Landforms and their Evolution Class 11 Solutions 2026-27

The answer sequence is (a), (d), (b), (d), and (a). The third item is answered as limestone region here because this chapter links limestone with solution-dominant chemical action. Concept used. The MCQ set checks the connection between geomorphic agents and landforms. Running water cuts downward most strongly in youth, canyons have step-like steep sides, karst landforms depend on solution in limestone, lapies are sharp karst ridges, and cirques are glacial basins.

1. In youth, streams flow on steeper gradients. Down-cutting dominates, so the answer to part (i) is youth stage.
2. A canyon is a deep valley with steep step-like side slopes. A gorge is steep too, but it is almost equal in width at top and bottom.
3. In this chapter, limestone areas are treated as solution-dominant karst areas. So chemical action is stronger than mechanical removal there.
4. Lapies are irregular limestone surfaces with sharp pinnacles, grooves and ridges. That matches option (d).
5. A cirque is a deep, long and wide glacial basin with steep concave head walls and side walls.

The correct sequence is (i) (a), (ii) (d), (iii) (b), (iv) (d), and (v) (a).

Incised meanders show that a river cut its winding course down into hard rock. Meanders in alluvial plains show lateral erosion and deposition on gentle slopes. Concept used. A meander is a loop-like channel pattern. It forms where flowing water works laterally, while an incised meander forms when an existing winding course becomes deeply cut into rock.

1. Incised meanders occur when a river with a winding course cuts deeply into bedrock.
2. They indicate strong vertical erosion, often linked with renewed down-cutting or uplift of the land.
3. The river keeps its curved path while deepening the valley.
4. Meanders in alluvial plains occur on gentle gradients and loose deposits.
5. They indicate active lateral erosion on the outer bank and deposition on the inner bank.
6. Such meanders also point to mature floodplain or delta-plain conditions.

Incised meanders indicate deep vertical cutting into rock, while alluvial meanders indicate lateral erosion and deposition on gentle floodplains.

Valley sinks or uvalas evolve when sinkholes and dolines join due to slumping or cave-roof collapse in limestone areas. Concept used. Karst topography forms where limestone is dissolved by surface water and groundwater. Sinkholes, dolines and uvalas are erosional karst depressions.

1. Rainwater and groundwater dissolve limestone along joints and bedding planes.
2. Small swallow holes and sinkholes form on the limestone surface.
3. Some sinkholes grow through solution, while others collapse into underground voids or caves.
4. A collapse sink is also called a doline.
5. When several sinkholes and dolines enlarge, their sides may slump.
6. Neighbouring depressions then join together.
7. The joined depression becomes a long, narrow to wide trench called a valley sink or uvala.

Uvalas evolve when sinkholes and dolines in limestone areas enlarge and join through slumping or cave-roof collapse.

Limestone is commonly jointed, cracked, bedded and soluble. Water percolates through openings, dissolves calcium carbonate, and flows underground. Concept used. Limestone is rich in calcium carbonate. Carbonated rainwater dissolves it, especially along cracks, joints and bedding planes, creating underground drainage paths.

1. Limestone areas often have many joints, cracks and bedding planes.
2. Rainwater enters these openings instead of staying on the surface.
3. The water becomes slightly acidic after absorbing carbon dioxide.
4. This carbonated water dissolves calcium carbonate in limestone.
5. The cracks and passages widen through solution.
6. Surface streams may disappear into swallow holes and continue as underground streams.
7. So underground flow becomes more common than surface run-off.

Underground flow is common in limestone areas because jointed and soluble limestone lets water percolate, dissolve rock and form subsurface channels.

The main linear depositional forms are lateral moraines along valley sides, medial moraines in the centre, terminal moraines at glacier ends, and eskers as sinuous ridges. Concept used. Glacial till is unsorted debris dropped by melting ice. Meltwater may also deposit sorted material as glacio-fluvial deposits.

1. Lateral moraines form along the sides of a glacial valley, parallel to the glacier.
2. Medial moraines form near the centre where two lateral moraines from joining glaciers meet.
3. Terminal moraines form at the toe or end of a glacier.
4. Ground moraines spread as irregular till sheets over the valley floor after retreat.
5. Eskers are sinuous ridges deposited by meltwater streams flowing within or below ice.
6. Outwash plains form at the foot of glacial mountains or beyond ice-sheet limits.

Linear glacial deposits include lateral moraines on valley sides, medial moraines in the centre, terminal moraines at the end, ground moraines on valley floors and eskers as sinuous ridges.

Wind works through deflation, abrasion and impact in deserts. It is not the only agent because sheet wash and rare rainstorms also shape desert landforms. Concept used. Wind is an aeolian agent. It can lift fine particles, drive sand against rock and move loose material where vegetation is sparse.

1. Wind lifts and removes dust and fine particles from dry surfaces. This is deflation.
2. Wind-blown sand strikes rock surfaces and wears them down. This is abrasion.
3. Moving sand grains also collide with rocks and other grains. This impact helps polish and shape surfaces.
4. Wind creates features such as pedestals, mushroom rocks, dunes and other aeolian forms.
5. However, wind is not the only agent in deserts.
6. Rare torrential rain, sheet wash, rills and mass movement can remove weathered debris quickly.
7. So desert erosional features are made by wind along with episodic water action and gravity.

