Which one of the following is depositional landform?

1. Geomorphic Processes: Erosion vs. Deposition (basic)

To understand the ever-changing face of our Earth, we must look at geomorphic processes — the natural forces that shape the landscape. While internal (endogenic) forces like volcanoes build mountains up, external (exogenic) forces act as the great levelers. These exogenic processes, driven primarily by the sun's energy and gravity, include weathering, mass wasting, erosion, and deposition Physical Geography by PMF IAS, Chapter 10, p.82.

Erosion is a dynamic and mobile process. It involves the 'acquisition and transportation' of rock debris. Think of it as the Earth’s natural sculptor: agents like running water, wind, glaciers, and waves pick up fragments of rock and move them away. Because erosion removes material and carries it elsewhere, it is known as a degradational process — it wears down the high points and relief of the land FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Chapter 6, p.43. While weathering breaks rocks down in one place, erosion is what actually hauls the pieces away.

Deposition is the necessary consequence of erosion. When the agents of erosion (like a slowing river or a dying breeze) lose their velocity and energy, they can no longer carry the weight of the debris. This material then settles in lower-lying areas. This process is called aggradation because it fills up depressions and builds new landforms. In short, erosion 'takes' while deposition 'gives' FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Chapter 6, p.38.

Feature	Erosion	Deposition
Primary Action	Removal and transport of materials.	Settling and accumulation of materials.
Impact on Landscape	Degradation (wearing down the surface).	Aggradation (building up the surface).
Kinetic Energy	Requires high energy from agents (fast water/wind).	Occurs when energy levels drop (slow water/wind).

Sources: Physical Geography by PMF IAS, Geomorphic Movements, p.82; FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geomorphic Processes, p.43; FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geomorphic Processes, p.38

2. Groundwater as a Geomorphic Agent (basic)

While we often think of water as a sculptor when it flows in mighty rivers, groundwater works as a silent, invisible architect beneath our feet. Unlike surface water which erodes primarily through physical force (abrasion), groundwater acts as a geomorphic agent mainly through chemical weathering. It moves through the joints, bedding planes, and pores of rocks, dissolving soluble minerals along the way.

The most distinctive landscape shaped by groundwater is known as Karst Topography, named after the Karst region in the Balkans. This occurs primarily in areas rich in limestone or dolomite (calcium carbonate). The magic happens through a process called carbonation: as rainwater falls through the atmosphere and seeps through decaying organic matter in the soil, it picks up CO₂, turning into a weak carbonic acid (H₂CO₃). This acidic water reacts with the limestone, dissolving it and carrying it away in solution. Fundamentals of Physical Geography, Chapter 6, p.40

The landforms created by groundwater are divided into two distinct categories based on whether the water is 'taking away' or 'leaving behind' minerals:

• Erosional Landforms: These are created by the dissolution of rock. They include sinkholes (funnel-shaped depressions where surface water disappears underground), lapis/lapies (irregular grooves and ridges on the surface), and caves or caverns formed by the removal of rock layers.
• Depositional Landforms: When mineral-rich water enters a cave, it may evaporate or lose its CO₂, causing the dissolved calcium carbonate to precipitate (harden) back into solid form. This creates spectacular features like stalactites, stalagmites, and pillars. Fundamentals of Physical Geography, Chapter 6, p.53

Sources: Fundamentals of Physical Geography, Geomorphic Processes, p.40; Fundamentals of Physical Geography, Landforms and their Evolution, p.53; Physical Geography by PMF IAS, Geomorphic Movements, p.90

3. Essentials of Karst Topography (intermediate)

Concept: Essentials of Karst Topography

4. Connected Concept: Fluvial Landforms (intermediate)

In the study of geomorphology, fluvial landforms refer to those shaped by the action of running water—primarily rivers. Rivers act as powerful agents of change through a continuous cycle of erosion, transportation, and deposition. As a river flows from its source in the highlands to its mouth at the sea, its energy levels shift, dictating whether it will carve into the earth or build new land. Physical Geography by PMF IAS, Fluvial Landforms and Cycle of Erosion, p.197

Fluvial Erosion occurs through several distinct physical and chemical mechanisms. Hydraulic Action is the sheer force of moving water wearing down rocks, while Abrasion (or Corrasion) happens when the river’s load (sand and pebbles) grinds against the riverbed like sandpaper. Over time, the river load itself undergoes Attrition, where particles collide and break into smaller, smoother fragments. Physical Geography by PMF IAS, Fluvial Landforms and Cycle of Erosion, p.197. In the upper course, Vertical Erosion (downcutting) dominates, creating deep V-shaped valleys. As the gradient levels out in the middle course, Lateral Erosion takes over, widening the valley floor and giving rise to winding curves known as Meanders.

