The 'Atlas Mountains' () are a
mountain range in northwest
Africa extending about 2,400 km (1,500 miles) through
Morocco,
Algeria, and
Tunisia. The highest peak is
Jbel Toubkal, with an elevation of
4,167 metres (13,671 ft) in southwestern Morocco. The second highest mountain is the M'Goun of 4071 meters. The Atlas ranges separate the
Mediterranean and
Atlantic coastlines from the
Sahara Desert. The population of the Atlas Mountains are mainly Berber tribes in Morocco and
kabyles in
Algeria.
The mountains are divided into additional and separate ranges, including the
Middle Atlas,
High Atlas and
Anti-Atlas. The lower
Tell Atlas running near the coast and the larger
Saharan Atlas running further south terminate in the
Aurès Mountains located in Algeria and
Tunisia.
Geology
Map showing the location of the Atlas Mountains across North Africa
The
basement rock of most of Africa was formed in the
Precambrian Era (approximately 4.5 billion to approximately 550 million years ago) and is much older than the Atlas mountains lying in Africa. The Atlas formed during three subsequent phases of Earth's history.
The tectonic boundary.
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.
North America,
Europe and
Africa were connected millions of years ago. The Anti-Atlas mountains are believed to have originally been formed as part of
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 in the eastern
United States. Some remnants can also be found in the later formed
Appalachians in North America.
A second phase took place during the
Mesozoic Era (before ~65 My) and 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. Most of the rocks forming the surface of the present High Atlas were deposited under the ocean at that time.
Finally, in the
Tertiary Era (~65 million to ~1.8 million years ago), the mountain chains that today comprise the Atlas were uplifted as the land masses of Europe and Africa collided at the southern end of the
Iberian peninsula. 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). In the case of the Africa-Europe collision, it is clear that tectonic convergence is partially responsible for the formation of the
High Atlas, as well as for the closure of the
Strait of Gibraltar and the formation of the
Alps and the
Pyrenees. 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. In fact, one of the most striking features of the Atlas to geologists is the relative small amount of crustal thickening and tectonic shortening despite the important altitude of the mountain range. Recent studies suggest that deep processes rooted in the Earth's mantle may have contributed to the uplift of the High and Middle Atlas.
[1][2]
Seismic activity
Because the Atlas mountains lie on the
fault zone, the area is seismically active. The city of
Blida in Algeria which lies today in the middle of the
Tell Atlas with a population of about 265,000 (2005) inhabitants was completely destroyed by strong quakes in the
19th century. Likewise the city of
Cheliff lying in
Algeria with a population of ~235,000 (2005) inhabitants suffered 5,000 fatalities in a 1980 earthquake of magnitude 7.3 on
Richter Scale.
Natural resources
The Atlas are rich in
natural resources. There are deposits of
iron ore,
lead ore,
copper,
silver,
mercury,
rock salt,
phosphate,
marble,
anthracite coal and
natural gas among other resources.
Subranges of the Atlas Mountains
The range can be divided into three general regions from west to east:
★ Middle Atlas, High Atlas, and Anti-Atlas (Morocco).
★
Saharan Atlas (Algeria).
★
Tell Atlas (Algeria, Tunisia).
Middle Atlas range
Main articles: Middle Atlas
The 'Middle Atlas' is a portion of the Atlas mountain range lying completely in Morocco. The Middle Atlas is the westernmost of three Atlas Mountains chains that define a large plateaued basin extending eastward into
Algeria. South of the Middle Atlas and separated by the
Moulouya and
Oum Er-Rbia rivers, the
High Atlas stretches for 700 km with a succession of peaks among which ten reach above 4,000 meters. North of the Middle Atlas and separated by the
Sebou River, the
Rif mountains are an extension of the
Baetic Cordillera (Baetic mountains, which include the
Sierra Nevada) in the south of Spain.
High Atlas
:''Main articles:
High Atlas''
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. At the Atlantic and to the southwest the range drops abruptly and makes an impressive transition to the coast and the Anti-Atlas range. To the north, in the direction of
Marrakech, the range descends less abruptly.
On the heights of
Ouarzazate the massif is cut through by the
Draa valley which opens southward. In this chaos of rocks the contrasts are astonishing: water runs in some places, forming clear basins. It is mainly inhabited by Berber people, who live in small villages and cultivate the high plains of
Ourika Valley.
Near
Barrage Cavagnac, there is a
hydroelectric dam that has created the artificial lake
Lala Takerkoust. The lake serves also as a source for fish for the local fishermen.
The largest villages and towns of the area are
Tahanaoute,
Amizmiz,
Asni,
Tin Mal,
Ijoukak, and
Oukaïmden.
Anti-Atlas ranges
Main articles: 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 km). In the south it borders the
Sahara. The easternmost point of the anti-Atlas is the
Djebel Sarhro mountains and its eastern boundary is set by sections of the
High Atlas range.
Saharan Atlas range
Main articles: Saharan Atlas
The Saharan Atlas of
Algeria is the eastern portion of the Atlas mountain range. Not as high as the Grand Atlas they are far more imposing than the Tell Atlas range that runs to the north of them and closer to the coast. The tallest peak in the range is the 2236 m 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. Today most of the population of the region are Berbers.
Tell Atlas range
Main articles: Tell Atlas
.jpg)
Panoramic view of typical Berber village (
Morocco - High Atlas Mountains).
The Tell Atlas is a mountain chain over 1,500 kilometers in length, belonging to the Atlas mountain ranges and stretching from Morocco, through Algeria to Tunisia. It parallels the
Mediterranean coast. Together with the Saharan Atlas to the south it forms the northernmost of two more or less parallel ranges which gradually approach one another towards the east, merging in ''Eastern Algeria''. At the western ends at the
Middle Atlas range in Morocco. The area immediately to the south of this range is high plateau, with lakes in the wet season and salt flats in the dry.
Aurès mountain range
Main articles: Aurès Mountains
The Aurès Mountains of Algeria and
Tunisia are the furthest eastern portion of the Atlas mountain range.
See also
★
Capsian culture
★
North Africa
★
Africa
References and notes
1. http://einstein.uab.es/c_geotectonica/WebAtlas/AtlasLitho.htm Potential field modelling of the Atlas lithosphere
2. http://einstein.uab.es/c_geotectonica/WebAtlas/MaterialAtlas/Ayarzaetal2005.pdf ''Crustal structure under the central High Atlas Mountains (Morocco) from geological and gravity data'', P. Ayarza, et.al., 2005, Tectonophysics, 400, 67-84
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