How does wind create deflation hollows?
A deflation hollow is a depression where wind has removed loose surface grains. It can occur behind beaches where vegetation has been disturbed and on exposed arid ground.
Removal of sediment
Sparse vegetation leaves sand and silt more easily lifted. As wind carries them away, the hollow can widen and deepen, with sand accumulating nearby. Moisture, roots, coarse gravel or groundwater may limit erosion, so the hollow does not deepen indefinitely. Heavy foot traffic or land use can help initiate some coastal examples.
Difference from a dune
The hollow records removal, whereas a dune records deposition; the same wind system can create both side by side. Shape alone cannot prove wind origin, since water can also carve basins. Sediment pathways, vegetation and changes through time need consideration. Conserving coastal dunes depends on the balance between natural sand supply and vegetation.