Indonesia is located between the Australian and Asian continental mainland and divides
the Pacific and Indian Oceans at the Equator. It is an archipelago composed of some
13,670 islands, of which more than 7,000 are uninhabited. There are five main islands in
Indonesia. These are: Java, Sumatra, Kalimantan, Sulawesi and Irian Jaya. Almost 95
percent of the people live on those main islands, and more than 62 percent make their
Most of the islands of Indonesia are mountainous. The lowlands, with a few exceptions, are relatively small. Most of Indonesia's mountains are the products of mountain-building forces associated with the intersection of two blocks, or plates, of the Earth's crust ”the Pacific Plate and the Indian Ocean Plate, which meet in Indonesia. These plates have long been moving slowly into the Eurasian Plate. The resulting pressure pushed up mountain ranges and created the numerous volcanoes of Indonesia, the contorted shapes of islands like Celebes, and the ocean deeps, such as the Java Trench. This trench, located south of Java, is about 24,000 feet deep.
Indonesia has more than 60 active volcanoes. They are in a zone that runs mainly through
western Sumatra and its offshore islands, central and southern Java, Bali, and Lombok,
and into the Lesser Sunda Islands. This area of intense volcanic activity called the "ring
of fire." A smaller zone of volcanoes lies in the northern parts of Celebes and the
Moluccas. The nonvolcanic areas of western Indonesia are on a southerly extension of the
Eurasian landmass known as the Sunda Shelf. In eastern Indonesia, such nonvolcanic
areas are on the northerly extension of the Australian landmass called the Sahul Shelf.
The land areas of the shelves are alluvial lowlands or eroded uplands.
The soils of the volcanic uplands are relatively fertile. However, frequent eruptions of volcanoes in Java and Bali not only cause much loss of