The Atlas Mountains are a series of mountain ranges in northwestern Africa, forming the geologic backbone of Morocco, Algeria, and Tunisia. They extend for more than 1,200 miles (2,000 kilometres), from the Moroccan port of Agadir in the southwest to Tunis, the Tunisian capital, in the northeast.
This significant geographic feature serves as a natural barrier between the Sahara Desert to the south and the coastal plains to the north, influencing climate, ecosystems, and human settlement in the region.
The Atlas Mountains are a mountain range in the Maghreb in North Africa. They separate the Sahara Desert from the Mediterranean Sea and the Atlantic Ocean; the mountain range stretches around 2,500 km (1,600 mi) through Morocco, Algeria and Tunisia.
The terms for 'mountain' are Adrar and adras in some Berber languages, and these terms are believed to be cognates of the toponym Atlas.
Across the mountains filter both air masses and human migrations. It is, however, only in the east-west direction that the Atlas Mountains facilitate movement. These are the conditions that create at the same time both the individuality and the homogeneity of the Atlas countries.
Read also: Egypt's Geological Wonder
Although the Saharan region is more likely to be described as the archetypal North African habitat, it is the well-watered mountains north of this vast desert that provide the foundation for the livelihood of most of the peoples of North Africa and a striking green or white background for many North African towns.
Their thick rim rises to form a high sill separating the Mediterranean basin to the north from the Sahara to the south, thus constituting a barrier that hinders, without completely preventing, communication between the two regions.
MOROCCO – The Mysteries of North Africa | 4K Travel Documentary
Physiography
The Atlas mountain system takes the shape of an extended oblong, enclosing within its ranges a vast complex of plains and plateaus.
The Atlas Mountains are divided into three main ranges, each with distinct geographical features and climate:
Read also: Cape Town Hike Guide
- The High Atlas
- The Middle Atlas
- The Anti-Atlas
Tell Atlas
The northern section is formed by the Tell Atlas, which receives enough rainfall to bear fine forests. The Tell Atlas is a mountain chain over 1,500 kilometres (900 mi) in length, belonging to the Atlas mountain ranges and stretching from Eastern Morocco to Tunisia, and through Algeria.
It parallels the Mediterranean coast and joins with the Saharan Atlas in Eastern Algeria and Tunisia. The area immediately to the south of the Tell Atlas is the high plateau of the Hautes Plaines, with lakes in the wet season and salt flats in the dry.
From west to east several massifs (mountainous masses) occur. The first of these is Er-Rif, which forms a half-moon-shaped arc in Morocco between Ceuta and Melilla; its crest line exceeds 5,000 feet (1,500 metres) above sea level at several points, reaching 8,058 feet at Mount Tidirhine.
East of the gap formed by the Moulouya River the Algerian ranges begin, among which the rugged bastion of the Ouarsenis Massif (which reaches a height of 6,512 feet), the Great Kabylie, which reaches 7,572 feet at the peak of Lalla Khedidja, and the mountains of Kroumirie in Tunisia are all prominent.
The highest summit of the Tell Atlas is the 2,308 m (7,572 ft) Lalla Khadidja in the Djurdjura range of Kabylia.
Read also: Explore the Bale Mountains
The eastern half of the Tell Atlas has the most humid climate of North Africa, with annual precipitation reaching well above 1,000 mm (39 in), and sometimes over 1,500 mm (59 in) like in the Collo Peninsula or near Ain Draham.
Saharan Atlas
The southern section, which is subject to desert influences, is appropriately called the Saharan Atlas. It includes in the centre a palisade formed by shorter ranges, such as the Ksour and Ouled-Naïl mountains, grouped into massifs between two mighty ranges-the Moroccan High Atlas to the west and the Aurès Mountains to the east.
The Saharan Atlas of Algeria runs east of the High Atlas, crossing Algeria from the Moroccan border and into Tunisia.
Though not as high as the High Atlas, they reach similar altitudes as the Tell Atlas range that runs to the north of them and closer to the coast.
The highest peak in the range, outside of the Aures Mountains, is the 2,236 m (7,336 ft) high Djebel Aissa. They mark the northern edge of the Sahara Desert.
The mountains see some rainfall and are better suited to agriculture than the plateau region to the north.
The Aures Mountains are often presented as being the easternmost part of the Saharan Atlas.
The Aurès Mountains are the easternmost portion of the Atlas mountain range. It covers parts of Algeria and Tunisia.
High Atlas
The High Atlas culminates in Mount Toubkal at 13,665 feet (4,165 metres), the highest point in the Atlas Mountains, which is surrounded by high snowcapped peaks; the Aurès Mountains are formed of long parallel folds, which reach a height of 7,638 feet at Mount Chelia.
The High Atlas in central Morocco rises in the west at the Atlantic coast and stretches in an eastern direction to the Moroccan-Algerian border. It has several peaks over 4,000 m (13,000 ft), including the highest summit in North Africa, Toubkal (4,167 m or 13,671 ft), and further east Ighil m'Goun (4,071 m or 13,356 ft), the second major summit of the range.
At the Atlantic and to the southwest, the range drops abruptly and makes a transition to the coast and the Anti-Atlas range. To the north, in the direction of Marrakesh, the range descends less abruptly.
