The oceanic trench which marks the outer, deep edge of the E. Indies subduction zone, where the Indo-Australian Plate is subducting beneath the Eurasian Plate. The trench is about 6 km deep along Java, but becomes shallower to the north-west because of progressive infilling by Bengal Fan turbidites. There is an outer, non-volcanic arc, formed of an accretionary wedge, and a fore-arc basin.