Topographically and geologically, Italian East Africa can be divided into three principal areas: (1) the "Ethiopian Plateau" which occupies the northwestern third of the country; (2) the "Rift Valley depression" which divides the entire country in two; and (3) the "Somaliland Plateau," the country south and east of the Rift Valley.

The Ethiopian Plateau consists of a series of tablelands, in many places of great elevation, with ranges of high and rugged mountains dispersed across its surface in rugged confusion. This high land area is composed of a thick series of lava flows which rest either on old plutonic rocks or upon a thin section of Mesozoic sediments.

The Rift Valley depression is a long, and generally narrow, trough which trends in a northeasterly direction across the country from the southwest corner of Abyssinia to near the junction of the Red Sea and the Gulf of Aden. Toward the northeast, the trough widens and the scarps which form its sides become continuous with those on the eastern side of the Red Sea and the south side of the Gulf of Aden. For the most part, the floor of the depression is covered by lava flows of Tertiary age.

The Somaliland Plateau is a great area of monotonous relief which slopes very gradually, from elevations near 5,000 feet along the Rift Valley and the Gulf of Aden, southeastward to the Indian Ocean. Most of this plateau is covered by sediments of Mesozoic and early Tertiary age.

End_of_Article - Last_Page 1879------------