accretion

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Related to accretionary: accretionary growth, accretionary prism

accretion

1. Botany the growing together of normally separate plant or animal parts
2. Pathol
a. abnormal union or growing together of parts; adhesion
b. a mass of foreign matter collected in a cavity
3. Law an increase in the share of a beneficiary in an estate, as when a co-beneficiary fails to take his share
4. Astronomy the process in which matter under the influence of gravity is attracted to and increases the mass of a celestial body. The matter usually forms an accretion disc around the accreting object
5. Geology the process in which a continent is enlarged by the tectonic movement and deformation of the earth's crust

accretion

(aggregation) The increase in mass of a body by the addition of smaller bodies that collide and stick to it. The relative velocity of any two colliding bodies must be low enough for them to coalesce on impact rather than fly apart. Once a large enough body forms, its gravitational attraction accelerates the accretion process. Accreting objects in the Universe are numerous and diverse. They include protoplanets, protostars, black holes, and X-ray binaries. The accretion process is thought to occur generally in the form of a disk. Accretion is now assumed to have had an important role in the formation of the planets from swarms of dust grains. In the outer Solar System the grains were like dirty snowflakes and thus accretion was accelerated. See Solar System, origin.

accretion

[ə′krē·shən]
(astronomy)
A process in which a star gathers molecules of interstellar gas to itself by gravitational attraction.
(civil engineering)
Artificial buildup of land due to the construction of a groin, breakwater, dam, or beach fill.
(geology)
Gradual buildup of land on a shore due to wave action, tides, currents, airborne material, or alluvial deposits.
The process whereby stones or other inorganic masses add to their bulk by adding particles to their surfaces. Also known as aggradation.
(meteorology)
The growth of a precipitation particle by the collision of a frozen particle (ice crystal or snowflake) with a supercooled liquid droplet which freezes upon contact.
References in periodicals archive ?
The up-drift, conventional groin effect accretionary fillet (formed during fluctuating long-shore drift periods) apparently creates a disequilibrium "feeder beach" to offshore bars as a result of subsequent periods of reversed long-shore transport, steep, high-energy waves, and offshore-directed currents.
A second pair of holes has been drilled into the Cascadia accretionary prism, where over 2 kilometers of sediments are being scraped off the subducting Juan de Fuca plate along the west coast of North America, and slowly compressed into rock.
These estimates, however, do not account for the 2 to 6 order of magnitude larger than predicted fluid-flow rates measured at numerous channelized fluid venting sites, for example, at the Barbados, Nankai, and Cascadia accretionary complexes.
The lateral stability of low-energy river systems and their accretionary nature frequently results in the preservation of high-quality, in situ, multiperiod cultural remains ([ILLUSTRATION FOR FIGURE 4 OMITTED]; TABLE 3), usually buried within or beneath thick sequences of fine-grained alluvium (Thomas et al.
Recent plate-tectonic models indicate that many areas known as "orogenic belts," where Earth's crust has been deformed by such mountain-building phenomena as thrusting, folding, and faulting, have evolved through convergent-plate-margin processes such as formation of accretionary prisms, accretion of various exotic terranes, and the collision of arcs and continents.
Recent studies of terrane accretion in the Canadian Cordillera suggest that some accretionary processes can be "thick-skinned", i.
Individual topics include interaction between normal faults and pre-existing thrust systems in analogue models; analogue and numerical modeling of accretionary prisms with a decollement in sediments; and the relation between effective friction and fault slip rate across the northern San Andreas fault system.
Annieopsquotch, Skidder) that were subsequently accreted to the Laurentian Margin to form the Annieopsquotch Accretionary Tract (Lissenberg et al.
The first is the recognition of a dynamic, accretionary, humanly-constructed and maintained environment.
The closing of ocean basins through subduction means that the ultimate fate of these turbidite sequences is to be highly fragmented and deformed in subduction zone accretionary wedges and eventually to form part of collisional orogenic belts, and become welded into the crystalline metamorphic fabric of continental crust.
Near the trench, the fore-arc exhibits complex deformation as sediments deposited in the trench are scraped off the downgoing plate and are plastered onto the inner trench wall to form an accretionary prism.