岛屿是巽他俯冲系统的吸积楔形(外弧)的一个暴露部分，印度板块俯冲到巽他板块之下。以沉积物为主的增生楔体的持续抬升，在相对较小的范围内暴露出与俯冲杂岩有关的各种岩石类型(蛇绿岩肢解、火山弧岩、沟坡沉积、海底扇浊积岩、上层沉积物以及陆架和礁礁环境的沉积物)，使其成为研究俯冲过程的理想区域。< / p >

(Unfortunately, other chapters with more detailed descriptions are not open access.)

Note that if some of the sediments are indeed volcanic in origin, it does not mean that volcanism is responsible for building the archipelago, like it was for the Chagos-Laccadives ridge for instance, to stay around India. It is the accretion of sediments in the subduction trench, and their subsequent uplift above the sea, that created the islands.