots that bind the soil together, making the slope unstable.

Answer: Weathering (which fractured the rocks and created soil) and gravity.

Answer: A key preventive measure would be afforestation or planting trees and vegetation on the slope to bind the soil and increase its stability. Building retaining walls can also help.