Posted: March 22, 2017

This new book chapter highlights the unique characteristics of soils across the United States and discusses their genesis. The chapter is part of a new International Encyclopedia of Geography.


Soil diversity in the United States reflects a vast array of parent materials and topography, as modified and affected by changing climate and organisms through time. Although complex in origin, US soils have been classified, mapped in detail, and interpreted for their suitability and limitations for land uses. This Herculean task was accomplished by the US Soil Survey via a hierarchical taxonomic system used to classify soils known as Soil Taxonomy. At the highest taxonomic level are the 12 soil orders. Mollisols are the most widespread soil order in the conterminous United States; Gelisols are most common in Alaska; and Andisols are most common in Hawai'i. The prevalence of Mollisols across the central part of the United States, in addition to a favorable plant growth climate, is responsible for the largest and most productive agricultural system in the history of civilization. The greatest challenge currently facing US soils is human misuse of soil. Although the Soil Survey helped correct past human behaviors that were unsustainable, ending decades of poor soil management, the future security of US soils will depend on aggressive education and research on soil management in the face of an ever-growing human population.

The International Encyclopedia of Geography