Match List-I with List-II and select the correct answer using the code given below the Lists : List-I (Weathering type) A. Chemical weathering B. Mechanical weathering C. Glacial deposits D. Deposition by ground- List-II (Landform/ Process) 1. Till 2. Oxidation 3. Plant roots 4. Stalactite Code :

1. Exogenic Geomorphic Processes (basic)

Welcome to your journey into the forces that shape our world! To understand the landscape around you—the rolling hills, the deep valleys, and the vast plains—we must first look at Exogenic Geomorphic Processes. The word 'Exo' means 'outside' and 'Genic' means 'origin.' Unlike internal (endogenic) forces that build mountains from within the Earth, exogenic forces are external forces that derive their energy primarily from the sun and the atmosphere. FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.), Chapter 6, p.37

Think of these processes as nature’s way of 'sculpting' the Earth. These forces work relentlessly to level the surface through a combined action known as Gradation. Gradation is a two-way street: it involves wearing down high points and filling up low points. As long as the atmosphere exists and the sun shines, these processes will continue their tug-of-war with the internal forces of the Earth.

While internal forces are the "builders" (creating relief variations), exogenic forces are the "levelers." However, the surface of the Earth is never perfectly flat because endogenic forces continuously elevate parts of the crust, ensuring there is always fresh material for the exogenic agents—like water, wind, and ice—to work upon. FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.), Chapter 6, p.37

Sources: FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.), Chapter 6: Geomorphic Processes, p.37

2. Fundamentals of Weathering (basic)

Welcome back! In our previous step, we looked at the broad landscape of geomorphology. Now, let’s zoom in on the very first step of landscape transformation: Weathering. Think of weathering as the "mechanical workshop" of nature where solid rock is broken down into smaller pieces or altered into new substances.

The most critical thing to remember is that weathering is an in-situ (on-site) process. Unlike erosion, which involves the transport of material by wind or water, weathering happens right where the rock stands. It is the static disintegration or decomposition of rocks and soil Physical Geography by PMF IAS, Geomorphic Movements, p.83. We generally categorize these processes into three main families:

• Physical (Mechanical) Weathering: This is the literal breaking of rocks into smaller fragments without changing their chemical identity. In dry climates, temperature fluctuations cause rocks to expand and contract, eventually leading to block disintegration Certificate Physical and Human Geography, Weathering, Mass Movement and Groundwater, p.37.
• Chemical Weathering: This involves a change in the chemical composition of the minerals. A classic example is Oxidation, where oxygen reacts with minerals like iron to form iron oxide (rust). This makes the rock crumble far more easily Certificate Physical and Human Geography, Weathering, Mass Movement and Groundwater, p.37.
• Biological Weathering: This is unique because it can be both mechanical and chemical. When a plant root grows into a crack and exerts physical pressure to widen it (root pry), it’s mechanical. When decaying organic matter produces humic acids that dissolve minerals, it’s chemical Fundamentals of Physical Geography, Geomorphic Processes, p.41.

Climate plays a master role here. Generally, warm and wet climates are the engines of rapid chemical weathering because moisture and heat accelerate chemical reactions. Conversely, dry climates are dominated by physical weathering processes Certificate Physical and Human Geography, Weathering, Mass Movement and Groundwater, p.37.

Sources: Physical Geography by PMF IAS, Geomorphic Movements, p.83, 91; Certificate Physical and Human Geography (GC Leong), Weathering, Mass Movement and Groundwater, p.37; Fundamentals of Physical Geography (NCERT 2025 ed.), Geomorphic Processes, p.41

3. Mass Movements and Slope Stability (intermediate)

Mass movements, also known as mass wasting, refer to the downslope movement of soil, regolith, and rock debris under the direct influence of gravity. Unlike erosion, where a medium like wind or water carries the material away, mass movement happens because gravity simply overcomes the internal strength of the slope material. This occurs when the shear stress (the force of gravity pulling down) exceeds the shear strength (the resistance provided by friction and cohesion of the material).

We classify these movements primarily by their speed and the moisture content of the material. At the slower end of the spectrum is Creep. This is an extremely slow, almost imperceptible movement that occurs on moderately steep, soil-covered slopes. You can identify creep by observing "drunken" trees with curved trunks, or telephone poles and fence posts that lean downslope over time Physical Geography by PMF IAS, Geomorphic Movements, p.86. Another slow process is solifluction, which is the slow downslope flow of soil saturated or lubricated with water, often seen in cold climates where the top layer of soil thaws while the deeper layers remain frozen Physical Geography by PMF IAS, Geomorphic Movements, p.86.

