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33-582: The River Dever / ˈ d iː v ər / is a chalk stream in Hampshire in the south of England . It rises at West Stratton near Micheldever and flows westwards for 11 mi (18 km) to meet the River Test at Wherwell . The source is at 80 metres (260 ft) Above Ordnance Datum (AOD) alongside the A33 , the main road north-east from Winchester , of Roman origin, and meanders west through

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 Most people first encounter chalk in school where it refers to blackboard chalk , which was originally made of mineral chalk, since it readily crumbles and leaves particles that stick loosely to rough surfaces, allowing it to make writing that can be readily erased.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,

231-485: Is fairly stable and rarely deviates from 10 °C (50 °F). On cold winter mornings, water vapour from the relatively warm stream condenses in the cold air above to form fog. Chalk is slightly soluble in rainwater because rain is naturally slightly acidic . The products of chalk weathering are dissolved in rainwater and are transported in stream flow. Chalk streams transport little suspended material (unlike most rivers), but are considered " mineral -rich" due to

264-433: Is given an overall ecological status, which may be one of five levels: high, good, moderate, poor and bad. There are several components that are used to determine this, including biological status, which looks at the quantity and varieties of invertebrates , angiosperms and fish. Chemical status, which compares the concentrations of various chemicals against known safe concentrations, is rated good or fail. Water quality of

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

330-582: 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

363-645: 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

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396-601: The River Thames , River Lea and River Colne ): Chalk streams of the Yorkshire Wolds : Chalk streams of Lincolnshire : There are several chalk streams in the Lincolnshire Wolds including Chalk streams of Kent: Chalk streams of Norfolk: Chalk streams of Suffolk: Chalk Chalk is a soft, white, porous , sedimentary carbonate rock . It is a form of limestone composed of

429-409: 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

462-595: The 20th and 21st centuries, much of that management has been aimed at producing the best conditions for fly fishing , and most specifically, dry fly fishing . The chalk streams hold a good number of wild salmonid fish species such as the brown trout ( Salmo trutta ), and grayling ( Thymallus thymallus ). In addition to these there are also considerable numbers of stocked brown trout and stocked rainbow trout ( Oncorhynchus mykiss ). The rich invertebrate life and characteristic transparent shallow water make chalk rivers and streams particularly suited to fly fishing. Many of

495-732: 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

528-680: The River Dever in 2019: 51°09′31″N 1°14′11″W  /  51.1585°N 1.2363°W  / 51.1585; -1.2363 Chalk stream The beds of the rivers are generally composed of clean, compacted gravel and flints , which are good spawning areas for Salmonidae fish species. Since they are fed primarily by aquifers , the flow rate, mineral content and temperature range of chalk streams exhibit less seasonal variation than other rivers. They are mildly alkaline and contain high levels of nitrate , phosphate , potassium and silicate . In addition to algae and diatoms ,

561-558: The Test, a highly abundant watercourse in Europe for large trout. It includes two trout farms , at the otherwise almost wholly green locality of Bransbury, and at Difford, north of Barton Stacey. The watermill at Weston Colley is a Grade II listed building /. The mill at Bransbury is also Grade II listed. The Environment Agency measures the water quality of the river systems in England. Each

594-447: The UK has caused the chalk streams to dry up. This has caused ecological damage and stagnant sewage that flows through the rivers and increasing phosphate levels. Although chalk streams are generally watercourses originating from chalk hills, including winterbournes , streams, and rivers, the term chalk stream is used even for larger rivers, which would normally be considered too large for

627-473: 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

660-559: The chalk stream springs are also used as sites for watercress production, due to the constant temperature and clean, alkaline , mineral-rich spring water. The Mid Hants Watercress Railway in Hampshire is so named on account of its use for transporting watercress to London from local chalk streams. A number of the chalk aquifers and associated groundwater sources related to chalk streams and rivers are used for water abstraction by local and national water utility companies. The over-abstracting of chalk streams by private water companies in

693-574: The dissolved calcium and carbonate ions . The surface water of chalk streams is commonly described as "gin clear". The channel bed consists of angular flint gravel derived from the natural flint deposits found embedded within the chalk geology that contains relatively low amounts of clay and silt deposits. The unique characteristics of chalk stream ecology are due to stable temperature and flow regimes combined with highly transparent water and lack of sand grade sediment particles. The chalk streams have been intensively managed for many generations. In

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726-512: 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 ,

759-401: The ground, where the chalk layer acts as an aquifer . The groundwater flows through the chalk bedrock, re-emerging lower down the slope in springs . The chalk acts as a temporary reservoir by regulating the amount of water supplied to the springs. This is why many chalk streams in the UK have stable flow regimes that vary only slightly over time. The temperature of the emerging surface water

792-651: 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

825-528: 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

858-406: 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

891-562: 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 —

924-667: 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

957-689: The scribe is / m i x l / , that means "great", and the latter part, if from the Common Brittonic , "water, river" as in Andover or the Candover Brook nearby. Alternatively the Old Welsh / m i x n / for "bog" is suggested by the earliest-known form, from 862 , Mycendefr , not relatively prevalent due to the gradient and alkaline water. It is essentially fed by very close chalk aquifers, likewise to its continuation

990-436: 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

1023-422: The streams provide a suitable habitat for macrophytes (including water crowfoot ) and oxygen levels are generally supportive of coarse fish populations. Of the 210 rivers classified as chalk streams globally, 160 are in England. A list of chalk streams in England gives a total of 224. Chalk is a highly porous and permeable rock, and rain falling onto chalk topography percolates directly into

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1056-757: The term stream . The Somme in northern France is a chalk stream on a larger scale. Winterbournes are known by different names depending on region: Chalk streams of the Southern England Chalk Formation in Berkshire , Hampshire , Wiltshire , Dorset and the Isle of Wight : Chalk streams of the Southern England Chalk Formation in the Chiltern Hills , Hertfordshire and Surrey (tributaries of

1089-516: The village of Micheldever , three hamlets: Weston Colley , Stoke Charity and Wonston , then its largest village, Sutton Scotney , followed by Upper and Lower Bullington . The river skirts to the north of Barton Stacey and through the hamlet of Bransbury , meeting the Test on Bransbury Common , opposite the east fields of Wherwell on the multi-channel Test's West Bank at 48 metres (157 ft) AOD. From Old English times some records have Myceldefer . The likely first sound-meaning denoted by

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