Which of the following islands are made of small coral atolls and reefs in the Arabian Sea ?

1. Classification of Indian Archipelagos (basic)

When we look at the physical map of India, our eyes often settle on the vast Himalayan peaks or the sprawling Indo-Gangetic plains. However, the Indian Archipelagos represent a fascinating physiographic division that extends India's sovereignty deep into the oceans. Geographers classify these islands into two distinct primary groups based on their geographic location and, more importantly, their geological origin. According to Contemporary India-I, Class IX NCERT, Chapter 2, p.7, the islands constitute one of the six major physiographic divisions of the country.

The first major group is the Andaman and Nicobar Islands, situated in the Bay of Bengal. These are not merely patches of land but are considered the elevated portions of submarine mountains. In fact, they are often viewed as a southward extension of the Arakan Yoma mountain range of Myanmar. Because of this, their origin is primarily tectonic and volcanic India Physical Environment, Class XI NCERT, Chapter 2, p.15. This group is much larger in scale, comprising about 572 islands and islets, and is characterized by hilly terrain and thick forest cover.

In sharp contrast, the Lakshadweep Islands in the Arabian Sea have a completely different biological birth story. Unlike the mountainous Andaman chain, Lakshadweep consists of coral formations. These islands are atolls—circular or horse-shoe-shaped coral reefs that enclose a central lagoon. They are built upon the submerged Chagos-Maldive-Laccadive Ridge by the tireless work of tiny marine organisms called coral polyps Geography of India, Majid Husain, Chapter 2, p.66. These islands are small, low-lying, and much fewer in number compared to their eastern counterparts.

Feature	Andaman & Nicobar Islands	Lakshadweep Islands
Location	Bay of Bengal	Arabian Sea
Geological Origin	Tectonic/Submerged Mountains	Coral Formations (Atolls)
Scale	Large group (~572 islands)	Small group (~36 islands)

Sources: CONTEMPORARY INDIA-I, Geography, Class IX NCERT, Physical Features of India, p.7, 14; INDIA PHYSICAL ENVIRONMENT, Geography Class XI NCERT, Structure and Physiography, p.15; Geography of India, Majid Husain (McGrawHill 9th ed.), Physiography, p.66

2. Tectonic and Volcanic Origins: Andaman & Nicobar (intermediate)

The Andaman and Nicobar Islands are not merely isolated patches of land in the Bay of Bengal; they represent the elevated peaks of a massive submerged mountain range. Geologically, these islands are considered a southward extension of the Arakan Yoma mountains in Myanmar. This mountain range was formed through intense tectonic activity during the same period as the Himalayas. While the main body of the archipelago is tectonic in origin—meaning they were pushed up by the collision of plates—the chain also features distinct volcanic elements. INDIA PHYSICAL ENVIRONMENT, Geography Class XI, Structure and Physiography, p.15

Within this archipelago, the distinction between the two groups is vital. The Andaman group is largely mountainous, featuring high peaks like Saddle Peak (738 m) in North Andaman, which is the highest point in the entire chain. Conversely, the Nicobar group, separated from the Andamans by the Ten Degree Channel, exhibits a physiography that is more influenced by coral origin and lower elevations. Geography of India, Majid Husain, Physiography, p.68 The region is also the only place in India with actual volcanic activity. Barren Island serves as India's only active volcano, having shown significant activity as recently as 2017, while Narcondam Island is a dormant or extinct volcanic peak located to its northeast. Physical Geography by PMF IAS, Volcanism, p.156

The unique location of these islands near the equator results in an equatorial climate characterized by high temperatures and convectional rainfall. This supports dense tropical rainforests with a diverse mix of Indian, Myanmarese, and Malaysian flora. Geography of India, Majid Husain, Regional Development and Planning, p.90 While the core of the islands is tectonic or volcanic rock, the coastlines are often fringed with beautiful coral deposits and beaches, providing a complex geological tapestry. INDIA PHYSICAL ENVIRONMENT, Geography Class XI, Structure and Physiography, p.15

Feature	Andaman Islands	Nicobar Islands
Primary Origin	Tectonic (extension of Arakan Yoma)	Mainly Coral/Tectonic mix
Highest Peak	Saddle Peak (738 m)	Mount Thuiller (642 m)
Volcanism	Home to Barren & Narcondam	Generally non-volcanic peaks

Sources: INDIA PHYSICAL ENVIRONMENT, Geography Class XI, Structure and Physiography, p.15; Geography of India, Majid Husain, Physiography, p.68; Geography of India, Majid Husain, Regional Development and Planning, p.90; Physical Geography by PMF IAS, Volcanism, p.156

