Contemporary evolution of the natural environment of the region between Antiatlas and Sahara (Morocco)
Skiba S., Krzemień K. (red.), 2008, Contemporary evolution of the natural environment of the region between Antiatlas and Sahara (Morocco), Prace Geograficzne, z. 118.
Język publikacji: angielski
Cena: 36.75 PLN (w tym 5% VAT).
Morphostructural and geomorphological outline of Morocco
Recent erosion measurements in Morocco
Physical geography of the Coude du Dra region
Soils of the southern part of Morocco
Properties of the desert soils of the Mhamid area
Reasons for development of the dune fields in the Coude du Dra region
Extorted forms of aeolian accumulation in the Coude du Dra region
The source of the Aeolian sediments in the Coude du Dra region
Surface features of sand grains from the Coude du Dra region (Morocco)
The geomorphological role of episodic rivers based on the example of the Oueds el Mut and el Feija (AntiAtlas Mountains, Morocco)
Natural and anthropogenic factors of the development of Erg Chebbi
Summary: Estimation of the factors determining the development of Erg Chebbi, especially the influence of the human activity on the increase of the deflation intensity in the source areas, were the aim of the studies presented in this paper. This erg, occurring in the south-eastern part of Morocco along the border with Algeria, is formed by 13 star dunes and complex transversal dunes, the latter developed in the margins of the erg, mainly in its eastern and southern parts. On the basis of the textural analysis of the dune and basement material, the degree of aeolization of the sediments and their source areas were determined. The results of the investigations indicated high degree of eolization and allochthonous source of the sediments which formed the dunes in Erg Chebbi. This is evidenced by high uniformity of the dune material within individual forms and in the erg as a whole, moreover by relatively large grain diameter, good sorting, negative values of the skewness index suggesting absence of the local fine-grain material supply and generally low participation of the local material poorly resistant to abrasion in the dune sediments. Taking into account the climatic conditions (mainly the wind velocity and direction) it was found that the areas of the vast hamadas, i.e. Guir in the east and north-east, and Kem-Kem in the west and south-west are the main source regions of the material building the star dunes in Erg Chebbi. These areas are largely not populated, and recently did not suffer any sudden changes of the natural conditions. Desertification of the source areas may be connected with the global climate changes and only in this context one may discuss the indirect human influence on the development of Erg Chebbi. Initial accumulation of the dune material was connected with the surface morphology of this area. Erg Chebbi formed in the lowest part of the depression, where two factors forcing sedimentation of the material transported by wind were present - this means the shallow or surface-reaching ground water and vegetation connected with these water conditions. The obtained results indicate as well the significant difference of the textural features of the dune sediments occurring in the surroundings of Erg Chebbi and the basement sediments. The dunes form a system with a distinct, linear shape connected with the network of the river beds. The source of the material of these dunes is connected with the material transported formerly by rivers, which subsequently became episodic rivers. One found that the present-day absence of flow in the river beds, which are source of material for these dunes, is connected with the decrease of precipitation and degradation of the plant assemblages, the latter resulting in poorer retention of water, and only in slight degree - with decrease of water supply caused by the local human activity. On the basis of the performed studies one also found that the fast change of certain environmental factors in the area of Erg Chebbi, resulting from strong recent anthropopression, was not in the past and is not presently of any real importance for the development of this dune field.
Słowa kluczowe (w języku angielskim): dune development reasons, star dunes, dune sediment source, sediment textural features, Erg Chebbi, NE Morocco.
Prace Geograficzne, 2008, z. 118, s. 119-134.
Instytut Geografii i Gospodarki Przestrzennej UJ
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