Saltation

A geomorphological process, a special case of the transportaton of sediment, involving particles that bounce along the bottom surface of the transporting fluid (a river, or the wind).

In particle sorting I discuss how the velocity of a moving fluid carrying sediment determines the size of the particles the fluid can carry. At a given velocity, the fluid can carry particles below a certain threshold size, but cannot carry particles above that size.

For particles right near the threshold, this situation is metastable -- minor variations in the current, and the orientation of a particle, carry it back and forth across the threshold repeatedly. In other words, the fluid picks up and drops the particle over and over; the particle will appear or bounce along the bottom surface of the current (the bottom of the river, or the ground).

Bouncing particles can cause small particles to break loose from themselves, or from the bottom. Saltation, then, contributes to the erosion of the surface in question.

Stephen J. Gould's concept of punctuated equilibrium has been linked with saltation by creationists who disingenuously hope to co-opt Gould's ideas for their own ends. This was vehemently rejected by Gould prior to his death as the punctuated equilibrium is ultimately Darwinian and gradualistic.

Gould's theory indicates long periods of stasis with short periods of high evolutionary rates. The short periods are those which the Creationists attempt to equate with saltation. This is wrong in that these periods are geological in scale and the short period is a relative term and does not preclude gradualism and small modifications cumulative over hundreds or thousands of generations at the core of Darwinism.

Sal*ta"tion (?), n. [L. saltatio: cf. F. saltation.]

1.

A leaping or jumping.

Continued his saltation without pause. Sir W. Scott.

2.

Beating or palpitation; as, the saltation of the great artery.

3. Biol.

An abrupt and marked variation in the condition or appearance of a species; a sudden modification which may give rise to new races.

We greatly suspect that nature does make considerable jumps in the way of variation now and then, and that these saltations give rise to some of the gaps which appear to exist in the series of known forms. Huxley.

© Webster 1913.