A meander is a fascinating example of simultaneous erosion and deposition. The water flows faster on the outer curve of the loop, creating a steep cliff-slope through intensive erosion. Conversely, the water slows down on the inner curve, lacking the energy to carry its load; this leads to deposition on the slip-off side, forming gentle convex slopes. Physical Geography by PMF IAS, Fluvial Landforms and Cycle of Erosion, p.199. Eventually, if the erosion on the outer curves becomes too extreme, the river may bypass the loop entirely, leaving behind a crescent-shaped water body known as an Oxbow Lake. Physical Geography by PMF IAS, Fluvial Landforms and Cycle of Erosion, p.200

Finally, as the river reaches the plains or the sea, its velocity drops significantly. This loss of energy forces the river to drop its remaining load—coarser materials first and finer sediments like silt later. FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI, Geomorphic Processes, p.43. This process of Aggradation creates depositional features such as Alluvial Fans at the base of mountains and Deltas at the river's mouth, where the main channel often splits into multiple distributaries. Physical Geography by PMF IAS, Fluvial Landforms and Cycle of Erosion, p.203

Sources: Physical Geography by PMF IAS, Fluvial Landforms and Cycle of Erosion, p.197, 199, 200, 203; FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI, Geomorphic Processes, p.43

5. Connected Concept: Glacial and Aeolian Features (intermediate)

When we study landforms created by deposition, we are looking at the final signature of an erosional agent. While weathering breaks rocks down, and erosion moves them, deposition happens when the agent (like ice or wind) loses its energy and drops its load. In this hop, we focus on the unique features left behind by Glacial and Aeolian (wind) processes.

Glaciers act like massive conveyor belts of ice, carrying everything from fine clay to giant boulders. This unsorted debris is called Till. The most prominent glacial depositional features are Moraines. These are long ridges of debris categorized by where they form: Terminal Moraines are found at the very end or 'toe' of a glacier, Lateral Moraines form along the sides of the glacial valley, and Medial Moraines occur in the center when two glaciers join FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Chapter 6, p.55-56. Another fascinating feature is the Drumlin—a smooth, oval, inverted boat-shaped mound of till. Drumlins are unique because their tapered end points in the direction the glacier was moving, providing a geographical record of past ice flow Physical Geography by PMF IAS, Major Landforms and Cycle of Erosion, p.233.

In contrast, Aeolian (wind) landforms are common in arid regions where there is little vegetation to hold the soil. Unlike glaciers, wind is a selective transporter, usually moving only sand and silt. This creates Sand Dunes, which are mounds or heaps of sand Physical Geography by PMF IAS, Major Landforms and Cycle of Erosion, p.237. The most iconic of these is the Barchan, a crescent-shaped dune with its 'horns' pointing downwind. These are often 'live' or active dunes, meaning they constantly migrate across the desert floor as the wind pushes sand up the gentle windward slope and lets it slip down the steeper leeward side GC Leong, Arid or Desert Landforms, p.72.

Feature	Agent	Key Characteristic
Moraine	Glacier (Ice)	Ridges of unsorted rock debris (Till).
Drumlin	Glacier (Ice)	Inverted boat shape; indicates movement direction.
Barchan	Aeolian (Wind)	Crescent-shaped sand dune; horns point downwind.

Sources: FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Chapter 6: Landforms and their Evolution, p.55-56; Physical Geography by PMF IAS, Major Landforms and Cycle of Erosion, p.233, 237; Certificate Physical and Human Geography, GC Leong, Arid or Desert Landforms, p.72

6. Karst Erosional Landforms: Sinkholes and Lapies (exam-level)

In the study of geomorphology, Karst topography represents a unique landscape shaped primarily by the chemical weathering of soluble rocks, most notably limestone (calcium carbonate) and dolomite. The term originates from the Karst region of the Balkans, where these features are classic Fundamentals of Physical Geography, NCERT, Chapter 6, p.52. The fundamental process here is carbonation: as rainwater falls through the atmosphere, it picks up carbon dioxide to form a weak carbonic acid (H₂CO₃), which then dissolves the rock over time, creating a variety of erosional landforms.

One of the first visible signs of this erosion is Lapies. When rainwater flows over a limestone surface, it eats away at the joints and cracks, carving out narrow, deep grooves or furrows. This leaves behind a rugged, fluted surface characterized by sharp, jagged ridges. In many regions, this is referred to as a "pavement" where the flat-topped blocks are called clints and the deep fissures separating them are called grikes Certificate Physical and Human Geography, GC Leong, Limestone and Chalk Landforms, p.79. It is important to distinguish Lapies (the landform) from Lapis Lazuli, which is a metamorphic gemstone and unrelated to karst processes.

