According to zipcodesexplorer, the Egyptian territory is a section of the great African plateaus: it therefore has an essentially rigid structure. The archaeozoic base, made up of very ancient gneisses and granites, emerges on extensive surfaces in the south-eastern part of the country, while elsewhere it is subjected to layers of different eras, formed by sedimentary rocks of both continental and marine origin. It is also affected by more recent magmatic intrusions of granite, diorites and syenites (these rocks with which many ancient monuments were built), present in the Aswân area (Aswan) and in the reliefs that border the country along the Red Sea. The geological events from which the current configuration of Egypt is derived are more or less the same that characterized the other regions of Africa. The flattening of the Precambrian base was followed by the formation of the layers of continental material which continued in different phases up to the Cretaceous; the Nubian sandstones that cover vast surfaces of southern Egypt are due to this sedimentary process. In the Cretaceous there was the beginning of the great tectonic episode, which ended in the Cenozoic, which led to the detachment between Africa and Western Asia and the birth of the Red Sea, and to which the origin of the reliefs that border the country is connected to E. These reliefs allow the archaeozoic formations to emerge, with powerful granite intrusions and volcanic expansions; they reach altitudes between 1500 and 2000 m, culminating in the 2187 m of Jabal Shā’ib al-Banāt (the highest elevation in the country, excluding the Sinai peninsula). In the Cenozoic there were extensive marine entrances, which are responsible for the limestone layers present in Middle and Lower Egypt. Up to this period, the hydrography was also different: the Nile, a river of smaller size and flow than the current ones, ran in correspondence with the depressions that open into the Western Desert; some meridian fractures that opened at the time of the tectonic movements connected with the birth of the Red Sea contributed to the formation of the new course. The hydrographic settlement began in the Pleistocene and was accompanied by the capture, far upstream of Egypt, of the Blue Nile by the White Nile. The river opened its course between sedimentary layers; it also underwent changes in its profile, with consequent abandonment of old terraces, narrowing of the bed, formation of alluvial bands and of the wide delta fan. The Nile valley has different dimensions and shapes also in relation to the geological structures it crosses. In Nubia it is devoid of alluvial belts and the river runs (indeed it ran before the creation of Lake Nasser) between rocky, arenaceous shores; downstream of Aswān, that is, after the first cataract, the valley floor opens up and the alluvial soils, very fertile, of dark earth, largely of basaltic origin, which make up the wealth of Egypt begin. The Nilotic valley divides the Egyptian territory into two parts: on the W the Libyan or Western Desert, and on the E the Arabian or Eastern Desert. The latter is a mountainous region, furrowed by fossil river courses that tend towards the Nile valley; it ends on the Gulf of Suez and on the Red Sea with a short flat selvedge, at the base of the same reliefs, all compacted by dejection fans formed by the ancient waterways that have carved the slope of the mountains. On the whole, the Eastern Desert forms an area which, given the presence of a hydrography although essentially fossil and in any case typical of the desert environment, is more habitable than that which extends to the W of the Nile. The Libyan Desert is instead a flat and sandy territory, made up of plateaus that exceptionally reach the altitude of 1893 m in the Jabal al ‘Uwaynāt in the southwestern extremity, just outside the border with Libya and Sudan. Except for these peripheral reliefs, it is moved only by the long and monotonous escarpments of the plateaus and by the depressions that open in the central and northern part and which represent the morpho-tectonic motif peculiar to this desert., which has the bottom at -133 m, flanked by the smaller one of Sīwah. Another marked depression is that of El Faiyûm, not far from the course of the Nile, from which it artificially receives the waters by means of an ancient canal that feeds the rich oasis. Other depressions, less deep, open to the S, between the Nubian tables. The Libyan Desert faces the Mediterranean with a coast formed to the W by low rocky escarpments; the coast assumes a particular morphology in correspondence with the delta, whose front reflects, with its regular profile, the symmetry of the apparatus, today hinged on the two branches of Rosetta and Damietta. Features lagoons (buheiret) follow one another along the delta contour, closed by sandy cords. The Sinai peninsula, which completes the picture of the Egyptian territory, is an isolated plate between the gulfs of Suez and ʽAqaba: the latter is the continuation of the Syrian-Palestinian trench, while the former corresponds to the structurally and conventionally dividing line between Asia and Africa, which continues along the isthmus, today cut by the Suez Canal. Overall, Sinai constitutes a region with its own distinct individuality. It is a mountainous territory that culminates to the S in the Jabal Kātrīnā (Jebel Caterina, 2642 m), a granite massif from which fossil river valleys descend; it is a harsh, arid environment, but here and there dotted with oases.