Landforms & Their Evolution – NDA Geography Notes

Introduction

Look at the Earth’s surface and you see an extraordinary variety — deep river valleys, flat sandy deserts, jagged mountain peaks with glaciers, smooth wave-cut cliffs, and strange underground caves full of stone formations. Every one of these shapes was created by a specific agent working on the underlying rock over thousands or millions of years.

This chapter is about how each type of landscape forms — through the work of rivers, glaciers, wind, ocean waves, or underground water. Each agent erodes rock, transports the debris, and deposits it elsewhere — creating characteristic landforms that can be recognised anywhere in the world.

NDA tests this chapter very heavily — through match-list questions pairing landforms with their agents, direct identification of landform types, and statement-based questions. This chapter requires knowing not just what each landform looks like, but which agent created it and whether it is erosional or depositional.

The chapter is organised by agent — rivers first, then glaciers, then wind, then coastal waves, then underground water.

Understand the Topic

The Framework — Erosional vs Depositional Landforms

Every agent of erosion creates two kinds of landforms.

Erosional landforms are formed by the wearing away of rock. The material is removed. The feature is a hollow, valley, cave, or cut feature.

Depositional landforms are formed by the dropping of material that was being carried. Material piles up. The feature is a mound, ridge, plain, or filled feature.

For each agent you need to know both types.

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Section 1 — Fluvial Landforms (Formed by Rivers)

Rivers are the most powerful agents of erosion on Earth’s land surface. A river does three things — erodes, transports, and deposits. Different things happen in different stages of a river’s course.

Upper Course: River flows steeply. High energy. Cuts downward into rock. Creates narrow, deep valleys.

Middle Course: Gradient gentler. River meanders — winds from side to side.

Lower Course: Nearly flat gradient. Low velocity. Deposits material. Creates plains and deltas.

Fluvial Erosional Landforms:

Gorge:
A narrow, deep valley with steep, almost vertical walls. Forms when a river cuts rapidly downward through hard rock.

Canyon:
A deep valley with steep, step-like (terraced) walls. Wider than a gorge. The Grand Canyon in the USA is the most famous example. [NDA 2019-II]

Gully:
A small channel cut by running water on a slope. Heavy rain erodes loose soil into gullies. [NDA 2008-II]

Waterfall:
Forms where a river flows over a sudden drop — usually where hard rock overlies softer rock. The softer rock erodes faster, creating a cliff.

Plunge Pool:
A hollow at the base of a waterfall, scoured by the falling water and debris. [NDA 2016-II]

Meander:
In the middle and lower course, a river develops winding bends called meanders. The outer bank of each bend erodes (where water moves faster). The inner bank deposits (where water moves slower).

A meander is a U-shaped bend in a river. An extremely tight meander is called a gooseneck — likely to become a cutoff or oxbow lake after a flood. Tectonic uplift can cause a river to cut downward along its meandering course, producing incised meanders. [NDA tested via CDS]

Oxbow Lake:
When a meander becomes so curved that the two arms nearly touch, a flood can cut through the narrow neck. The old curved loop is abandoned and left as a crescent-shaped lake — an oxbow lake. [NDA tested via CDS]

Order of river features from upstream to downstream:
Falls → Meanders → Oxbow lake → Delta. [NDA tested via CDS]

Rejuvenation:
When the land is uplifted or sea level drops, a river gains new energy and starts cutting downward again. This is called rejuvenation — the river becomes young again even in its lower course. [NDA tested via CDS]

Fluvial Depositional Landforms:

Delta:
At the river’s mouth, where it meets a sea or lake, the water slows suddenly and drops all its load. Over time this builds a flat, triangular landform called a delta. The Ganga-Brahmaputra delta (Sundarbans) is the world’s largest delta.

Natural Levee:
Raised banks along a river, built up by flood deposits. When a river floods, it deposits coarse material immediately beside its banks — building up ridges.

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Drainage Patterns:

Rivers develop different patterns depending on the shape of the land and the rock beneath.

