What is the most common type of soil in the US?
Answers
The US soil taxonomic hierarchy includes orders, suborders, great groups, subgroups, families and series, with each series representing a unique kind of soil. In the United States, over 19,000 soil series have been identified.[1] The percentages of land area (in the US and associated territories, etc.) occupied by soils of the twelve orders have been estimated[1] as:
type percent
Alfisols 13.9
Andisols 1.7
Aridisols 8.3
Entisols 12.3
Gelisols 8.7
Inceptisols 9.7
Mollisols 21.5
Oxisols 0.02
Spodosols 3.5
Ultisols 9.2
Vertisols 2.0
Alfisols and Inceptisols occur widely in the US, but the circumstances of their occurrence would be difficult to characterize briefly. The Alfisols have a subsurface ("B") horizon characterized by phyllosilicate clay accumulation (suggesting illuviation of such clay from above). The Inceptisols have a weakly developed B horizon as a consequence of weathering and/or other processes.
Andisols are found in areas where soils have formed in certain kinds of volcanic ejecta (usually pumice and/or volcanic ash).
Aridisols occur in parts of the western United States which are too dry for the growth of mesophytic plants.
Entisols, which exhibit little soil profile development, are characteristic of areas where soil parent materials have quite recently been deposited, e.g. on recent river alluvium.
In the US, Gelisols occur only in parts of Alaska; they are characterized by having permafrost within 100 cm of the surface.
Histosols are organic soils lacking permafrost within 100 cm of the surface; they are characteristically formed on wet sites, e.g. bogs, some fens and some muskeg areas. Some Histosols have been drained, especially to permit cultivation.