Andaman and Nicobar Islands

Topic: Structure and Physiography of India: Himalayas, Plains, Peninsula, Coasts and Islands · NCERT: Class 6, Ch 2 "Oceans and Continents"; Class 7, Ch 1 "Geographical Diversity of India"; Class 11, Ch 1 "India - Location"; Class 11, Ch 2 "Structure and Physiography"; Class 11, Ch 5 "Natural Vegetation"; Class 11, Ch 6 "Natural Hazards and Disasters: Causes, Consequences and Management"

Meaning

The Andaman and Nicobar Islands are a group of about 572 islands and islets in the Bay of Bengal, between 6°–14°N and 92°–94°E. They are the raised tops of an undersea mountain chain that continues the Arakan Yoma of Myanmar. The Ten Degree Channel divides them into the Andaman group in the north and the Nicobar group in the south.

They matter because they are India's only volcanic and earthquake-prone island chain, with Barren Island, India's only active volcano. They also guard India's eastern sea routes near the Strait of Malacca. The Great Nicobar project keeps them in the news.

Explanation

How they formed: tectonic origin

• What they are: the elevated parts of submarine mountains. "Submarine" means under the sea.
• Link to the mainland: the undersea chain continues the Arakan Yoma of Myanmar. The Arakan Yoma is the southern extension of the Purvanchal and Himalayan system. So the Andamans are a drowned branch of the same mountain-building that raised the Himalayas.
• Cause → process → result:
• Cause: the Indo-Australian plate and the south-eastern Eurasian plate keep pushing into each other [5].
• Process: the Indian side slides under the plate to its east. Sea-floor rock and mud get crumpled and pushed up into a long north–south ridge.

• Result: the highest parts of the ridge rise above the sea as islands.

• Volcanic arc: some smaller islands are volcanic. They lie in a volcanic arc (a curved line of volcanoes that forms where one plate sinks under another) east of the main chain.

• Earthquake risk: the area sits on the fault (a crack in the crust where blocks of rock move) whose movement caused the 26 December 2004 tsunami [5].

Parts, channels and peaks

• Andaman group (north): North, Middle and South Andaman, Little Andaman, and others.
• Nicobar group (south): Car Nicobar, Little Nicobar, Great Nicobar, and others.
• Islet groups: Ritchie's archipelago and the Labyrinth islands, both near the Andaman group. An archipelago is a cluster of islands close together. An islet is a very small island.
• Channels, north to south:
• Duncan Passage lies between South Andaman and Little Andaman.
• Ten Degree Channel lies between Little Andaman and Car Nicobar. It is about 150 km wide, runs along 10°N and separates the Andaman group from the Nicobar group.

• Six Degree Channel lies between Great Nicobar and Sumatra (Indonesia). It links the Bay of Bengal and the Andaman Sea with the Strait of Malacca route.

• Peaks, highest to lowest:

• Saddle Peak, North Andaman, 738 m (the highest)
• Mount Thuiller, Great Nicobar, 642 m
• Mount Diavolo, Middle Andaman, 515 m
• Mount Koyob, South Andaman, 460 m

Volcanoes: Barren Island and Narcondam

• Barren Island is India's only active volcano.
• It is a stratovolcano [5]: a steep, cone-shaped volcano built of layers of lava, rock pieces and ash.
• It lies about 135 km north-east of Port Blair, in the Andaman Sea [4].
• The island is about 3 km wide. It has a 2 km-wide caldera on its western side [4][5]. A caldera is a large bowl-shaped hollow left when a volcano blows out or collapses. This one formed in an explosive eruption in the Pleistocene (the Ice Age period) [5].
• It stands 354 m above sea level but rises about 2,250 m from the sea floor [4]. So most of the volcano is under water.
• It is the only historically active volcano in the volcanic arc between Sumatra and Myanmar [4].

• Recent eruptions: on 24 August 2005, smoke drifted east over the Andaman Sea [5]. On 5 April 2006, it sent up a plume of ash and steam [4].

• Narcondam Island is dormant. It has not erupted in recorded history but could erupt again. It lies north-east of Barren Island, in the same arc.

Climate, vegetation and coasts

• Convectional rain (rain caused by hot air rising):
• The sun heats the land and sea strongly every day.
• Warm, moist air rises and cools, and its water vapour condenses into clouds.

• Rain falls almost every day, often in the afternoon.

• Why it happens here: the islands lie close to the equator and are surrounded by warm sea.

• Vegetation: equatorial forest, which is dense, evergreen and has many layers. More than 75% of the islands' area is under forest [2].
• Coasts: coral deposits and fine beaches.

