Calcareous Soil Profile, Seven Sisters Country Park - geograph

Calcareous () is an adjective meaning "mostly or partly composed of calcium carbonate", in other words, containing lime or being

chalk Chalk is a soft, white, porous, sedimentary carbonate rock. It is a form of limestone composed of the mineral calcite and originally formed deep under the sea by the compression of microscopic plankton that had settled to the sea floor. C ...

y. The term is used in a wide variety of scientific disciplines.

In zoology

''Calcareous'' is used as an adjectival term applied to anatomical structures which are made primarily of calcium carbonate, in animals such as gastropods, i.e.,

snail A snail is, in loose terms, a shelled gastropod. The name is most often applied to land snails, terrestrial pulmonate gastropod molluscs. However, the common name ''snail'' is also used for most of the members of the molluscan class ...

s, specifically about such structures as the operculum, the clausilium, and the love dart. The term also applies to the calcium carbonate

tests Test(s), testing, or TEST may refer to: * Test (assessment), an educational assessment intended to measure the respondents' knowledge or other abilities Arts and entertainment * ''Test'' (2013 film), an American film * ''Test'' (2014 film), ...

of often more or less microscopic Foraminifera. Not all tests are calcareous;

diatoms A diatom (Neo-Latin ''diatoma''), "a cutting through, a severance", from el, διάτομος, diátomos, "cut in half, divided equally" from el, διατέμνω, diatémno, "to cut in twain". is any member of a large group comprising sev ...

and radiolaria have siliceous tests. The molluscs are calcareous, as are

calcareous sponge The calcareous sponges of class Calcarea are members of the animal phylum Porifera, the cellular sponges. They are characterized by spicules made of calcium carbonate in the form of calcite or aragonite. While the spicules in most species ha ...

s ( Porifera), that have spicules which are made of calcium carbonate.

In botany

''Calcareous grassland'' is a form of grassland characteristic of soils containing much calcium carbonate from underlying chalk or

limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms w ...

rock.

In medicine

The term is used in pathology, for example in ''calcareous

conjunctivitis Conjunctivitis, also known as pink eye, is inflammation of the outermost layer of the white part of the eye and the inner surface of the eyelid. It makes the eye appear pink or reddish. Pain, burning, scratchiness, or itchiness may occur. Th ...

'', and when referring to ''calcareous

metastasis Metastasis is a pathogenic agent's spread from an initial or primary site to a different or secondary site within the host's body; the term is typically used when referring to metastasis by a cancerous tumor. The newly pathological sites, the ...

'' or ''calcareous deposits'', which may both be removed surgically.

In geology

Calcareous open-cast mine in Gornozavodsk

The term ''calcareous'' can be applied to a

sediment Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sand ...

sedimentary rock Sedimentary rocks are types of rock that are formed by the accumulation or deposition of mineral or organic particles at Earth's surface, followed by cementation. Sedimentation is the collective name for processes that cause these particles ...

, or

soil Soil, also commonly referred to as earth or dirt, is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life. Some scientific definitions distinguish ''dirt'' from ''soil'' by restricting the former ...

type which is formed from, or contains a high proportion of, calcium carbonate in the form of calcite or aragonite.

Marine sediments

Calcareous sediments are usually deposited in shallow water near land, since the carbonate is precipitated by marine organisms that need land-derived nutrients. Generally speaking, the farther from land sediments fall, the less calcareous they are. Some areas can have interbedded calcareous sediments due to storms, or changes in ocean currents. Calcareous ooze is a form of calcium carbonate derived from planktonic organisms that accumulates on the sea floor. This can only occur if the ocean is shallower than the

carbonate compensation depth Carbonate compensation depth (CCD) is the depth in the oceans below which the rate of supply of calcite ( calcium carbonate) lags behind the rate of solvation, such that no calcite is preserved. Shells of animals therefore dissolve and carbonate ...

(CCD). Below this depth, calcium carbonate begins to dissolve in the ocean, and only non-calcareous sediments are stable, such as siliceous ooze or

pelagic red clay Pelagic red clay, also known as simply red clay, brown clay or pelagic clay, is a type of pelagic sediment.Rothwell, R.G., (2005) ''Deep Ocean Pelagic Oozes'', Vol. 5. of Selley, Richard C., L. Robin McCocks, and Ian R. Plimer, Encyclopedia of Ge ...

Calcareous soils

Calcareous soils are relatively alkaline, in other words they have a high pH. This is because of the very weak acidity of carbonic acid. Note that this is not the only reason for a high soil pH. They are characterized by the presence of calcium carbonate in the parent material and may have a calcic horizon, a layer of secondary accumulation of carbonates (usually calcium or Mg) in excess of 15% calcium carbonate equivalent and at least 5% more carbonate than an underlying layer.

List of calcareous rivers

* Ganga

Man made deposits

Calcareous deposits can form in water carrying pipes. An example of this is Sunday stone.

In electrochemistry

Calcareous coatings, or calcareous deposits, are mixtures of calcium carbonate and magnesium hydroxide that are deposited on cathodically protected surfaces because of the increased pH adjacent to the surface.

References

{{wiktionary Sedimentary rocks Soil chemistry