We know soil is of two types depending on origin, namely residual soil and transported soil; we have discussed many posts about both types of soil. Residual soil may be formed due to weathering of both hard rock and chemically reactive rocks.
Thus residual soil may be found by chemical and physical weathering of different types of rocks. The rocks may be of
a. Sedimentary rock
b. Metamorphic rock
c. Igneous rock
The content of residual soil and contamination too depends on the rock types from which they formed and the process under which they weathered.
Soils formed in such manner usually contain silty sands or sandy silts. As contamination there may contain
-some mica particles
-some clay particles
Particle shapes of residual soil are found more angular than particles of sedimentary deposits. In many cases, soil contains pebbles of angular to subangular shape. Large pieces of rocks may remain in residual soil which are not weathered or remain under weathering.
Dear reader in our next post we will discuss about effect of rainfall on residual soil.