33-693: The River Lydden is a 15.25 miles (24.55 km) tributary of the River Stour that flows through Blackmore Vale in Dorset , England. Its headwaters rise at the foot of the scarp slope of the Dorset Downs near Buckland Newton . These headwaters streams coalesce south of Pulham , from where the river flows north-east to it confluence with the Wonston Brook. Continuing in a northerly direction it passes King’s Stag, to Twoford bridge where it
66-447: A phosphate mineral) is also sometimes present, as nodules or as small pellets interpreted as fecal pellets. In some chalk beds, the calcite has been converted to dolomite , CaMg(CO 3 ) 2 , and in a few cases the dolomitized chalk has been dedolomitized back to calcite. Chalk is highly porous, with typical values of porosity ranging from 35 to 47 per cent. While it is similar in appearance to both gypsum and diatomite , chalk
99-642: Is mined from chalk deposits both above ground and underground . Chalk mining boomed during the Industrial Revolution , due to the need for chalk products such as quicklime and bricks . Most people first encounter chalk in school where it refers to blackboard chalk , which was originally made of mineral chalk, since it readily crumbles and leaves particles that stick loosely to rough surfaces, allowing it to make writing that can be readily erased. Blackboard chalk manufacturers now may use mineral chalk, other mineral sources of calcium carbonate, or
132-469: Is also used for " blackboard chalk " for writing and drawing on various types of surfaces, although these can also be manufactured from other carbonate-based minerals, or gypsum . Chalk is a fine-textured, earthy type of limestone distinguished by its light colour, softness, and high porosity. It is composed mostly of tiny fragments of the calcite shells or skeletons of plankton , such as foraminifera or coccolithophores . These fragments mostly take
165-428: Is applied to the hands and feet to remove perspiration and reduce slipping. Chalk may also be used as a house construction material instead of brick or wattle and daub : quarried chalk was cut into blocks and used as ashlar , or loose chalk was rammed into blocks and laid in mortar. There are still houses standing which have been constructed using chalk as the main building material. Most are pre- Victorian though
198-518: Is commonly used as a drying agent to obtain better grip by gymnasts and rock climbers. Glazing putty mainly contains chalk as a filler in linseed oil . Chalk and other forms of limestone may be used for their properties as a base . Chalk is a source of quicklime by thermal decomposition , or slaked lime following quenching of quicklime with water. In agriculture , chalk is used for raising pH in soils with high acidity . Small doses of chalk can also be used as an antacid . Additionally,
231-618: Is crossed by the A357 between Lydlinch and Bagber , beyond which it meets its main tributary the Caundle Brook . The lower Lydden then flows beneath the listed Bagber Bridge where it is crossed by a minor road, to join the Stour near King’s Mill south west of Marnhull . River Stour, Dorset The River Stour is a 61 mi (98 km) river which flows through Wiltshire and Dorset in southern England , and drains into
264-467: Is famous for its water mill and town bridge, which still bears the notice warning potential vandals that damaging the bridge is punishable by penal transportation . The river flows through a myriad of differing settings and scenery ( reed bed , open water, coastal, estuarine, river, streams, lowland heath) and as such is host to species such as the pipistrelle bat , harbour porpoise , great crested newt , medicinal leech , Desmoulin's whorl snail and
297-515: Is identifiable by its hardness, fossil content, and its reaction to acid (it produces effervescence on contact). In Western Europe, chalk was formed in the Late Cretaceous Epoch and the early Palaeocene Epoch (between 100 and 61 million years ago). It was deposited on extensive continental shelves at depths between 100 and 600 metres (330 and 1,970 ft), during a time of nonseasonal (likely arid) climate that reduced
330-522: Is navigable as far upstream as Tuckton (the tidal limit) and whilst there is a low bridge at Iford, it is possible to navigate as far as the rapids which are 0.9 miles (1.5 km) upstream of Iford Bridge. Spring tides have been known to penetrate a further 0.9 miles (1.5 km) upstream, as far as Blackwater Bridge (the A338 road ). Boats can be hired from several yards and landings in the harbour and estuary area with kayaking and canoeing being popular on
363-582: Is now usually made of talc (magnesium silicate). Chalk beds form important petroleum reservoirs in the North Sea and along the Gulf Coast of North America. In southeast England, deneholes are a notable example of ancient chalk pits. Such bell pits may also mark the sites of ancient flint mines, where the prime object was to remove flint nodules for stone tool manufacture. The surface remains at Cissbury are one such example, but perhaps
