The fifth largest island of the Malay Archipelago, forming part of the Republic of Indonesia. It is situated between the Java Sea and the Indian Ocean and is separated from Sumatra on the west by Sunda Strait and from Bali on the east by Bali Strait. With an overall length of about 620 miles (1,000 km) and an average width of little more than 100 miles (160 km) in the west and east and about 60 miles (95 km) in the center, Java, with adjacent Madura, covers a total area of 52,009 square miles (134,703 sq km) and is thus by far the smallest of the five main islands of Indonesia.
The Land. Java, although relatively centrally placed in Indonesia, is distincdy untypical of it in several important respects. It has a much lower proportion of land above 1,000 feet (300 meters), and also of coastal swamps, than exists on the other main islands. Thus, uniquely, its most characteristic land forms are gently sloping surfaces, of between 300 and 2,000 feet (90-610 meters), associated with well-drained river valleys and the lower slopes of individual vol¬canoes. Furthermore, over all but the western third of the island the widespread volcanic soils are neutral-basic in character, and hence highly fertile.
And finally, in the same east-central area there is a distinct and very sunny dry season of about four months, which is particularly favorable for the ripening and harvesting of rice. These characteristics, which differentiate Java from the rest of the islands of Indonesia, enhance the island’s potential for producing food.
Over the entire length of the island the landscape cul¬minates in one or more of a series of great volcanoes, of which Semeru, 12,060 feet (3,676 meters) is the highest, Sumbing, 11,060 feet (3,371 meters) the most beautiful, and Kelud, 5,679 feet (1,731 meters) the most explosive. Except for three clusters, respectively forming the Priangan, Dieng, and Tengger plateaus in the west, center, and east, all the main volcanoes are well spaced out, and nearly all lie nearer to the southern than to the northern coast.
With the main water parting thus close to the Indian Ocean shore of the island, the majority of the larger rivers drain northward toward the Java Sea, although some, such as the Solo and Brantas, also flow for a considerable east-west distance^ Fringing the entire length of the northern shore is a contin¬uous and almost completely swamp-free coastal plain, most of it between 15 and 30 miles (24-48 km) wide; in marked contrast, much of the southern side of the island has little or no coastal plain.
In its primeval state most of Java was well forested, although true tropical rain forest predominated only in the western part, giving place eastward to less dense monsoon forest, which in turn degenerated into a much poorer covering over extensive limestone terrain, notably in southern Yogyakarta and parts of Madura. With the great population growth in Java beginning in the mid-19th century, two thirds of the island was brought under cultivation, and clearing for this and other forms of land use reduced the forest cover to the minimum necessary to preserve the ecological balance.
Thus, continuous stands of forest are now restricted mainly to the higher uplands, and any further inroads into these are apt to trigger off serious erosion, lead¬ing to the clogging of vital drainage and irrigation channels in the adjacent lowlands.