Relief
Algeria is characterized by five distinct geographical zones running parallel to the Mediterranean and following each other from north to south: the coastal Tell, the Tellian Atlas, the high plateaus, the Saharan Atlas and the Sahara. Smaller, well-defined areas such as Kabylia, the Aurès and the oases of the Sahara overlap these larger regions.
The Tell is the northernmost region. Benefiting from a Mediterranean climate, it is a narrow coastal strip where most of the larger towns and food crops are concentrated. Mostly steep, rocky and riven with coves, the coast, with its typically Mediterranean relief and colors, dominates the sea with its cornice-like roads. To the south, the region is bounded by a 1,200 km long and 125 km wide mountain range, the Tellian Atlas, which runs parallel to the coast from the Tlemcen region to the Moroccan border around Annaba.
The Atlas includes the Tlemcen mountains, the Ouarsenis east of Oran (1,985 m), the Sahel mountains of Algiers, the Djurdjura massif (Lalla Khadidja, 2,308 m) and the Constantinois mountains, separated by valleys and plains, including the Sig plain, the Oued Chélif valley, the Mitidja plain south of Algiers, the Annaba plain and the Oued Seybouse, and the high plains of Sétif and Constantine. The Oued Chélif, Algeria's main river, rises in the Atlas Mountains and flows 700 km into the Mediterranean. To the northeast of the Saharan Atlas, a short distance from the coast, the Djurdjura massif forms a limestone barrier whose isolated peaks, glistening with snow late after winter, can exceed 2,000 m in altitude. Springs and snow supply the torrents that have carved the slopes into deep ravines on their way to the Sebaou wadi, which is constrained by an uneven relief. The deep faults have led man to settle on the ridges. TheTellian Atlas rises to a region of high plateaus that run diagonally, at an average altitude of 1,000 m, from southern Morocco to north-western Tunisia. The vast steppe plains are carved by depressions (chott el-Chergui and chott el-Hodna) which, while they retain water during the wet season, become salty lakes in the dry season. Battered by the winds, the high stony plateaus crumble under the summer heat, while the winters are very cold. Little vegetation survives, apart from a few herd-grazed grasses and esparto grass, a western grass that has long been a source of wealth in Algeria. The eastern high plains are home to cereal crops. The landscape changes slightly around Bou Saada, the main town in the highlands, surrounded by palm groves and a few dunes.
Parallel to the high plateaus, the Saharan Atlas is made up of several successive mountain ranges: Jebel Amour to the southwest, Jebel Ouled Naïl in the center and the Ziban Mountains and Aurès to the northeast. More watered than the high plateaus, the Saharan Atlas is a good grazing area before descending to the fourth major geographical zone, the Sahara.
South of Constantine and Batna, the Tellian Atlas joins the Saharan Atlas in the limestone massif of the Aurès, made up of small rocky chains whose crests are often wooded with oak and cedar. From passes sometimes exceeding 2,000 meters in altitude to valleys whose red earth is the delight of oases, you can go from a forest landscape to a picture announcing the near Sahara. The Aurès, populated by farming Chaoui Berbers, has often been the source of rebellions against successive Algerian invaders, resistance facilitated by the massif's isolation, difficult access and relief.
The Sahara occupies over 85% of Algeria's territory, i.e. 2 million km2 or, roughly speaking, 2,000 km from west to east (from Tindouf to Djanet) and 1,500 km from north to south (from Laghouat to In-Guezzam on the Niger border). It is made up of dry valleys (oued Saoura), immense sandy plains (Grand Erg occidental and oriental in the north), plateaus (Tademaït, Tassilis, Tanezrouft) and mountain ranges such as the Hoggar, a volcanic massif 800 km wide and culminating at Mount Tahat at 2,908 meters according to the Bibendum and 3,003 or 3,010 meters according to other sources. Far from images of dunes and sand, the Sahara's face is constantly changing. The regs (vast stony expanses) are sometimes bordered by ergs (dunes), hamadas (cratered limestone or sandstone plateaus), serirs (rock-covered plateaus), tassilis (plateaus) or sebkhas (salt-covered depressions). The oases of the Zibans, M'Zab Valley, Touat, Gourara, Tassili n'Ajjer and Hoggar punctuate these often lunar landscapes.
Hydrography
Algeria's watercourses are fairly unremarkable, as they usually dry up at the bottom of a wadi. But all it takes is a good downpour for them to come back to life, and sometimes dangerously so for the buildings that have quietly settled there, since the wadi hasn't "been there" for a good ten years. As for the rivers, which flow all year round, their courses are fairly small, in small basins directed towards the sea. On the high plateaus, when the flow is too low to carve out a valley, the water stagnates in chotts, where it becomes impregnated with salt; the Melrhir (-40 m), el-Hodna and ech-Chergui chotts are the largest of these, following from east to west a line parallel to the Atlas Mountains, which begin at Gabès in Tunisia.
The country's largest river is the Oued Chélif, which rises in the Tellian Atlas south of Médéa, flows parallel to the sea and empties 700 km further into the Mediterranean above Mostaganem. The Kabyle Oued Sébaou descends from the Djurdjura mountains and empties into the sea just west of Dellys. In the Tellian Atlas, a number of highly mineral springs have therapeutic virtues that were already known to the Romans, who built the first spas here. The ancient rivers of the Sahara that were born in the Saharan Atlas have disappeared. What remains are their valleys, which, when seen from the air, are so numerous that they give a surprisingly clear outline to the land. When they have gone underground, the wadis feed the wells of the oases and palm groves.
