Metamorphism
Metamorphism
Metamorphism refers to the physical and chemical changes that rocks undergo when exposed to conditions of high temperature , high pressure, or some combination thereof. Rocks that have undergone metamorphism exhibit chemical and structural changes that result from the partial or complete recrystallization of minerals within them. These transformations occur while the rock is in the solid state, i.e., no melting occurs during metamorphism. The conditions of high temperature and pressure under which metamorphism occurs are typically the result of processes such as mountain building, plate convergence, volcanism, and sedimentation .
Any type of rock may be metamorphosed and several agents can be involved in altering a parent rock into its metamorphic product. The composition of the parent rock limits the mineral composition of the product, although subsurface gases and fluids may contribute new elements. Thermal energy at depth, either from the geothermal gradient or from plutonic activity, may provide the energy for recrystallization of the rock. As the temperature increases, volatile components such as water and carbon dioxide can be released causing chemical changes to the minerals within the parent rock. In addition, the temperature increase may cause the rock to behave plastically in response to stresses acting on it, frequently resulting in a contorted appearance. Pressure on the parent rock may be a result of the overlying rock, known as lithostatic or confining pressure, or may be due to forces acting in a particular direction due to tectonic activity, known as directed pressure. Pressures within the rock may cause the instability of certain minerals in favor of those that are more stable under the new conditions. The pressure may also be localized on irregularities on the boundaries of individual grains. Recrystallization of a rock undergoing directed pressure typically results in the development of a foliated rock fabric, in which the axes of the minerals are aligned with the differential pressures based on the stability of the crystal lattice to those pressures. The development of such crystals during metamorphism may be heavily influenced by amount of time that the rock is exposed to the conditions. The mobilization of ions that supports crystal growth within the rock can require extensive periods of time to produce larger mineral grains.
Metamorphism may occur in a number of forms, each having different results and areal extent. Contact metamorphism is the baking of country rock immediately adjacent to an intruded magma body. This type of metamorphism, also known as thermal metamorphism, is caused by the high temperatures associated with an igneous intrusion. The rock is altered only in a zone, called an aureole, which can range from a few centimeters to several hundred meters in width. These zones may occur very near the surface and pressure plays an insignificant role in the process. In the case of cataclastic or dynamic metamorphism, rocks in a localized zone undergo mechanical disruption without significant mineralogical change. This is a near-surface phenomenon that is often associated with faulting and occurs at low temperature. Regional metamorphism, as the name suggests, encompasses large areas and is associated with large mountain building and plutonic events. Relatively high temperature and intense, directed pressures are common in this process. The differential stress associated with regional, or dynamothermal, metamorphism frequently yields foliated rock.
See also Metamorphic rock; Shock metamorphism
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Canvas coterie. (growing appeal of canvas shoes)
Magazine article from: Footwear News; 8/3/1992; ; 700+ words
; ...shopping lists these days. Mass producers of canvas sneakers may be gobbling a large slice of the canvas pie, but big-name designers are carving...footsteps of fashion leaders, rubber-bottomed canvas shoes for spring '93 include lace-up versions...
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Canvas attributes, Part II: in part two of this article we will focus on test different products and different brands when selecting digital inkjet canvas.
Magazine article from: Wide-Format Imaging; 10/1/2006; ; 700+ words
; ...two most common fine art canvas options are 100 percent cotton canvases and poly/cotton blend canvases...canvases (or "poly/cotton canvases") have become the most widely used canvas base. Poly/cotton canvases are of not inferior in print...
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Canvas attributes, Part 1: points to consider when selecting digital inkjet canvas.
Magazine article from: Wide-Format Imaging; 9/1/2006; ; 700+ words
; ...most visually appealing canvas prints, is to test several different canvases for color gamut, Dmax...competitor who uses a canvas with superior resolution. It should be noted that canvases with excessive texture...peaks and valleys in the canvas texture can cause ink...
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Canvas Attributes Part II.
