Parent Rock

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parent rock

[′per·ənt ‚räk]
The rock mass from which parent material is derived.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Parent Rock


the upper layer of rock on which soil forms under the influence of biological and biochemical processes and human activity. The properties of the parent rock are changed in the process of soil formation through the effect of other soil formation factors such as climate and vegetation, but to a large extent the properties of the parent rock still determine the properties of the soils—mineralogical and chemical composition, texture (granulometric composition), physical properties, and fertility as a whole.

Parent rocks are distinguished according to origin (for example, alluvial and igneous), chemicomineralogical properties (carbonaceous, feldspar, quartz), and texture (sandy, loamy, clayey). Since parent rock greatly affects the soil characteristics, soil maps usually show parent rocks in addition to the genetic soil group (chernozems, podzols). The properties of the parent rock often determine the formation of different independent genetic groups of soils: types (for example, soddy-calcareous soils), genera (residually calcareous, residually solonetz), varieties based on texture, and classes based on the genesis of the parent rock.


The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
In drilling three holes are drilled at suitable location in parent rock. During drilling one hole is made vertical while other two holes are made horizontal.
Therefore, the mineral compositions of the parent rock in the study area became the main determinant factor of the extreme clay content in the altered volcanic materials [20].
Metallic mallets and thick chisels are used to split stone blocks from the parent rock before cutting them into suitable sizes.
But its true parent rock probably formed in the same part of the solar system as Vesta.
This study which will be conducted over 13 months, by a grouping of two Tunisian and Canadian consulting firms with a budget of 2 million dinars (part of the State budget), will help analysise the assumptions of extraction and exploitation of unconventional hydrocarbons (fracturing technique to search for hydrocarbons within the parent rock and mainly shale gas) to determine the sites of the deposits and present the international experiences in this field.
where [F.sub.R] is resultant force on the rock fragment due to the front blade surface; [F.sub.N] is resultant force on the overcut area due to the rear blade surface; [[PHI].sub.b] is friction angle between the cutting blade and the dense core; [[PHI].sub.B] is friction angle between the cutting blade and the parent rock; g is normal vector of the front blade surface; U is chip removal velocity vector; [g.sub.[beta]] is unit vector normal to the rear blade surface; and [[alpha].sub.[beta]] is unit vector normal to the rear surface of the inward cutting blade.
Gneiss types vary with the parent rock from which they formed originally, and there are many grades of gneiss.
The melt inclusions are hypothesized to be the product of partial melting during high-grade metamorphism of the parent rock, which produced a silica-rich melt and an alumina-rich residue from which the sapphires crystallized.
Chemical weathering of the rocks is one of important surficial process that causes geochemical redistribution of elements and is controlled by various factors such as topography, parent rock type, climate conditions, plant and biological activities (Bardossy, 1982; Bogatyrev et al., 2009).
According to studies, humus horizons of black soil and solonetzes are enriched in microelements relative to the parent rock material (Table 1).
Therefore, within flat terrain macroforms (automorphic conditions) the regular change of soil morphological structure is determined primarily by bioclimatic (bioenergy) potential of landscape zone, by the properties of the parent rock and soil formation period.

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