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הצוקים הלבנים הם צוקים שנמצאים בחופה הדרום-מזרחי של בריטניה הגדולה מול מצר דובר. שמם של הצוקים נובע מסלעי הקירטון מהם עשוים הצוקים, המודגשות על ידי אבן צור שחורה. הצוקים נמצאים במחוז קנט ליד עיר הנמל החשובה דובר.

לצוקים ערך סמלי בממלכה המאוחדת כי הם נמצאים מול החלק הצר ביותר של תעלת למאנש, הוא מצר דובר, ובסביבתם נחתו במהלך ההיסטוריה פולשים שניסו לכבוש את אנגליה.

מיקום

The cliffs are part of the coastline of Kent in England between approximately 51°06′N 1°14′E and 51°12′N 1°24′E, at the point where Great Britain is closest to continental Europe. On a clear day they are visible from the French coast. The chalk cliffs of the Alabaster Coast of Normandy in France are part of the same geological system.

The White Cliffs are at one end of the Kent Downs designated Area of Outstanding Natural Beauty. In 1999 a sustainable National Trust visitor centre was built in the area. The Gateway building, designed by van Heyningen and Haward Architects, houses a restaurant, an information centre on the work of the National Trust, and details of local archaeology, history and landscape.

גיאולוגיה

During the Late Cretaceous, between 100 and 66 million years ago, Great Britain and much of Europe were submerged under a great sea. The sea bottom was covered with white mud formed from fragments of coccoliths, the skeletons of tiny algae that floated in the surface waters and sank to the bottom and, together with the remains of bottom-living creatures, formed muddy sediments. It is thought that the sediments were deposited very slowly, probably half a millimetre a year, equivalent to about 180 coccoliths piled one on top of another. Up to 500 metres of sediments were deposited in some areas. The weight of overlying sediments caused the deposits to become consolidated into chalk. British chalk deposits are considered stratigraphically to belong in the Chalk Group.

Due to the Alpine orogeny, a major mountain building event during the Cenozoic, the sea-floor deposits were raised above sea level. Until the end of the last glacial period, the British Isles were part of continental Europe, linked by the unbroken Weald-Artois Anticline, a ridge that acted as a natural dam to hold back a large freshwater pro-glacial lake, now submerged under the North Sea. The land masses remained connected until between 450,000 and 180,000 years ago when at least two catastrophic glacial lake outburst floods breached the anticline and destroyed the ridge that connected Britain to Europe. A land connection across the southern North Sea existed intermittently at later times when periods of glaciation resulted in lower sea levels. At the end of the last glacial period, around 10,000 years ago, rising sea levels finally severed the last land connection.

The cliffs' chalk face shows horizontal bands of dark-coloured flint which is composed of the remains of sea sponges and siliceous planktonic micro-organisms that hardened into the microscopic quartz crystals. Quartz silica filled cavities left by dead marine creatures which are found as flint fossils, especially the internal moulds of Micraster echinoids. Several different ocean floor species such as brachiopods, bivalves, crinoids, and sponges can be found in the chalk deposits, as can sharks' teeth.

In some areas, layers of soft, grey chalk known as a hardground complex can be seen. Hardgrounds are thought to reflect disruptions in the steady accumulation of sediment when sedimentation ceased and/or the loose surface sediments were stripped away by currents or slumping, exposing the older hardened chalk sediment. A single hardground may have been exhumed 16 or more times before the sediments were compacted and hardened (lithified) to form chalk.

Cliff erosion and change

Thousands of years ago, the cliffs were eroding at 20–60 mm (0.75–2.3 in) a year. Research shows that the erosion rate over the last 150 years has increased to 220–320 mm (8.7–12.6 in) a year, and that the erosion is caused by the loss of beach underneath the cliffs exacerbated by stronger storms and human activity such as gravel extraction. Despite this, the cliffs are expected to survive for tens of thousands of years more.

In 2001, a large chunk of the cliff edge, as large as a football pitch, fell into the Channel. Another large section collapsed on 15 March 2012, another on 4 February 2020, and another on 3 February 2021.

אקולוגיה

The chalk grassland environment above the cliffs provides an excellent environment for many species of wild flowers, butterflies and birds, and has been designated a Special Area of Conservation and a Site of Special Scientific Interest. Rangers and volunteers work to clear invasive plants that threaten the native flora. A grazing programme involving Exmoor ponies has been established to help to clear faster-growing invasive plants, allowing smaller, less robust native plants to survive. The ponies are managed by the National Trust, Natural England, and County Wildlife Trusts to maintain vegetation on nature reserves.

The cliffs are the first landing point for many migratory birds flying inland from across the English Channel. After a 120-year absence, in 2009 it was reported that ravens had returned to the cliffs. Similar in appearance but smaller, the jackdaw is abundant. The rarest of the birds that live along the cliffs is the peregrine falcon. In recent decline, the skylark also makes its home on the cliffs. The cliffs are home to fulmars and to colonies of black-legged kittiwake, a species of gull. Since bluebirds are not indigenous to the UK, some believe that bluebirds, as mentioned in the classic World War II song "(There'll Be Bluebirds Over) The White Cliffs of Dover", composed by American artists, may actually refer to swallows and/or to house martins, which make an annual migration to continental Europe, many of them crossing the English Channel at least twice a year.

