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crust: Definition, Synonyms and Much More from Answers.com

  • ️Fri Sep 14 2007

Dictionary:

crust

  

(krŭst) pronunciation

n.

    1. The hard outer portion or surface area of bread.
    2. A piece of bread consisting mostly of the hard outer portion.
    3. A piece of bread that has become hard and dry.
  2. A pastry shell, as of a pie or tart.
  3. A hard crisp covering or surface: snow with a firm crust.
  4. A hard deposit formed on the interior of a wine bottle as the wine matures.
  5. Geology.
    1. The exterior portion of the earth that lies above the Mohorovičić discontinuity.
    2. The outermost solid layer of a planet or moon.
  6. The hard outer covering or integument of certain plants and animals, such as lichens and crustaceans.
  7. Pathology. An outer layer or coating formed by the drying of a bodily exudate such as pus or blood; a scab.
  8. Informal. Insolence; audacity; gall.

v., crust·ed, crust·ing, crusts.

v.tr.

  1. To cover with a crust.
  2. To form into a crust.

v.intr.

  1. To become covered with a crust.
  2. To harden into a crust.

[Middle English cruste, from Old French crouste, from Latin crūsta.]

crustless crust'less adj.

The low-density outermost layer of the Earth above the Mohorovičić discontinuity (the Moho), a global boundary that is defined as the depth in the Earth where the compressional-wave seismic velocity increases rapidly or discontinuously to a value in excess of 4.7 mi/s (7.6 km/s; the upper mantle). The crust is also the cold, upper portion of the Earth's lithosphere, which in terms of plate tectonics is the mobile, outer layer that is underlain by the hot, convecting asthenosphere. See also Asthenosphere; Lithosphere; Moho (Mohorovičić discontinuity); Plate tectonics.

Continental crust

The Earth's continental crust has evolved over the past 4 billion years, and is highly variable in geologic composition and internal structure. The worldwide mean thickness of continental crust is 24 mi (40 km), with a standard deviation of 5.4 mi (9 km). The thinnest continental crust (found in the Afar Triangle, northeast Africa) is about 9 mi (15 km) thick, and the thickest crust (the Himalayan Mountains in China) is about 47 mi (75 km) thick. Ninety-five percent of all continental crust has a thickness within two standard deviations of the mean thickness, between 13 mi (22 km) and 37 mi (58 km). The Antarctic continent has a crustal thickness of 24 mi (40 km) in the ancient, stable (cratonic) region of East Antarctica, and about 12 mi (20 km) in the recently stretched (extended) crust of West Antarctica. Continental margins, which mark the transition from oceanic to continental crust, range in thickness from about 9 mi (15 km) to 18 mi (30 km). See also Continental margin.

Despite its geologic complexity, the continental crust may generally be divided into four layers: an uppermost sedimentary layer, and an upper, middle, and lower crust composed of crystalline rocks. The sedimentary cover of the continental crust is an important source of natural resources. This cover averages 0.6 mi (1 km) in thickness, and varies in thickness from zero (for example, on shields) to more than 9 mi (15 km) in deep basins. In stable continental crust of average thickness (25 mi or 40 km), the crystalline upper crust is commonly 6–9 mi (10–15 km) thick and has an average composition equivalent to a granite. The middle crust is 3–9 mi (5–15 km) thick and has a composition equivalent to a diorite; and the lower crust is 3–12 mi (5–20 km) thick and has a composition equivalent to a gabbro. Due to increasing temperature and pressure with depth, the metamorphic grade of rocks increases with depth, and the rocks within the deep continental crust generally are metamorphic rocks, even if they originated as sedimentary or igneous rocks. See also Diorite; Gabbro; Granite; Metamorphic rocks.

Crustal properties vary systematically with geologic setting, which may be divided into six groups: orogens (mountain belts), shields and platforms, island arcs (volcanic arcs), continental magmatic arcs, rifts, extended (stretched) crust, and forearcs. Orogens are typified by thick crust [average thickness is 29 mi (46 km), but the maximum thickness is as much as 47 mi (75 km) in the Himalayas]. Shields and platforms, such as the Canadian Shield and the Russian Platform, commonly have an approximately 26-mi-thick (42-km) crust, including a 3–6 mi-thick (5–10 km) lower crust. In comparison with shields, island arcs (such as Japan) have thinner crusts and significantly shallower middle and lower crustal layers due to the intrusion of mafic (that is, low silica content) plutons. Continental magmatic arcs, such as the Cascades volcanoes of the northwestern United States, intrude preexisting continental crust, and therefore they are generally 3–9 mi (10–15 km) thicker than island arcs. Continental rifts, such as the East African and Rio Grande rifts, have an average crustal thickness of about 22 mi (36 km). Extended continental crust, such as the Basin and Range Province of the western United States, averages 18 mi (30 km) in thickness. Forearcs are regions that were formed oceanward of volcanic arcs, such as much of the west coast of North America. They typically have thin crust, about 15 mi (25 km), and have a thick (9 mi or 15 km) upper crustal section that consists of relatively low-density metasedimentary rocks. See also North America; Oceanic islands; Pluton; Rift valley; Sedimentary rocks; Volcano.

