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Saudi Arabia
The Great Deserts
Three great deserts isolate Najd from north, east, and south
as the Red Sea escarpment does from the west. In the north, the
An Nafud--sometimes called the Great Nafud because An Nafud is
the term for desert--covers about 55,000 square kilometers at
an elevation of about 1,000 meters. Longitudinal dunes--scores
of kilometers in length and as much as ninety meters high, and
separated by valleys as much as sixteen kilometers wide--characterize
the An Nafud. Iron oxide gives the sand a red tint, particularly
when the sun is low. Within the area are several watering places,
and winter rains bring up short-lived but succulent grasses that
permit nomadic herding during the winter and spring.
Stretching more than 125 kilometers south from the An Nafud in
a narrow arc is the Ad Dahna, a narrow band of sand mountains
also called the river of sand. Like the An Nafud, its sand tends
to be reddish, particularly in the north, where it shares with
the An Nafud the longitudinal structure of sand dunes. The Ad
Dahna also furnishes the beduin with winter and spring pasture,
although water is scarcer than in the An Nafud.
The southern portion of the Ad Dahna curves westward following
the arc of the Jabal Tuwayq. At its southern end, it merges with
the Rub al Khali, one of the truly forbidding sand deserts in
the world and, until the 1950s, one of the least explored. The
topography of this huge area, covering more than 550,000 square
kilometers, is varied. In the west, the elevation is about 600
meters, and the sand is fine and soft; in the east, the elevation
drops to about 180 meters, and much of the surface is covered
by relatively stable sand sheets and salt flats. In places, particularly
in the east, longitudinal sand dunes prevail; elsewhere sand mountains
as much as 300 meters in height form complex patterns. Most of
the area is totally waterless and uninhabited except for a few
wandering beduin tribes.
Data as of December 1992
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