Soil Genesis and Development, Lesson 5 - Soil Classification and Geography Glossary


Sediments deposited by the running water of streams or rivers. Alluvium may occur on terraces well above present streams, on the present flood plains or deltas, or as a fan at the base of a slope. (SSSA)


1. The absence of molecular oxygen (O2). 2. Anaerobic soil -- a condition that exists in soils when they are flooded or compacted.

B horizon

The B horizon is typically a mineral subsurface horizon. B horizons are zones of accumulation, called illuviation, such as an accumulation of clay, soluble salts, and/or iron. Minerals in the B horizon may be undergoing transformations such as chemical alteration of clay structure. The dominant processes in a B horizon are transformations and additions.


Permanently frozen material underlying the solum. (ii) A perennially frozen soil horizon.

soil taxonomy

The classification and naming of soils.