saltasjon

Saltasjon, also spelled saltation in English, is a term used in several scientific disciplines to describe a leap-like, discrete step in a process rather than smooth, continuous change. The word derives from Latin saltare, “to leap.”

In geomorphology and sediment transport, saltasjon refers to the hop-and-bounce movement of particles, typically sand or silt, carried by a fluid such as wind or water. Particles are intermittently lifted from a surface, travel short ballistic paths, and impact the surface again, possibly ejecting other grains. This mode of transport operates above a threshold flow velocity and depends on particle size, density, surface roughness, and fluid conditions. Saltation is a key mechanism in dune formation and riverbed sediment dynamics.

In evolutionary biology, saltasjon describes abrupt, large-scale evolutionary changes believed to occur in a single step due to macromutations or chromosomal rearrangements. This view contrasts with gradualism, the idea that evolution proceeds mainly through many small increments. While macromutations and rapid shifts remain topics of discussion, modern evolutionary theory emphasizes a spectrum of changes, with saltation as a historical concept rather than a universally accepted mechanism.

In genetics and botany, the term is sometimes used to refer to sudden, large phenotypic changes arising from significant genetic alterations, including polyploidy in plants. The usage and emphasis of saltation vary by discipline and context, but across fields it generally denotes leap-like changes rather than gradual transitions.