The narrow spine of the Hog's Back between Farnham and Guildford forms the western extremity of the North Downs, whilst the cliffs between Folkestone and Deal terminate the ridge in the east. The North Downs cuesta has a steep south-facing scarp slope and a more gentle north-facing dip slope. Its southern boundary is defined by the low-lying Vale of Holmesdale at the foot of the escarpment, in which the underlying stratum is primarily gault clay. The northern boundary is less apparent but occurs where the chalk submerges below the more recent Paleocene deposits.