As the dissolution process deepens, surface depressions known as Sinkholes (or swallow holes) emerge. These are funnel-shaped openings through which surface water "sinks" into the underground drainage system. Over time, as multiple sinkholes expand and merge through continued erosion and roof collapse, they form progressively larger depressions. We categorize these by scale: from small dolines to mid-sized uvalas, and finally to massive, flat-floored depressions called poljes, which can cover hundreds of square kilometers Physical Geography, PMF IAS, Major Landforms and Cycle of Erosion, p.228.

Feature	Description	Primary Process
Lapies	Jagged ridges and narrow grooves on a limestone surface.	Surface dissolution along joints.
Sinkhole	Funnel-shaped depression where water enters the ground.	Dissolution or ceiling collapse.
Uvala	A large, irregular depression formed by merging dolines.	Coalescence of erosional voids.

Sources: Fundamentals of Physical Geography, NCERT, Landforms and their Evolution, p.52; Certificate Physical and Human Geography, GC Leong, Limestone and Chalk Landforms, p.79; Physical Geography, PMF IAS, Major Landforms and Cycle of Erosion, p.228

7. Karst Depositional Landforms: Speleothems (exam-level)

While the erosion of limestone creates the vast subterranean voids we know as caves, the process of deposition is what truly "decorates" these underground landscapes. In Karst topography, these mineral deposits are collectively known as speleothems. The science behind them is a beautiful cycle of chemistry: as groundwater enriched with calcium bicarbonate [Ca(HCO₃)₂] enters an air-filled cave, it experiences a change in pressure and temperature. This causes the water to lose carbon dioxide (degassing) or evaporate, leaving behind solid calcium carbonate (limestone) once again Certificate Physical and Human Geography, Limestone and Chalk Landforms, p.79.

The two most iconic speleothems are distinguished primarily by their direction of growth. Stalactites are slender, icicle-like formations that hang from the cave ceiling. They grow downward as mineral-rich water trickles through the roof; as the water evaporates, it leaves behind a thin ring of calcite. Conversely, stalagmites rise from the cave floor. These form when the water dripping from the ceiling or from the tip of a stalactite hits the ground. Because the impact of the drip spreads the mineral content, stalagmites are typically shorter, fatter, and more rounded than their ceiling-hung counterparts FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Landforms and their Evolution, p.53.

Over thousands of years, these features can evolve into even more complex structures. If a stalactite growing down and a stalagmite growing up eventually meet and fuse, they form a continuous pillar or column. The variety in their shapes is immense—stalagmites can appear as simple mounds, flat discs, or even miniature craters depending on the rate of dripping and the concentration of minerals in the water FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Landforms and their Evolution, p.53.

Feature	Position	Physical Appearance
Stalactite	Cave Ceiling	Sharp, slender, tapering downward like an icicle.
Stalagmite	Cave Floor	Broad base, rounded or bulging, grows upward.
Pillar	Floor to Ceiling	A complete column formed by the union of the two.

Sources: Certificate Physical and Human Geography, GC Leong, Limestone and Chalk Landforms, p.79; FUNDAMENTALS OF PHYSICAL GEOGRAPHY, NCERT, Landforms and their Evolution, p.53

8. Solving the Original PYQ (exam-level)

Now that you have mastered the fundamental processes of Karst topography, this question serves as the perfect test of your ability to distinguish between erosional and depositional features. The core building block here is understanding the lifecycle of calcium carbonate: first, it is dissolved by acidic groundwater (erosion), and later, it precipitates out of the solution when conditions change (deposition). As you look at the options, you must ask yourself: "Is this landform a hole left behind, or a structure built up?" A depositional landform is the result of this constructive process where minerals accumulate over time.

To arrive at the correct answer, let's trace the journey of a water droplet inside a limestone cavern. When mineral-rich water drips from the ceiling, the evaporation of water or the release of carbon dioxide causes minerals to solidify. As explained in FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.), a Stalagmite is the mound-shaped deposit that grows upward from the cave floor. This makes (A) Stalagmite the only correct depositional feature among the choices. In contrast, Sinkholes and Caves are the empty spaces created by the removal of rock; they are the results of erosion, not deposition.

Finally, it is vital to spot the common "phonetic trap" UPSC has set with option (B). Lapis (specifically lapis lazuli) is a metamorphic gemstone, not a landform. It is included here to confuse students who might be thinking of Lapies—which are actually grooved, erosional limestone surfaces. By carefully categorizing each term according to the geomorphic process that created it, you can avoid these distractors and identify Stalagmite as the definitive depositional feature.