Where does terrace collide?

In crystal growth, a terrace is a flat, atomically smooth plane of a crystal surface, bounded by steps, across which adsorbed atoms diffuse until they attach at a step edge, in the terrace–step–kink picture of how a face advances. Burton, Cabrera, and Frank's 1951 The growth of crystals and the equilibrium structure of their surfaces built the theory in which growth proceeds by atoms crossing terraces and joining steps, often fed by a spiral around a screw dislocation. The referent is a surface feature on a crystal, measured in atomic layers and step spacing, and it is unrelated to a river bench or a farmed hillside beyond the shared image of a flat step.[1]

Unit

A flat, step-bounded plane of a crystal surface, in atomic layers

Recovery means

Not applicable

Measured by

Resolved by scanning tunnelling and atomic-force microscopy as terrace width and step height

In geomorphology, a river terrace is a bench along a valley that marks a former floodplain level, left stranded above the present channel when the river later cut down into its bed, so a flight of terraces records successive stages of incision. Gao and colleagues' 2016 Climatic and tectonic controls on strath terraces along the upper Weihe River reads such a staircase to separate the climatic and tectonic signals driving the downcutting. The referent is a landform recording past valley-floor levels, dated and measured by height above the river, and it is a different thing from a crystal surface or a farm bench despite the shared stepped form.[2]

Unit

The height and age of an abandoned valley-floor level above the channel

Recovery means

Not applicable

Measured by

Mapped and dated by terrace height above the modern channel and the age of terrace deposits