windbleached

Windbleached is a geological term describing rock or mineral surfaces that have been lightened in color by wind-driven abrasion and related weathering processes. It refers to the removal or thinning of darker surface patinas, varnishes, lichens, and oxides through wind-blown sand and particles, exposing lighter underlying material. The effect is common in arid deserts and along wind-exposed coastal cliffs where strong aeolian activity abrades the surface.

The process involves mechanical erosion of the outermost weathered rind and coatings, sometimes aided by differential weathering that preferentially wears away darker layers. In coastal settings, salt spray can contribute to surface alteration, enhancing the pale appearance. Windbleached surfaces often display a smoother texture with micro-scratches and a contrast to adjacent sheltered areas that retain darker patinas or coatings.

Characteristics commonly observed include a lighter color relative to the surrounding rock, reduced or absent surface varnish or patina, and a relatively even, sometimes glassy or smoothly abraded finish. The phenomenon can reveal the color of the underlying rock and provide clues about past aeolian conditions, such as wind intensity and duration.

Windbleaching is distinct from sun-bleaching or chemical bleaching, being primarily a mechanical weathering result of wind-driven abrasion, though it may occur in combination with other weathering processes. It is used in geological descriptions to help interpret surface weathering histories in desert and coastal environments.