๐ Class 11 Geography – Chapter 7
Landforms and Their Development
✨ Geo-shapes (เคญू-เคเคृเคคिเคฏाँ)
- The factors of erosion (เค เคชเค्เคทเคฏ) play a major role in shaping the earth’s surface.
- Important agents: Rivers, Winds, Glaciers, and Waves.
- These agents break the rocks, carry sediments (เคाเคฆ) and deposit them elsewhere.
- As a result, two main types of landforms are created:
- Erosional Landforms (เค्เคทเคฐเคฃाเคค्เคฎเค เคเคृเคคिเคฏाँ)
- Depositional Landforms (เคจिเค्เคทेเคชाเคค्เคฎเค เคเคृเคคिเคฏाँ)
๐ Geomorphology (เคญू-เคเคृเคคि เคตिเค्เคाเคจ)
- The scientific study of the history of the Earth’s surface.
- It includes:
- Surface shapes (เคเคृเคคि)
- Materials (เคชเคฆाเคฐ्เคฅ)
- Processes (เคช्เคฐเค्เคฐिเคฏाเคँ) which form the land surface.
๐️ Major Landforms
- Volcano ๐ (เค्เคตाเคฒाเคฎुเคी)
- Canyon ๐️ (เคเคนเคฐी เคाเคी)
- Mountain ⛰️ (เคชเคฐ्เคตเคค)
- Plain ๐พ (เคฎैเคฆाเคจी เค्เคทेเคค्เคฐ)
- Island ๐️ (เคฆ्เคตीเคช)
- Lake ๐️ (เคीเคฒ)
- Waterfall ๐ง (เคเคฒเคช्เคฐเคชाเคค)
- Valley ๐ (เคाเคी)
⛏️ Erosional Landforms (เค्เคทเคฐเคฃाเคค्เคฎเค เคเคृเคคिเคฏाँ)
Formed by rivers:
- V-shaped valley (V เคเคाเคฐ เคी เคाเคी)
- Gorge (เคธंเคเคฐी เคเคนเคฐी เคाเคी)
- Canyon (เคैเคจ्เคฏเคจ)
- Waterfall (เคเคฒเคช्เคฐเคชाเคค)
- Eroded fissures (เคฆเคฐाเคฐें)
๐️ Depositional Landforms (เคจिเค्เคทेเคชाเคค्เคฎเค เคเคृเคคिเคฏाँ)
Formed by deposition of sediments:
- River terraces (เคจเคฆी เคตेเคฆिเคा)
- Oxbow lake (เคोเคुเคฐ เคीเคฒ)
- Braided river (เคुंเคซिเคค เคจเคฆी)
๐ River / Flowing Water (เคจเคฆी / เคช्เคฐเคตाเคนिเคค เคเคฒ)
The river creates different landforms in three stages of its life cycle:
1️⃣ Youth Stage (เคฏुเคตा เค เคตเคธ्เคฅा – เคชเคฐ्เคตเคคीเคฏ เค्เคทेเคค्เคฐ)
- Found in mountainous regions.
- Few rivers in number.
- Forms V-shaped valleys.
- Flood plains are absent or very narrow.
- Presence of swamps and lakes in wide divides.
2️⃣ Mature Stage (เคช्เคฐौเคข़ เค เคตเคธ्เคฅा – เคฎैเคฆाเคจी เค्เคทेเคค्เคฐ)
- Found in plains.
- Large amount of water with many tributaries (เคธเคนाเคฏเค เคจเคฆिเคฏाँ).
- Valleys are still V-shaped but much deeper.
- Broad flood plains develop.
- The river starts forming meanders (เคुเคฎाเคตเคฆाเคฐ เคฎोเคก़).
3️⃣ Old Age Stage (เคช्เคฐौเคข़ाเคตเคธ्เคฅा – เคกेเคฒ्เคा เค्เคทेเคค्เคฐ)
- Found in delta regions.
- Tributaries become fewer.
- River slope becomes gentle (เคงीเคฎा เคขเคฒाเคจ).
- Flows freely in wide flood plains.
- Creates river estuaries (เคฎुเคนाเคจा), natural levees (เคช्เคฐाเคृเคคिเค เคคเคเคฌंเคง), oxbow lakes etc.
