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White Cliffs Of DoverThe white cliffs of Dover, immortalized in popular song and verse (by Blur and others), are cliffs facing the Strait of Dover near the major port town of Dover, England, in the county of Kent. The cliff face, which reaches up to 350 feet high, owes its striking faade to its composition of chalk (pure white lime) accentuated by streaks of black flint. The cliffs trace their origins to the Cretaceous Period, approximately 136 million years ago, when the area between Britain in the west and Sweden/Poland in the east was submerged under deep tropical waters. Subjected to the great pressures of the sea, the emptied skeletons of coral, sponges and other small sea creatures turned to sediment and began to accumulate on the ocean floor. By approximately 70 million years ago, this process had formed a mass of silica-specked chalk covering huge areas between Britain and the Baltic Sea — white cliffs like those of Dover (but smaller) are also found on the Danish islands of Mon and Langeland or the coasts of the island of Rügen in Germany. The chalk layer used to lay high above sea level during the ice ages and in many places additionally was covered with glaciers. After the ice ages, they were exposed to the rising sea. Owing to the exceptional softness of chalk, tidal forces have since then significantly eroded this land mass away, in Dover to form the English Channel. The cliff face continues to erode at an average rate of one centimeter per year, although occasionally—most recently in 2001—large chunks of the edge, up to several meters at once, will fall into the channel with little warning. Visitors are therefore urged to remain at least five meters back from the edge. Behind the cliff face are miles of hidden tunnels that were built during the Dark Ages and later played a role in the defense of Britain during the Napoleonic Wars. Shakespeare Cliff marks the point where England most nearly approaches continental Europe. Many different kinds of birds nest on the cliff face, including colonies of kittiwake and peregrine falcon.
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