On the faster side, we encounter Rapid Movements. These are often triggered by heavy rainfall or seismic activity. A Debris Avalanche is a prime example of a rapid flow mass movement, often occurring in humid regions where the soil is completely saturated FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.), Geomorphic Processes, p.46. When a large block of rock moves as a single unit along a definite fracture or plane, it is termed a Block Slide Environment and Ecology, Majid Hussain, Natural Hazards and Disaster Management, p.43.

Stability can be improved through retaining walls, terracemaking, or planting ground cover, which increases the binding strength of the soil. However, despite human efforts, the persistent pull of gravity—especially in the form of soil creep—is a constant geological force Environment and Ecology, Majid Hussain, Natural Hazards and Disaster Management, p.43.

Sources: Physical Geography by PMF IAS, Geomorphic Movements, p.86; FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.), Geomorphic Processes, p.46; Environment and Ecology, Majid Hussain, Natural Hazards and Disaster Management, p.43

4. Pedogenesis: The Process of Soil Formation (intermediate)

Pedogenesis is the scientific term for the complex process of soil formation. It is important to understand that soil is not merely a collection of broken rock particles; it is a living system that takes millions of years to form just a few centimeters in depth NCERT Class X Contemporary India II, Chapter 1, p.8. The process begins with the weathering mantle—the layer of loosened rock material created by physical and chemical weathering. This mantle serves as the basic "input" or raw material for pedogenesis to occur NCERT Class XI Fundamentals of Physical Geography, Chapter 6, p.44.

The transformation from rock debris to mature soil follows a fascinating biological sequence. First, the weathered material is colonized by pioneer species like bacteria, mosses, and lichens. These organisms contribute organic acids that further break down minerals. As they die, their remains accumulate as humus (organic matter). This enrichment allows for the growth of grasses and ferns, and eventually trees. Simultaneously, burrowing animals and insects mix the material, creating a porous, sponge-like structure that can retain water and permit air passage—essential qualities for a "mature" soil NCERT Class XI Fundamentals of Physical Geography, Chapter 6, p.44.

Pedogenesis is governed by the interaction of five fundamental factors. These factors do not act in isolation but work in union to determine the soil's characteristics, such as texture, color, and chemical properties NCERT Class X Contemporary India II, Chapter 1, p.9:

• Parent Material: The original rock or deposited debris that determines the basic mineral composition and texture.
• Climate: The most influential factor, specifically moisture and temperature, which control the rate of weathering and organic decomposition.
• Topography (Relief): Steep slopes may have thin soil due to erosion, while flat areas accumulate thicker layers.
• Biological Activity: Plants, animals, and microorganisms add organic matter and assist in aeration.
• Time: Soil maturity depends on how long the pedogenic processes have been acting without significant disruption.

Sources: NCERT Class XI Fundamentals of Physical Geography, Chapter 6: Geomorphic Processes, p.44; NCERT Class X Contemporary India II, Chapter 1: Resources and Development, p.8-9

5. Chemical and Biological Weathering Mechanisms (exam-level)

While mechanical weathering physically breaks rocks, chemical weathering is more like a laboratory reaction taking place in nature. It involves the in-situ decomposition of minerals, where the very atomic structure of the rock is altered. For these reactions to occur efficiently, three catalysts are essential: water, air (oxygen and carbon dioxide), and heat. This is why chemical weathering is most aggressive in warm, humid tropical climates and almost non-existent in cold, dry deserts Certificate Physical and Human Geography, GC Leong, Weathering, Mass Movement and Groundwater, p.37.

One of the most common chemical processes is Oxidation. This occurs when minerals react with oxygen in the air or water. A classic example is iron-rich rocks; when exposed to moisture and oxygen, the iron turns into iron oxide (rust). This new compound is weaker, crumbles easily, and often gives the rock a distinct brownish or reddish crust Certificate Physical and Human Geography, GC Leong, Weathering, Mass Movement and Groundwater, p.37. Another critical process is Hydration, where water is chemically added to a mineral's structure. This causes the mineral to expand in volume, creating internal physical stress that eventually leads to exfoliation or granular disintegration Physical Geography by PMF IAS, Geomorphic Movements, p.91.

