Wet soil will appear darker than dry soil.[1] However, the presence of water also affects soil color by affecting the oxidation rate. Soil that has a high water content will have less air in the soil, specifically less oxygen. In well drained (and therefore oxygen rich) soils, red and brown colors caused by oxidation are more common, as opposed to in wet (low oxygen) soils where the soil usually appears grey or greenish by the presence of reduced (ferrous) iron oxide.[1] The presence of other minerals can also affect soil color. manganese oxide causes a black color, glauconite makes the soil green, and calcite can make soil in arid regions appear white.[1]