Over time, the concepts of the series category and of individual series have changed, but more than 16,000 series are now defined and named. These definitions are the framework within which most of the detailed information about soils of the United States is identified with soils at specific places. These definitions also provide the principal medium through which detailed information about the soil and its behavior at one place is projected to similar soils at other places. Link to Official Soil Series Descriptions Rigorous standards for definitions of soil series ensure that names and descriptions for the same kinds of soils are consistent from survey to survey.
Consistency is a major objective of the correlation process.
The classes of the soil series category are not static. As new knowledge is acquired, definitions of some established series must be modified. New series are defined for newly recognized kinds of soils. Changes in criteria or limits of taxa in higher categories often require modification of definitions of member series. Keeping records of series names and updating definitions of series is a continuing process.