This page contains a list of user images about Chalk which are relevant to the point and besides images, you can also use the tabs in the bottom to browse Chalk news, videos, wiki information, tweets, documents and weblinks.
From the Grammy Nominated album The Truth About Love available now - http://smarturl.it/tal Music video by P!nk featuring Nate Ruess performing Just Give Me ...
Watch judges' comments at http://itv.com/XFactor (UK ONLY) Watch James Arthur sing Impossible by Shontelle Sweeeeet! As potential Winner's Singles go, this o...
WATCH BLOOPERS & MORE: http://bit.ly/ZELDAxtras DOWNLOAD THE SONG: http://smo.sh/13NrBp8 DOWNLOAD UNCENSORED SONG: http://smo.sh/WMYpsf GET LEGEND OF SMOSH T...
Thrift Shop on iTunes: http://itunes.apple.com/us/album/thrift-shop-feat.-wanz-single/id556955707 The Heist physical deluxe edition: http://www.macklemoremer...
Music video by Rihanna performing Rehab. YouTube view counts pre-VEVO: 19591123. (C) 2007 The Island Def Jam Music Group.
Music video by Rihanna performing Unfaithful. (C) 2006 The Island Def Jam Music Group #VEVOCertified on Feb. 15, 2012. http://vevo.com/certified http://youtu...
Music video by Rihanna performing Russian Roulette. (C) 2009 The Island Def Jam Music Group.
So i was pretty hesitant to make this video... but after all of your request, here is my Draw My Life video! Check out my 2nd Channel for more vlogs: http://...
Download "Stay" from Unapologetic now: http://smarturl.it/UnapologeticDlx Music video by Rihanna performing Stay ft. Mikky Ekko. © 2013 The Island Def Jam Mu...
YOLO is available on iTunes now! http://smarturl.it/lonelyIslandYolo THE LONELY ISLAND - THE WACK ALBUM - JUNE 11th! Pre-order THE WACK ALBUM DIRECT: http://...
Play the DUDE PERFECT GAME here! iPhone - http://bit.ly/DPGameiPhone Android - http://bit.ly/DPGameAndroid iPad - http://bit.ly/DPGameiPad Tweet! http://bit....
Don't be these people. Mapoti See Bloopers and Behind-The-Scenes Here!: http://youtu.be/dfpo7uXwJnM Huge thank you and shout out to Dtrix: http://www.youtube...
Macklemore & Ryan Lewis present the official music video for Can't Hold Us feat. Ray Dalton. Can't Hold Us on iTunes: https://itunes.apple.com/us/album/cant-...
This video accidentally turned out kind of sad, ME SO SOWWY IT NOT POSED TO BE SAD WHO WANTS HUGS AND COOKIES? Also, FYI for anyone attempting this, it takes...
Pre-order new album Unapologetic, out worldwide Monday, November 19: http://smarturl.it/UnapologeticDlx Music video by Rihanna performing Diamonds. ©: The Is...
Music video by Rihanna performing Pon de Replay. YouTube view counts pre-VEVO: 4166822. (C) 2005 The Island Def Jam Music Group.
Music video by Rihanna performing Only Girl (In The World). (C) 2010 The Island Def Jam Music Group #VEVOCertified on February 16, 2011. http://www.vevo.com/...
Ellen weighed in on the conversation surrounding the policies of Abercrombie & Fitch.
Its a simple math equation really... Click to see Bloopers and The making of this video here!: http://www.youtube.com/watch?v=nccOGxj27J8 Follow me on TWITTE...
Please take a second and LIKE+FAV this video! :D I worked really hard on it. Also : SHARE THIS VIDEO with friends:) Twitter/Facebook/Websites *brofist* More ...
The Needles, situated off the Isle of Wight, are part of the extensive Southern England Chalk Formation.
|calcite (calcium carbonate)|
Chalk (pron.: //) is a soft, white, porous sedimentary rock, a form of limestone composed of the mineral calcite. Calcite is calcium carbonate or CaCO3. It forms under reasonably deep marine conditions from the gradual accumulation of minute calcite plates (coccoliths) shed from micro-organisms called coccolithophores. It is common to find chert or flint nodules embedded in chalk. Chalk can also refer to other compounds including magnesium silicate and calcium sulfate.
Chalk has greater resistance to weathering and slumping than 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.
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 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 Møns Klint in Denmark.
Ninety million years ago the chalk downland of Northern Europe was ooze accumulating at the bottom of a great sea. Protozoans such as foraminifera lived on the marine debris that showered down from the upper layers of the ocean. Their shells were made of calcite extracted from the rich sea-water. As they died a deep layer gradually built up and eventually, through the weight of overlying sediments, became consolidated into rock. Later earth movements related to the formation of the Alps raised these former sea-floor deposits above sea level.
Chalk is composed mostly of calcium carbonate with minor amounts of silt and clay. It is normally formed underwater, commonly on the sea bed, then consolidated and compressed during diagenesis into the form commonly seen today. During diagenesis silica accumulates to form chert or flint nodules within the carbonate rock.
Chalk is used to make quicklime and slaked lime, mainly used as lime mortar in buildings. 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 the most famous is the extensive complex at Grimes Graves in Norfolk.
The traditional uses of chalk have in some cases been replaced by other substances, although the word "chalk" is often still applied to the usual 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 4 in (10 cm) long.
- Sidewalk chalk is similar to blackboard chalk, except that it is formed into larger sticks and often colored. It is used to draw on sidewalks, streets, and driveways, mostly by children, but also by adult artists.
- In agriculture chalk is used for raising pH in soils with high acidity. The most common forms are CaCO3 (calcium carbonate) and CaO (calcium oxide).
- In field sports, including grass tennis courts, powdered chalk was used to mark the boundary lines of the playing field or 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.[not in citation given]
- In gymnastics, rock-climbing, weight-lifting and tug of war, chalk — now usually magnesium carbonate — is applied to the hands to remove perspiration and reduce 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).
- Toothpaste also commonly contains small amounts of chalk, to serve as a mild abrasive.
- Polishing chalk is chalk prepared with a carefully controlled grain size, for very fine polishing of metals.
- Chalk is a source of quicklime by thermal decomposition, or slaked lime following quenching with water.
- Builder's putty also mainly contains chalk as a filler in linseed oil.
- Woodworking joints may be fitted by chalking one of the mating surfaces. A trial fit will leave a chalk mark on the high spots of the corresponding surface. Chalk transferring to cover the complete surface indicates a good fit.
- Fingerprint powder
- Taken orally, in small doses, as an antacid.
See also 
|Wikimedia Commons has media related to: Chalk|