The back-arc deformation may be either extensional or compressional. The overriding plate will shorten when its motion is directed towards the trench, resulting in a compression of the back-arc region.[5] This type of deformation is associated with a shallow dipping subducted slab.[5] Inversely, an overriding plate moving away from the trench will result in extension, and a back-arc basin will form.[5] This extensional deformation is associated with a steeply dipping slab.[5]