Accretion

ACCRETION (from the Latin word "accretio", which means "buildup" * EN: accretion; DE: Akkretion; FR: accroissement; ES: acrecimiento; RU: аккреция) is the process of the increase of the size of the inorganic body by its buildup at its periphery by the crushed or deformed, melted, dissolved substance from the (environment) surrounding space. The term is of the broad and multi-meaning usage.

1) The accretion of the planet is the condensation of the clastic particles of the protoplanetary cloud into the massive body of the planet. They distinguish the homogeneous accretion, with the maintenance of the uniform composition of the planet during the largest part of the process, and the heterogeneous accretion, with the change of the composition of the buildup shells.

2) The accretion of the continent is the growth of the continent by the way of the attachment and material-structural transformations of the crust of the oceanic segments into the continental crust. There are distinguished the concentric accretion, with the sequential building up by the ever younger shells from the periphery of the ancient continental nuclei (North America, Australia), and the agglomerative accretion, with the unifying into the monolith of the continental masses, which are of the different ages and different sizes, and have the independent internal structure (Eurasia). The opposite process, namely the destruction (the breaking of the continents into the fragments), is the process of the same scale, functionally linked, and simultaneous. The similar phenomena are observed in the oceanic segments of the crust.

3) The lithogeneous accretion is the formation of the new mineral in the sedimental rock (sediment), which is growing from the centre of the origin to the periphery as the result of the sequential addition from the outside, or of the redistribution in the surrounding rock (sediment), of the concretion forming substance (the nodules of flint, phosphorite, iron, manganese, etc.).

4) The volcanic accretion is the sticking of the lava bombs during the volcanic eruptions, or the buildup of the lava balls on the surface of the lava flow (for example, the aa-lavas of the Hawaii islands) during the sticking of the new quantities of lava around its solidified fragment.

5) The accretion of the watercourse or the water body of the natural or artificial origin is the filling by the natural or artificial sediments, sludges, which leads to its degeneration (degradation). The wider usage of the "Accretion" term is possible for the characterization of the certain phenomena in the natural or technological processes.