At least three processes provide new continental crust. The first is the accretion and consolidation of island arcs, such as Japan or the Aleutian Islands, onto a continental margin. The second process is the tectonic underplating of oceanic crust at active subduction zones. In this process, the continental crust grows from below as oceanic crust is welded to the base of the continental margin, either when subduction stops or when subduction steps oceanward and a new trench is formed. This process has been identified in western Canada and southern Alaska. The third process is the magmatic inflation of the crust at continental arcs, rifts, and regions of crustal extension. This process has been identified in many regions. See also Geodynamics.

Oceanic crust

The surface of the ocean crust, except for some locally high volcanoes and plateaus, resides some 1–3 mi (2–5 km) below sea level, and about another kilometer below the average level of the continents. The ocean crust represents the youngest and geologically most dynamic portion of the Earth's surface. Most of it was produced at mid-ocean ridges during the process of sea-floor spreading. The ridges define the trailing edges, or accreting boundaries, of the major lithospheric plates that are moving about the surface of the Earth at present. Thus, the oldest rocks of the ocean crust date back no earlier than the rifting episodes that created most of these plates and initiated the most recent phase of continental drift, the Pangaean breakup, in Late Jurassic times. See also Jurassic; Mid-Oceanic Ridge.

There are fault slices of types of ocean crust on land, known as ophiolites, where nearly or entirely complete cross sections through the crust can be mapped and sampled. These strongly indicate that the ocean crust consists in downward sequence of submarine extrusives (usually pillow basalts), feeder dikes (often vertically sheeted), or sills, gabbros, and peridotites. There is much uncertainty, however, about the extent to which typical ophiolites, most of which formed in island-arc or backarc environments, can represent abyssal ocean crust, which is produced at the major accreting plate boundaries. Moreover, the physical correspondence of the rocks in ophiolites to ocean crust is often complicated by their complex structure and extent of alteration and metamorphism, particularly in the ultramafic sections.

This multipurpose word has many meanings, including the hardened outer layer of a cooked food such as bread; a thin layer of pastry covering a pie, pâté, etc.; and the sediment of organic salts deposited in a bottle of aged red wine.

Outermost solid part of the Earth, essentially composed of a range of igneous and metamorphic rock types. In continental regions, the crust is made up chiefly of granitic rock, whereas the composition of the ocean floor corresponds mainly to that of basalt and gabbro. On average, the crust extends 22 mi (35 km) downward from the surface to the underlying mantle, from which it is separated by the Mohorovicic discontinuity (the Moho). The crust and top layer of the mantle together form the lithosphere.

For more information on crust, visit Britannica.com.

Another name for the sediment thrown off by red wines as they age in bottles. The use of the term crust is generally associated with vintage port (see port).

In geology, the outermost layer of the Earth. It overlies the mantle.

  • The crust includes the continents and the ocean bottom and is generally estimated to be about five to twenty-five miles thick.
  • The crust is made from relatively lightweight rocks that floated to the surface when the Earth was molten early in its history.

    • Genre: Comedy
    • Movie Type: Sports Comedy, Animal Picture
    • Themes: When Animals Attack, Underdogs, Boxers
    • Director: Mark Locke
    • Main Cast: Kevin McNally, Perry Fitzpatrick
    • Release Year: 2003
    • Country: UK
    • Run Time: 86 minutes

    Plot

    The phrase "jumbo shrimp" gains a whole new meaning in this broad comedy from the United Kingdom. Bill (Kevin McNally) is a former boxer who, now in middle age, owns and operates a run-down bar and spends a bit too much time sampling his wares. One day, Bill's friend Hamid (Madhav Sharma), a self-styled entrepreneur with no shortage of get-rich-quick schemes, offers to cut him in on something remarkable -- while the Mantis Shrimp of the Philippines, an unusual breed with club-like stumps instead of claws, rarely grows over six inches in length, he's discovered a living specimen which is a whopping seven feet long. Hamid is certain there must be big money in exhibiting the massive crustacean, and Bill comes up with a remarkable plan -- teach the critter to box, and then have it take on all comers on a TV show! Crust was the first feature from writer/director Mark Locke. ~ Mark Deming, All Movie Guide

