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
Oceanic trench was not recognized until well into the 20th century. The term “trench” does not appear in Murray and Hjort’s (1912) classic oceanography book. Instead they applied the term “deep“ for the deepest parts of the ocean, such as Challenger Deep. Experiences from World War I battlefields emblazoned the concept of a trench as an elongate depression defining an important boundary, perhaps leading to the term “trench” being used to describe natural features in the early 1920s. The term was first used in a geologic context by Scofield two years after the war ended to describe a structurally controlled depression in