3. Western Coastal Plains and Continental Shelves (intermediate)

The Western Coastal Plains of India are a fascinating geological feature, born not just from river deposits, but from the dramatic faulting and subsidence of the Arabian Sea during the Eocene period Geography of India by Majid Husain, Physiography, p.63. Unlike the broad, delta-filled plains of the East Coast, the Western Coastal Plain is a narrow strip sandwiched between the steep Western Ghats and the sea. Because the land tilted or subsided, the coastline is relatively straight and deep, allowing the sea to penetrate closer to the land. This makes the west coast a classic example of a submerged coastline (particularly the northern part), which provides the perfect depth for natural ports and harbours like Kandla, Mumbai, and Marmagao INDIA PHYSICAL ENVIRONMENT, Geography Class XI (NCERT 2025 ed.), Structure and Physiography, p.14.

Geographically, we divide this coast into distinct sections from north to south. The Kachchh and Kathiawar coasts in Gujarat give way to the Konkan coast (Mumbai to Goa), the Kannad Plain in Karnataka, and finally the Malabar coast in Kerala CONTEMPORARY INDIA-I, Geography, Class IX (NCERT 2025 ed.), Physical Features of India, p.13. One of the most unique features of the southern stretch (Malabar) is the presence of 'Kayals' or backwaters. These are shallow lagoons and inlets that run parallel to the coast, serving as vital hubs for fishing, inland navigation, and the famous snake boat races.

An interesting nuance for UPSC is the continental shelf. While the coastal plain is narrow, the western continental shelf is remarkably wide and shallow, especially off the coast of Mumbai. This wide shelf is a treasure trove for India, housing massive petroleum reserves (like Mumbai High) and providing some of the world's richest fishing grounds due to the sunlight reaching the shallow seabed. Furthermore, the rivers on this side, like the Narmada and Tapti, flow through steep gradients and don't carry enough silt to form deltas; instead, they form estuaries, keeping the coastline sharp and well-defined.

Feature	Northern/Central West Coast (Konkan)	Southern West Coast (Malabar)
Geological Nature	Primarily Submergent	Primarily Emergent
Key Features	Deep natural harbours, rocky cliffs	Lakes, lagoons (Kayals), and sandbars

Sources: Geography of India by Majid Husain, Physiography, p.63; INDIA PHYSICAL ENVIRONMENT, Geography Class XI (NCERT 2025 ed.), Structure and Physiography, p.14; CONTEMPORARY INDIA-I, Geography, Class IX (NCERT 2025 ed.), Physical Features of India, p.13; Physical Geography by PMF IAS, Major Landforms and Cycle of Erosion, p.224

4. Biological Foundations: How Corals Build Islands (basic)

To understand how the Lakshadweep Islands were formed, we must first look at the tiny biological architects behind them: coral polyps. These are small, soft-bodied organisms related to jellyfish that live in massive colonies. They extract calcium salts from the surrounding seawater to build hard, protective skeletons of calcium carbonate (CaCO₃) Physical Geography by PMF IAS, Major Landforms and Cycle of Erosion, p.219. As these polyps die, their skeletons remain, and new generations grow directly on top of them, gradually building massive structures over thousands of years.

This biological construction is powered by a fascinating symbiotic relationship. Inside the clear tissues of the coral polyps live microscopic algae called zooxanthellae. Through photosynthesis, these algae provide the coral with food and energy, while the coral provides the algae with a safe home and nutrients Environment, Aquatic Ecosystem, p.50. Because this process requires sunlight, reef-building corals are restricted to shallow, clear, and warm tropical waters where temperatures stay above 20 °C Certificate Physical and Human Geography, Islands and Coral Reefs, p.99. This is why the Lakshadweep islands, located in the warm Arabian Sea, are such a perfect environment for coral growth.

The transformation from a underwater reef to a circular island (an atoll) follows a specific geological journey known as Darwin’s Subsidence Theory. It begins with a volcanic island surrounded by a reef; as the island slowly sinks (subsides) into the ocean, the corals continue to grow upward to stay near the sunlight. Eventually, the central volcanic peak disappears entirely beneath the waves, leaving behind a ring-shaped reef enclosing a central lagoon Certificate Physical and Human Geography, Islands and Coral Reefs, p.101. The Lakshadweep islands are the classic example of these atolls, built upon the submerged Chagos-Maldive-Laccadive Ridge Geography of India, The Indian Islands, p.66.

