Geology of Indonesia active volcanoes formed Sumatra, Java, Bali, and Nusa Tenggara islands, most of which, particularly Java and Bali, emerged within the last 2–3 million years. The Pacific and Australian plate movements controlled the tectonics of the eastern portion of Indonesia. The tectonics processes in Indonesia formed major structures in Indonesia. The most prominent fault in the west of Indonesia is the Semangko Fault or the Great Sumatran Fault, a dextral strike-slip fault along Sumatra Island (about 1900 km). The formation of this fault zone is related to the subduction zone in the west of Sumatra. Palu-Koro fault is another major structural
Australia–Indonesia border westward from the point where the territorial waters of the two countries touch the western limits of East Timor's territorial waters claim at 10° 28' S, 126° 00' E, to 13° 05' 27.0" S, 118° 10' 08.9" E in the Indian Ocean. The third is between the Australian external territory of Christmas Island and the Indonesia island of Java, in the Indian Ocean. The boundary is established by four treaties, the fourth of which has been signed but not yet ratified. The Agreement between the Government of the Commonwealth of Australia and the Government of the Republic of Indonesia establishing