• Insequent = no apparent reason for its path (random)
• Consequent = course determined by original slope of land
• Subsequent = direction controlled by rock structure
• Resequent = flows in same direction as consequent but at lower level
  [NDA tested via CDS]

The rivers of North-West Europe are good examples of trellis drainage — the main river and its tributaries join at right angles, like a garden trellis. [NDA 2019-II]

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Section 2 — Glacial Landforms (Formed by Ice)

A glacier is a large, slow-moving mass of ice that forms where more snow falls each year than melts. Over time, accumulated snow compresses into ice. The weight causes the ice to flow slowly downhill.

Glaciers are powerful erosion agents — they pick up rocks and use them to grind down the bedrock beneath.

Glacial Erosional Landforms:

Cirque (Corrie):
A bowl-shaped hollow cut into a mountainside at the head of a glacier. Snow accumulates in a hollow, converts to ice, and the ice slowly moves outward, carving the hollow deeper. A small lake called a tarn often forms at the bottom. [NDA 2010-II | NDA 2014-II]

U-Shaped Valley:
Rivers create V-shaped valleys by cutting downward. Glaciers are much wider and heavier — they erode the entire valley floor and widen the sides, creating a characteristic flat-bottomed U shape. [NDA 2010-I | NDA tested via CDS]

Horn:
When three or more cirques form on different sides of a mountain peak, the glaciers eat away from all sides. The central peak becomes a sharp, pyramid-shaped peak called a horn. The Matterhorn on the Swiss-Italian border is the most famous. [NDA 2016-II]

Col:
A low point or pass between two peaks on a ridge. Forms when two cirques on opposite sides of a ridge erode back toward each other. [NDA tested via CDS]

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Glacial Depositional Landforms:

Moraine:
Material carried by a glacier (rocks, gravel, sand — collectively called glacial till) is deposited as ridges called moraines.

• Terminal moraine — at the farthest point the glacier reached
• Lateral moraine — along the sides of the glacier
• Medial moraine — when two glaciers merge
  [NDA 2010-I]

Drumlin:
A smooth, elongated, egg-shaped hill made of glacial till. Drumlins are always oriented in the direction the glacier moved. A landscape of many drumlins is called basket-of-eggs topography — because the rounded hills look like a basket of eggs from above. [NDA 2021-I | NDA tested via CDS]

Esker:
A long, winding ridge of sand and gravel deposited by meltwater streams flowing within or beneath a glacier. Eskers look like raised roads running across the landscape.

Periglacial Landforms:

Pingo:
A mound of earth-covered ice found in periglacial (near-glacier) environments with permafrost. Water under the ground freezes, expands, and pushes up a dome of soil above it. [NDA tested via CDS]

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Section 3 — Aeolian Landforms (Formed by Wind)

Wind is the dominant agent of landform creation in deserts. In areas with little vegetation and dry, loose material, wind picks up sand and dust and carries it for great distances.

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Wind Erosional Landforms:

Mushroom Rock (Pedestal Rock):
Wind near the ground carries more sand than wind higher up. This means erosion is most intense near the ground. When wind erodes a rock, the base is cut away faster than the top, creating a mushroom shape. Wind is strongest at the base of a mushroom rock. [NDA 2009-II]

Inselberg:
An isolated, steep-sided rock hill rising abruptly from a flat desert plain. It is a remnant of harder rock that has resisted erosion while the surrounding softer rock was worn away. [NDA 2010-I]

Yardang:
An elongated ridge of rock carved and streamlined by wind erosion, pointing in the direction of the prevailing wind. [NDA 2014-II]

Wind Depositional Landforms:

Barchan (Barkhan):
The most common desert sand dune shape. A crescent-shaped dune with horns pointing downwind. The windward side is gently sloping; the leeward side is steep. [NDA 2010-II | NDA 2014-II | NDA tested via CDS]

Loess:
Fine dust particles carried by wind for hundreds of kilometres and deposited in thick layers far from their source. Wind-deposited dust is called loess. It is extremely fertile. The famous fertile soil of North China and parts of Europe is loess. [NDA tested via CDS]

Playa:
A flat, dry lake bed in a desert basin. After rare rains, water forms a temporary shallow lake. When the water evaporates, it leaves a flat, hard surface of dried mud and salt. The fine-grained bed of an ephemeral (temporary) desert lake is also called a playa. [NDA 2021-II]

The lowest part of a bolson (desert basin) is occupied by a playa. Playa is classified as an arid landform. [NDA 2024-II]

Bajada:
A gently sloping plain formed by the merging of several alluvial fans at the base of a mountain in a desert. Also called a peripediment. [NDA tested via CDS]

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Section 4 — Marine/Coastal Landforms (Formed by Waves)

Waves are the dominant agent of erosion and deposition along coastlines. They carry enormous energy and crash against cliffs, cut into rock, and carry and deposit sand.

