GEO • SHS 1Term 2WAEC / WASSCE SyllabusVIP Lesson
Coastal Landforms & Marine Processes
Marine erosion (hydraulic action, corrasion, attrition, solution), erosional landforms (cliffs, wave-cut platforms, caves, arches, stacks), depositional features, and coastal management in Ghana.
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Real-World Context & Relevance in Ghana
The Keta Sea Defence Wall in the Volta Region was engineered to protect historical coastal settlements from destructive tidal waves and coastal recession.
Key Syllabus Learning Objectives
- 1Explain the four mechanical and chemical processes of wave erosion
- 2Illustrate the progressive evolutionary sequence from sea cave to arch, stack, and stump
- 3Evaluate coastal depositional landforms and assess sea defense measures protecting vulnerable Ghanaian towns
1
Comprehensive Syllabus Study Notes
• Marine Processes of Coastal Erosion:
- Hydraulic Action: The physical force of pounding ocean waves crashing against rock faces, compressing air in cracks until rocks shatter.
- Abrasion / Corrasion: Boulders, pebbles, and sand hurled by breaking waves against coastal cliffs, acting like sandpaper.
- Attrition: Rock fragments in wave water collide against one another, becoming smaller, rounded, and smoother.
- Solution / Corrosion: Soluble minerals (e.g. calcium carbonate in limestone) dissolved by the chemical action of acidic seawater.
• Features of Marine Erosion:
- Sea Cliffs & Wave-Cut Platforms: Notch cut at cliff base retreats inland, leaving a flat bedrock terrace exposed at low tide.
- Headlands and Bays: Formed on discordant coastlines where soft rock erodes quickly into bays while resistant hard rock stands out as headlands.
- Cave-Arch-Stack-Stump Sequence: Wave refraction attacks lines of weakness in a headland -> Cave cut through to form an Arch -> Roof of arch collapses leaving an isolated pillar called a Stack -> Wave erosion at base fells stack into a Stump.
• Features of Marine Deposition:
- Beaches, Spits, Sandbars, Tombolos (spit linking mainland to an island), and Lagoons (open and closed lagoons).
• Coastal Management in Ghana:
- Rapid coastal erosion threatens communities along the Keta, Ada, and Axim coastlines. Government interventions include the Keta Sea Defence Wall Project and rip-rap boulders to protect against rising tidal waves.
- Marine Processes of Coastal Erosion:
- Hydraulic Action: The physical force of pounding ocean waves crashing against rock faces, compressing air in cracks until rocks shatter.
- Abrasion / Corrasion: Boulders, pebbles, and sand hurled by breaking waves against coastal cliffs, acting like sandpaper.
- Attrition: Rock fragments in wave water collide against one another, becoming smaller, rounded, and smoother.
- Solution / Corrosion: Soluble minerals (e.g. calcium carbonate in limestone) dissolved by the chemical action of acidic seawater.
- Features of Marine Erosion:
- Sea Cliffs & Wave-Cut Platforms: Notch cut at cliff base retreats inland, leaving a flat bedrock terrace exposed at low tide.
- Headlands and Bays: Formed on discordant coastlines where soft rock erodes quickly into bays while resistant hard rock stands out as headlands.
- Cave-Arch-Stack-Stump Sequence: Wave refraction attacks lines of weakness in a headland -> Cave cut through to form an Arch -> Roof of arch collapses leaving an isolated pillar called a Stack -> Wave erosion at base fells stack into a Stump.
- Features of Marine Deposition:
- Beaches, Spits, Sandbars, Tombolos (spit linking mainland to an island), and Lagoons (open and closed lagoons).
- Coastal Management in Ghana:
- Rapid coastal erosion threatens communities along the Keta, Ada, and Axim coastlines. Government interventions include the Keta Sea Defence Wall Project and rip-rap boulders to protect against rising tidal waves.
Practical Example:
The Keta Sea Defence Wall in the Volta Region was engineered to protect historical coastal settlements from destructive tidal waves and coastal recession.
Core Takeaway:
Remember the erosion progression for headlands: Crack -> Cave -> Arch -> Stack -> Stump. Always draw a neat cross-section diagram in Section B!
WAEC / WASSCE Examiner Tips
- Remember the erosion progression for headlands: Crack -> Cave -> Arch -> Stack -> Stump. Always draw a neat cross-section diagram in Section B!
Common Candidate Pitfalls & Errors to Avoid
- Drawing the wave approaching the shore head-on and still showing strong longshore drift, when drift needs a slanted approach.
- Calling a spit a bar, although a bar closes an estuary while a spit stays attached at one end.
- Forgetting that a breakwater starves the downdrift beach it was never meant to protect.
- Dividing distance by an erosion rate and reporting the answer as metres rather than years.
- Confusing deposition with erosion when explaining salt marshes and lagoons behind a barrier bar.
Topic Mastery Checklist
- Explain the four mechanical and chemical processes of wave erosion
- Illustrate the progressive evolutionary sequence from sea cave to arch, stack, and stump
- Evaluate coastal depositional landforms and assess sea defense measures protecting vulnerable Ghanaian towns
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