Mole Gap to Reigate Escarpment and there are well developed river cliffs where alluvial fans have diverted the River Mole against the valley sides. Mole Gap to Reigate Escarpment Mole Gap to Reigate Escarpment is a biological and geological Site of Special Scientific Interest west of Reigate in Surrey. It is a Geological Conservation Review site and a Special Area of Conservation. Part of it is a Nature Conservation Review site, Grade I. Two small private nature reserves in the site are managed by the Surrey Wildlife Trust, Dawcombe and Fraser Down. This eight mile long site on the North Downs contains an outstanding range
River Mole is thought to have merged with the River Wey near Byfleet and then flowed in a north-easterly direction via Richmond to meet the proto-Thames near Ware in Hertfordshire, (today the Mole and Wey are less than apart at their closest point near Painshill Park). During the Middle Pleistocene period, a large ice sheet built up across much of the East of England, reaching as far south as St Albans and Chelmsford, blocking the path of the proto-Thames. Glacial meltwater from the Anglian ice sheet, caused the Thames to divert southwards and flood the valley of the Mole–Wey river, thus adopting