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
Mariana Trench poles than at the equator. As a result, parts of the Arctic Ocean seabed are at least closer to the Earth's centre than the Challenger Deep seafloor. In 2009, the Marianas Trench was established as a United States National Monument. Xenophyophores have been found in the trench by Scripps Institution of Oceanography researchers at a record depth of below the sea surface. On 17 March 2013, researchers from the Scottish Association for Marine Science reported data that suggested microbial life forms thrive within the trench. The Mariana Trench is named for the nearby Mariana Islands (in turn named Las Marianas