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
Christianity in Indonesia East Nusa Tenggara, and North Sulawesi. Among Indonesian provinces in 2010, Sumatra's northern-most province, Aceh, reported the fifth-smallest number of Christians (53,624) or 0.23% of Christians within Indonesia. Aceh had the second-smallest percentage (among religions reported in the province) of Christians (1.19%), effectively tying with Gorontalo for the smallest percentage of Catholics (0.07%) and including the third-smallest percentage of Protestants (1.12%). Aceh operates Sharia law and all regencies are 99%+ Muslim, with the exception of Aceh Singkil (11.2% Christian) and Southeast Aceh (18.7% Christian). Both areas' Christian populations consist of ethnic groups whose homelands lie outside Aceh—in Aceh Singkil, Christians