Although the Western Desert is essentially a flat rocky plateau, much of its vast expanse is covered by eolian (wind blown) sand and the Great Sand Sea of Egypt is part of one of the largest sand-covered areas on earth. The Great Sand Sea extends from the Libyan border west of Siwa Oasis in a generally southerly direction touching the oases of Farafra and Dakhla on the east and ending at the Gilf Kebir at its southernmost tip.
The sand dunes, which cover a large part of the Western Desert, have a variety of forms and complexity that depend on the wind regime and sand abundance. In the north, longitudinal dunes known as seif (sword) or irq predominate, while to the south barchan or crescent-shaped dunes are more common. Some other forms, such as parallel wavy dune complexes are found but are less common. Dunes move at a more or less fixed rate in the direction of the prevailing wind. Thus, the southernmost fingers of the Great Sand Sea are encroaching on the wadis of Gilf Kebir.
Between large longitudinal
seif dunes there are often inter-dune valleys
that can support a wealth of plant and animal life.
Mobile dune types are less well supplied with wildlife.
Phytogenic mounds that form round such plants as Nitraria
retusa, Calligonum comosum or Tamarix
spp. add greatly to this habitat's diversity and create
niches for animals and birds.
The waterless expanse
of this desert is home to an assemblage of animals that
are well adapted to living without water and gain their
moisture from their food. Many animals have evolved
behavioral or morphological features that enable them
to survive the extremely hot climate or for locomotion
on soft sand. The Lesser Sand Viper, Cerastes vipera,
which can easily be confused with hornless specimens
of the Horned Viper, Cerastes cerastes, is
only found in sandy habitats. Another denizen of the
sands is the Sandfish, Scincus scincus, so
named because of its habit of "swimming" through
the sand.
A number of birds inhabit the sands especially the Hoopoe Lark, Alaemon alaudipes, which is easily distinguished from other larks by the long, slightly curved bill that gives it its name and also by its remarkable display flight.
Mammals of the region
include the now extremely rare Slender-horned Gazelle,
Gazella leptoceros. This animal lives largely
on such plants as Nitraria retusa, Cornulaca
monacantha and Calligonum comosum. An
immensely appealing animal of the sands is the tiny
Fennec Fox, Vulpes zerda, which may be one
of the most well adapted desert carnivores in the world.
They dig rather deep burrows so that exposure to heat
during the day is reduced to a minimum and appear to
be the only desert carnivores that can live entirely
without water. In the southwest of the Great Sand Sea,
immediately to the north of Gilf Kebir, the curious
phenomenon known as Libyan Desert silica glass is found.
The pieces of glass can be pale green or creamy in color,
can be clear or opaque and weigh from a few grams to
seven or eight kilograms. These beautiful pieces of
glass, lying between the sand dunes, are natural formations
and studies during most of the twentieth century have
failed to reveal their origin. In 1998, it was discovered
that a giant lime-green scarab, the centerpiece of King
Tutankhamun's jeweled, ceremonial pectoral was not,
as had previously been thought, made of chalcedony but
was Libyan Desert silica glass.
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