Theme 3: Rocks and Weathering

Q: Name and explain two processes of mechanical weathering.

Freeze–thaw: Water enters cracks, freezes, expands by 9%, widens cracks.
Onion skin weathering (Exfoliation): Temperature fluctuations cause surface layers to peel away in sheets.

Q: What are two examples of chemical weathering?

Carbonation: Rainwater with dissolved CO₂ forms carbonic acid, dissolving limestone.

Hydrolysis: Minerals (e.g. feldspar in granite) react with water, forming clay.

Q: How do organisms contribute to weathering?

Plant roots widen cracks; lichens and moss produce organic acids; burrowing animals disturb rock.

Q: List four factors that influence the rate of weathering.

• Climate

• Rock type

• Vegetation

• Relief

• Time