In Pleistocene times drainage down the Nile Valley appears to have become definitely established and probably the river in the lower part of its course eventually washed up against and broke down the separating barrier of gravel between the Fayûm and the Nile Valley, so that part of its waters obtained access to the depression, formed a lake on the lowest part, and gradually rose until the whole basin, up to the level of the channel connecting it with the Nile Valley, became filled. Every year thousands of tons of sediment were carried in by the floods and spread out on the floor in the shape of a fan. Probably later, as the Nile level fell, the valley and the depression again became disconnected, until the more modern river, with its gradually rising bed, again attained the requisite altitude. In early historic times the alluvial deposits had probably silted up the lake in its southern central part, and when in the XIIth dynasty the district was first taken in hand by Amenemhat I this part of it must have had the character of a huge marsh, nearly surrounded by open water, rapidly deepening towards the north.
Section VII.—THE NORTHERN DESERT REGION.
The Plateau bounding the Fayûm depression to the north.All along the north-west and north sides the ground rises rapidly from the base of the dip-slope of the plain in a series of escarpments to the summit of the rim of the depression, averaging 340 metres above sea level. Northwards from the summit stretches a rolling pebbly desert, the prevailing character of which is a dark brown, relieved by lighter brown grey and yellow patches, and especially flecked by the light sandy slopes of the undulations. Although the latter seldom rise to any considerable height above the general level of the plain, from the top of the most modest eminence an immense view in every direction can frequently be obtained. The monotony of this desert is only relieved by the occasional belts of sand, which although extremely narrow in width, run for immense distances in almost absolutely straight lines, and in a N.N.W.—S.S.E. direction. Although none of these dunes actually reach the rim of the escarpment we may mention here the beautiful Ghart el Khanashat, an almost straight and apparently unbroken ridge of sand, extremely narrow but of great length. Near its southern extremity the width does not exceed 100 metres; the slopes on both sides are frequently as much as 30°. The commencement of the Ghart el Khanashat was observed on a march from Wadi Natrûn to Mogara; it lay some way to the south of a line joining those two localities but could not be accurately fixed from the line of route. The belt dies out 24 kilometres from the rim of the Fayûm depression, its termination being particularly abrupt, although the height of the ridge diminishes gradually throughout the last kilometre or two. The line of the belt if continued would almost strike the western extremity of the Birket el Qurûn; near its termination the desert is almost flat, the surface being finely gravelly, with numerous groups of silicified trees; tufts of coarse grass grow in some profusion on the sandy ground at the base of the ridge on either side. A fairly well-marked road from the Birket el Qurûn to the Wadi Natrûn passes the end of the ridge and continues northwards at a distance of 200 metres from the east side of the dunes, although apparently gradually diverging eastwards.
Except to the north and north-west of Tamia, where a somewhat extensive and fairly level plain exists, the ground, as already mentioned, rises from the limits of the central plain in a series of escarpments to the summit of the rim of the depression. These cliff lines are broadly speaking three in number and represent the escarpments of the three great rock-stages which build up the northern part of the Fayûm, i.e., the Birket el Qurûn series, the Qasr el Sagha series, and the Fluvio-marine series. It would serve no useful purpose describing these different cliffs in detail; their positions and characters are apparent on the accompanying maps. The intervening plateaux are for the most part dip-slope plains formed of hard bands of rock, which resisting denudation, are left protecting the underlying strata while the softer beds above are cut back at a comparatively rapid rate.
Desert west and south-west of Gar el Gehannem.In December 1902 and March 1903 a traverse was made through the unexplored country west and south-west of Gar el Gehannem, finally connecting up with Wadi Rayan. The highest escarpment, i.e. that of the Fluvio-marine series, dies out about 20 kilometres west of Gar el Gehannem, gradually merging into the undulating gravel-covered plain. The lower escarpments, those of the Qasr el Sagha and Birket el Qurûn series, continue to a considerable distance in a south-westerly direction, although gradually losing the characters of well-marked cliffs. In fact westwards of this the depression gradually shallows, until at a point some 50 kilometres south-west of Gar el Gehannem the floor has attained the level of the ordinary desert plateau, on which the outcrops of the beds of successive rock-stages follow one another in regular order from south to north, but without forming well-marked topographical features, as in the depression.
Hills, capped with dark hard ferruginous silicified grits and puddingstone, were met with in the extreme south-west extension of the depression; these deposits, which will be referred to more fully later, considered in conjunction with the similar beds occurring within the oasis of Baharia, and in the hills of Gar el Hamra, on the plateau immediately to the north-east of that depression, are of considerable interest and importance, especially in connection with the question of the position of the early rivers which in Eocene and later times brought down quantities of trees and animals, the remains of which are so abundant throughout the later Fayûm deposits.
Jebel el Qatrani and escarpments north of the Birket el Qurûn.The boldest part of the region is the area lying between the Birket el Qurûn and the summit of the depression to the north. All three lines of cliff are here high and precipitous, and the uppermost escarpment, well known by the name of Jebel el Qatrani, formed of a highly coloured series of sandstones and clays and capped for a distance of many kilometres by a thick bed of hard black basalt, is of a most striking character. The eastern extremity of Jebel el Qatrani is perhaps the most conspicuous point in the whole region; here the two conical black basalt-capped cliff-outliers, known as Widan el Faras, stand side by side, and from their summits the eye commands the whole region from the pyramid of Lahûn on the one side, across Rayan to the south, up to the extreme limits of the depression to the south-west. The rim of Jebel el Qatrani has a fairly constant level of about 340 metres above the sea. From Widan el Faras the escarpment trends northwards for a few kilometres before again resuming an easterly direction, which is continued till the well-marked bluff of Elwat Hialla is reached. From this summit the pyramids of Dashûr, Saqâra and Giza are visible to the north, as well as Cairo and the Nile Valley southwards, backed by the bluffs on the Eastern desert limestone plateau.
To the south the isolated peaks of Garat el Gindi and Garat el Faras form conspicuous landmarks on the more or less open plain which stretches to Tamia and the limits of the Fayûm cultivated lands. Eastwards the escarpments continue in a broken irregular manner; the upper ones are gradually lost in an undulating plain, while the lower eventually join those forming the northern part of the ridge separating the Fayûm from the Nile Valley.
[6]For fuller details of the cultivated lands, water-supply, etc., of the Fayûm, the reader is referred to the excellent description by Sir Hanbury Brown in his work The Fayum and Lake Moeris, London, 1892.