'Handbook of Hejaz' [‎9v] (25/204)

3 —
short
:t '. tlle II.—PHYSICAL CHARACTER.
iatives
1. — R elief.
Hejaz is the northern part of the uptilted edge of the
Arabian continental shelf and consists, mainly, of its short
and steep return westward, together with the narrow fringe
of Red Sea littoral formed of detritus and coral at its foot;
but we include in it also a strip of the main shelf itself,
i.e. the uppermost level of the central Arabian steppe.
Hejaz. therefore, falls naturally into three parallel zones :
(I) Lowland littoral (Tihamah); (2) Mountainous acclivity
('Aqabah) up to and including the Gable Ridge; (3) Strip
of declivity towards the steppe desert of Central Arabia.
(1) The first of these zones, the Tihamah, is well-marked
and of one general surface throughout, sandy, dusty, and
coralline ; but it varies much in breadth, being very narrow
in the northern part (Midian), and broadening to a twenty or
thirty-mile dimension behind Yambo' and again south of
Rabugh.
(2) The second zone is more complicated, owing to
denudation having acted variously on a slope, from 80 to
100 miles long, composed of different formations and rising
to from 5,000 to 8,000 feet above sea-level. Harder rocks
have been left upstanding in mountainous massifs on all parts
of this slope, and, in places, lava-capped harmh, preserving all
below it from denudation, maintains the original level of the
shelf far westward, as well as eastward, of the Gable Ridge.
One such seam of harder rock lies a little back from the
sea along virtually the whole coastline, and, in Midian, where
the rock is granitic, its summits stand up .from 7,000 to 9,000
feet, forming a Coastal Range higher in places than the