Murzuq Desert
Encyclopedia
Murzuq Desert, Idehan Murzuq, Idhan Murzuq, (also Murzaq, Murzuk, and Murzak), is a primarily erg
desert
in southwestern Libya
. It is considered part of the Sahara
desert complex, although it is separated from the southern Sahara by the Tibesti Mountains
and the Tassili n'Ajjer
.
photograph, taken from low earth orbit
, shows classic large and small sand masses of the central Sahara Desert, where wind is a more powerful land-shaping agent than water. “Draa” dunes (from the Arabic for “arm”) are very large masses of sand, and they appear here as the broad network of yellow-orange sand masses, with smooth-floored, almost sand-free basins between them. These sand masses lie in the western part of Libya's vast Marzuq Sand Sea (centered at 24.5°N 12°W). Geologists think that the draa of the Marzuq were probably formed by winds different from the prevailing north-northeast winds of today.
Numerous smaller dunes have developed on the backs of the draa. Three distinct dune types are visible: longitudinal dunes , which are more or less parallel with the north winds; transverse dunes, which are usually more curved and formed at right angles to the wind; and star dunes, in which several linear arms converge towards a single peak.
The upwind sides of the sand masses appear smoother than the downwind side. Wind is moving sand grains almost all the time. This means that the draa and the dunes are all moving as sand is added on the upwind side and blown off the downwind side. Small sand masses move much faster than large sand masses. The draa are almost stationary, but the smaller dunes move relatively quickly across their backs. When the smaller dunes reach the downwind side of the draa, they are obliterated; their sand is blown across the basins as individual grains.
Erg (landform)
An erg is a broad, flat area of desert covered with wind-swept sand with little or no vegetative cover. The term takes its name from the Arabic word ʿarq , meaning "dune field"...
desert
Desert
A desert is a landscape or region that receives an extremely low amount of precipitation, less than enough to support growth of most plants. Most deserts have an average annual precipitation of less than...
in southwestern Libya
Libya
Libya is an African country in the Maghreb region of North Africa bordered by the Mediterranean Sea to the north, Egypt to the east, Sudan to the southeast, Chad and Niger to the south, and Algeria and Tunisia to the west....
. It is considered part of the Sahara
Sahara
The Sahara is the world's second largest desert, after Antarctica. At over , it covers most of Northern Africa, making it almost as large as Europe or the United States. The Sahara stretches from the Red Sea, including parts of the Mediterranean coasts, to the outskirts of the Atlantic Ocean...
desert complex, although it is separated from the southern Sahara by the Tibesti Mountains
Tibesti Mountains
The Tibesti Mountains are a range of inactive volcanoes located on the northern edge of the Chad Basin in the Borkou- and Tibesti Region of northern Chad. The massif is one of the most prominent features of the Central-Sahara desert and covers an area of approximately 100,000 km². The northern...
and the Tassili n'Ajjer
Tassili n'Ajjer
Tassili n'Ajjer is a mountain range in the Algerian section of the Sahara Desert. It is a vast plateau in south-east Algeria at the borders of Libya, Niger and Mali, covering an area of 72,000 sq...
.
Sand Sea
This detailed astronautAstronaut
An astronaut or cosmonaut is a person trained by a human spaceflight program to command, pilot, or serve as a crew member of a spacecraft....
photograph, taken from low earth orbit
Low Earth orbit
A low Earth orbit is generally defined as an orbit within the locus extending from the Earth’s surface up to an altitude of 2,000 km...
, shows classic large and small sand masses of the central Sahara Desert, where wind is a more powerful land-shaping agent than water. “Draa” dunes (from the Arabic for “arm”) are very large masses of sand, and they appear here as the broad network of yellow-orange sand masses, with smooth-floored, almost sand-free basins between them. These sand masses lie in the western part of Libya's vast Marzuq Sand Sea (centered at 24.5°N 12°W). Geologists think that the draa of the Marzuq were probably formed by winds different from the prevailing north-northeast winds of today.
Numerous smaller dunes have developed on the backs of the draa. Three distinct dune types are visible: longitudinal dunes , which are more or less parallel with the north winds; transverse dunes, which are usually more curved and formed at right angles to the wind; and star dunes, in which several linear arms converge towards a single peak.
The upwind sides of the sand masses appear smoother than the downwind side. Wind is moving sand grains almost all the time. This means that the draa and the dunes are all moving as sand is added on the upwind side and blown off the downwind side. Small sand masses move much faster than large sand masses. The draa are almost stationary, but the smaller dunes move relatively quickly across their backs. When the smaller dunes reach the downwind side of the draa, they are obliterated; their sand is blown across the basins as individual grains.