Where it occurs

• Bay of Bengal, on India's eastern side, between 6°–14°N and 92°–94°E.
• Neighbours: the islands are closer to Myanmar (north) and Indonesia (Sumatra, south) than to the Indian mainland.
• Capital: Port Blair in South Andaman. The Cellular Jail is here, where the British held Indian freedom fighters.
• Barren Island and Narcondam: in the Andaman Sea, east of the main chain.
• Great Nicobar: India's southernmost island. Galathea Bay on this island is the site of the planned International Container Transhipment Terminal. Its planned capacity is 14.2 million TEU (one TEU is one standard 20-foot shipping container) [2].
• Galathea Bay is about 40 nautical miles from the East–West international shipping route, and its water is naturally more than 20 m deep [2][3].
• The Great Nicobar Island Development Project has been taken up since 2021 and is estimated to cost about ₹72,000 crore. It also includes a greenfield airport, a 450 MVA gas and solar power plant, and a township [2].

• Environmental clearance was given on 11 November 2022 [3], with 42 conditions [2].

• People of Great Nicobar: about 237 Shompen (hunter-gatherers and a PVTG, or Particularly Vulnerable Tribal Group) and about 1,094 Nicobarese (coastal fishing people) [2].

Don't confuse with

• Lakshadweep Islands: these are coral islands (atolls) in the Arabian Sea, about 36 of them, flat and low. The Andaman and Nicobar Islands are tectonic, number about 572, and are hilly with dense forest.
• Nine Degree and Eight Degree Channels: these are in the Arabian Sea (Lakshadweep). The Ten Degree Channel is in the Bay of Bengal and separates Little Andaman from Car Nicobar.
• Narcondam: it is dormant. Barren Island is the active one, India's only active volcano.
• Duncan Passage vs Ten Degree Channel: Duncan Passage lies inside the Andaman group (South Andaman–Little Andaman). The Ten Degree Channel lies between the Andaman and Nicobar groups.

Prelims Hooks

• Origin: raised tops of submarine mountains continuing the Arakan Yoma (tectonic, not coral).
• Barren Island: India's only active volcano, a stratovolcano about 135 km north-east of Port Blair [4][5]. Narcondam is dormant.
• Channels, north to south: Duncan Passage (South Andaman–Little Andaman) → Ten Degree Channel (Little Andaman–Car Nicobar) → Six Degree Channel (Great Nicobar–Sumatra).
• Peaks, highest to lowest: Saddle Peak (North Andaman, 738 m) > Mount Thuiller (Great Nicobar, 642 m) > Mount Diavolo (Middle Andaman, 515 m) > Mount Koyob (South Andaman, 460 m).
• Islet groups: Ritchie's archipelago and the Labyrinth islands lie near the Andaman group.
• Galathea Bay (Great Nicobar) is the planned transhipment port site, about 40 nautical miles from the East–West shipping route [2].

Mains Points

• Origin shapes the islands' features and risks (GS-I):
• They are the raised tops of a plate-boundary mountain chain.
• So they are hilly, large and forested, with volcanoes in places.

• They are also prone to earthquakes and tsunamis, as the 2004 tsunami showed [5].

• Strategic value (GS-I/III):

• The islands are India's "outposts" near the Six Degree Channel and the Malacca route, about 40 nautical miles from the East–West shipping lane [2].
• They extend India's Exclusive Economic Zone and naval reach.

• Today Indian cargo is transhipped (moved from one ship to another) at Colombo, Singapore and Klang. A deep-water port at Galathea Bay aims to reduce this dependence [2].

• Development vs ecology on Great Nicobar (GS-III):

• Costs: the project diverts 1.82% of the islands' forest cover, and up to 7.11 lakh trees may be cut. Compensatory afforestation (planting new forest to make up for lost forest) is planned in Haryana, far from the island. Of the project area, 84.10 sq km overlaps the tribal reserve [2]. Galathea Bay's beaches are also a nesting site for the leatherback turtle.
• Disaster risk: the island lies in a seismically sensitive and cyclone-prone zone [2], close to the fault behind the 2004 tsunami [5].
• Way forward: independent monitoring committees, tree felling in phases, and buildings designed to withstand disasters [2].

Related concepts

• Saddle Peak
• Ten Degree Channel
• Lakshadweep Islands
• Nine Degree Channel
• Eight Degree Channel
• Minicoy Island

Read more

• The Islands: Andaman and Nicobar, and Lakshadweep