Wave types and the four erosion processes
Constructive waves -- low, long, strong swash, weak backwash -- deposit and build a beach. Destructive waves -- steep, high-energy, weak swash, strong backwash -- erode. Four erosion processes: hydraulic action (water force and compressed air split rock in cracks), abrasion (waves fling sand and pebbles at the cliff), attrition (fragments collide, becoming smaller and rounder, not cliff erosion) and solution (weak acids dissolve chalk or limestone).
Erosion and deposition landforms
Hard rock forms a headland, softer rock a bay. Hydraulic action and abrasion widen a crack into a cave, cut it through to an arch, whose roof collapses to a stack, then a worn-down stump; a retreating cliff leaves a wave-cut platform. Longshore drift moves sediment along the coast: swash up the beach at the wave's angle, backwash straight back down. Deposition builds a beach, a spit where the coast bends, or a bar where a spit seals a bay, trapping a lagoon.
Holderness Coast -- erosion case study
The Holderness Coast, between Flamborough Head and Spurn Point, is soft boulder clay -- among Europe's fastest-eroding coasts, retreating one to two metres a year. At Mappleton, rock armour and two rock groynes (around 1991) trap south-drifting sediment and protect the village. At Great Cowden to the south less sediment arrives, so erosion speeds up -- a terminal groyne effect. Drifting sediment builds Spurn Point spit; low-value farmland elsewhere is left to managed retreat.
Drawn from real examiner reports.
Longshore drift: swash/backwash reversed
A weak topic across all four sittings. In diagrams swash and backwash get reversed: swash moves material UP the beach at the wave's approach angle, backwash then straight back DOWN under gravity. Candidates also drop "along the beach" (net direction) and "with each wave" (it repeats), describing a single swash-backwash pair rather than ongoing drift.
Digest (## 2.3): swash/backwash direction reversed in diagrams, "along the beach" and "with each wave" omitted (s23 Paper 42 Q1c, w23 Paper 21 Q5a-b).
Stack vs stump landform mix-ups
Precise landform names get confused. A stack is a tall pillar separated from the headland; a stump is the low, worn-down remnant left once the stack erodes further -- calling one the other is an error. Whole scenes get misread (a headland and arch as "a river with a bridge"), so check it is coast, not river; "arch" written "arc" reads as a cave.
Digest (## 2.3): a stack misidentified as a stump, a headland/arch scene misdescribed (e.g. "a river with a bridge"), "arch" misspelled "arc" (s22 Paper 11 Q3a(i), w22 Paper 22 Q4a(i)).
Groynes are not walls or fences
Groynes are often misread as walls or fences, but a groyne runs perpendicular to the beach, out to sea. Asked how one works, weak answers give only "it reduces wave power", which earns nothing alone. The credited mechanism is that it traps sediment moving by longshore drift, building a wider beach that absorbs wave energy before reaching the cliff behind.
Digest (## 2.3): groynes mistaken for walls/fences and "how they work" left generic ("reduces wave power") instead of trapping sediment/blocking longshore drift (w22 Paper 11 Q3a(i)-(ii)).
Erosion is not weathering
Examined as distinct terms. Erosion is the wearing away AND removal of rock by a moving agent -- waves or currents. Weathering is the in-situ breakdown of rock with no transport (e.g. freeze-thaw or salt action). Calling the coastal process "weathering" loses the removal idea: hydraulic action, abrasion, attrition and solution are erosion, not weathering.
Attrition does not erode the cliff
The four processes are easy to blur. Abrasion is waves hurling sand and pebbles AT the cliff. Attrition is the load colliding WITH ITSELF -- fragments knock together and become smaller and rounder; it changes the sediment, not the cliff. Hydraulic action is water force and compressed air in cracks; solution dissolves chalk or limestone.
Constructive vs destructive waves
Easy to reverse. A constructive wave is low and long, strong swash, weak backwash, so it deposits and BUILDS a beach. A destructive wave is steep and high-energy, weak swash, strong backwash, so it ERODES. Do not swap the swash/backwash strengths, and do not say destructive waves build beaches -- their strong backwash drags material out to sea.
Wind does not carry sand along the beach
A tested wrong belief: that longshore drift is the wind blowing sand or shingle along the beach. Really, the prevailing wind drives waves onto the coast at an angle; the swash carries sediment up the beach at that angle; the backwash drags it straight back down, a zig-zag net drift. The wind only sets the wave angle; the swash-and-backwash cycle does the transport.
Digest (## 2.3): wind is sometimes said to move beach material directly rather than driving the angled waves whose swash and backwash move it (s23 Paper 42 Q1c, w23 Paper 21 Q5a-b).
Level 3 on the 7-mark case study
Name a real coast and places within it (Holderness -- Mappleton, Spurn Point), name the actual structures (rock armour, groynes), link each cause to its response, and judge effectiveness -- including a limitation like the terminal groyne effect.
Answer the command word
Match the verb. "Describe" = what a pattern is, with data; "explain" = the cause; "compare" = use "whereas / more than", not two separate descriptions; "suggest" = plausible reasons for an unfamiliar case. Describe done as explain is the commonest error.
Name the process at each stage
Formation questions (cave-arch-stack, or a spit) are marked on the SEQUENCE plus the process at each step. Instead of "the waves erode it", name each stage: hydraulic action and abrasion widen a crack to a cave, cut through to an arch, whose roof collapses to a stack.
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