Geology of Indonesia

This is a brief summary of the geology of Indonesia.

The tectonics of Indonesia are very complex, as it is a meeting point of several tectonic plates. Indonesia is located between two continental plates: the Eurasian Plate (Sunda Plate) and Australian Plate (Sahul Shelf); and between two oceanic plates: the Philippine Sea Plate and Pacific Plate.

The subduction of the Indian oceanic plate beneath the Eurasian continental plate formed the volcanic arc in western Indonesia, one of the most seismically active areas on the planet with a long history of powerful eruptions and earthquakes. This chain of 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 feature formed in the central part of Indonesia. This fault runs across the central part of Sulawesi Island and extends offshore to the west across Makassar Strait and ends in the Mangkalihat Peninsula in Borneo. The fault is named after the capital city of Central Sulawesi, Palu, on the west coast of Sulawesi and the Koro River, which is formed by the fault zone.

Sorong fault is a significant left lateral fault in the eastern part of Indonesia, named after Sorong City. It has east-west orientation and extends from the northern part of West Papua to East Sulawesi for about 2000 km.

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