Welcome to GattPrep!
Hello rock detective! 🕵🏽♀️
In the last lesson, we learned how rocks form. But did you know that even the strongest rocks don’t last forever? They slowly break down over time. This breakdown process is called weathering—and it’s happening all around you!
In this lesson, you’ll explore what weathering is, the three main types of weathering, and how it affects the environment. You’ll also see how weathering shapes landscapes and helps form soil.
Weathering is the breakdown of rocks into smaller particles by natural forces like wind, water, temperature, and living things.
🧠 Note: Weathering does not move the rock particles—that’s called erosion. Weathering breaks it down, erosion carries it away.
There are three main types:
This happens when rocks are broken into smaller pieces without changing their chemical composition.
Temperature changes – Rock expands in heat and contracts in cold, causing cracks (called exfoliation).
Frost action – Water enters cracks, freezes and expands, breaking the rock.
Pressure release – When overlying rocks are removed, pressure drops and the rock surface peels off.
📌 Example: Cracked rocks in deserts or mountains.
This involves changes in the chemical composition of the rock due to reactions with water, oxygen, acids, etc.
Oxidation – Oxygen reacts with iron to form rust (reddish rocks).
Hydration – Minerals absorb water and expand.
Carbonation – Carbon dioxide in rainwater forms carbonic acid, which dissolves limestone.
Hydrolysis – Reaction between water and minerals forms clay.
📌 Example: Sinkholes in limestone areas.
Living things contribute to rock breakdown.
Plant roots – Grow into cracks and widen them.
Burrowing animals – Bring rocks to the surface.
Microorganisms – Produce weak acids that react with rocks.
📌 Example: Roots breaking through concrete.
Weathering plays a key role in:
Soil formation 🌾
Changing landscapes (valleys, cliffs)
Weakening buildings and roads over time
🧠 Problem:
You see reddish-brown rocks on a hill that crumble easily. What type of weathering is most likely happening, and what caused the color?
✅ Step-by-Step Solution:
The reddish color suggests oxidation, a form of chemical weathering.
Oxygen is reacting with iron in the rock.
✔️ Answer: Chemical weathering (oxidation) caused the red color.
(a) Weathering that changes the chemical composition of rocks is called _______ weathering.
(b) Water freezing in rock cracks causes _______ weathering.
(c) Roots breaking rocks apart is an example of _______ weathering.
Answers:
(a) chemical
(b) physical
(c) biological
| Process | Type of Weathering |
|---|---|
| (i) Rusting of iron in rocks | A. Physical |
| (ii) Roots growing into cracks | B. Biological |
| (iii) Freezing water in cracks | C. Chemical |
Answers:
(i) → C, (ii) → B, (iii) → A
Q: Why is weathering important for soil formation?
Sample Answer:
Weathering breaks down rocks into smaller particles, which mix with organic matter to form soil.
Here’s what you’ve learned:
Weathering breaks down rocks into smaller pieces, but doesn’t move them.
It can be:
Physical (breaks by force),
Chemical (breaks by reaction),
Biological (breaks by life).
Weathering helps form soil and shapes the Earth’s surface.
Look around your school or neighborhood. Can you spot a cracked wall, broken pavement, or crumbling stone?
Which type of weathering do you think caused it—and why?
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