GEO • SHS 1Term 1WAEC / WASSCE SyllabusVIP Lesson
Weathering and Mass Movement
Mechanical/physical, chemical, and biological weathering; factors influencing weathering; mass wasting: soil creep, mudflow, and landslides in Ghana.
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Real-World Context & Relevance in Ghana
Periodic rock falls and landslides along the Peduase-Ayi Mensah highway on the Akuapem ridge illustrate mass wasting hazards in Ghana.
Key Syllabus Learning Objectives
- 1Distinguish clearly between mechanical, chemical, and biological weathering
- 2Analyze the physical mechanisms of exfoliation and oxidation
- 3Identify signs and hazards of mass wasting (soil creep, landslides) along Ghanaian slopes
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Comprehensive Syllabus Study Notes
• Weathering Defined: The in-situ (on-site) disintegration and decomposition of rocks by physical, chemical, and biological agents without transportation.
• Weathering Processes:
- Physical / Mechanical: Disintegration into smaller fragments without chemical alteration. Mechanisms: Exfoliation (onion-skin peeling due to rapid diurnal temperature changes in northern Ghana), frost wedging, block disintegration.
- Chemical: Rock decay involving chemical reaction. Mechanisms: Carbonation (acid rain dissolving limestone), Oxidation (iron minerals rusting and crumbling), Hydration, Hydrolysis. Prevalent in humid southern Ghana.
- Biological: Fracturing by plant roots, burrowing earthworms, rodents, and human quarrying.
• Mass Wasting: Downslope movement of weathered rock debris under the direct force of gravity.
- Slow movements: Soil creep (bent tree trunks, tilted fence posts).
- Rapid movements: Landslides, rockfalls, mudflows (common along the Aburi-Accra escarpment during torrential rainy seasons).
- Weathering Defined: The in-situ (on-site) disintegration and decomposition of rocks by physical, chemical, and biological agents without transportation.
- Weathering Processes:
- Physical / Mechanical: Disintegration into smaller fragments without chemical alteration. Mechanisms: Exfoliation (onion-skin peeling due to rapid diurnal temperature changes in northern Ghana), frost wedging, block disintegration.
- Chemical: Rock decay involving chemical reaction. Mechanisms: Carbonation (acid rain dissolving limestone), Oxidation (iron minerals rusting and crumbling), Hydration, Hydrolysis. Prevalent in humid southern Ghana.
- Biological: Fracturing by plant roots, burrowing earthworms, rodents, and human quarrying.
- Mass Wasting: Downslope movement of weathered rock debris under the direct force of gravity.
- Slow movements: Soil creep (bent tree trunks, tilted fence posts).
- Rapid movements: Landslides, rockfalls, mudflows (common along the Aburi-Accra escarpment during torrential rainy seasons).
Practical Example:
Periodic rock falls and landslides along the Peduase-Ayi Mensah highway on the Akuapem ridge illustrate mass wasting hazards in Ghana.
Core Takeaway:
Weathering is disintegration in situ; erosion involves detachment AND transportation. Do not confuse the two.
WAEC / WASSCE Examiner Tips
- Weathering is disintegration in situ; erosion involves detachment AND transportation. Do not confuse the two.
Common Candidate Pitfalls & Errors to Avoid
- Using weathering and erosion as the same word, when weathering is the in-situ breakdown and erosion carries the material away.
- Explaining chemical weathering with heat alone, although moisture is what carries the reacting solutions into the rock.
- Claiming mass movement needs a steep cliff, when creep operates on slopes too gentle for the eye to detect.
- Describing laterite as soil deposited by a river instead of the residual iron-rich mantle of deep tropical weathering.
- Listing control measures for slope failure without naming the process each measure interrupts.
Topic Mastery Checklist
- Distinguish clearly between mechanical, chemical, and biological weathering
- Analyze the physical mechanisms of exfoliation and oxidation
- Identify signs and hazards of mass wasting (soil creep, landslides) along Ghanaian slopes
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