How were the Andaman and Nicobar Islands formed geologically?

The Andaman and Nicobar Islands are geologically significant as part of a vast island arc. They were formed as the above-sea extensions of submarine ridges, specifically connecting the Rakhine Mountains and the Patkai Range in the north to the Mentawai Ridge in the south.1

The islands are composed of sandstone, limestone, and shale that date to the Cenozoic Era, meaning they were formed within the last 65 million years. Structurally, the islands represent the peaks of a submerged mountain range that stretches approximately 620 miles (1,000 km) between Myanmar and the Indonesian island of Sumatra. This ridge system also serves as a boundary between the Bay of Bengal to the west and the Andaman Sea to the east. Additionally, the region is associated with the Sunda Trench, a seismically active area that underscores the ongoing geological dynamism of the region.123