Java and Bali to the east. Borneo lies to the north and Christmas Island is to the south. It is the world's 13th largest island. Java is surrounded by the Java Sea to the north, Sunda Strait to the west, the Indian Ocean to the south and Bali Strait and Madura Strait in the east. Java is almost entirely of volcanic origin; it contains thirty-eight mountains forming an east–west spine that have at one time or another been active volcanoes. The highest volcano in Java is Mount Semeru (). The most active volcano in Java and also in Indonesia is Mount
Geology of the Pacific Ocean as the Aleutian Arc off Alaska and the Kermadec-Tonga Subduction Zone north of New Zealand. As a result of the collision of the Nazca Plate and the South American Plate, the Andes Mountains emerged in western South America, close to the Peru–Chile Trench. Many large fracture zones aligned in an east-west direction, occur in the floor of the northeastern Pacific. The Pacific is a broad ocean basin (unlike the narrow Atlantic Ocean) and extends over a width of between New Guinea and Peru. The andesite line, a zone of intense volcanic and seismic activity, is a major regional distinction in