"العراق والخليج الفارسي" [و‎‎٩‎٢] (٨٦٢/١٨٨)

DESCRIPTION OF THE LAND 115
mountains in a deep trench to the point where it enters the plain of
Zakho, within 10 miles of its junction with the Khabur.
The Western and Southern Deserts of Iraq
These deserts are formed on the lower gentle slope of the Arabian
plateau to the north of the sand-deserts of northern Arabia, the Great
Nafud and its eastern extensions, the Dahana and the Ardh al Madhu.
In the west they merge into the Hamad, the dry Syrian desert; in the
north and north-east they are bounded by the Euphrates escarpment
and delta; in the south-east and south they are continued across the
political boundaries of Kuwait and Saudi Arabia.
The greater part of the deserts are composed of rocky steppe, of
sandstone and limestones (Cretaceous and Eocene), and of later Ter
tiary covering layers (fig. 2), but there are differences of type and
characteristics which permit regional classification as follows:
The Southern Deserts: (a) Ad Dibdibba
(b) Al Hajara
(c) The Euphrates sand-belt and Ar
Rahab.
The Western Desert of Al Wadiyan.
The Sand-deserts of Northern Arabia 1
Although the Great Nafud, Dahana, and Ardh al Madhu sand-
deserts lie outside Iraq territory, a brief description of them is rele
vant, for their northern edge is the true physical frontier, and the
characteristics of these sand-belts determine to some extent the main
currents of movement within the desert boundaries of Iraq.
The Great Nafud is a wilderness of deep sand, 180 miles long from
west to east, 140 miles broad from north to south, which separates the
Hamad of Syria and Transjordan, with the western desert of Iraq,
from the Jabal Shammar and Nejd regions of central Arabia. To
wards its eastern end, about longitude 43 0 , the depth of sand de
creases and its place is taken by long tongues of shallow sand-layers
projecting eastwards over the hard stony desert. The most remarkable
of these tongues are the Dahana and the Ardh al Madhu. The latter
is a strip of sand averaging 8—10 miles in width and stretching for
100 miles to the Wadi Batin, which forms the most marked feature to
the east and in its lower course separates the territory of Kuwait from
Iraq. The Dahana sand-belt is about 11 miles wide where it leaves
1 See folded map at end of the volume and fig. 29.