Chalk

Information about Chalk

The Needles, situated on the Isle Of Wight, are part of the extensive Southern England Chalk Formation.

Chalk (IPA: /ˈtʃɔːk/) is a soft, white, porous sedimentary rock, a form of limestone composed of the mineral calcite. It forms under relatively deep marine conditions from the gradual accumulation of minute calcite plates (coccoliths) shed from micro-organisms called coccolithophores. It is common to find flint and chert nodules embedded in chalk.

Chalk is relatively resistant to erosion and slumping compared to the clays with which it is usually associated, thus forming tall steep cliffs where chalk ridges meet the sea. Chalk hills, known as chalk downland, usually form where bands of chalk reach the surface at an angle, so forming a scarp slope. Because chalk is porous it can hold a large volume of ground water, providing a natural reservoir that releases water slowly through dry seasons. .

Chalk has been quarried since prehistory, providing building material and marl for fields. In southeast England, deneholes are a notable example of ancient chalk pits.

The Chalk Formation is a European stratigraphic unit deposited during the late Cretaceous Period. It forms the famous White Cliffs of Dover in Kent, England.The Champagne region of France is mostly underlain by chalk deposits, which contain famous caves beneath the hills.

Traditional uses

The traditional uses of chalk have in many cases been replaced by other substances, although the word "chalk" is often still applied to the replacements.

Blackboard chalk is a substance used for drawing on rough surfaces, as it readily crumbles leaving particles that stick loosely to these surfaces. Although traditionally composed of natural chalk, modern blackboard chalk is generally made from the mineral gypsum (calcium sulfate), often supplied in sticks of compressed powder about 10 cm long.
In lawn tennis, powdered chalk was used to mark the boundary lines of the court. This gives the advantage that, if the ball hits the line, a cloud of chalk or pigment dust can be seen. Nowadays the substance used is mostly titanium dioxide.
In gymnastics, rock-climbing, billiards, bouldering, weight-lifting and tug of war, chalk—now usually magnesium carbonate—is applied to the hands to prevent slipping.
Tailor's chalk is traditionally a hard chalk used to make temporary markings on cloth, mainly by tailors. Nowadays it is usually made from talc (magnesium silicate).
Sidewalk chalk is made of sticks of colored chalk (now mostly gypsum) used to draw on sidewalks, streets, and driveways. It is often done by children, but in many cities, talented adult artists create masterpieces on the walkways.

Sedimentary rock is one of the three main rock groups (the others being igneous and metamorphic rock). Rock formed from sediments covers 75-80% of the Earth's land area, and includes common types such as chalk, limestone, dolomite, sandstone, conglomerate and shale.
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Limestone is a sedimentary rock composed largely of the mineral calcite (calcium carbonate: CaCO₃). Limestone often contains variable amounts of silica in the form of chert or flint, as well as varying amounts of clay, silt and sand as disseminations, nodules, or layers
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A mineral is a naturally occurring substance formed through geological processes that has a characteristic chemical composition, a highly ordered atomic structure and specific physical properties.
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calcite]] The carbonate mineral, calcite, is a chemical or biochemical calcium carbonate corresponding to the formula CaCO₃ and is one of the most widely distributed minerals on the Earth's surface.
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Coccoliths are individual plates of calcium carbonate formed by coccolithophores (single-celled algae such as Emiliania huxleyi) which are arranged around them in a coccosphere.
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Coccolithophores (also called coccolithophorids) are single-celled algae, protists and phytoplankton belonging to the class haptophytes. They are distinguished by special calcium carbonate plates (or scales) of unknown purpose called coccoliths
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Flint (or flintstone) is a hard, sedimentary cryptocrystalline silicate form of the mineral quartz, categorized as a variety of chalcedony and broadly part of the mineral group known as silicas.
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Chert (IPA: /ˈtʃəː(r)t/) is a fine-grained silica-rich cryptocrystalline sedimentary rock that may contain small fossils.
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Erosion is displacement of solids (soil, mud, rock and other particles) usually by the agents of currents such as, wind, water, or ice by downward or down-slope movement in response to gravity or by living organisms (in the case of bioerosion).
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Clay is a naturally occurring material, composed primarily of fine-grained minerals, which show plasticity through a variable range of water content, and which can be hardened when dried or fired.
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cliff or bluff is a significant vertical, or near vertical, rock exposure. Cliffs are categorized as erosion landforms due to the processes of erosion and weathering that produce them. Cliffs are common on coasts, in mountainous areas, escarpments and along rivers.
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hill is a landform that extends above the surrounding terrain, in a limited area. Hills often have a distinct summit, although in areas with scarp/dip topography a hill may refer to a particular section of scarp slope without a well-defined summit (e.g. Box Hill).
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A downland is an area of open chalk hills. This term is especially used to describe the chalk countryside in southern England. Areas of downland are often referred to as Downs.
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In geomorphology, an escarpment is a transition zone between different physiogeographic provinces that involves an elevation differential, often involving high cliffs. Most commonly, an escarpment, also called a scarp (from the Italian scarpa^[1]
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Groundwater is water located beneath the ground surface in soil pore spaces and in the fractures of lithologic formations. A unit of rock or an unconsolidated deposit is called an aquifer when it can yield a usable quantity of water.
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Marls are calcium carbonate or lime-rich muds or mudstones which contain variable amounts of clays and calcite or aragonite. The term is most often used to describe lacustrine (lake) sediments but may also be used for marine deposits.
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Motto
Dieu et mon droit (French)
"God and my right"
Anthem
No official anthem specific to England — the anthem of the United Kingdom is "God Save the Queen".
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A Denehole (alternatively Dene hole or Dene-hole) is an underground structure consisting of a number of small chalk caves entered by a vertical shaft. The name is given to certain caves or excavations in England, which have been popularly supposed to be due to the
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Chalk Formations of Europe are thick deposits of chalk, a soft porous white limestone, deposited in a marine environment during the upper Cretaceous Period. They appear most prominently in England.
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Europe is one of the seven traditional continents of the Earth. Physically and geologically, Europe is the westernmost peninsula of Eurasia, west of Asia. Europe is bounded to the north by the Arctic Ocean, to the west by the Atlantic Ocean, to the south by the Mediterranean Sea,
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The Cretaceous Period is one of the major divisions of the geologic timescale, reaching from the end of the Jurassic Period (i.e. from 145.5 ± 4.0 million years ago (Ma)) to the beginning of the Paleocene epoch of the Tertiary Period (about 65.5 ± 0.3 Ma).
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white cliffs of Dover, are cliffs which form part of the British coastline facing the Strait of Dover and France. The cliffs are part of the North Downs formation. The cliff face, which reaches up to 350 feet high, owes its striking façade to its composition of chalk (pure white
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Kent

Geography
Status Ceremonial & (smaller) Non-metropolitan county
Region South East England
Area
- Total
- Admin. council
- Admin.
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Champagne wine region (archaic English: Champany) is a historic province within the Champagne administrative province in the northeast of France.
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Motto
Liberté, Égalité, Fraternité
"Liberty, Equality, Fraternity"
Anthem
"La Marseillaise"

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chalkboard or blackboard is a reusable writing surface on which text or drawings are made with chalk or other erasable markers. Blackboards were originally made of smooth, thin sheets of black or dark grey slate stone.
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Gypsum is a very soft mineral composed of calcium sulfate dihydrate, with the chemical formula CaSO₄·2H₂O.

Crystal varieties

Gypsum occurs in nature as flattened and often twinned crystals and transparent cleavable masses called selenite.
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