Andaman and Nicobar Islands (Physical Geography)

These islands aren’t really islands. They’re the peaks of a mountain range that sank beneath the sea, with one peak still active enough to erupt.

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Indian Geography · IndGeo0031

Andaman & Nicobar: A Sunken Mountain Range

Bay of Bengal

Where the Arakan Yoma range’s higher ground vanished beneath the waves.

Andaman & Nicobar

The exposed ridge tops of that same submerged mountain range.

Barren Island

India’s only confirmed active volcano, fed by the same plate boundary.

572 islands

Only 38 permanently inhabited

Saddle Peak

Highest point, ~733 m

Ten Degree Channel

Splits Andaman from Nicobar

Same fault, different disaster

The same Indian–Burma plate boundary that raised these islands and fuels Barren Island’s volcano also triggered the 2004 tsunami that killed over 2,000 people here.

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Must Know

• The Andaman and Nicobar Islands form a chain of about 572 islands in the Bay of Bengal, of which only 38 are permanently inhabited.
• Geologically, they are the submerged extension of the Arakan Yoma mountain range of Myanmar. Only the highest ridges stay above the sea.
• They sit where the Indian plate is being pushed under the Burma microplate, a convergent tectonic boundary.
• The Ten Degree Channel separates the Andaman group in the north from the Nicobar group in the south.
• Saddle Peak, on North Andaman, is the group’s highest point at about 733 metres.

Good to Know

• Barren Island, in the Andaman group, holds India’s only confirmed active volcano.
• That volcanic activity comes from the same plate boundary that pushed the islands up in the first place.
• This origin sets the Andaman and Nicobar Islands apart from Lakshadweep, which formed from coral growth on a submerged plateau, not a sunken mountain range.
• The Nicobar Islands, further south, continue the same underwater ridge system that runs on toward Sumatra’s Mentawai Islands.

Test Yourself

Please wait…

1. Geologically, the Andaman and Nicobar Islands are best described as what?

The submerged extension of the Arakan Yoma mountain range of Myanmar

A coral atoll built up on a submerged plateau

A cluster of volcanic islands unrelated to any mainland range

A delta formation built by Bay of Bengal river silt

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Great to Know

• The same tectonic collision that raised these islands also makes them highly earthquake-prone.
• On 26 December 2004, an undersea megathrust earthquake off Sumatra sent a tsunami into the islands, over 2,000 people died, and roughly 40,000 were left homeless.
• In the southern Nicobar Islands, the tsunami reached heights of up to 15 metres.
• That earthquake also permanently shifted parts of the islands’ coastline, sinking some areas and raising others.
• For how this physical setting shapes the islands’ vegetation, see IndGeo0132 — Forest Ecology of the Andaman and Nicobar Islands.