Archipelago extending from the Malay Peninsula to the Moluccas .
The islands make up most of the land area of Indonesia, with only northern and northwestern Borneo and the eastern portion of Timor not under Indonesian political control. They include the Greater Sunda Islands ( Sumatra , Java , Borneo, Sulawesi , and adjacent smaller islands) and the Lesser Sunda Islands ( Bali , Lombok , Sumbawa , Sumba , Flores, Timor, Alor, and adjacent smaller islands). Most of the islands are part of a geologically unstable and volcanically active island arc . Malay cultures and languages predominate in the area.