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49-512: Marl makes up the lower part of the cliffs of Dover , and the Channel Tunnel follows these marl layers between France and the United Kingdom. Marl is also a common sediment in post- glacial lakes , such as the marl ponds of the northeastern United States. Marl has been used as a soil conditioner and neutralizing agent for acid soil and in the manufacture of cement . Marl or marlstone is

98-541: A carbonate -rich mud or mudstone which contains variable amounts of clays and silt . The term was originally loosely applied to a variety of materials, most of which occur as loose, earthy deposits consisting chiefly of an intimate mixture of clay and calcium carbonate , formed under freshwater conditions. These typically contain 35–65% clay and 65–35% carbonate. The term is today often used to describe indurated marine deposits and lacustrine (lake) sediments which more accurately should be named 'marlstone'. Marlstone

147-500: A campaign for donations to buy 170 acres (0.7 km ) 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

196-443: 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 ropes over the cliff's edge. Shakespeare mentions rock samphire in his play King Lear and includes

245-541: 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 (1,600 ft) of sediments were deposited in some areas. The weight of overlying sediments caused

294-489: 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

343-451: 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 name Albion , an ancient or poetic term referring to Great Britain ,

392-400: 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". Fan Bay Deep Shelter is a series of tunnels constructed during World War II. The tunnels were opened to

441-549: 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

490-531: 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. During the Late Cretaceous , between 100 million and 66 million years ago, Great Britain and much of Europe were submerged under

539-424: A very low permeability , they have been exploited for construction of the Channel Tunnel between England and France and are being investigated for the storage of nuclear waste . Marl is one of the oldest soil amendments used in agriculture. In addition to increasing available calcium, marl is valuable for improving soil structure and decreasing soil acidity and thereby making other nutrients more available. It

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588-466: 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

637-534: 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. Further large sections collapsed on 15 March 2012, 4 February 2020, and on 3 February 2021. The chalk grassland environment above

686-588: Is a 10-mile-long (16 km) sandbank at the southern end of the North Sea lying six miles (10 km) off the Deal coast. The area consists of a layer of fine sand approximately 82 ft (25 m) deep resting on a chalk platform belonging to the same geological feature that incorporates the White Cliffs of Dover. More than 2,000 ships are believed to have been wrecked on the Goodwin Sands because they lie close to

735-413: Is an indurated (resists crumbling or powdering) rock of about the same composition as marl. This is more correctly described as an earthy or impure argillaceous limestone . It has a blocky subconchoidal fracture, and is less fissile than shale . The dominant carbonate mineral in most marls is calcite , but other carbonate minerals such as aragonite or dolomite may be present. Glauconitic marl

784-706: Is closest to continental Europe , on a clear day the cliffs are visible from France, approximately 20 miles (32 km) away. A celebrated UK landmark, the cliffs have featured on commemorative postage stamps issued by the Royal Mail , including in their British coastline series in 2002 and UK A-Z series in 2012. The cliffs are part of the coastline of Kent in England between approximately 51°06′N 1°14′E  /  51.100°N 1.233°E  / 51.100; 1.233 and 51°12′N 1°24′E  /  51.200°N 1.400°E  / 51.200; 1.400 , at

833-422: Is easily recognizable in core samples and helped establish the right level for excavating the tunnel. Marl soil has poor engineering properties, particularly when alternately wetted and dried. The soils can be stabilized by adding pozzolan ( volcanic ash ) to the soil. Some marl beds have a very low permeability and are under consideration for use in the storage of nuclear waste . One such proposed storage site

882-554: Is marl containing pellets of glauconite , a clay mineral that gives the marl a green color. Glauconite is characteristic of sediments deposited in marine conditions. The lower stratigraphic units of the chalk cliffs of Dover consist of a sequence of glauconitic marls followed by rhythmically banded limestone and marl layers. Such alternating cycles of chalk and marl are common in Cretaceous beds of northwestern Europe. The Channel Tunnel follows these marl layers between France and

931-633: Is the Wellenberg in central Switzerland. A marl lake is a lake whose bottom sediments include large deposits of marl. They are most often found in areas of recent glaciation and are characterized by alkaline water, rich in dissolved calcium carbonate, from which carbonate minerals are deposited. Marl lakes have frequently been dredged or mined for marl, often used for manufacturing Portland cement . However, they are regarded as ecologically important, and are vulnerable to damage by silting , nutrient pollution , drainage , and invasive species . In Britain, only

980-639: The Late Cretaceous . The cliffs, on both sides of the town of Dover in Kent , stretch for eight miles (13 km). The White Cliffs of Dover form part of the North Downs . A section of coastline encompassing the cliffs was purchased by the National Trust in 2016. The cliffs are part of the Dover to Kingsdown Cliffs Site of Special Scientific Interest and Special Area of Conservation . The point where Great Britain

