How parent materials influence the soil color?

Question

How parent materials influence the soil color?

Answer 1

One of the most important factors is the type of rock from which the inorganic material in the soil originated. The parent rock provides the soil with a great deal of the chemical backbone for the soil.  The elements contained in the parent rock will contribute to the color of the soil.  However, other factors do come into play, such as volume of rainfall.

For example: Parent rock that contains iron will usually lend a reddish color to the soil.

Calcareous soils develop from a lime-stone parent rock.  A sub type of this soil is Terra-Rossa.  When there is a high rainfall volume, even if it is only seasonal, this causes leaching with in turn leaves behind a residual deposit that is rich in iron hydroxides - this is what gives it its red colour and its nickname of red rendzina.

Another type of soil that contains iron from the parent rock is Gley soils. These occur when the pore spaces between the grains become saturated with water and contain no air. This lack of oxygen leads to anaerobic conditions which reduce the iron in the parent rock. This gives the soil a characteristic grey/blue colour with flecks of red.