Barchan

A barchan is a crescent-shaped dune with horns pointing downwind. It forms where sand is limited and winds are relatively steady.

Saltation: The hopping movement of sand grains driven by wind or flowing water. Hopping grains strike the dune and help move sand toward its crest.
Dune: A hill or ridge of loose sediment shaped by wind or water. Barchans are one distinctive form within the broader family of dunes.
Transverse dune: A long ridge of sand oriented roughly perpendicular to the prevailing wind. Unlike isolated barchans, transverse dunes commonly form where sand is abundant.
Dune field: An area containing a group or system of dunes. Patterns across a barchan field show how dunes interact and migrate together.
Sand transport by wind: The movement of sediment by wind through suspension, saltation, and surface creep. Its processes supply the grains that build and reshape barchans.
Crescentic dune: A curved dune with arms extending from a central body. Barchans are crescentic dunes distinguished by limited sand and horns pointing downwind.
Longitudinal dune: An elongated dune ridge aligned approximately parallel to prevailing winds. Its ridge orientation contrasts with the crescent and downwind-pointing horns of a barchan.
Remote sensing of dunes: The use of satellite, aerial, or radar data to observe dune landscapes. Repeated imagery measures barchan migration over large or inaccessible areas.
Dune migration: The movement of a dune across a surface as sediment is eroded from one side and deposited on another. Barchans advance downwind as grains pass over their crests and slip faces.
Horns (geomorphology): The projecting ends of a crescent-shaped landform, including certain dunes. Their downwind orientation is a defining visual cue for barchans.

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