Landforms & Their Evolution – NDA Geography Notes

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.

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.

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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. Material is removed, creating hollows, valleys, caves, and cut features.

Depositional landforms are formed by the dropping of material that was being carried. Material piles up, creating mounds, ridges, plains, and filled features.

For each agent you need to know both types.

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Fluvial Landforms: Formed by Rivers

Rivers are the most powerful agents of erosion on Earth’s land surface. They erode, transport, and deposit. Different processes dominate 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 that erodes faster.

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. The outer bank of each bend erodes (where water moves faster); the inner bank deposits (where water moves slower). An extremely tight meander is called a gooseneck. Tectonic uplift can cause a river to cut downward along its meandering course, producing incised meanders.

Fluvial Depositional Landforms

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 as a crescent-shaped lake.

Delta: at the river’s mouth, water slows suddenly and drops its load. Over time this builds a flat, triangular landform. The Ganga-Brahmaputra delta (Sundarbans) is the world’s largest delta.

Natural Levee: raised banks along a river, built up by flood deposits. Coarse material is deposited immediately beside the banks during floods.

River feature sequence upstream to downstream: Falls → Meanders → Oxbow lake → Delta.

Drainage Patterns

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

Consequent = course determined by original slope of land | Subsequent = direction controlled by rock structure | Insequent = no apparent reason (random) | Resequent = flows in same direction as consequent but at lower level.

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

Rejuvenation: when the land is uplifted or sea level drops, a river gains new energy and starts cutting downward again even in its lower course, producing incised meanders.

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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. The weight causes ice to flow slowly downhill, picking up and dragging rocks across the bedrock.

Glacial Erosional Landforms

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

U-Shaped Valley: glaciers are much wider and heavier than rivers. They erode the entire valley floor and widen the sides, creating a characteristic flat-bottomed U shape. Rivers create V-shaped valleys; glaciers create U-shaped valleys. [NDA 2010-I]

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

Col: a low point or pass between two peaks on a ridge, formed when two cirques on opposite sides erode back toward each other.

Glacial Depositional Landforms

Moraine: material carried by a glacier (glacial till) deposited as ridges. Types: Terminal moraine (at the farthest point reached), Lateral moraine (along the sides), Medial moraine (when two glaciers merge). [NDA 2010-I]

Drumlin: a smooth, elongated, egg-shaped hill made of glacial till. 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]

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

Periglacial Landforms

Pingo: a mound of earth-covered ice found in permafrost environments (near glaciers). Underground water freezes, expands, and pushes up a dome of soil above it. Pingos are periglacial features: not directly formed by glacial ice.

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Aeolian Landforms: Formed by Wind

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

Wind Erosional Landforms

Mushroom Rock (Pedestal Rock): wind near the ground carries more sand than wind higher up, so erosion is most intense near the ground. The base is cut away faster than the top, creating a mushroom shape. [NDA 2009-II]

Inselberg: an isolated, steep-sided rock hill rising abruptly from a flat desert plain. A remnant of harder rock that resisted erosion while 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]

Loess: fine dust particles carried by wind for hundreds of kilometres and deposited in thick layers far from their source. Extremely fertile. The famous fertile soil of North China and parts of Europe is loess.

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. [NDA 2021-II | NDA 2024-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.

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Coastal Landforms: Formed by Waves

Waves carry enormous energy and crash against cliffs, cut into rock, and carry and deposit sand along coastlines.

Coastal Erosional Landforms

Cliff: a steep, often vertical rock face along a coastline. Waves undercut the base, 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]

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, forming 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 them from the mainland. Hazardous for settlements because they are easily swept away by storms.

★ IMPORTANT Stack is NOT a depositional coastal feature: it is erosional. This exact question appeared in NDA 2018-I. Tombolo, sand bar, and spit are all depositional. Stack = erosional. [NDA 2018-I]

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Karst Landforms: Formed by Underground Water

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

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 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.

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 tiny calcium carbonate deposits that build up over thousands of years. [NDA 2015-II]

Stalagmites: calcium carbonate deposits that grow upward from the floor of limestone caves, directly below stalactites. [NDA 2015-II]

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

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

Memory device: Stalactites = ceiling. Stalagmites = mound from the ground. The letters give you the location.

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Types of Islands

Island Type	Example	How Formed	NDA Tag
Continental island	Madagascar	Piece of a continent that separated	[NDA 2015-I]
Coral island	Maldives	Built up from coral reefs	[NDA 2015-I]
Volcanic island	Andaman and Nicobar Islands	Formed by volcanic activity	[NDA 2015-I]
Mountain island	Mauritius	—	[NDA 2015-I]

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Mountain Types

Fold Mountains: Alps (Europe), Andes (South America), Rockies (North America), Himalayas, all fold mountains formed by compression at convergent plate boundaries.

Mount Fuji (Japan) is a composite strato-volcano: NOT a fold mountain. It was built by volcanic eruptions, not by tectonic compression. [NDA 2023-II]

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