Most of Kakadu was under a shallow sea about 140 million years ago, with the escarpment wall formed from sea cliffs and Arnhem Land from a flat plateau above the sea. Currently the escarpment rises 330 metres above the plateau and stretches 500 kilometres along the East edge of the park and on into Arnhem Land. The escarpment varies from near vertical cliffs in the Jim Jim Falls area to isolated outliers and stepped cliffs in the North.