Vegetation plays a major role in stabilising the surface of the dune sand, developing root systems in the unconsolidated substrate, creating a layer of calm air immediately above the surface and adding organic matter which will also help to hold the sand together. If the vegetation is removed (for example by rabbit burrowing) this protection is gone. Strong winds can then pick up the sand and blow it elsewhere. A 'hole' is created in the surface of the dunes called a blowout.

Formation of blowouts is an entirely natural process in the dunes. The very highly specialised plants of the early stages of dune succession (such as Marram) are very susceptible to damage and strong winds are experienced at the coast.

The sand surface of the blowout may eventually be recolonised by plants and 'heal' over. Sand Sedge Carex arenaria is well adapted to do this by sending underground rhizomes across the sand just below the surface, with shoots growing upwards to the surface at regular intervals.

The blowout may continue to increase to an extremely large size. There is an enormous blowout on Ravenmeols Local Nature Reserve called the Devil's Hole.

If the surface is eroded down to the level of the water table wet sand will be exposed. The wind cannot pick up wet sand as the water holds the sand grains together and the hollow will not become any deeper. This creation of a surface of wet sand is how a secondary dune slack is formed.