Geology of Indonesia

 Sumatra, Java, Madura, and Kalimantan lie on the Sunda Shelf and geographers have conventionally grouped them, (along with Sulawesi), as the Greater Sunda Islands. At Indonesia's eastern extremity is western New Guinea, which lies on the Sahul Shelf. Sea depths in the Sunda and Sahul shelves average 200 metres (656 ft) or less. Between these two shelves lie Sulawesi, Nusa Tenggara (also known as the Lesser Sunda Islands), and the Maluku Islands (or the Moluccas), which form a second island group where the surrounding seas in some places reach 4,500 metres (14,764 ft) in depth. The term "Outer Islands" is used inconsistently by various writers but it is usually taken to mean those islands other than Java and Madura.