Environmental Engineering Reference
In-Depth Information
flaps and folds, including two massive arrays, separated by a longitudinal groove
(the Cheliff depression); other main features are: the massif of Dahra, near Miliana;
the Djurdjura (reaching 2308 m at Lalla Khadıdja, the highest point of Atlas Tell)
and the mountains of Tlemcen (elevation 1841 m); Saida (1180 m); the massive
Ouarsenis (1983 m); the Titeri mountains and the chain of Biban. The Atlas chain
continues in Tunisia, in the mountains of Medjerda.
The Saharan Atlas mountains, separated from the Atlas Tell by a series of
plateaus, stretch for approximately 700 km from the Moroccan border region to
Biskra, beyond which they continue in the Aures mountains. They consist of a
regular succession of folds grouped in clumps, and reach a height of 2326 m at
Mount Chelia. In the Western Atlas the Tell is split into a coastal range (Rif) and
the Middle Atlas further inland. Between the two mountain chains, the corridor
of Taza creates a natural route of communication between Morocco and Algeria.
To the west the Saharan Atlas extends as the High Atlas, in a WSW-ENE direc-
tion, for approximately 750 km entirely in Morocco, from the plain of Tamlelt to
Thira Cape. This is the highest part of the Atlas chain, with an average elevation
of 2000 m and culminating at 4165 m s.m. in Mount Toubkal; the eastern sector is
mainly composed of Jurassic limestone, while the western one is formed of crys-
talline rocks, raised a considerable height by powerful vertical movements. The
presence of glacial cirques and valleys testifies to events of the glacial Neozoic.
The Atlas system is located in the path of oceanic air masses and receives abun-
dant rainfall, especially on slopes exposed to the west. Its highest peaks are very
snowy winter, and in the High Atlas are permanently covered with snow. The still
active tectonics and the evolution of the climate during the Pleistocene are the main
factors affecting the geomorphological dynamics of the landscapes. This is clearly
evident in the forms shaped by the erosion of the slopes at lower altitudes, char-
acterized by the presence of vertical walls engraved deep into the high mountain
plateaus. This combination of morphologies is accompanied by the geographic lo-
cation: a zone of transition between the temperate Mediterranean climate to an arid
one, more properly related to the physiographic system of the Mediterranean coasts
of Africa.
4.7.2 The Baetic Cordillera and the Sierra Nevada
The Baetic mountain chain is an impressive complex of ridges in the south and
southeast of the Iberian Peninsula, extending approximately 1000 km from the Strait
of Gibraltar to Cape Nao. It is bounded to the south by the Mediterranean, and to
the north by the valley of the Guadalquivir River. It comprises several mountainous
areas, mostly arid and barren, and includes the Sierra Nevada, which culminates in
Mount Mulhacen at 3482 m.
The geological setting is linked to the tectonic collision during the Alpine
Orogeny with the African plate. Since the Tortonian, the situation in the Baetic
Cordillera and northern Morocco has been compressive in a NNW-SSE to N-S
direction, combined with an east-west extension.
