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
Hjort Trench Hjort Trench The Hjort Trench is a linear topographic depression south of Macquarie Island in the southwest Pacific Ocean. Geologically, the depression is considered to be the seafloor expression of an ocean-ocean subduction zone, where the Australian plate is thrusting beneath the Pacific Plate. As the southernmost portion of the Macquarie Ridge Complex, the Hjort Trench lies in an area of diagonal convergence produced by the transform fault evolution of the Emerald Fracture Zone. Frequent seismic events, most less than 20 km deep, characterize the transpression along this plate boundary. The deepest point of Hjort trench is approximately 6.3 km