Reef Type	Description
Fringing Reef	Attached directly to the shore of a volcanic island.
Barrier Reef	Separated from the land by a wide, deep lagoon.
Atoll	A circular reef surrounding a lagoon, with no central island visible.

Sources: Physical Geography by PMF IAS, Major Landforms and Cycle of Erosion, p.219; Environment, Aquatic Ecosystem, p.50; Certificate Physical and Human Geography, Islands and Coral Reefs, p.99, 101; Geography of India, The Indian Islands, p.66

5. Marine Conservation: India's Coral Ecosystems (exam-level)

India’s marine biodiversity is anchored by its coral reefs, often described as the "rainforests of the ocean" due to their immense biological productivity. These ecosystems are built by tiny marine organisms called coral polyps, which secrete calcium carbonate to form sturdy structures. In India, these reefs cover approximately 19,000 sq km and are categorized into four major regions for intensive management: the Gulf of Mannar, the Gulf of Kachchh, Lakshadweep, and the Andaman and Nicobar Islands Geography of India, Majid Husain, Natural Vegetation and National Parks, p.53. While they all share high biodiversity, their physical structures differ significantly based on their geological origins.

The distribution of these reefs is a fascinating study of India's physical geography. For instance, the Lakshadweep Islands are unique as India's only atoll formation — circular or semi-circular reefs that develop around a subsiding volcanic seafloor on the Chagos-Maldive-Laccadive Ridge. In contrast, the Andaman and Nicobar Islands primarily feature fringing reefs, which are contiguous with the shoreline and represent the most common reef form in the country Environment, Shankar IAS Academy, Aquatic Ecosystem, p.51.

Reef Type	Key Characteristics	Primary Locations in India
Fringing Reefs	Grow directly from the shore; most common type.	Andaman and Nicobar Islands
Patch Reefs	Isolated, discontinuous patches shoreward of larger structures.	Gulf of Mannar, Gulf of Kachchh, Palk Bay
Atolls	Circular reefs enclosing a central lagoon; built on submerged ridges.	Lakshadweep

Conservation of these fragile ecosystems is governed by the Coastal Regulation Zone (CRZ) notifications. These regulations, updated most recently in 2018, aim to balance economic aspirations like tourism and housing with the strict conservation principles required to protect ecologically sensitive zones (CRZ-I) Environment, Shankar IAS Academy, Aquatic Ecosystem, p.54-56. Despite these protections, Indian reefs face severe threats from coral bleaching (driven by global warming), marine pollution, and increased sediment loads. To spearhead scientific monitoring, the National Coral Reef Research Centre has been established at Port Blair Environment and Ecology, Majid Hussain, BIODIVERSITY, p.54.

Sources: Geography of India, Majid Husain, Natural Vegetation and National Parks, p.53; Environment, Shankar IAS Academy, Aquatic Ecosystem, p.51, 54, 56; Environment and Ecology, Majid Hussain, BIODIVERSITY, p.54

6. The Chagos-Laccadive Submerged Ridge (exam-level)

The Chagos-Laccadive Ridge (CLR) is one of the most fascinating submarine features of the Indian Ocean, acting as a giant volcanic "footprint" left behind by the Indian Plate as it journeyed northwards. To understand its origin, we must look at Hotspot Volcanism. Unlike most volcanoes that form at plate boundaries, a hotspot is a stationary plume of intense heat rising from deep within the Earth's mantle. Approximately 66 million years ago, the Indian Plate passed over the Réunion Hotspot, triggering the massive eruptions that created the Deccan Traps in western India PMF IAS, Hotspot Volcanism, p.165.

As the Indian Plate continued its northward trek, the stationary hotspot essentially "punched" through the moving crust at different intervals, creating a 2,500 km long linear chain of volcanic peaks. This chain includes the Laccadives (Lakshadweep), the Maldives, and the Chagos Archipelago. Over millions of years, as the volcanic activity ceased and the oceanic crust cooled, these volcanic islands began to subside (sink) below the sea level. However, because they were located in warm, shallow tropical waters, coral polyps began to colonize the sinking peaks, building massive structures of calcium carbonate NCERT Class IX, Physical Features of India, p.14.

Today, the Chagos-Laccadive Ridge is a "submerged" ridge because the original volcanic base is underwater. What we see on the surface—such as the 36 islands of Lakshadweep—are actually atolls: ring-shaped coral reefs that rest upon these ancient, sunken volcanic foundations. This makes the islands of the Arabian Sea fundamentally different from the Andaman and Nicobar Islands, which are primarily the elevated portions of submerged mountain ranges (the Arakan Yoma) formed by tectonic activity Geography of India by Majid Husain, Chapter 2, p.66.

