Central Java ash makes Central Java highly fertile agriculture land. Paddy fields are extensive, except in the southeastern Gunung Kidul region partly due to the high concentration of limestone and its location in a rain shadow from the prevailing weather. The largest rivers are the Serayu in the west, which empties into the Indian Ocean, and the Solo which flows into East Java. On the eve of the World War II in 1942, Central Java was subdivided into 7 residencies (Dutch "residentie" or plural "residenties", Javanese "karésiḍènan" or "karésidhènan") which corresponded more or less with the main regions of this area. These
Romanche Trench the French navy ship "La Romanche", commanded by captain Louis-Ferdinand Martial which on 11 October 1883 made soundings that revealed the trench. The boat was coming to France after a few months scientific mission near cape Horn, part of the first International Polar Year. The trench has a depth of , is long and has an average width of and allows for a major circulation of deep ocean basin water from the west Atlantic to the east Atlantic basins. Deep water flow through the trench is from west to east with a rate of 3.6 Sverdrups (million m³/s) of water.