Dome dunes often form as barchan dunes evolve under shifting wind conditions. Specifically, they seem to arise when barchan dunes are reshaped by winds that blow from a slightly different direction than the original prevailing wind.
Here's a more detailed explanation of the process:
- Origin from Barchans: The process typically starts with barchan dunes, which are crescent-shaped dunes that form under unidirectional wind conditions.
- Wind Direction Shift: When the wind direction changes slightly (e.g., shifting from a consistent north wind to a north-northeast wind), the barchan's shape is altered.
- Asymmetrical Reshaping: The barchan's limbs (the extending "horns" of the crescent) respond differently to the new wind direction. In the referenced example, the southeast limb extends, while the northwest limb erodes.
- Ridge Obliqueness: This differential erosion and extension cause the dune's ridge (the crest) to become oblique, or angled, to the overall direction of sand movement. This change in orientation contributes to the developing dome shape.
- Development into a Dome: Over time, the reshaped barchan loses its distinct crescent shape and gradually evolves into a more rounded, dome-like form.
In summary, dome dunes are often a result of barchan dunes adapting to changes in wind direction, leading to asymmetrical reshaping and eventual formation of a dome-like structure.
