🌍 Class 11 Geography
Chapter – 6 : Geomorphic Processes (भू-आकृतिक प्रक्रियाएँ)
🌋 Tectonic Forces (टेक्टोनिक बल)
- The Earth’s surface is uneven (असमान).
- This is due to internal forces (आंतरिक बल) of the Earth.
- These forces move the lithospheric plates (भूपर्पटी प्लेटें) → creating landforms and uneven surfaces.
- Such forces are called Tectonic Forces (टेक्टोनिक बल).
👉 When landforms rise unevenly, the exogenic forces (बहिर्जन्य बल) generated by the Sun try to level (समतल करना) them through erosion (अपक्षय) & weathering (अपक्षरण).
🌎 Geomorphological Processes (भू-आकृतिक प्रक्रियाएँ)
- The interaction of endogenic forces (अंतर्जन्य बल) & exogenic forces (बहिर्जन्य बल) forms landforms.
- Both processes are constantly active (सदैव सक्रिय) on Earth’s surface.
- Together they are called Geomorphic Processes (भू-आकृतिक प्रक्रियाएँ).
📌 As a result → diverse resources (संसाधन) & livelihood base (जीविका आधार) are formed.
Types of Forces:
- Intrinsic (अंतर्जन्य बल) → lift and uplift the Earth’s surface.
- Extrinsic (बहिर्जन्य बल) → wear down and level the surface.
🪨 Denudation (अपक्षरण)
- Due to various exogenic geomorphic processes like:
- Weathering (अपक्षरण)
- Erosion (अपक्षय)
- Mass movement (भूस्खलन)
- Transportation (परिवहन)
👉 The upper cover of rocks (चट्टानों की ऊपरी परत) gets removed → called Denudation (अपक्षरण).
☀️ Weathering (अपक्षरण)
- Weathering is a mechanical, chemical & biological process (यांत्रिक, रासायनिक व जैविक प्रक्रिया).
- Rocks break & decay (टूटना व विघटन होना) at their original place.
🔎 Types of Weathering Processes (अपक्षरण की प्रक्रियाएँ)
1️⃣ Exfoliation (पर्त उतरना)
- Outer layers of rocks peel off like onion skin (प्याज़ की परतों की तरह उतरना).
- Common in dome-shaped landforms (गुम्बदाकार स्थलरूप).
- Erosion removes the upper cover → flaky bands form.
2️⃣ Contraction & Expansion (सिकुड़न और फैलाव)
- Minerals in rocks expand (फैलना) with heat & contract (सिकुड़ना) with cooling.
- Repetition weakens rocks → they break down (टूटना).
3️⃣ Freezing & Frost Wedging (हिम व पाला विदारण)
- Water fills cracks of rocks (चट्टानों की दरारें).
- On cooling → water turns into ice (बर्फ).
- Ice expands → creates pressure → rocks crack & break (दरार पड़ना व टूटना).
- Repetition deepens cracks → disintegration of rocks.
🔹 Tectonic Forces (भूगर्भीय बल)
- 🌐 Earth’s surface is uneven (असमान) due to internal forces.
- These forces move lithospheric plates, creating various landforms.
- Sun’s energy-driven exogenic forces (बाहरी बल) try to level the uneven surface by erosion & denudation.
🔹 Geomorphological Processes (भूरूपीय प्रक्रियाएँ)
- Endogenic forces (आंतरिक बल) lift the surface.
- Exogenic forces (बाहरी बल) keep leveling them.
- Both processes together → formation of landforms.
- Example processes: denudation, erosion, mass movement.
🔹 Denudation (अपक्षय)
- Removal of the upper cover of rocks due to weathering, erosion, transport & mass movement.
☀️ Weathering (अपक्षरण)
👉 Breaking of rocks at their original place due to mechanical, chemical & biological processes.
🔸 Types of Weathering
- Chemical Weathering (रासायनिक अपक्षरण)
- Rocks disintegrate due to chemical reactions.
- Example:
- Salt dissolving in moisture
- Iron rusting in humid air
- ✅ Types of Chemical Weathering
- Solution (विघटन): Minerals like nitrate, sulphate dissolve in water.
- Carbonation (कार्बोनेशन): Carbonic acid (from CO₂ + rainwater) dissolves limestone.
