||FORMATION OF PROTECTIVE DUNES
Definition characters description and diffusion
The artificial protective dunes called afreg originate from the sand transported by the wind that accumulted when it finds an obstacle or a deposit of sand, which stop the grains of sand from bouncing ahead. Over time the afregs grow higher and the oasis takes on the shape of a sand crater with a tilled bottom. The leaves of the palms close off the top of these large funnels that maintain an ideal microclimate inside.
General characters description and diffusion
In the Algerian region of the Souf of the Great Eastern Erg, the excavation of these depressions out of the sand shapes an extraordinary landscape where the perpetual movement of the erg, which is composed of long dune lines, is modulated by hundreds of craters. The latter look as if they are floating on the sand, which could submerge them at any moment, whereas the destructive strength of the erg is actually turned in favour of the oasis, which absorbs moisture from the erg and thus can protect itself from the wind and the heat.
Advantages and sustainability
Dunes protect the microclimate by shielding against wind and heat while helping the absorption of moisture. The dunes are constantly moving in adaptation to the outer climate while still maintaining the microclimate inside.