East Java also decided to join Indonesia. East Java province borders the Java Sea in the north, the Strait of Bali in the east, the Indian Ocean in the south, as well as the Central Java province in the west. The length of the east-west stretch of about 400 km. The width of the stretch of the north-south in the west about 200 km, but in the eastern part of narrower by about 60 km. Madura is the largest island in East Java, separated from the mainland Java by the Strait of Madura. Bawean Island is located about 150 km north of
Mariana Trench during the "Challenger" expedition in 1875, using a weighted rope, which recorded a depth of . In 1877, a map was published called "Tiefenkarte des Grossen Ozeans" ("Deep map of the Great Ocean") by Petermann, which showed a "Challenger Tief" ("Challenger deep") at the location of that sounding. In 1899, USS Nero, a converted collier, recorded a depth of . In 1951, "Challenger II" surveyed the trench using echo sounding, a much more precise and vastly easier way to measure depth than the sounding equipment and drag lines used in the original expedition. During this survey, the deepest part of