Biological weathering is unique because it bridges the gap between physical and chemical processes. It is the contribution of living organisms—plants, animals, and microbes—to the breakdown of rocks. We can categorize its actions as follows:

• Biological-Mechanical: The most prominent example is root pry. As plant roots grow into narrow crevices, they exert tremendous outward pressure, acting like a wedge to split the rock apart Physical Geography by PMF IAS, Geomorphic Movements, p.91.
• Biological-Chemical: Microorganisms and decaying organic matter release organic acids (like humic acid) and carbon dioxide into the soil. These acids increase the solubility of minerals, accelerating the chemical decomposition of the underlying bedrock NCERT Class XI Fundamentals of Physical Geography, Geomorphic Processes, p.40.

Sources: Certificate Physical and Human Geography, GC Leong, Weathering, Mass Movement and Groundwater, p.37; Physical Geography by PMF IAS, Geomorphic Movements, p.90-91; NCERT Class XI Fundamentals of Physical Geography, Geomorphic Processes, p.40

6. Depositional Landforms: Glaciers and Groundwater (exam-level)

When glaciers melt or groundwater loses its mineral-carrying capacity, they drop the material they have been transporting. This process creates distinct depositional landforms. In glacial environments, the most fundamental material is glacial till—an unassorted mixture of coarse and fine debris dropped directly by melting ice. Unlike water-borne sediments, till is unstratified (not layered) and the rock fragments are often angular because they haven't been rounded by long-distance water transport FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.), Chapter 6, p.55.

The most iconic glacial depositional features are moraines. These are long ridges of debris categorized by where they form relative to the glacier. Terminal (or end) moraines form at the snout or 'toe' of the glacier, marking its furthest advance. Lateral moraines form along the sides of the glacial valley, while medial moraines occur in the center when two glaciers join and their lateral moraines merge. If a glacier retreats rapidly, it may leave a thin, irregular sheet of debris across the valley floor called a ground moraine Physical Geography by PMF IAS, Major Landforms and Cycle of Erosion, p.233.

In contrast, groundwater deposition primarily occurs through chemical precipitation, typically in limestone (karst) regions. As water saturated with calcium carbonate drips from cave ceilings, it evaporates, leaving behind mineral deposits. Stalactites are icicle-shaped forms hanging from the ceiling, while stalagmites rise from the cave floor where the water drops land. Over time, these two may meet to form a continuous pillar or column.

Sources: FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.), Chapter 6: Landforms and their Evolution, p.55-56; Physical Geography by PMF IAS, Major Landforms and Cycle of Erosion, p.233

7. Solving the Original PYQ (exam-level)

You have just mastered the fundamental geomorphic processes, and this question is the perfect test of your ability to categorize Exogenic forces. At its core, this PYQ requires you to distinguish between Weathering (the breakdown of rocks in situ) and Deposition (the accumulation of weathered material by agents like ice and water). By applying your knowledge that weathering is either Chemical (altering molecular structure) or Mechanical (physical disintegration), and recognizing the distinct signatures left by moving ice versus percolating water, you can systematically dismantle this match-the-following format.

Let's walk through the logic: Oxidation is a classic chemical reaction where minerals react with oxygen, making it a clear match for Chemical weathering. While Plant roots are biological, they exert physical pressure by wedging into rock crevices—a process known as root pry—placing them under Mechanical weathering according to Physical Geography by PMF IAS. Moving to depositional landforms, remember that Till is the hallmark of glaciers—unsorted, unstratified debris dropped directly by melting ice as explained in FUNDAMENTALS OF PHYSICAL GEOGRAPHY, NCERT Class XI. Finally, Stalactites represent the slow, drip-by-drip accumulation of minerals from Groundwater in karst topography. This leads us directly to the sequence 2-3-1-4, making (A) the correct answer.

UPSC often sets traps by exploiting the overlap between categories. For instance, options (B), (C), and (D) might tempt you if you confuse the agent with the process. A common pitfall is misclassifying plant roots solely as "biological" and failing to see their physical (mechanical) impact, or mixing up the depositional features of wind, water, and ice. By ensuring you can differentiate between erosional and depositional landforms—and knowing that Till is specifically glacial whereas Stalactites are specifically groundwater—you can easily avoid the "distractor" sequences that shuffle these specific pairings.