State whether the following is true or false.
Debris accumulating at a cliff foot protects the cliff from further attack.
Answer: A
The talus absorbs wave energy that would otherwise reach the cliff base. Retreat resumes only once the material has been removed by the waves. Cliff retreat is episodic rather than steady. Long records are needed to establish an average rate.
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A ria is
Answer: B
Rising sea level flooded the valley, producing a branching inlet that deepens seaward. A fjord differs in being glacially over-deepened with a shallow sill at its mouth. Both are inherited from a lower sea level stand.
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Match each coastal inlet type with its origin.
List I
A. Ria
B. Fjord
C. Estuary
D. Lagoon
List II
1. a river mouth with mixing of fresh and salt water
2. a drowned river valley
3. a water body enclosed behind a barrier
4. a drowned glacial trough with a sill
Answer: C
The first two are inherited from past sea level and ice conditions rather than from present processes. The last two are defined by their water exchange rather than by their origin. The two classifications answer different questions.
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A delta forms where
Answer: D
The balance between fluvial supply and marine redistribution decides whether a delta builds. Deltas are classified as river, wave or tide dominated according to which process prevails. The front shape reveals which agent dominates.
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Match each delta type with its dominant process.
List I
A. Birdsfoot delta
B. Cuspate delta
C. Estuarine delta
D. Arcuate delta
List II
1. tide dominated with elongated sand ridges
2. river dominated with weak marine action
3. a balance of river and wave influence
4. wave dominated and smoothed at the front
Answer: A
Correct answer: A-2, B-4, C-1, D-3
Delta shape records which process dominates. A birdsfoot delta such as the Mississippi forms where the river overwhelms weak waves and tides and builds distributary fingers seaward. An arcuate delta such as the Nile reflects a balance between river supply and wave rework. A cuspate delta is smoothed and pointed by strong wave action from both sides. An estuarine delta is tide dominated, with sand ridges elongated along the flow.
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Assertion (A): Many major deltas are now retreating rather than advancing.
Reason (R): Upstream dams and diversions have cut the sediment supply reaching the coast.
Answer: B
Both are true and the reason gives the principal cause, and subsidence and sea level rise add to the problem. The Nile, Mississippi and Indus deltas are all documented examples. Subsidence compounds the loss of sediment supply.
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A barrier island is
Answer: C
Correct answer: an elongated sand island separated from the mainland by a lagoon
A barrier island is a long shore-parallel ridge of sand standing offshore with a lagoon or back-barrier marsh behind it, breached at intervals by tidal inlets. Barriers migrate landward as sea level rises, by overwash carrying sand across the crest, which is why holding one in place with defences generally destroys the lagoon behind it.
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Assertion (A): Barrier islands migrate landward over long periods.
Reason (R): Storm overwash transfers sediment from the seaward face to the landward side.
Answer: D
Both are true and the reason gives the mechanism, and sea level rise accelerates the process. Fixing the island in place by hard defences interrupts the supply that sustains it. Overwash is the mechanism that keeps the island alive.
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Consider the following statements about barrier islands.
1. Overwash during storms moves sediment to the landward side.
2. The island migrates landward as sea level rises.
3. Hard defences on the seaward face assist the natural migration.
Answer: A
The first two are correct and describe the natural behaviour. The third is the opposite of what happens, since fixing the seaward face prevents the overwash the migration depends on. Hard defence and natural migration are incompatible.
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Beach cusps are
Answer: B
Correct answer: regularly spaced crescentic features along the swash zone
Beach cusps are a series of seaward-pointing horns separated by embayments, spaced remarkably regularly along the swash zone. They form by self-organisation, the swash circulation and the developing morphology reinforcing one another, and the spacing scales with the swash excursion. They are a small-scale illustration of the morphodynamic feedback the topic ends with.
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