Sources: Physical Geography by PMF IAS, Hotspot Volcanism, p.165; CONTEMPORARY INDIA-I, NCERT Class IX, Physical Features of India, p.14; Geography of India by Majid Husain, Physiography, p.66

7. Specific Topography of the Lakshadweep Archipelago (exam-level)

While the Andaman and Nicobar Islands are essentially the submerged extensions of mountain ranges, the Lakshadweep Archipelago tells a completely different geological story. These islands are purely coral in origin, built upon the submerged Chagos-Laccadive Ridge, which is a volcanic feature under the Arabian Sea. Located roughly 220 to 440 km off the Malabar Coast of Kerala, this group consists of 36 small islands, only 11 of which are inhabited INDIA PHYSICAL ENVIRONMENT, Geography Class XI (NCERT 2025 ed.), Structure and Physiography, p.15. In 1973, the islands formerly known as the Laccadive, Minicoy, and Amindive islands were unified under the name Lakshadweep CONTEMPORARY INDIA-I, Geography, Class IX (NCERT 2025 ed.), Physical Features of India, p.14.

The topography is defined by atolls — horseshoe-shaped or circular coral reefs that enclose a central lagoon. These atolls are formed by the continuous accumulation of calcium carbonate from coral polyps in shallow, warm waters. A unique topographic detail often noted in the archipelago is the presence of storm beaches on the eastern seaboard, which consist of unconsolidated pebbles, shingles, cobbles, and boulders INDIA PHYSICAL ENVIRONMENT, Geography Class XI (NCERT 2025 ed.), Structure and Physiography, p.15. The islands are extremely low-lying, with the highest point rarely exceeding a few meters above sea level.

To understand the spatial arrangement of this archipelago, we look at the channels that divide them. The Nine Degree Channel is a crucial topographic marker, separating the large island of Minicoy in the south from the rest of the archipelago (the Laccadive/Canannore group) to the north INDIA PHYSICAL ENVIRONMENT, Geography Class XI (NCERT 2025 ed.), Structure and Physiography, p.15.

Feature	Description
Origin	Coral accumulation on the Chagos-Laccadive submerged ridge.
Major Island	Minicoy is the largest island of the group.
Key Channel	The Nine Degree Channel separates Minicoy from the main group.
Ecological Note	The Pitti Island is an uninhabited bird sanctuary.

Sources: INDIA PHYSICAL ENVIRONMENT, Geography Class XI (NCERT 2025 ed.), Structure and Physiography, p.15; CONTEMPORARY INDIA-I, Geography, Class IX (NCERT 2025 ed.), Physical Features of India, p.14; Geography of India, Majid Husain (McGrawHill 9th ed.), Regional Development and Planning, p.91

8. Solving the Original PYQ (exam-level)

You've just explored the fascinating world of coral polyps and the geological origins of India’s maritime territories. This question brings those building blocks together by asking you to distinguish between islands formed by tectonic activity and those formed by biological accretion. In your recent lessons, we discussed the Chagos-Maldive-Laccadive Ridge, a submerged volcanic feature that serves as the foundation for these unique structures. To answer this correctly, you must apply the concept of atoll formation—where circular reefs enclose a central lagoon—specifically to the geography of the Arabian Sea.

When walking through the reasoning, your first mental filter should be location. Since the question specifies the Arabian Sea, you must narrow your focus to the western coast of the Indian peninsula. Reflect on the structural differences: while some islands are high-altitude volcanic peaks or mountain extensions, Lakshadweep is composed of 36 to 39 low-lying islands built entirely through the perpetual deposition of calcium carbonate. This direct application of the 'biological origin' concept confirms that Lakshadweep is the correct answer, a fact reinforced by Geography of India by Majid Husain.

UPSC often includes 'trap' options to test the precision of your spatial awareness. Andaman is a classic distractor; it is located in the Bay of Bengal and is a tectonic extension of the Arakan Yoma mountains, not a coral atoll. While the Maldives are indeed coral atolls in the same ridge system, the question seeks the specific territory defined by these features within the Indian context. Sri Lanka, on the other hand, is a continental island separated by a shallow sea. By isolating the specific combination of location (Arabian Sea) and composition (coral atolls), you avoid these common pitfalls as described in NCERT Class IX: Contemporary India-I.