Wind erodes by deflation, abrasion and impact, but desert erosion also involves sheet wash, rare rainstorms and gravity-driven movement.

Running water dominates because it erodes, transports and deposits material. In humid regions it works through rivers; in arid regions it acts powerfully during rare heavy rain and sheet floods. Concept used. Running water has two forms: overland flow as sheet wash and linear flow as streams and rivers. Both can erode, carry and deposit earth materials.

1. In humid regions, heavy rainfall supplies regular surface run-off and stream flow.
2. Overland flow first removes material as sheet erosion.
3. The flow may concentrate into rills and then gullies.
4. Gullies deepen, widen and join to form a network of valleys.
5. Youthful rivers cut downward and form V-shaped valleys, gorges, canyons, potholes and waterfalls.
6. With time, gradients become gentler and lateral erosion increases.
7. Rivers then form meanders, floodplains, natural levees, point bars, oxbow lakes and deltas.
8. Deposition becomes stronger where velocity falls or where rivers enter plains, lakes or seas.
9. In arid climates, water is less frequent but can be very intense when rain falls.
10. Bare rock, weak vegetation cover and loose debris let sheet floods act quickly.
11. Short-lived streams can move large amounts of sediment from slopes to piedmonts and basins.
12. Alluvial fans and other deposits form where streams leave mountains and enter low-gradient plains.
13. Therefore running water shapes both humid and arid landscapes, though its timing and style differ.

Running water dominates landform development because it erodes, transports and deposits material in both regular humid drainage and episodic arid floods.

Limestone changes most in humid climates because water is available for solution. The dominant process is solution of calcium carbonate, producing karst landforms. Concept used. Limestone is mainly calcium carbonate. Carbonated rainwater dissolves it, so solution and precipitation become the key processes in limestone areas.

1. Limestone behaves differently because the amount of water changes with climate.
2. Humid climates have more rain and groundwater movement.
3. Rainwater absorbs carbon dioxide and becomes weak carbonic acid.
4. This water dissolves calcium carbonate in limestone along cracks, joints and bedding planes.
5. The dominant geomorphic process is solution. Precipitation deposition follows inside caves when dissolved calcium carbonate is redeposited.
6. In humid limestone areas, solution can create swallow holes, sinkholes, dolines and uvalas.
7. Continued solution may leave sharp ridges and grooves called lapies.
8. Where water moves horizontally underground, caves and tunnels may form.
9. Inside caves, dripping water may deposit calcium carbonate as stalactites from the roof.
10. Stalagmites rise from the floor below the drip points.
11. When stalactites and stalagmites join, columns or pillars form.
12. In arid climates, water is limited, so solution is weaker and karst features are less strongly developed.
13. Thus limestone landscapes are controlled mainly by solution in water-rich settings.

Limestone responds strongly to humid water-rich conditions because solution dissolves calcium carbonate and creates karst landforms such as sinkholes, caves, lapies, stalactites and stalagmites.

Glaciers reduce mountains through plucking, abrasion and the movement of heavy ice loaded with debris. Deposits and outwash later create smoother lowland surfaces. Concept used. A glacier is a moving mass of ice. Its great weight and slow movement allow it to erode bedrock and transport unsorted debris.

1. Glaciers move because of gravity, though they move much more slowly than running water.
2. The heavy ice presses strongly on the valley floor and sides.
3. Glaciers pluck blocks from bedrock, especially where joints and cracks are present.
4. Rock fragments frozen into the ice scrape the floor and sides. This is abrasion.
5. Abrasion and plucking deepen and widen valleys into U-shaped troughs.
6. Glaciers cut cirques at valley heads and sharpen ridges into horns and aretes.
7. They also lower divides by headward erosion of cirque walls.
8. As glaciers carry debris downhill, they remove material from high mountain areas.
9. When the glacier melts, it drops unsorted till as moraines and ground moraine.
10. Meltwater spreads sorted sand, gravel, silt and clay as outwash deposits.
11. Over long periods, high rugged mountains are lowered, valleys are widened and lower plains or outwash plains develop.
12. The process is slow but powerful because the ice mass is heavy and carries sharp debris.

Glaciers reduce mountains by plucking, abrasion, valley widening, divide lowering, debris transport and later deposition of till and outwash.

Observe one local site and record its landforms, materials and active processes. Link each observation with running water, wind, groundwater, waves, glaciers or gravity where relevant. Concept used. The project applies the chapter to a nearby place. A good field note connects visible shape, surface material and the process that may have produced or modified it.

1. Choose a safe local site such as a school ground, park, river bank, roadside slope, field, pond edge or hill path.
2. Identify visible landforms: slope, valley side, small channel, plain, mound, depression, bank, terrace or dune-like sand patch.
3. Record the surface material: clay, sand, silt, gravel, pebbles, hard rock, alluvium, soil or mixed debris.
4. Look for process evidence. Rills show running water; loose slope debris may show mass movement.
5. Cracks, discolouration and loose fragments may show weathering.
6. Sorted sand or silt near water may show deposition.
7. If the area is limestone-rich, note sink-like depressions or underground drainage signs if visible.
8. Write a short conclusion linking landform, material and process.

A good project identifies local landforms, records their materials and explains the likely processes using direct field evidence.