Coasts - Erosional Landforms

Question 1

headlands & bays

Answer 1

1. headland = area of land surrounded by water on 3 sides, bay = area of water surrounded by land on three sides. (1), e.g. Swanage Bay & Peveril Point (headland) (1)
2. they form on discordant coastlines where bands of rock of alternating resistance run perpendicular to coast (1)
3. less resistant rock (e.g. clay) is eroded away faster by hydraulic action & abrasion & corrosion than resistant rock which = bay (1)
4. called diff erosion (1)
5. hydraulic action = wave action traps & compresses air into cracks in the rock, fracturing it over time = pieces of rock break off (2)
6. abrasion = rocks & pebbles & sand r hurled against a cliff by waves = erodes in a sandpaper motion (2)
7. ⇒ leaves bands of stronger rocks (e.g. granite) = headland protruding out to sea (1)
8. headland protects bay from storm waves = waves reaching shore in a bay are constructive waves = beach formed thru deposition (1)

Question 2

wave cut platform

Answer 2

1. wave action conced at foot of a headland on weakness e.g. fault lines (1)
2. if fetch is long & prevailing wind comes from the same direction, waves hitting the foot of headland will be high energy waves (1)
3. hydraulic action & abrasion open up the weaknesses to form a wave cut notch (1)
4. ↳ starts to undercut the cliff = overhang (1)
5. hydraulic action = wave action traps & compresses air into cracks in the rock, fracturing it over time = pieces of rock to break off (2)
6. corrosion = carbonic acid in sea water dissolves rock = more erosion (2)
7. more undercutting = cliff to collapse under force of g (1)
   eventually the cliff retreats inland yet retains steepness (1)
8. fallen rocks lie at base of cliff till repeated attrition makes them small enough for removal by wave action & coastal currents + rocks also act as ammunition in abrasion process (1)
9. as cliff retreats, eroded remains r gradually planed off via sea = gentle sloping shelf of rock visible at low tide (1)
10. e.g. Kimmeridge Bay, Dorset (1)

Question 3

arch/stack

Answer 3

1. lines of weakness in cliff of a headland e.g. joints r hydraulic actioned (1)
2. hydraulic action pressurises air in cracks = widens & weakens rock = breaks it up (2)
3. abrasion = rocks & pebbles & sand r thrown against cliff by waves, scouring & eroding cliff in a sandpaper motion (2)
4. eventually cracks widen & develop = opens up & forms a sea cave (1), eg Tilly Whim caves, Dorset
5. wave refraction affects all 3 sides of headland
6. if 2 caves r aligned, the waves cut thru headland from both sides = natural arch (1) e.g. Durdle Door (1)
7. wave-cut notches continue to be hydraulic actioned, corrasion & corrosion = widening base of arch (1)
8. eventually arch is enlargened & roof becomes unsupported so it collapses under force of g (1)
9. leaves an isolated pillar of rock separated from mainland = stack (1) e.g. Old Harry, Dorset. (1)