The blacksoil plains of the Top End are the product of thousands of years of erosion from the ancient landscape where the hills were once mountains of Everest proportion!  The soils are the particles from the hills and escarpments, that were once so much larger than they are today.  This erosion has worn down these rock formations and the rivers have moved the material to the lowlands where it forms the rich soils of the floodplains and coastal flats today.  These blacksoil plains are very productive as they contain many nutrients leached from the surrounding areas.  Recent research has also shown that algaes are a really important nutrition source and are driven by the floodwaters and the available nutrients and sunlight.  These alages are vital parts of the food chains in these systems.