1029-480: 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

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1078-540: 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

1127-488: 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. 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

1176-462: The 18th century. The marl was normally extracted close to its point of use, so that almost every field had a marl pit, but some marl was transported greater distances by railroad. However, marl was gradually replaced by lime and imported mineral fertilizers early in the 19th century. A similar historical pattern was seen in Scotland. Marl was one of a few soil amendments available in limited quantities in

1225-411: 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

1274-639: 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. South Foreland Lighthouse is a Victorian-era lighthouse on the South Foreland in St. Margaret's Bay , which was once used to warn ships approaching the nearby Goodwin Sands . Goodwin Sands

1323-580: The United Kingdom. Upper Cretaceous cyclic sequences in Germany and marl– opal -rich Tortonian - Messinian strata in the Sorbas Basin related to multiple sea drawdown have been correlated with Milankovitch orbital forcing. Marl as lacustrine sediment is common in post- glacial lake -bed sediments. Chara , a macroalga also known as stonewort, thrives in shallow lakes with high pH and alkalinity , where its stems and fruiting bodies become calcified. After

1372-477: The alga dies, the calcified stems and fruiting bodies break down into fine carbonate particles that mingle with silt and clay to produce marl. Marl ponds of the northeastern United States are often kettle ponds in areas of limestone bedrock that become poor in nutrients ( oligotrophic ) due to precipitation of essential phosphate . Normal pond life is unable to survive, and skeletons of freshwater molluscs such as Sphaerium and Planorbis accumulate as part of

1421-589: The bottom marl. In Hungary, Buda Marl is found that was formed in the Upper Eocene era. It lies between layers of rock and soil and may be defined it as both "weak rock and strong soil." Marl is the dominant rock type in the Vaca Muerta Formation in Argentina. Marl has been used as a soil conditioner and neutralizing agent for acid soil and in the manufacture of Portland cement . Because some marls have

1470-591: 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

1519-405: 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

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1568-463: The cliffs is excellent 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

1617-554: 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

1666-468: 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 in the 1740s as the development of heavy artillery made capturing ports an important part of warfare. During

1715-629: 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 ,

1764-443: 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

1813-411: 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

1862-461: 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. 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)

1911-600: The major shipping lanes through the Straits of Dover . It went out of service in 1988 and is now owned by the National Trust for Places of Historic Interest or Natural Beauty . The cliffs have great symbolic value in Britain because they face towards continental Europe across the narrowest part of the English Channel (approximately 20 miles (32 km) between coasts), where invasions have historically threatened and against which

1960-571: The manufacture of Portland cement. It is abundant and yields better physical and mechanical properties than metakaolin as a supplementary cementitious material and can be calcined at a considerably lower temperature. The Channel Tunnel was constructed in the West Melbury Marly Chalk, a geological formation containing marl beds. This formation was chosen because of its very low permeability, absence of chert , and lack of fissures found in overlying formations. The underlying Glauconitic Marl

2009-483: The marl lakes of the more remote parts of northern Scotland are likely to remain pristine into the near future. White cliffs of Dover The White Cliffs of Dover are the region of English coastline facing the Strait of Dover and France. The cliff face, which reaches a height of 350 feet (110 m), owes its striking appearance to its composition of chalk accented by streaks of black flint , deposited during

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2058-573: The point where Great Britain is closest to continental Europe – the Strait of Dover is approximately 20 miles (32 km) across. On a clear day the cliffs 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

2107-491: The reduced content of calcium carbonate versus straight lime, expressed as the calcium carbonate equivalent. Because the carbonate in marl is predominantly calcium carbonate, magnesium deficiency may be seen in crops treated with marl if they are not also supplemented with magnesium. Marl has been used in Pamlico Sound to provide a suitable artificial substrate for oysters in a reef-like environment. Marl has been used in

2156-535: The southern United States, where soils were generally poor in nutrients, prior to about 1840. By the late 19th century, marl was being mined on an industrial scale in New Jersey and was increasingly being used on a more scientific basis, with marl being classified by grade and the state geological survey publishing detailed chemical analyses. Marl continues to be used for agriculture into the 21st century, though less frequently. The rate of application must be adjusted for

2205-526: 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

2254-507: Was derived from the Latin albus (meaning 'white') as an allusion to the white cliffs. 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

2303-446: Was named in honour of Dame Vera Lynn. 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,

2352-467: Was opened. In 1999, a new gallery on the second floor centred on the Dover Bronze Age Boat was opened. 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

2401-584: Was used sporadically in Britain beginning in prehistoric times and its use was mentioned by Pliny the Elder in the 1st century. Its more widespread use from the 16th century on contributed to the early modern agricultural revolution. However, the lack of a high-energy economy hindered its large-scale use until the Industrial Revolution . Marl was used extensively in Britain, particularly in Lancashire , during

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