In figure 5-2 what is the layer labeled y composed of

In the soil profile, the remains of plants and animals are present in a layer known as the humus layer. The topsoil or the A horizon refers to a zone of leaching and the habitat of various species. The subsoil or the B horizon refers to a zone where the organic matter and soluble salts are leached from the A horizon is accumulated.  

The weathered part of the rock, which produces the parent substance over which a soil establishes makes the C horizon, and the unweathered part of the parent substance forms the D horizon. Thus, from the given diagram it is clear that the layer Y comprises unweathered part of the parent material.  

igneous rocks are formed by solidification of cooled magma (molten rock), with or without crystallization, either below the surface as intrusive (plutonic) rocks or on the surface as extrusive (volcanic) rocks.  

the composition depends on the source magma. there are almost a thousand types of composition found till now.  

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