    Cast

    Madhav Sharma - Hamid "Anything-U-Need" Choudhury
    Bob Mason
    Enzo Cilenti
    Naomie Harris
    Louise Mardenborough - Shaz
    Ulrika Jonsson

    Credit

    Mark Locke - Director; Mark Locke - Screenwriter

    Similar Movies

    Gus; MVP: Most Valuable Primate; Ed; Air Bud

    The outermost layer of a planet or moon, above the mantle.

    pronunciation

    IN BRIEF: The hardened outside surface of bread; the pastry cover of a pie.

    pronunciation A crust eaten in peace is better than a banquet partaken in anxiety. — Aesop, (620-560 BC), Greek writer, Aesop’s Fables: animal stories illustrating human challenges.

    Tutor's tip: He crossed (past tense of cross) the kitchen to cut the pie crust (a pastry shell).

    Wikipedia: crust (geology)

    Earth cutaway from core to exosphere.

    In geology, a crust is the outermost layer of a planet.

    The crust of the Earth is composed of a great variety of igneous, metamorphic, and sedimentary rocks. The crust is underlain by the mantle. The upper part of the mantle is composed mostly of peridotite, a rock denser than rocks common in the overlying crust. The boundary between the crust and mantle is conventionally placed at the Mohorovicic discontinuity, a boundary defined by a contrast in seismic velocity. Earth's crust occupies less than 1% of Earth's volume.

    The oceanic crust of the Earth is different from its continental crust. The oceanic crust is  km ( mi) to  km ( mi) thick[1] and is composed primarily of basalt, diabase, and gabbro. The continental crust is typically from  km ( mi) to  km ( mi) thick, and it is mostly composed of less dense rocks than is the oceanic crust. Some of these less dense rocks, such as granite, are common in the continental crust but rare to absent in the oceanic crust.

    The temperature of the crust increases with depth, reaching values typically in the range from about  °C ( °F) to  °C ( °F) at the boundary with the underlying mantle. The crust and underlying relatively rigid mantle make up the lithosphere. Because of convection in the underlying plastic, although non-molten, upper mantle and asthenosphere, the lithosphere is broken into tectonic plates that move.

    Origin of the Earth's crust

    Earth is considered to have differentiated from an aggregate of planetesimals into its core, mantle and crust within about 100 million years of the formation of the planet, 4.6 billion years ago. The primordial crust was very thin, and was likely recycled by much more vigorous plate tectonics and destroyed by significant asteroid impacts, which were much more common in the early stages of the solar system. There is a theory that the Moon was formed by one such very large impact.

    The Earth has likely always had some form of basaltic oceanic crust, but there is evidence it has also had continental style crust for as long as 3.8 to 3.9 billion years. The oldest crust on Earth is the Narryer Gneiss Terrane in Western Australia at 3.9 billion years, and certain parts of the Canadian Shield and the Fennoscandian Shield are also of this age.

    The majority of the current Earth's continental crust was formed primarily between 4.6 billion years and 3.9 billion years ago, in the Hadean. The vast majority of rocks of this age are located in cratons where the crust is up to  km ( mi) thick. The lower density of the continental crust as compared to the oceanic crust prevents it being destroyed by subduction. Crust formation is linked to periods of intense orogeny or mountain building; these periods coincide with the formation of the supercontinents such as Rodinia, Pangaea and Gondwana. The crust forms not so much by accumulation of granite and metamorphic fold belts, but by depletion of the mantle to form buoyant lithospheric mantle.