- Hydration (हाइड्रेशन): Rocks like calcium sulphate absorb water, expand & break.
- Oxidation & Reduction (ऑक्सीकरण व अपचयन): Rusting of iron due to oxygen & moisture.
- Physical Weathering (भौतिक अपक्षरण)
- Rocks break into smaller fragments due to temp. change, gravity, wet-dry cycle.
- ✅ Types of Physical Weathering
- Unloading (भारमुक्ति): Surface pressure release cracks rocks.
- Temperature Change (ताप परिवर्तन): Expansion & contraction weaken rocks.
- Frost Action (हिम क्रिया): Water in cracks freezes → expands → breaks rocks.
- Salt Weathering (लवण अपक्षरण): Salt crystals expand & break rocks.
- Biological Weathering (जैविक अपक्षरण)
- Due to organisms & plants.
- 🌱 Roots break rocks.
- 🐜 Earthworms, termites, rats create burrows.
- Humans → agriculture, mining accelerate it.
🔹 Carbonation Process (कार्बोनेशन प्रक्रिया)
- Carbonates & bicarbonates react with minerals → carbonic acid dissolves rocks.
- Results in formation of underground caves (विशाल गुफाएँ).
🎯 Importance of Weathering (महत्व)
- Helps in soil formation.
- Concentrates valuable minerals like iron, copper, manganese.
- Creates new landforms useful for humans.
⛰️ Mass Movement (भूस्खलन/सामूहिक संचलन)
👉 Downward movement of rock debris under gravity.
🔸 Factors Responsible
- Removal of slope base
- Increase in slope angle
- Overloading (rainfall, sediments, human activity)
- Earthquake shocks & vibrations
- Deforestation
🔹 Types of Mass Movement
- Soil Flow (मृदा प्रवाह): Wet clay & silt slide down slopes like snake-like patterns.
- Mud Flow (कीचड़ प्रवाह): Heavy rainfall + weathered debris → mud flows down valleys (disastrous).
- Avalanche (हिमस्खलन): Rapid movement of ice, snow or debris down steep slopes (faster than mud flow).
Soils, Deposition & Erosion
☁️ Depositing (अवसादन)
- Deposition is the result of erosion (अपक्षय का परिणाम).
- When the slope decreases, the eroded material gets deposited.
🌱 What is Soil? (मृदा क्या है?)
- Soil is a natural mixture (प्राकृतिक मिश्रण) found on the surface.
- It has the capacity to nourish plants and animals (पौधों व जानवरों को पोषित करने की क्षमता).
🔑 Factors Affecting Soil Formation (मृदा निर्माण को प्रभावित करने वाले कारक)
- Climate (जलवायु):
- Affects weathering of parent rock (जनक शिला का अपक्षय).
- Heavy rainfall → increases humus but also washes away fertility.
- Parent Material (जनक पदार्थ):
- Soil type = depends on rock weathering.
- Example → South India → Black Soil (काली मृदा) due to basalt rocks.
- Relief (स्थलाकृति):
- Thin soil layer in hilly areas, thick soil in plains.
- Biological Activities (जैव क्रियाएँ):
- Vegetation cover + microorganisms → make soil fertile.
- Time (समय):
- Old soils → rich & more fertile.
🪨 How Weathering Affects Soil Formation? (अपक्षय का प्रभाव)
- Weathered rock material = basis of soil.
- Includes → rotten parts of plants, animals (humus – यूमस).
- Also contains gases + nutrients dissolved in water.
- Soil forms slowly over long time periods.
⚡ Soil Forming Factors (Active & Passive)
✅ Active Factors (सक्रिय कारक):
- Climate + biological activities.
- Cause continuous decomposition & disintegration (अपघटन व विघटन).
- Soil formation = fast.
❌ Passive Factors (निष्क्रिय कारक):
- Parent material, relief & time.
- No direct action.
- Soil formation = slow.
💨 Erosion (अपक्षय)
- Cutting of rocks (शिलाओं का कटाव) by → flowing water, groundwater, glaciers, wind, sea waves & currents.
- Transports debris from one place to another.
🏔️ Floor Balance (तल संतुलन)
- Nature has high mountains & deep valleys.
- Reduction of this difference by erosion = Floor Balancing (तल संतुलन).