๐ Erosional Landforms (เค्เคทเคฐเคฃाเคค्เคฎเค เคเคृเคคिเคฏाँ)
๐ Valleys (เคाเคिเคฏाँ)
- Valleys begin with small streams (เคोเคी เคจเคฆिเคฏाँ).
- These streams gradually become wider, deeper, and longer → finally form valleys.
- Valleys are classified based on length, width, and shape:
- V-shaped Valley (V เคเคाเคฐ เคी เคाเคी)
- Gorge (เคธंเคเคฐी เคเคนเคฐी เคाเคी)
- Canyon (เคैเคจ्เคฏเคจ)
๐️ Gorge (เคธंเคเคฐी เคाเคी)
- A deep, narrow valley with steep slopes on both sides.
- Width of gorge is almost same at top and bottom.
- Commonly formed in hard rock regions.
๐️ Canyon (เคैเคจ्เคฏเคจ)
- Has steep slopes like a gorge but:
- Wider at the top than the bottom.
- Usually formed by horizontal stratification (เคชเคฐเคคเคฆाเคฐ เคธंเคฐเคเคจा) of sedimentary rocks.
๐ง Pot Hole / Water Socket (เคเคฒ เคเคก्เคขा)
- When rock pieces get stuck in river bed and rotate continuously → form a circular trough (เคเคฐ्เคค).
- This is called a Pot Hole.
๐ Plunge Pool (เคเคฐ्เคคเคूเคช)
- A deep & large depression (เคเคนเคฐा เคเคก्เคขा) formed at the base of a waterfall.
- Created by:
- Falling water pressure
- Circular rotation of boulders (เคฌเคก़े เคชเคค्เคฅเคฐ)
- Helps in deepening valleys.
๐ชจ River Terraces (เคจเคฆी เคตेเคฆिเคा)
- Step-like landforms on the sides of a river valley.
- Represent remnants of old flood plains.
- Formed due to vertical erosion of flood plains.
- Can occur at different heights, showing past river levels.
๐น Types of River Terraces
- Paired Terraces (เคฏुเค्เคฎ เคตेเคฆिเคा) –
- Found at equal height on both river banks.
- Unpaired Terraces (เค เคฏुเค्เคฎ เคตेเคฆिเคा) –
- Present only on one side OR at different heights.
๐น Causes of River Terrace Formation
- Decrease in river water flow.
- Climate change → change in river area.
- Tectonic activity (เคญूเคंเคชीเคฏ เคाเคฐเคฃ).
- Change in sea level (for rivers near coasts).
๐ Waterfall (เคเคฒเคช्เคฐเคชाเคค)
- When a river flows over hard rock (เคเคाเคต-เคฐोเคงी เคเค्เคाเคจ) followed by soft rock (เคเคธाเคจी เคธे เคเคเคจे เคตाเคฒी เคเค्เคाเคจ):
- Soft rock erodes faster → river bed develops a sudden drop → forms a waterfall.
⛲ Cascade / Kshiprika (เค्เคทिเคช्เคฐिเคा)
- When hard and soft rocks occur alternately in the river bed:
- River forms a step-like pattern.
- Creates several small waterfalls → called Kshiprikas / Cascades.
Landforms and Their Evolution (Notes in English)
✴️ Depositional Landforms
1️⃣ Alluvial Fan (เคเคฒोเคข़ เคชंเคा)
- When rivers descend from mountainous regions, their flow slows down.
- Pebbles & sediments get deposited in a fan-shaped form.
- This depositional feature is called Alluvial Fan.
2️⃣ Delta (เคกेเคฒ्เคा)
- At the mouth of rivers (before meeting the sea), flow becomes very slow due to gentle slope (เคฎंเคฆ เคขाเคฒ).
- Sediments are deposited in a triangular shape → called Delta.
3️⃣ Flood Plains (เคฌाเคข़ เคฎैเคฆाเคจ)
- Just as valleys are formed by erosion, floodplains are formed by deposition.
- Fine materials like sand, clay, pebbles get deposited on river banks during annual floods.
- These flat lands are called Flood Plains.
4️⃣ Meanders / River Vispar (เคจเคฆी เคตिเคธเคฐ्เคช)
- S-shaped curves formed in the plains due to slow flow & heavy load.