    Composition of the crust

    The common rock constituents of the Earth's crust are nearly all oxides; chlorine, sulfur and fluorine are the only important exceptions to this and their total amount in any rock is usually much less than 1%. F. W. Clarke calculated that a little more than 47% of the Earth's crust consists of oxygen. It occurs principally in combination as oxides, of which the chief are silicon, aluminium, iron, calcium, magnesium, potassium and sodium oxides. Silica is a major constituent of the crust occurring as the silicate minerals, which are the most common minerals of igneous and metamorphic rocks. From a computation based on 1672 analyses of all kinds of rocks Clarke arrived at the following as the average percentage composition by mass:

    Plates in the crust of the earth, according to the plate tectonics theory

    Oxide Percent
    SiO2 59.71
    Al2O3 15.41
    CaO 4.90
    MgO 4.36
    Na2O 3.55
    FeO 3.52
    K2O 2.80
    Fe2O3 2.63
    H2O 1.52
    TiO2 0.60
    P2O5 0.22
    total 99.22

    All the other constituents occur only in very small quantities, and total less than 1%.[2]. Density for the upper crust varies between 2.69 g/cm3 and 2.74 g/cm3 and for lower crust between 3.0 g/cm3 and 3.25 g/cm3[1].

    See also

    References

    1. ^ a b Structure and composition of the Earth. Australian Museum Online. Retrieved on 2007-09-14.
    2. ^ This article incorporates text from the Encyclopædia Britannica Eleventh Edition article "Petrology", a publication now in the public domain.

    External links

    Structure of the Earth
    Crust • Upper mantle • Lithosphere • Asthenosphere • Mesosphere • Mantle • Outer core • Inner core • Plate tectonics

    map-bms:Kerak bumi

    be-x-old:Зямная караzh-yue:地殼

    This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)

    Dansk (Danish)
    n. - skorpe, tørt brødstykke, job, frækhed, dejlåg, aflejring, sårskorpe, bundfald, hård facade
    v. tr. - dække med skorpe, danne skorpe af
    v. intr. - dækkes med skorpe

    idioms:

    • crust of the earth    jordskorpe

    Nederlands (Dutch)
    korst (brood/wond etc.), schaal van schaaldier, levensonderhoud, bovenlaag(je), wijnsteen, brutaliteit

    Français (French)
    n. - (lit, fig) croûte, croûte (de sang, de boue), dépôt (de vin, de cristaux de tartre), (US) culot
    v. tr. - se couvrir d'une croûte
    v. intr. - former une croûte, s'encroûter

    idioms:

    • crust of the earth    l'écorce terrestre

    Deutsch (German)
    n. - Kruste
    v. - verkrusten, überkrusten, eine Kruste bilden

    idioms:

    • crust of the earth    Erdkruste

    Ελληνική (Greek)
    n. - κρούστα, κόρα (ψωμιού κ.λπ.), φύλλο πίτας κ.λπ., επίστρωμα, επίπαγος, τσίπα, πέτσα, κέλυφος, καύκαλο, κακάδι πληγής, (γεωλ.) φλοιός (της γης κ.λπ.), θράσος

    idioms:

    • crust of the earth    φλοιός της γης

    Italiano (Italian)
    crosta

    idioms:

    • earth's crust    crosta terrestre

    Português (Portuguese)
    n. - crosta (f)

    idioms:

    • earth's crust    crosta (f) da terra (Geol.)
    • upper crust    crosta (f) superior (Geol.)

    Русский (Russian)
    корка

    idioms:

    • earth's crust    земная кора
    • upper crust    элита

    Español (Spanish)
    n. - corteza
    v. tr. - encostrar, incrustar
    v. intr. - encostrarse

    idioms:

    • crust of the earth    corteza terrestre

    Svenska (Swedish)
    n. - skorpa, sårskorpa, jordskorpa, skare, skal, avsättning, fräckhet (sl.)

    中文（简体） (Chinese (Simplified))
    外壳, 面包皮, 坚硬的外壳, 盖以硬皮, 结硬皮

    idioms:

    • crust of the earth    地壳

    中文（繁體） (Chinese (Traditional))
    n. - 外殼, 面包皮, 堅硬的外殼
    v. tr. - 蓋以硬皮
    v. intr. - 結硬皮

    idioms:

    • crust of the earth    地殼

    한국어 (Korean)
    n. - 빵 껍질, 딱딱한 표면, 겉보기
    v. tr. - 겉껍질로 덮다
    v. intr. - 껍질이 생기다

    日本語 (Japanese)
    n. - パンの皮, パイの皮, 堅い表面, 外皮
    v. - 覆う

    idioms:

    • earth's crust    地殻

    العربيه (Arabic)
    ‏(الاسم) قشرة الخبز, القشرة الأرضيه‏

    עברית (Hebrew)
    n. - ‮קרום, קליפה, שכבה קשה, שכבת הסלע החיצונה של כדור-הארץ‬
    v. tr. - ‮הקרים‬
    v. intr. - ‮הקרים, קרם‬

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