Issaouane Erg


The Issaouane Erg is an erg in Algeria's portion of the Sahara desert, covering an area of approximately 26,000 km².

Formation and development

Towards the end of the Pliocene epoch, 2.5 million years ago, when the Sahara had a humid tropical climate, the waters of the Tassili n'Ajjer carried large amounts of rock material into the Illizi basin, where it was deposited as sand. During the dry periods of the Pleistocene and Holocene, 1.6 million years ago to about 3,000 years ago, the dunes of the Issaouane Erg formed within this basin. At that time, wind speeds were much higher at certain times, resulting in higher dunes than would be possible today. The presence of both longitudinal and barchan dunes with star dunes atop suggests that wind regimes have changed over time. The formation of these stationary complex dunes can take hundreds of thousands of years, while changes in wind patterns can also take thousands of years until new dune formations have been created.. The sediment balance of the erg is positive except in the southeastern part with the long dunes, where the erg loses sand.

Topography

The Issaouane Erg is located north of the mountain range Tassili n'Ajjer. To the east, it borders Erg Bourarhet and the Idehan Ubari sand sea, Libya and in the north, the Issaouane Erg ends at the Tinrhert Plateau. To the west lies the smaller Erg Tiffernine, connected to it by a narrow passage 47 km wide. To a large extent it follows the 500-m contour of the surrounding landscape. The northern section features compound dunes, sometimes also star dunes. Between the dunes are depressions covered with sand and sabkhah, left after the evaporation of accumulated water.
The southern half consists of linear dunes, up to 120 km long, often 2 to 3 km wide, with secondary dunes on top. Their orientation from northeast to southwest indicates the prevailing wind direction at the time of their formation. In between are gassi, which are sand-free areas with reg or salty clayed crust soils. The highest dunes of the erg rise up on its southwestern edge, where the sand has accumulated. Two dunes rise 270 m above the bedrock. In the northwest of the erg, there is a hill that protrudes from the erg: Khannfoussa, 646 m high and about 200 m above the surrounding bedrock.

Climate

Data from Bordj Omar Driss:
The climate is classified as BWh by the Köppen-Geiger
  • Average temperature of coldest month: January, 11°C
  • Average temperature of hottest month: July, 35°C
Data from Issaouane Erg:
  • Average precipitation: 25 mm/year
  • Annual evapotranspiration is estimated at 22 mm/year.
  • Most likely precipitation: December, January
  • The driest months: July, August
  • Predominant wind and direction of the current sand flow : from the southwest or west

Settlements, routes

There are no settlements within the erg. Close to the edge of the erg, in the northwest, is the town of Bordj Omar Driss, a few kilometers west of which is Zaouia Sidi Moussa. In the southeast, the city of Illizi borders the erg.
Within the erg, there are tracks and roads leading to oil production areas, some of which are already covered in sand again. The CW2 route leads from Illizi along the edge of the erg through the Oued Irarraren to the northwest. Later, it turns north and leads to Bordj Omar Driss. However, the last 180 km or so are still unpaved, so they are only passable with off-road vehicles.

Prehistory and History

Neolithic artifacts, sculptures and paintings have been found in the Issouane Erg from the Kiffian culture. Hand axes from the Acheulean period were also found. In the 19th century, and probably even earlier, a trade route led through the erg, following a path from Ouargla through the Grand Erg Oriental via Zaouia Sidi Moussa and through the erg to the southeast. It continued eastward via the Oued Irarraren and finally ended in Ghat, the junction of the great caravan route between Tripoli and the Sahel. During that century, there were many rezzous by the Tuareg of the Kel Ajjer on the Chaambas, an Arab ethnic group further north, and vice versa, using this route. Both used to visit the zaouia in Temassinine, a Muslim tomb, to ask for success or to give thanks. In 1880, French Colonel Paul Flatters was traveling along this route on a scientific expedition. The aim was to explore a possible route for the planned Trans-Saharan railway line. In 1904, the French Fort Flatters was built east of Temassinine, and in 1909, Fort Polignac was built near what later became Illizi. Transport caravans now regularly traveled this route, loaded with supplies.

Natural resources

There are two large natural gas and oil fields south of Bordj Omar Driss: Tin Fouye Tabankort oil and gas field and Ain Tsila oil and gas field. More small oil fields are also being exploited in the same area. A natural gas and a liquefied gas pipeline also run from the Libyan border through this area towards Hassi Messaoud.