Surrey is divided in two by the chalk ridge of the North Downs, running east-west. The ridge is pierced by Surrey's principal rivers, the Wey and the Mole, which are tributaries of the Thames, The River which constituted the northern border of the county before modern local government reorganisations. To the north of the Downs the land is mostly flat, forming part of the basin of the Thames.
The geology of this area is dominated by London Clay in the east, Bagshot Sands in the west and alluvial deposits along the rivers. To the south of the Downs in the western part of the county are the sandstone Surrey Hills, while further east is the plain of the Low Weald, rising in the extreme south-east to the edge of the hills of the High Weald. The Downs and the area to the south form part of a concentric pattern of geological deposits which also extends across southern Kent and most of Sussex, predominantly composed of Wealden Clay, Lower Greensand and the chalk of the Downs.
Much of Surrey is in the Metropolitan Green Belt. It contains a good deal of mature woodland (reflected in the official logo of Surrey County Council, a pair of interlocking oak leaves). Among its many notable beauty spots are Box Hill, Leith Hill, Frensham Ponds, Newlands Corner and Puttenham & Crooksbury Commons. Surrey is the most wooded county in England, with 22.4% coverage compared to a national average of 11.8% and as such is one of the few counties not to include new Woodlands in their strategic plans. Box Hill has the oldest untouched area of natural woodland in the UK, one of the oldest in Europe. Surrey also contains England's principal concentration of lowland heath, on sandy soils in the west of the county.