entirely absent. In this area the long north-facing scarp of the South Downs and the longer south-facing scarp of the North Downs face one another across the Weald. For similar reasons, the Chalk is largely absent from the rather smaller area to the south of the Purbeck-Wight Monocline, save for the downs immediately north of Ventnor on the Isle of Wight. Some of the best exposures of the Chalk are where these ranges intersect the coast to produce dramatic, often vertical cliffs as at Flamborough Head, the White Cliffs of Dover, Seven Sisters, Old Harry Rocks (Purbeck) and The Needles on the Isle of Wight. The Chalk, which once extended across the English Channel, gives rise to similar cliff features on the French coast. Offshore and elsewhere Northern Ireland In the 'Ulster Cretaceous Province' of Northern Ireland the clastic-dominated Hibernian Greensands Group and the overlying Ulster White Limestone Group are the stratigraphical equivalents of the Chalk Group of England. They are best exposed near the Antrim coast. Scotland In the 'Scottish Chalk Province' (extending from Mull to Skye) the Inner Hebrides Group is the stratigraphical equivalent of England's Chalk Group. It comprises largely sandstones and mudstones though the Santonian age Gribun Chalk Formation of Mull and nearby Morvern is recognised. The Low Countries The Dutch () and Belgian () equivalents of the Chalk Group are basically continuous and crop out as a slightly northwest dipping monocline in a belt from the German city of Aachen to the city of Mons, where they join Cretaceous deposits of the Paris Basin. North of Namur the Cretaceous is overlain by younger Paleocene and Eocene deposits of the Landen Group. In the Low Countries, the Chalk Group succession is divided into five formations, from top to base: the Houthem Formation, consisting of Paleocene calcareous arenites; the Maastricht Formation, consisting of Maastrichtian chalk and calcareous arenites; the Gulpen Formation, consisting of Campanian to Maastrichtian chalk; the Vaals Formation, consisting of alternating Campanian clays, glauconiferous sands and silts; the Aachen Formation, consisting of Santonian glauconiferous sands and silts. In Belgium, the Houthem Formation is sometimes not included in the Chalk Group because it is not a Cretaceous formation. Some stratigraphers therefore prefer to put it in the lower Paleogene Hesbaye Group. The English Channel The Channel Tunnel linking England and France was constructed by tunnelling through the West Melbury Marly Chalk (formerly the 'Chalk Marl' -