Anaerobic means that they do not need oxygen to live. If you walk past a wetland and smell a rotten egg smell, what you are actually smelling is sulfur being produced by these anaerobic bacteria. Click to enlarge. Mineral Soil Mineral soils are usually made up of sand, silt, and clay, with some organic matter at the soil surface. Mineral soils that are wet most of the time are often considered gleyed.
Gleyed soil has a gray, greenish gray, or bluish gray color.
Click to enlarge. In soil layers that are wet and then dry, something called mottling may occur. Soil that is saturated for a short time may be more brightly colored with grayish mottles. Soil that is not hydric usually is bright colored near the surface and does not have mottles. Click to enlarge.