Greensand Ridge

West of the Weald the Lower Greensand has produced a more extensive area of hills and valleys, including the highest point in Sussex, Blackdown.

When fresh the rocks have a greenish colouration owing to the presence of glauconite, but on exposure to the atmosphere this is rapidly oxidised to limonite, giving rise to a yellow or reddish brown staining.

[6] Broadly speaking, the Greensand Ridge runs along the northern edge of the Weald in a west-east arc from Surrey into Kent, just south of and parallel to the chalk escarpment of the North Downs.

In some places the clay vale is very narrow: for example at Oxted the gap between summits of the Greensand Ridge and the North Downs is less than 2 kilometres (1.2 mi).

The Greensand Ridge, capped by the resistant sands and sandstones of the Hythe Beds, reinforced by bands of chert, rises steeply as a series of high, wooded escarpments between Gibbet Hill, Hindhead (272 metres (892 ft)), north of Haslemere, and the ridge's highest point, Leith Hill (294 metres (965 ft)).

In the area around Haslemere local anticlinal features are superimposed on the main axis of the Wealden anticline, causing the outcrop of resistant Hythe Beds to widen from 2 kilometres (1.2 mi) to more than 12 kilometres (7.5 mi) and to produce an escarpment that is particularly marked between Haslemere and Midhurst, where Blackdown rises to 280 metres (920 ft), the highest point in Sussex.

South of here the Vale of Fernhurst has been eroded down into the Low Weald by what is now a small stream following a line of a gentle west-east trending upfold.

Valley slope processes in the Vale of Fernhurst have resulted in escarpments to the north and south that are steep enough to have collapsed by land slipping.

Geology still confuses by using interchangeably the Weald and the "Wealden Anticline" that embraces all the land bounded by the chalk escarpments of the North and South Downs, including the Greensand hills.

[10] Principal settlements lying on the southern part of the Greensand in Sussex, adjacent to the South Downs, include Storrington (at the eastern end of the ridge) and Midhurst.

Settlements on the main part of the ridge, running from Surrey into Kent include Haslemere, Godalming, Reigate and Redhill, Oxted and Sevenoaks.

The route passes through or close to Godalming, Cranleigh, Dorking, Reigate, South Nutfield, Oxted, Westerham, Sevenoaks, Maidstone and Ashford.