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#1732772058166396-645: The Cretaceous Period was named for these deposits. The name Cretaceous was derived from Latin creta , meaning chalk . Some deposits of chalk were formed after the Cretaceous. The Chalk Group is a European stratigraphic unit deposited during the late Cretaceous Period. It forms the famous White Cliffs of Dover in Kent , England, as well as their counterparts of the Cap Blanc Nez on
429-644: The English Channel . The catchment area for the river and its tributaries is listed as 480 square miles (1,240 km ). It is sometimes called the Dorset Stour to distinguish it from other rivers of the same name in Kent, Suffolk and the Midlands. According to Brewer's Dictionary of Britain & Ireland , the name Stour rhymes with hour and derives from Old English meaning "violent", "fierce" or
462-409: The bedding or as nodules in seams , or linings to fractures , embedded in chalk. It is probably derived from sponge spicules or other siliceous organisms as water is expelled upwards during compaction. Flint is often deposited around larger fossils such as Echinoidea which may be silicified (i.e. replaced molecule by molecule by flint). Chalk is so common in Cretaceous marine beds that
495-471: The harbour into the English Channel. From source to estuary, the river falls approximately 750 feet (230 m) over its 60 mi (97 km) length. For many miles the river is followed by the route of the now disused Somerset and Dorset Joint Railway , which bridged the river four times in a 9 mi (14 km) section between Sturminster Newton and Blandford Forum. Because much of
528-437: The starlet sea anemone . There are many fish that live and use the river, which include; barbel, bream, chub, dace, grayling, perch, pike, roach, rudd, salmon, tench & trout. The harbour at Christchurch has also been used to land oysters, crab, lobster and cuttlefish, all of which were fished from the harbour itself. Bass and mullet are known to use the estuary for feeding and as a nursery. Downstream of Blandford Forum,
561-643: The "darksome pools o' stwoneless Stour" in his The Water Crowvoot . The source of the river is fed from greensand springs at Stourhead , in Wiltshire, where it forms a series of artificial lakes which are part of the Stourhead estate owned by the National Trust . It flows south into Dorset through the Blackmore Vale and the towns of Gillingham and Sturminster Newton . At Marnhull
594-402: The "fierce one". The river burst its banks at Christchurch during the 2013–14 winter floods and 100 residents were evacuated. The Stour valley has produced rich evidence for early human (Palaeolithic) activity. Gravel pits in the lower reaches of the river (many underlying modern day Bournemouth) produced hundreds of Lower Palaeolithic handaxes when they were quarried, particular during
627-732: The North American interior. Chalk is also found in western Egypt (Khoman Formation) and western Australia ( Miria Formation ). Chalk of Oligocene to Neogene age has been found in drill cores of rock under the Pacific Ocean at Stewart Arch in the Solomon Islands . There are layers of chalk, containing Globorotalia , in the Nicosia Formation of Cyprus , which formed during the Pliocene . Chalk
660-521: The Stour is host to an insect known as the Blandford Fly ( Simulium posticatum ) which is known for leaving painful bites on humans. Attempts have been made to rid the fly from the area with a special spray used on the larval habitats of the fly. The harbour at Christchurch and the lower reaches of the Stour and the Avon are host to a multitude of marinas, boat clubs and landing stages. The Stour
693-643: The Stour is joined by the River Cale and then (two miles downstream) by the River Lydden. At Blandford Forum the river breaks through the chalk ridge of the Dorset Downs , and from there flows south east into the heathlands of south east Dorset. At Wimborne Minster it is joined by the River Allen , and at its estuary at Christchurch it is joined by the River Avon before it flows through
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#1732772058166726-473: The amount of erosion from nearby exposed rock. The lack of nearby erosion explains the high purity of chalk. The coccolithophores, foraminifera, and other microscopic organisms from which the chalk came mostly form low-magnesium calcite skeletons, so the sediments were already in the form of highly stable low-magnesium calcite when deposited. This is in contrast with most other limestones, which formed from high-magnesium calcite or aragonite that rapidly converted to
759-649: The forces of that kingdom against Locrinus. The two armies fight a battle at the river Stour where Locrinus is slain and Gwendolen becomes the ruler of both kingdoms, becoming the first queen regnant of the Kings of the Britons . The Stour also appears in more occasional fashion in The Faerie Queene . Thomas Hardy wrote about Overlooking the River Stour , while William Barnes similarly referenced
