What condition leads to the formation of redoximorphic features?

The formation of redoximorphic features in soil is primarily associated with the alternating saturation and unsaturation conditions. Redoximorphic features are indicative of the processes that occur during periods when soils are both saturated with water (anaerobic conditions) and then subsequently unsaturated (aerobic conditions).

During saturation, the lack of oxygen restricts the microbial processes that typically oxidize iron and manganese minerals found in the soil, leading to the formation of reduced, often greyish colors. When the soil becomes unsaturated, oxygen can penetrate, which allows for the oxidation of these minerals, resulting in the formation of brightly colored ochre, reddish, or yellow hues. This interplay of oxidation and reduction creates the characteristic mottling and patterns observed in redoximorphic features.

In contrast, extended periods of drought would not create the conditions necessary for this phenomenon, nor would continuous exposure to sunlight directly influence the redox processes occurring in the soil. The placement of heavy construction fill could physically alter the soil but would not inherently create the redoximorphic features associated with natural soil processes related to moisture fluctuation. Thus, the alternating saturation and unsaturation of soil serves as the critical condition leading to the development of these distinct redoximorphic characteristics.