Several species of cliff nesting birds nest on the cliff face, including fulmar and colonies of Black-legged Kittiwake. Visitors are, therefore, urged to remain well away from the cliff edge. A further large section collapsed into the English Channel on 15 March 2012.
This occurred in 2001, when a large chunk of the edge, as large as a football pitch, fell into the channel. The cliff face continues to weather at an average rate of 1 centimetre (0.39 in) per year, although occasionally large pieces will fall. In a 2005 poll of Radio Times readers, the cliffs were named as the third greatest natural wonder in Britain. White cliffs like those of Dover are also found on the Danish islands of Møn and Langeland and the island of Rügen in Germany. Flint and quartz are also found in the chalk. The cliffs are composed mainly of soft, white chalk with a very fine-grained texture, composed primarily of coccoliths, plates of calcium carbonate formed by coccolithophores, single-celled planktonic algae whose skeletal remains sank to the bottom of the ocean during the Cretaceous and, together with the remains of bottom-living creatures, formed sediments. Because crossing at Dover was the primary route to the continent before air travel, the white line of cliffs also formed the first or last sight of the UK for travellers. The cliffs have great symbolic value for Britain because they face towards Continental Europe across the narrowest part of the English Channel, where invasions have historically threatened and against which the cliffs form a symbolic guard. The cliffs spread east and west from the town of Dover in the county of Kent, an ancient and still important English port.
The cliff face, which reaches up to 107 metres (351 ft), owes its striking facade to its composition of chalk accentuated by streaks of black flint. The cliffs are part of the North Downs formation. The White Cliffs of Dover are cliffs which form part of the British coastline facing the Strait of Dover and France.