Far back in time, some 150 millions years ago, molten magma might have oozed from earth's crust along the dilated ocean floor at the foot of a submarine ridge. The phenomenon appears to have taken a long time thus creating mid-ocean rise known to many Geologists as 'whale back tumours'. These islands with a few expectations are volcanic in orgin. We are in fact at the tip of a risen undulating lava plateau, the core of which goes deep down beyond the ocean floor. This hypothesis is conformity with the expanding earth theory.
Source: Naval Marine Museum, Samudrika, Port Blair.