Weathering and Erosion Processes
Delhi Police & SSC Exams Preparation
1. Introduction
The Earth's surface is continuously shaped by two types of forces: Endogenic (internal) — like volcanoes and earthquakes, and Exogenic (external) — like weathering, erosion, and deposition. This article focuses on weathering and erosion, the key processes that wear down mountains and shape plains, valleys, and rivers.
Key Forces:
- Endogenic: Internal forces (volcanoes, earthquakes)
- Exogenic: External forces (weathering, erosion)
- Process: Continuous surface transformation
- Result: Landform development
Significance:
Understanding how Earth's surface features are formed and transformed over time
Exam Trick: "WED = Weathering → Erosion → Deposition"
2. What is Weathering?
Definition:
- Process: Breaking down of rocks on Earth's surface by natural forces
- Agents: Temperature, wind, water, and biological activity
- Location: Happens in-situ (rocks break but do not move)
- Importance: First step in soil formation
Key Points:
Weathering weakens rocks without moving them, preparing material for erosion and transport
Exam Trick: "Weathering = Weakening without Movement"
3. Types of Weathering
| Type | Description | Example |
|---|---|---|
| Physical (Mechanical) | Breakdown by temperature, water, wind | Expansion & contraction of rocks |
| Chemical | Change in rock composition due to chemical reactions | Rusting of iron rocks |
| Biological | Caused by living organisms like plants, animals, and microbes | Roots breaking rocks |
4. Physical Weathering
Main Processes:
- Exfoliation: Outer layers peel off due to temperature changes (deserts)
- Frost Action: Water freezes in cracks, expands and breaks rocks
- Thermal Expansion: Rocks expand by day, contract by night causing cracks
- Abrasion: Rock particles carried by wind or water wear down surfaces
Characteristics:
Caused by physical changes in temperature or pressure without chemical alteration
Exam Trick: "ETF → Exfoliation, Thermal, Frost = Physical Weathering Trio"
5. Chemical Weathering
Main Processes:
- Oxidation: Iron reacts with oxygen forming rust
- Carbonation: CO₂ + water = carbonic acid dissolving limestone
- Hydration: Minerals absorb water, swell and weaken
- Solution: Minerals dissolve completely in water
Characteristics:
Occurs when minerals react with water, oxygen or CO₂ forming new compounds
Exam Trick: "OCHS → Oxidation, Carbonation, Hydration, Solution"
6. Biological Weathering
Causes:
- Plant roots growing into cracks, breaking rocks
- Burrowing animals loosening soil and rock particles
- Lichens and mosses secreting acids that dissolve rocks
- Microbial activity breaking down mineral components
Impact:
Living organisms contribute significantly to rock breakdown through physical and chemical means
Exam Trick: "Roots, Rats, and Reactions = Bio Weathering"
7. What is Erosion?
Definition:
- Process: Removal and transportation of weathered material
- Agents: Rivers, wind, glaciers, and sea waves
- Movement: Material transported from one place to another
- Result: Formation of new landforms
Key Difference:
Weathering = Breakdown, Erosion = Movement of broken material
Exam Trick: "Weathering breaks, erosion takes!"
8. Agents of Erosion
| Agent | Type of Landform Created | Example |
|---|---|---|
| River (Running Water) | Valleys, waterfalls, deltas | Ganga, Brahmaputra |
| Wind (Aeolian) | Sand dunes, mushroom rocks | Thar Desert |
| Glacier (Ice) | U-shaped valleys, moraines | Himalayas |
| Sea Waves (Marine) | Cliffs, arches, beaches | Konkan Coast |
| Groundwater | Caves, sinkholes | Meghalaya, Karst regions |
Exam Trick: "RWGSM → River, Wind, Glacier, Sea, Groundwater"
9. River Erosion Stages
Upper Course:
- Vertical erosion dominant
- V-shaped valleys
- Waterfalls and gorges
- Steep gradient
Middle Course:
- Lateral erosion begins
- Meanders form
- Gentler gradient
- Flood plains develop
Lower Course:
- Deposition dominant
- Deltas form
- Flood plains extensive
- Very gentle gradient
Exam Trick: "V → M → D = Valley, Meander, Delta"
10. Difference Between Weathering & Erosion
| Feature | Weathering | Erosion |
|---|---|---|
| Meaning | Breaking down of rocks | Wearing away & movement |
| Movement | No movement | Material transported |
| Agents | Heat, water, wind, plants | Rivers, wind, glaciers |
| Result | Soil formation | New landforms |
| Example | Rock cracks due to heat | Sand carried by wind |
Exam Trick: "W = Weakens, E = Escorts away"
11. Landforms Formed by Erosion
| Agent | Erosional Landform | Depositional Landform |
|---|---|---|
| River | V-shaped valley, Gorge | Delta, Flood plain |
| Wind | Mushroom rock | Sand dunes |
| Glacier | U-shaped valley | Moraines |
| Sea | Cliffs, Caves | Beaches |
| Groundwater | Sinkholes | Stalactites, Stalagmites |
Exam Trick: "Eats → Builds → Erosion destroys, deposition builds"
PYQs (Delhi Police, SSC & State Exams)
Which of the following is an agent of erosion?
Options: (a) Wind (b) Forest (c) Temperature (d) Clouds
Category: Erosion Agents
Show Answer
Wind
The process of breaking down of rocks in situ is called —
Options: (a) Erosion (b) Weathering (c) Deposition (d) Transportation
Category: Weathering Definition
Show Answer
Weathering
Which of the following is a result of chemical weathering?
Options: (a) Frost action (b) Carbonation (c) Root wedging (d) Abrasion
Category: Chemical Weathering
Show Answer
Carbonation
The process by which river carries eroded material to another place is —
Options: (a) Weathering (b) Deposition (c) Transportation (d) Folding
Category: Erosion Process
Show Answer
Transportation
The landform formed by river deposition at its mouth is called —
Options: (a) Valley (b) Delta (c) Canyon (d) Plateau
Category: Depositional Landforms
Show Answer
Delta
Final Exam Tips
Weathering occurs in-situ, erosion involves
movement
Agents of erosion = water, wind, ice, waves
Carbonation = chemical weathering
V-shaped valley = river erosion
U-shaped valley = glacier erosion
Mushroom rock = wind erosion
Sinkhole = groundwater erosion
Remember Formula: WED → Weathering (Break) + Erosion
(Move) + Deposition (Make)
Master Geography for Delhi Police Exam!
Join Courage Library for comprehensive study materials and expert guidance.
Be a Couragian!