Greensand Ridge

The Greensand Ridge is an extensive, prominent, often wooded, mixed greensand/sandstone escarpment in south-east England. It runs to and from the East Sussex coast, around the Weald, a former dense forest in Sussex, Surrey and Kent. It reaches its highest elevation, 294 metres (965 ft), at Leith Hill in Surrey—the second highest point in south-east England, while another hill in its range, Blackdown, is the highest point in Sussex at 280 metres (919 ft). The eastern end of the ridge forms the northern boundary of Romney Marsh.

The Greensand Ridge, formed of Lower Greensand, much of which is sandstone and where hardest is locally termed Bargate stone, is a remnant of the Weald dome, part of the great Weald-Artois Anticline that runs from south-east England into northern France.

The Weald dome consists of a series of geological strata laid down in the Cretaceous that have subsequently been lifted up, formed into a dome (i.e. anticline) and then deformed and faulted. The top-most and therefore youngest layer of the dome is Chalk, laid down in the Upper Cretaceous. Below it lie successively older strata of alternating clays and sandstones laid down in the Lower Cretaceous, namely Upper Greensand, Gault Clay, Lower Greensand, Weald Clay and the Hastings Beds. Differential fluvial erosion has virtually flattened the dome into a series of hills and vales. On the surface the strata of which the dome is composed crop out in a series of concentric circles, shaped like a horseshoe, with the more resistant chalk and sandstones forming hills and ridges (such as the North and South Downs, the Greensand Ridge, and the High Weald), and the weaker clays forming vales (such as the Low Weald) between them. The very resistant rocks of the Lower Greensand, in particular the Hythe Beds, have produced prominent escarpments that form an arc around the northern edge of the Low Weald, running parallel to and just south of the chalk escarpment of the North Downs. This stretch of the Greensand has become the most closely identified with the term "Greensand Ridge", and it includes the second highest point in south-east England, Leith Hill in Surrey. West of the Weald the Lower Greensand has produced a more extensive area of hills and valleys, including the highest point in Sussex, Blackdown. On the south side of the Weald the Lower Greensand also forms another arc of rather less pronounced hills parallel to and just north of the South Downs, which become less prominent the further east one goes.

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