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Once mountains exist, what starts to break them down?
- Building forces raise the land into mountains.
- Then outside forces begin to break it down .
- This breaking down happens in two steps .
- First the rock is broken — this is weathering .
- Then the pieces are carried away — this is erosion .
What is weathering, and what are its types?
What are the three types of weathering?
Weathering
breaks rock in place
1. Physical
Rock breaks into pieces
By heat, frost or wind
Example:
Cracks from day-night heat
2. Chemical
Minerals react and change
Water, air or acid act
Example:
Rusting; rock dissolving
3. Biological
Living things break rock
Example:
Roots splitting a rock
Fig. 2.8 — The three types of weathering: physical, chemical and biological
Definition — Weathering
Weathering is the breaking down of rock into smaller pieces on the spot.
It does not involve any movement of the pieces — only the breaking.
It does not involve any movement of the pieces — only the breaking.
What is erosion, and how does it differ from weathering?
| Type | Caused by | Common where |
|---|---|---|
| Water erosion | Rivers, rain, waves | River banks, coasts |
| Wind erosion | Strong dry winds | Deserts, dry regions |
| Glacial erosion | Moving ice | Snowy mountains |
| Coastal erosion | Sea waves | Along the seashore |
Definition — Erosion
Erosion is the wearing away and
carrying away
of soil and rock by natural agents.
Unlike weathering, erosion moves the broken material to a new place.
Unlike weathering, erosion moves the broken material to a new place.
Types of erosion
Fig. 2.9 — Erosion by running water and by wind
What is the full breaking-down cycle called?
How do outside forces reshape the land?
Weathering — rock breaks in place
↓
Erosion — pieces are carried away
↓
Deposition — the pieces are dropped and build new landforms
- So the cycle is break → carry → drop .
- The third step, deposition , quietly builds deltas, beaches and plains.
The full cycle — weathering breaks, erosion carries, deposition drops
How does erosion affect human life?
- Erosion strips away the fertile topsoil farmers need.
- It can wash away land, houses and roads near rivers and coasts.
- It makes hillsides unstable for building and mining.
- So erosion shapes the land but also hurts livelihoods .
🔎 Let’s Explore
Look at the photographs in Fig. 2.9 and note the type of erosion in each. How are farmers affected by erosion caused by water and by wind?
📜 Don’t Miss Out
The
Sindhu-SarasvatB;
civilisation used clever water-management methods —
contouring, bunding, terracing
, dams and canals — to fight soil erosion. The
Zabo system
of Nagaland still uses earthen bunds and check dams on hill slopes to save soil and water.
Related NCERT Questions — try them now
NCERT Question 6 — How are deforestation and erosion associated
How are deforestation and erosion associated with each other? Explain.
NCERT Question 7 — Develop a plan to protect the land
Develop a plan to protect the land in your local area from erosion.
