The principal outlying islands include the North Sentinel, a dangerous island of about 73 km², lying about 29 km off the west coast of the South Andaman. About 29 km west of the Andamans are the dangerous Western Banks and Dalrymple Bank, rising to within a few fathoms of the surface of the sea and forming, with the two Sentinel Islands, the tops of a line of submarine hills parallel to the Andamans.

Andamans is the only place in India with an active volcano. Barren Island, northeast of Port Blair, became active in 1990s after being quiescent for almost two hundred years. It erupted again in May 2005, experts pointing to the post-tsunami change in tectonic plates as the likely cause. The isolated extinct volcano of Narcondam, rising 710 m out of the sea, is 114 km east of North Andaman. Plans are afoot to make volcano tourism popular.

Also 64 km to the east is the Invisible Bank, with one rock just awash, and 55 km southeast of Narcondam is a submarine hill rising to 689 m below the surface of the sea. Narcondam, Barren Island and the Invisible Bank, a great danger of these seas, are in a line almost parallel to the Andamans inclining towards them from north to south.