Tunisia is divided into two almost equal parts by a series of salt lakes (chotts), the largest of which is the Chott el Djerid. The boundary runs to the south of a line from Tamerza (near the Algerian frontier) by way of Gafsa to Maknassy and from there to the Gulf of Gabès. To the north is the steppe country of southern Tunisia, which becomes increasingly barren towards the south and beyond the chotts gives place to the desert. Within Tunisia the string of chotts begins in the west with the Chott el Rharsa and is continued by the Chott el Djerid (110km/68mi long by 70km/43mi wide) and its eastern offshoot the Chott el Fedjadj (90km/56mi long by up to 20km/12.5mi wide), which together form the largest salt lake in the Sahara (7,700sq.km/2,975sq.miles). Within this region are the two largest areas of oases in Tunisia: to the north the Bled el Djerid around Tozeur, Nefta, El Oudiane and El Hamma, to the southeast the Nefzaoua oases round Kebili and Douz.
In this region there are more than 3million date palms: hence the name of Bled el Djerid, the Land of Palms (djerid = "palm"). These charming oases, set amid an alien landscape, are now popular tourist attractions, and there are numerous ambitious projects for the planned development of the tourist trade.
Origins
The scenically very impressive depression occupied by the lakes, part of which is below sea level, was formed by tectonic movements in the late Tertiary era, some 1.5million years ago. The depression is believed to have been flooded by the sea at one time and then dried out. In spring and autumn heavy rain and underground springs of water coming from the hills to the north lead to the formation of great expanses of shallow pools and salt marshes. The rain, however, soon evaporates (the evaporation rate being five times higher than the rainfall), leaving the salt washed out of the rock on the surface. Great areas are covered with a shimmering bluish-white crust of salt, which crystallizes in huge and bizarrely shaped masses. Under the salt lakes are huge fossil reserves of water, which irrigate the surrounding oases and frequently emerge on the surface as fresh-water springs (aioun, singular ain). It is highly dangerous to leave the proper track (see below) and try to cross the chotts, since in many places the salt crust does not rest on solid ground and may collapse. In spring the Chott el Rharsa and Chott el Fedjadj are a favored breeding ground for flamingoes, who fly in from northern Tunisia, build their nests, produce and rear their young and then fly off again at the beginning of July. Deposits of colored salt crystals, mirages (optical illusions produced by the refraction of light in unevenly warmed layers of air) and the occasional dust-storms on exceptionally hot afternoons are among the unusual experiences that visitors may encounter in this strange landscape.
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Chott el Djerid
