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WEATHERING - Coggle Diagram
WEATHERING
Definition
Weathering is the breakdown of rock in situ (in the same place) by physical, chemical, or biological processes.
PHYSICAL (MECHANICAL) WEATHERING**
Rocks break into smaller pieces without chemical change.
🔹 Types:
❄️ Freeze–Thaw Weathering
Water enters cracks in rock
Temperature drops below 0°C → water freezes
Ice expands by about 9%
This puts pressure on the rock
Repeated freezing and thawing widens cracks
Eventually rock breaks apart
Common in------ Mountain areas
Places with temperatures around freezing (e.g. parts of Ireland in winter)
🌡️ Thermal Expansion (Onion-Skin Weathering)
Rocks heat up in the day → expand
Cool down at night → contract
Outer layers peel off over time
Common in: Hot deserts
Salt Weathering
Salty water enters cracks
Water evaporates → salt crystals form
Crystals grow and push rock apart
COMMON NEAR-Coastal areas
Chemical Weathering
Rock is chemically changed or dissolved
🔹 Types:
🌧️ Carbonation
Rainwater mixes with carbon dioxide → forms carbonic acid
This reacts with rocks like limestone
Slowly dissolves the rock
👉 Very important in limestone regions (karst landscapes)
Oxidation
Oxygen reacts with minerals (especially iron)
Causes “rusting” in rocks
Weakens the rock
Hydrolysis
Water reacts with minerals → forms new minerals (like clay)
Weakens rock structure
👉 Chemical weathering is faster in:
Warm + wet climates
Biological Weathering
Caused by living organisms
🔹 Examples:
Plant roots grow into cracks → force rocks apart
Burrowing animals break up soil and rock
Lichens/moss release weak acids → dissolve rock
Weathering and Landforms
Weathering helps shape landscapes:
Breaks down mountains
Forms soil
Creates features like:
Cliffs
Valleys
Karst landscapes (limestone areas)