- Erosion on the outer bank & deposition on the inner bank increases the curve.
- Over time, meanders get cut off → forming Ox-bow Lakes (เคोเคนूเคฐ เคीเคฒ).
5️⃣ Braided River (เคुंเคซिเคค เคจเคฆी)
- In the lower valleys, rivers deposit sediments.
- River divides into many channels separated by sand bars (เคฐेเคคीเคฒी เคฆीเคตाเคฐें).
- Such rivers are called Braided Rivers.
๐ง Landforms by Groundwater
- Groundwater moves through joints, cracks, holes → dissolves limestone (เคूเคจा-เคชเคค्เคฅเคฐ).
- Creates erosional & depositional landforms.
๐ Erosional Landforms by Groundwater
- Sinkholes / Swallow Holes (เคเคฐ्เคค/เคुเคฒเคจเคถीเคฒ เคเคฐ्เคค): Funnel-shaped depressions, depth 0.5 to 30+ meters.
- Solution Sink (เคตिเคฒเคฏเคจ เคเคฐ्เคค): Formed at bottom of limestone rocks by dissolving action.
- Lapies (เคฒैเคชिเคธ): Sharp, irregular ridges formed when limestone dissolves along cracks.
๐️ Depositional Landforms by Groundwater
- Stalactite (เคธ्เคैเคฒेเค्เคाเคเค): Hanging pillar from cave roof formed by deposition of lime.
- Stalagmite (เคธ्เคैเคฒैเค्เคฎाเคเค): Rising pillar from cave floor due to lime deposition.
- Pillar (เคธ्เคคंเคญ): When stalactite & stalagmite join → Lime Pillar (เคूเคจा เคธ्เคคंเคญ).
❄️ Landforms by Glaciers
- Glacier: Slow-moving mass of ice flowing from mountains to valleys.
Types of Glaciers
- Continental Glaciers (เคฎเคนाเคฆ्เคตीเคชीเคฏ เคนिเคฎเคจเคฆ): Spread over vast areas.
- Valley Glaciers (เคाเคी เคนिเคฎเคจเคฆ): Flow in mountain valleys.
Features
- Flow is very slow (few cm to few meters/day).
- Moved mainly by gravity (เคुเคฐुเคค्เคตाเคเคฐ्เคทเคฃ).
๐ชจ Erosional Landforms by Glaciers
- Cirque (เคธเคฐ्เค): Bowl-shaped hollow at glacier head.
- Tarn Lake (เคाเคฐ्เคจ เคीเคฒ): Lake formed in cirque by melting ice.
- Horn (เคถ्เคฐृंเค): Sharp peak formed when several cirques meet.
⛰️ Depositional Landforms by Glaciers
- Drumlin (เคก्เคฐเคฎเคฒिเคจ): Oval hill of sand & gravel deposited by glacier.
- Roche Moutonnรฉe / Sheep Rock (เคถीเคช เคฐॉเค): Rock with gentle slope on one side, steep on the other.
- Fiord (เคซिเคฏोเคฐ्เคก): Deep glacial trough filled with sea water along coast.
๐️ Landforms by Wind (Aeolian Landforms)
- Winds act mainly in desert & semi-arid regions (เคฎเคฐुเคธ्เคฅเคฒ เคต เค เคฐ्เคง-เคถुเคท्เค เค्เคทेเคค्เคฐ).
- Erosion & deposition depend on wind speed & load carried.
๐ฌ️ Erosional Landforms by Wind
- Mushroom Rock / Rock Pedestal (เคฎเคถเคฐूเคฎ เคเค्เคाเคจ): Rock shaped like an umbrella due to wind abrasion.
๐ Depositional Landforms by Wind
- Barchans (เคฌाเคฐเค़ाเคจ): Crescent-shaped sand dunes.
- Slope is gentle on one side, steep on the other.
- Move forward with strong winds.
๐ชจ Other Important Landforms
- Monadnock (เคฎोเคจाเคกเคจॉเค): Isolated residual hill left after erosion.
- Inselberg (เคंเคธेเคฒเคฌเคฐ्เค): Steep isolated hill in deserts formed by erosion.