On the heights of Ouarzazate the massif is cut through by the Draa Valley which opens southward. It is mainly inhabited by Berber people, who live in small villages and cultivate the high plains of the Ourika Valley. Near Barrage Cavagnac there is a hydroelectric dam that has created the artificial lake Lalla Takerkoust.
Middle Atlas
The Middle Atlas is completely in Morocco and is the northernmost of its three main Atlas ranges. The range lies north of the High Atlas, separated by the Moulouya and Oum Er-Rbia rivers, and south of the Rif mountains, separated by the Sebou River.
To the west are the main coastal plains of Morocco with many of the major cities and, to the east, the high barren plateau that lies between the Saharan and Tell Atlas. The high point of the range is the jbel Bou Naceur (3340 m).
The Middle Atlas experiences more rain than the ranges to the south, making it an important water catchment for the coastal plains and important for biodiversity.
Anti-Atlas
The Anti-Atlas extends from the Atlantic Ocean in the southwest of Morocco toward the northeast to the heights of Ouarzazate and further east to the city of Tafilalt (altogether a distance of approximately 500 kilometres or 300 miles). In the south it borders the Sahara.
The easternmost point of the anti-Atlas is the Jbel Saghro range and its northern boundary is flanked by sections of the High Atlas range. It includes the Djebel Siroua, a massif of volcanic origin with the highest summit of the range at 3,304 m.
Geology
If the relief of the Atlas region is relatively simple, its geology is complex. In essence, the two Atlases comprise two different structural regions.
The basement rock of most of Africa was formed during the Precambrian supereon and is much older than the Atlas Mountains lying on the continent.
The first tectonic deformation phase involves only the Anti-Atlas, which was formed in the Paleozoic Era (~300 million years ago) as the result of continental collisions. The Anti-Atlas Mountains are believed to have originally been formed as part of the Alleghenian orogeny.
These mountains were formed when Africa and America collided and were once a chain rivaling today's Himalayas. Today, the remains of this chain can be seen in the Fall Line region in the Eastern United States.
A second phase took place during the Mesozoic Era (before ~66 My). It consisted of a widespread extension of the Earth's crust that rifted and separated the continents mentioned above. This extension was responsible for the formation of many thick intracontinental sedimentary basins including the present Atlas.
In the Paleogene and Neogene Periods (~66 million to ~1.8 million years ago), the mountain chains that today constitute the Atlas were uplifted, as the land masses of Europe and Africa collided at the southern end of the Iberian Peninsula.
The Tell Atlas originally arose out of a basin filled with sediment, which was dominated to the north by a marginal rim, of which the massifs of Tizi Ouzou, Collo, and Edough are the remnants. Its elevation took place during a lengthy mountain-building process that was marked by upheavals in the Paleogene and Neogene periods (i.e., about 65 to 2.6 million years ago); over the cluster of folds that were uplifted from the rift valley were spread sheets of flysch (deposits of sandstones and clays), which were carried down from the north over the top of the marginal rim.
Thus the Tell Atlas represents an example of a young folded mountain range still in the process of formation, as is shown by the earth tremors to which it is subject.
To the south the Saharan Atlas belongs to another structural grouping, that of the vast plateaus of the African continent, which form part of the ancient base rock largely covered by sediments deposited by shallow seas and by alluvial deposits.
The Saharan Atlas is the result either of the mighty folding of the substructure that raised up fragments of the base rock-such as the horst (uplifted block of the Earth’s crust), which constitutes the Moroccan High Atlas-or else of the crumpling into folds of the Earth’s crust during the Jurassic Period (about 200 to 145 million years ago) and the Cretaceous Period (about 145 to 65 million years ago).
Such convergent tectonic boundaries occur where two plates slide towards each other forming a subduction zone (if one plate moves underneath the other), and/or a continental collision (when the two plates contain continental crust). However, there is a lack of evidence for the nature of the subduction in the Atlas region, or for the thickening of the Earth's crust generally associated with continental collisions.
One of the most striking features of the Atlas to geologists is the relatively small amount of crustal thickening and tectonic shortening despite the important altitude of the mountain range.
Map of the Atlas Mountains
Drainage
The seasonal character of the rains, which fall in torrents, determines the characteristics of drainage in the Atlas: the runoff feeds streams that are of great erosive capacity and that have cut their way down through the thickness of accumulated layers of sediment to form deep narrow gorges difficult to cross.
The pre-Roman fortress of Cirta (now called Constantine) in Algeria stands on a rock sculptured out by one such stream, the winding Rhumel River.
The great Maghribian wadis (French: oueds; channels of watercourses that are dry except during periods of rain) issue from the Atlas ranges. Among the more perennial rivers are the Moulouya, which rises from the Middle Atlas, and the Chelif, which rises from the Amour Mountains.
Destructive of the soils of their headstreams, they deposit their loads of silt at the foot of the mountain ranges or else leave a long line of conical deposits locally known as dirs (“hills”).
Soils
Good soil is sparse at higher altitudes in the Atlas region. Most often nothing is to be found but bare rock, debris, and fallen materials incessantly renewed by landslides.
Two materials predominate-limestone, which forms ledges that are half-buried in rough debris, and marls (chalky clays) cut by erosion into a maze of ravines and crumbling gullies. The rarer sandstones favour forest growth.
Popular articles:
tags: #Africa