Coastal Erosional Landforms:

Cliff:
A steep, often vertical rock face along a coastline. Waves undercut the base, eventually causing the rock above to collapse.

Notch:
At the base of a sea cliff, waves cut a horizontal indent into the rock. As the notch deepens, the cliff above becomes unstable and collapses. [NDA 2018-I]

Sea Cave:
Where there is a weak zone in a cliff, waves concentrate erosive energy and cut a cave into the cliff face.

Sea Arch:
If two caves on opposite sides of a headland meet, they form a natural arch — a bridge of rock with open water beneath. [NDA 2018-I]

Stack:
When a sea arch collapses, the seaward pillar is left as an isolated column of rock rising from the sea. A stack is an erosional feature — not depositional. [NDA 2018-I]

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Coastal Depositional Landforms:

Beach:
Sand, pebbles, and shell fragments deposited by waves along the shoreline.

Spit:
A long, narrow ridge of sand extending from the land into the sea. Forms where a coastline changes direction. [NDA 2018-I]

Tombolo:
A sand or gravel bar connecting an island to the mainland. [NDA 2018-I]

Sand Bar:
A ridge of sand deposited parallel to the coastline.

Barrier Island:
A small chain of sand islands that form offshore, far from the coast. Lagoons or shallower marshes separate barrier islands from the mainland. They are hazardous for settlements because they are easily swept away by storms. [NDA tested via CDS]

Stack is NOT a depositional coastal feature — it is erosional. [NDA 2018-I]

Section 5 — Karst Landforms (Formed by Underground Water in Limestone Areas)

Limestone is made of calcium carbonate. Slightly acidic rainwater (containing dissolved carbon dioxide) dissolves limestone slowly. Over thousands of years this creates a unique landscape called karst topography.

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Surface Karst Features:

Lapies (Lapiés):
The grooved, furrowed surface of limestone dissolved by rainwater. Sharp ridges separated by channels. [NDA 2016-II]

Sinkhole (Doline):
A circular depression in the ground formed when the roof of an underground limestone cavern collapses, or when the ground slowly dissolves and subsides. The most common feature of karst terrain. A sinkhole is a depression — NOT formed by upliftment. [NDA tested via CDS]

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Underground Karst Features:

Stalactites:
Calcium carbonate deposits that hang down from the ceiling of limestone caves — like icicles. Water drips from the ceiling, evaporates, and leaves behind a tiny deposit of calcium carbonate. Over thousands of years these build into long, hanging formations.

Memory trick: Stalactites hang from the ceiling (both have a ‘c’). Stalagmites grow from the ground (both have a ‘g’).

Stalactites hang as icicles from the ceiling. Stalagmites rise upward from the floor of the cave. [NDA 2015-II]

Stalagmite:
Calcium carbonate deposits that grow upward from the floor of limestone caves — directly below stalactites.

Pillar (Column):
When a stalactite and a stalagmite grow long enough to meet, they form a pillar or column.

Stalactites, stalagmites, and pillars are depositional landforms of underground water. [NDA 2019-II]

Stalactites and stalagmites are features of karst topography. [NDA tested via CDS]

Types of Islands

NDA 2015-I tested island types:
A. Continental island — Madagascar (piece of continent that separated)
B. Coral island — Maldives (built up from coral reefs)
C. Volcanic island — Andaman and Nicobar Islands (formed by volcanic activity)
D. Mountain island — Mauritius
Answer: (b) A-2, B-4, C-3, D-1

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Mountain Types

Mount Fuji (Japan) is a volcanic mountain — a composite cone volcano. It is NOT a fold mountain. The Alps, Andes, and Rockies are all fold mountains. [NDA 2023-II]

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