Among the wildflowers are several varieties of orchids, the rarest of which is the early spider orchid, which has yellow-green to brownish green petals and looks like the body of a large spider. Rock samphire is an edible, salt tolerant succulent plant that grows on the cliff's slopes. The oxtongue broomrape is an unusual plant that lives on the roots of a host plant. It has yellow, white, or blue snapdragon-like flowers and about 90 per cent of the UK's population is found on the cliffs. Viper's-bugloss, a showy plant in vivid shades of blue and purple with red stamens, also grows along the cliffs.

The abundance of wildflowers provides homes for about thirty species of butterfly. The rare Adonis blue can be seen in spring and again in autumn. Males have vibrant blue wings lined with a white margin, whereas the females are a rich chocolate brown. This species' sole larval food plant is the horseshoe vetch and it has a symbiotic relationship with red or black ants. The eggs are laid singly on very small foodplants growing in short turf. This provides a warm microclimate, suitable for larval development, which is also favoured by ants. The caterpillar has green and yellow stripes to provide camouflage while it feeds on vetch. The ants milk the sugary secretions from the larval "honey glands" and, in return, protect the larvae from predators and parasitoids, even going so far as to bury them at night. The larvae pupate in the upper soil, and continue to be protected by the ants, often in their nests, until the adults emerge in the spring or autumn.

Similar in appearance, but more abundant, is the chalkhill blue, a chalk grassland specialist that can be seen in July and August. Threatened species include the silver-spotted skipper and straw belle. The well-known red admiral can be seen from February until November. The marbled white, black and white with a white wing border, can be seen from June to August.

היסטוריה

A possible Iron Age hillfort has been discovered at Dover, on the site of the later castle. The area was also inhabited during the Roman period, when Dover was used as a port. A lighthouse survives from this era, one of a pair at Dover which helped shipping navigate the port. It is likely the area around the surviving lighthouse was inhabited in the early medieval period as archaeologists have found a Saxon cemetery here, and the church of St Mary in Castro was built next to the lighthouse in the 10th or 11th century.

It is thought that the Old English name for Britain, Albion, was derived from the Latin albus (meaning 'white') as an allusion to the white cliffs.

Dover Castle

Dover Castle, the largest castle in England, was founded in the 11th century. It has been described as the "Key to England" owing to its defensive significance throughout history. The castle was founded by William the Conqueror in 1066 and rebuilt for Henry II, King John, and Henry III. This expanded the castle to its current size, taking its curtain walls to the edge of the cliffs. During the First Barons' War the castle was held by King John's soldiers and besieged by the French between May 1216 and May 1217. The castle was also besieged in 1265 during the Second Barons' War. In the 16th century, cannons were installed at the castle, but it became less important militarily as Henry VIII had built artillery forts along the coast. Dover Castle was captured in 1642 during the Civil War when the townspeople climbed the cliffs and surprised the royalist garrison, giving a symbolic victory against royal control. Towards the end of the war many castles were slighted, but Dover was spared.

The castle had renewed importance from the 1740s as the development of heavy artillery made capturing ports an important part of warfare. During the Napoleonic Wars, in particular, the defences were remodelled and a series of tunnels were dug into the cliff to act as barracks, adding space for an extra 2,000 soldiers. The tunnels mostly lay abandoned until the Second World War.

Second World War

The cliffs have great symbolic value in 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 National Trust calls the cliffs "an icon of Britain", with "the white chalk face a symbol of home and wartime defence." Because crossing at Dover was the primary route to the continent before the advent of air travel, the white line of cliffs also formed the first or last sight of Britain for travellers. During the Second World War, thousands of allied troops on the little ships in the Dunkirk evacuation saw the welcoming sight of the cliffs. In the summer of 1940, reporters gathered at Shakespeare Cliff to watch aerial dogfights between German and British aircraft during the Battle of Britain.

Vera Lynn, known as "The Forces' Sweetheart" for her 1942 wartime classic "(There'll Be Bluebirds Over) The White Cliffs of Dover" celebrated her 100th birthday in 2017. That year she led a campaign for donations to buy 170 acres (0.7 km²) of land atop Dover's cliffs when it was feared that they might be sold to developers; the campaign met its target after only three weeks. The National Trust, which owns the surrounding areas, plans to return the land to a natural state of chalk grassland and preserve existing military structures from the Second World War. In June 2021, a wildflower meadow on White Cliffs of Dover was named in honour of Dame Vera Lynn.

אתרי עניין

Dover Museum

Dover Museum was founded in 1836. Shelled from France in 1942 during the Second World War, the museum lost much of its collections, including nearly all its natural history collections. Much of the surviving material was left neglected in caves and other stores until 1946. In 1948 a temporary museum was opened and in 1991 a new museum of three storeys, built behind its original Victorian façade, was opened. In 1999, a new gallery on the second floor centred on the Dover Bronze Age Boat was opened.

Samphire Hoe Country Park

Samphire Hoe Country Park is a nature reserve on a new piece of land created from the rock excavated during the construction of the Channel Tunnel. It covers a 74-acre (30 ha) site at the foot of Shakespeare Cliff, between Dover and Folkestone. There is an education shelter with a classroom and exhibition area. Staff and volunteers are available to answer questions and provide information about the wildlife in the reserve. The building's design incorporates eco-construction criteria. The nature reserve is named after the edible plant rock samphire, which grows on the cliffs and used to be gathered by hanging from ropes over the cliff's edge. Shakespeare mentions rock samphire in his play King Lear and includes a reference to this trade with the lines "Half-way down / Hangs one that gathers samphire; dreadful trade!" (Act IV, Scene VI Lines 14–15). This refers to the dangers involved in collecting rock samphire on sea cliffs. Shakespeare Cliff was named after the reference to this "dreadful trade".