792-512: The form of calcite plates ranging from 0.5 to 4 microns in size, though about 10% to 25% of a typical chalk is composed of fragments that are 10 to 100 microns in size. The larger fragments include intact plankton skeletons and skeletal fragments of larger organisms, such as molluscs , echinoderms , or bryozoans . Chalk is typically almost pure calcite, CaCO 3 , with just 2% to 4% of other minerals. These are usually quartz and clay minerals , though collophane (cryptocrystalline apatite ,
825-607: The late 19th century and the first half of the 20th century. Archaeological investigations around 2010 near Corfe Mullen suggested that some of the artefacts from those quarries may be around 400,000 to 500,000 years old. In Medieval Welsh literature , the river was said to be the sight of an important battle and the dividing line between ancient Cornwall and Loegria (England). According to Geoffrey of Monmouth 's Historia Regum Britanniae , King Locrinus divorces Queen Gwendolen in favour of his secret lover, Estrildis . Returning to her native Cornwall, Gwendolen assembles all
858-587: The mineral calcite and originally formed deep under the sea by the compression of microscopic plankton that had settled to the sea floor . Chalk is common throughout Western Europe , where deposits underlie parts of France, and steep cliffs are often seen where they meet the sea in places such as the Dover cliffs on the Kent coast of the English Channel . Chalk is mined for use in industry, such as for quicklime , bricks and builder's putty , and in agriculture , for raising pH in soils with high acidity . It
891-528: The mineral gypsum ( calcium sulfate ). While gypsum-based blackboard chalk is the lowest cost to produce, and thus widely used in the developing world , use of carbonate-based chalk produces larger particles and thus less dust, and it is marketed as "dustless chalk". Coloured chalks, pastel chalks, and sidewalk chalk (shaped into larger sticks and often coloured), used to draw on sidewalks , streets, and driveways , are primarily made of gypsum rather than calcium carbonate chalk. Magnesium carbonate chalk
924-406: The more stable low-magnesium calcite after deposition, resulting in the early cementation of such limestones. In chalk, absence of this calcium carbonate conversion process prevented early cementation, which partially accounts for chalk's high porosity. Chalk is also the only form of limestone that commonly shows signs of compaction. Flint (a type of chert ) is very common as bands parallel to
957-562: The most famous is the extensive complex at Grimes Graves in Norfolk . Chalk was traditionally used in recreation. In field sports, such as tennis played on grass, powdered chalk was used to mark the boundary lines of the playing field or court. If a ball hits the line, a cloud of chalk or pigment dust will be visible. In recent years, powdered chalk has been replaced with titanium dioxide . In gymnastics, rock-climbing, weightlifting and tug of war , chalk — now usually magnesium carbonate —
990-667: The other side of the Dover Strait . The Champagne region of France is mostly underlain by chalk deposits, which contain artificial caves used for wine storage . Some of the highest chalk cliffs in the world occur at Jasmund National Park in Germany and at Møns Klint in Denmark . Chalk deposits are also found in Cretaceous beds on other continents, such as the Austin Chalk , Selma Group , and Niobrara Formations of
1023-403: The river too. The Stour Valley Way is a designated long-distance footpath that follows almost all of the course of the river. White Mill , an 18th-century watermill on the river near Sturminster Marshall , is owned by the National Trust and open to the public. Chalk Chalk is a soft, white, porous , sedimentary carbonate rock . It is a form of limestone composed of
River Lydden - Misplaced Pages Continue
1056-583: The river's course is across clay soil, the river's waterlevel varies greatly. In summer, low water level makes the river a diverse and important habitat , supporting many rare plants . In winter, the river often floods , and is therefore bordered by wide and fertile flood plains . A number of towns and villages in Dorset are named after the river, including East Stour , West Stour , Stourpaine , Stourton Caundle , Stour Row , Stour Provost , Sturminster Newton , and Sturminster Marshall . Sturminster Newton
1089-436: The small particles of chalk make it a substance ideal for cleaning and polishing. For example, toothpaste commonly contains small amounts of chalk, which serves as a mild abrasive . Polishing chalk is chalk prepared with a carefully controlled grain size, for very fine polishing of metals. French chalk (also known as tailor's chalk) is traditionally a hard chalk used to make temporary markings on cloth, mainly by tailors . It
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