Magazine article from: Wide-Format Imaging; 10/1/2006; 700+ words
; ...two most common fine art canvas options are 100 percent cotton canvases and poly/cotton blend canvases...canvases (or "poly/cotton canvases") have become the most widely used canvas base. Poly/cotton canvases are of not inferior in print...
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CANVAS ENTERS MAINSTREAM CLOSET STORAGE.
Magazine article from: HFN The Weekly Newspaper for the Home Furnishing Network; 9/15/2003; ; 700+ words
; ...YORK-Closet storage is going soft. Canvas closet organization products have grown...Rubbermaid, noted that like many trends, canvas started in the furniture and high-end...and the mainstream. You see a lot of canvas [closet storage items] in Lowe's...
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Canvas 8: all-in-one graphics app has important new features. (Reviews).
Magazine article from: Macworld; 4/1/2002; ; 700+ words
; Canvas, from Deneba, brings together drawing...applications in one package. The latest version, Canvas 8, has an improved tool set, new scripting...improvements, and it's Carbonized for OS X. Canvas is a good tool for some graphic designers...
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Canvas On Demand Sends Photo Albums to the Wall.
PR Newswire; 2/15/2006; 678 words
; ...important athletic win, Canvas On Demand has the perfect collage choices." From the Canvas On Demand home page (http...yourself? View examples of canvases and read testimonials from real customers at the Canvas on Demand Web site, http...
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Canvas editions infuse art sales: prints on canvas, particularly giclees, are a hot commodity for dealers and collectors. (Special Report).
Magazine article from: Art Business News; 3/1/2003; ; 700+ words
; ...framed without glass. Canvas has an elegance and stature...prints." Giclees on canvas account for about two...We are doing more canvases than paper," noted...vibrancy in the giclee canvases," she said. "Basically...computer and output it on canvas. There is no film...
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Canvas transfers: offer an affordable alternative: art buyers are often impressed by canvas transfers, which offer the look of an original painting at a fraction of an original's price.
Magazine article from: Art Business News; 12/1/2002; ; 700+ words
; ...the look of an original by transferring it onto canvas. Because the look of canvas transfers often suggests the look of an original...attention of art buyers and sellers everywhere. "Canvas transfers have been extremely popular for us...
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Canvas Systems Standardizes on Salesforce with Rapid Rollout in Less than One Month.
PR Newswire; 9/27/2007; 700+ words
; Canvas Systems increase information sharing and...business services, today announced that Canvas Systems has standardized on Salesforce Software...a-Service CRM. Using Salesforce CRM, Canvas Systems has significantly improved information...
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SIC 2394 Canvas and Related Products
Encyclopedia entry from: Encyclopedia of American Industries
...Establishments primarily engaged in manufacturing canvas bags are classified under SIC 2393: Textile Bags. NAICS Code(s) 314912 (Canvas and Related Product Mills) In the early 2000s, most companies primarily producing canvas and related products were small. Approximately...
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canvas
Book article from: The Oxford Pocket Dictionary of Current English
...surface for oil painting: [as adj. ] a canvas bag. ∎ a piece of...painting. ∎ a variety of canvas with an open weave, used as a basis for...embroidery. ∎ ( the canvas ) the floor of a boxing or wrestling ring...
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shaped canvas
Book article from: The Concise Oxford Dictionary of Art and Artists
shaped canvas. A term that began to be used in the 1960s...and so on. The phrase ‘shaped canvas’, however, usually alludes...x2018;inventor’ of the shaped canvas in this sense, but its most prominent...
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Canvas
Dictionary entry from: Dictionary of Collective Nouns and Group Terms
Canvas paintings collectively; sails collectively; tents collectively; also used figuratively to mean ‘ a wide range, a large expanse. ’ Example: canvas of fancy, 1822.
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canvas board
Book article from: The Oxford Dictionary of Art
canvas board. Sheet of cardboard or pasteboard covered with sized and primed cloth, usually cotton. It was first made commercially in the 1870s and is now chiefly used by amateurs as a cheap substitute for canvas. See also academy board .
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