The Geology of Indonesia/Plate Tectonic
Indonesia is a meeting place of two tectonic plates, Indo-Australian_Plate and Eurasia (Sunda Plate). The Australian plate was moved northward and subducted under the Eurasian plate. The subduction zone can be traced from northern tip of Sumatra until the Lesser Islands, that creates deep submarine trench. Most of the earthquake also concentrate in this subduction zone. This subduction also trigger the formation of volcanic range from Sumatra, Java to Lesser Islands.
The center part of Indonesia also experienced another subduction of Pacific plate that move southwesterly under the Eurasian plate. This subduction create the formation of volcanoes in the North Sulawesi, Sangihe and Halmahera.
The Australian and Pacific plate collides in the eastern part of Indonesia and formed the mountain range in Papua, with Puncak Jaya / Carstenz Pyramide as the highest peak.
Below is a regional cross section of Indonesia from west to east showing the relationship of the tectonic components of Indonesia, their depth, and structural features.