The high ground on each bank of the Humber Esstuary consists of the Yorkshire
and Lincolnshire Wolds of cretaceous chalk and, to the west, the low limestone
escarpment leading to Brough-on-Humber on the north and the Lincoln Edge southwards,
separated from the Wolds by the Ancholme River vally; the Edge is a much more
prominent feature than its northern counterpart. To east and west of this high
ground low-lying, and in olden days marshy, terrain surrounds the estuary and
the rivers which drain into it.
During the last Ice Age what is now the Humber Estuary formed part of 'Lake Humber' which was dammed by glacial moraine to the east and drained to the south along the Ancholme Valley. Later, the river cut a channel eastwards to the sea and the River Ancholme reversed its course and the present drainage system was formed.
After glacial retreat at the end of the last Ice Age a surface of barren Boulder Clay called till was left, trees began to grow and even today their roots can still be seen following cracks in the surface of the till.
A woodland of oak and alder grew up and fallen leaves and branches formed a layer of peat especially in the hollows, the deepest of which were waterlogged ponds containing many freshwater snails and other shells.
Rising sea-levels in Neolithic and Early Bronze Age times brought tidal salt water up the estuary, poisoning and drowning the woodland and leaving dead stools of trees on the bank. Sediment deposited by this incursion formed the silty estuarine clay with many marine shells that can be seen today
From very early Mesolithic times in the case of the Lincoln Edge, the Wolds and Jurassic escarpment have been heavily settled and used for overland communication. The estuary would have been a formidable barrier. Ferries crossing it were registed in the Domesday Book but evidence of much earlier crossings have been found..