Stratification

Stratification is the process by which a system develops or is divided into distinct layers, or strata. The term is used across disciplines to describe hierarchical organization or layered structure, often with implications for function and history.

In geology, stratification refers to the layering of sedimentary rocks into beds separated by bedding planes. Each layer records a particular environment and time interval, and stratigraphic sequences are used to interpret Earth's history.

In sociology, social stratification describes a system by which a society ranks people in a hierarchy based on attributes such as wealth, occupation, education, and prestige. It tends to influence access to resources and life chances, with varying degrees of mobility.

Stratification is also important in environmental and earth systems, including soil horizons (labeled O, A, E, B, C) and in limnology, where lakes can develop vertical temperature or chemistry layers that limit mixing.

In research design and genetics, stratification governs sampling and analysis. Stratified sampling divides a population into homogeneous subgroups to improve precision. Population stratification in genetics refers to systematic allele frequency differences between groups that can confound studies.

In materials science and engineering, stratification describes layered structures such as laminates and coatings, where individual layers provide distinct mechanical, thermal, or chemical properties.