Which of the following statements regarding barrier islands is/are correct? 1. These are small chain of sand islands that form offshore, far from the coast. 2. Lagoons or shallower marshes separate the barrier islands from the mainland. 3. Such locations are hazardous for settlements because they are easily swept away by storms and hurricanes. Select the correct answer using the code given below.
- (a)1 only
- (b)1 and 2 only
- (c)2 and 3 only
- (d)1, 2 and 3
Correct — C, 2 and 3 only. Statement 2 is right: a barrier island is separated from the mainland by a shallow water body, and lagoons, bays, tidal creeks and salt marshes are exactly what fill that gap. Statement 3 is right too — these are low ridges of loose sand that storms overwash and reshape, so settlements on them are exposed and the shoreline itself migrates. Statement 1 is the one that fails, because barrier islands form parallel to and close to the coast, not far offshore; NOAA describes a barrier island as a constantly changing deposit of sand that forms parallel to the coast.
- (a)1 only — Takes the single false statement and rejects the two true ones. The 'far from the coast' wording is what makes statement 1 wrong — barrier islands hug the shore, typically a few kilometres out at most.
- (b)1 and 2 only — Carries statement 1 in, so it fails on the same wording. It also drops the storm hazard, which is one of the best-attested facts about barrier islands.
- (d)1, 2 and 3 — Would be right if statement 1 said 'parallel to and close to the coast'. As printed it says the islands form far from the coast, and that single phrase is the discriminator.
A barrier island is a long, narrow ridge of sand built by waves and longshore drift, lying parallel to a coastline and separated from it by a lagoon, bay or tidal marsh. They form best where the coastal plain is gently sloping, sediment is plentiful (often near river deltas) and tectonic activity is low. Because they are made of unconsolidated sand, they migrate landward over time and are overwashed and breached during storms — behaviour that protects the mainland by absorbing wave energy but leaves anything built on the island itself at risk.
Statement-code items are usually decided by a single adjective, and here it is 'far'. Every other clause in statement 1 is fine — barrier islands are indeed small chains of sand islands that form offshore. The word 'far' converts a correct description into a wrong one, because the defining relationship of a barrier island is proximity and parallelism to the shore. India's own best-known example is the sand spit and barrier system that encloses Chilika Lake in Odisha, where the barrier and the lagoon behind it are inseparable parts of one landform. If you can place statement 1 as false and statement 3 as obviously true, the code follows without needing to settle statement 2 independently.
- NOAA defines a barrier island as a constantly changing deposit of sand that forms parallel to the coast.
- Barrier islands are separated from the mainland by tidal creeks, bays and lagoons.
- They form best near river deltas, on flat coastal terrain with low tectonic activity.
- Dunes and grasses on barrier islands absorb wave energy, giving the mainland a smaller storm surge and less flooding.
- Overlooking the single word 'far' in statement 1 — barrier islands form close to and parallel to the coast.
- Treating 'protects the mainland from storms' and 'is itself hazardous for settlement' as contradictory; both are true of the same landform.
- Confusing a barrier island with a coral atoll or an offshore oceanic island, which have entirely different origins.
Asked as a three-statement code item in which one adjective, not one fact, decides the answer — a very common CDS geomorphology pattern.
Which one of the following is NOT a coastal depositional feature ?
- (a) Tombolo
- (b) Sand bar
- (c) Stack
- (d) Spit
Answer(c) Stack
Places the barrier island in its family. Bars and spits are the same depositional machinery that builds barrier islands, and separating them from erosional forms is the skill both items reward.
- practice — not a real PYQ
A barrier island is typically separated from the mainland by
- (a)a deep ocean trench
- (b)a lagoon or shallow bay
- (c)a fault scarp
- (d)a submarine canyon
Answer(b) a lagoon or shallow bay — the shallow water body behind the barrier is part of the landform's definition.
- practice — not a real PYQ
Which one of the following coastal features is formed when a spit grows across a bay and encloses a water body behind it?
- (a)Stack
- (b)Tombolo
- (c)Bar and lagoon
- (d)Wave-cut platform
Answer(c) Bar and lagoon — a bar sealing a bay leaves a lagoon behind it, the same relationship a barrier island has with the water it shelters.