Physical Description. – Physically, Italian Somalia can be divided into four regions, significantly different for the geological constitution, for the shape and altitude of the soil, for the climatic conditions, and therefore also for the biogeographical, anthropogeographic and economic ones: northern Somalia, the Central Somalia, Southern Somalia and Oltregiuba.
Central Somalia. – Central Somalia includes the ancient sultanate of Obbia and Ogadēn: it is limited to NE. from Nogal, to SW. from Uebi Scebeli, while to E. the Indian Ocean bathes it. In this region, which at least in its coastal part is very arid, the calcareous plateau gradually but very quickly moves away from the sea, which is thus bordered to the North. by a little high tabular coast, then by little marked reliefs and vast plagues of shifting dunes, or barely fixed by a thin scrub of acacias.
Beyond these modest reliefs there are large depressed areas, in which all the waters coming from the interior are lost at the time of the rains, forming brackish or salty ponds with saline encrustations or chalky deposits, limited by sandy terraces covered with scrub, until the ground begins again gradually to rise inwards and to cover itself with shrubs. The coastal strip below 300 m., Which is about sixty kilometers wide a little Somalia di Ilig, extends for 200 km. at the height of Obbia, 250 km. at the height of Harardere. This is the most ungrateful, most sterile, and least known region of the whole colony. The small population, made up especially of groups of the Habaer Ghidir (Hauìa) tribe, and in the interior from Marrehàn (Darod) is dedicated to nomadic and semi-nomadic pastoralism, which supplies the usual products: sheep are bred, especially cattle and camels. In some areas, such as Harardere, the Habar Ghidir grow swarms, and produce some durum beans, watermelons and watermelons.
Oltregiuba. – Oltregiuba is the territory between Juba and the western border, which for great stretches follows the 41st meridian. It has physical characteristics similar to those of southern Somalia, essentially differing from it by a slightly higher rainfall, at least towards the coast. This is bordered by a series of islets, the Dundas Islands, also known as the Baiuni by the population of fishermen who live there, and which for some somatic and ethnic characteristics is similar to people of Malaysia. The chain of fixed dunes, covered with scrubland, also extends along the coast here and is inhabited by Harti shepherds, of the great Darod stock; therefore it stops at the mouth of the main rivers: Lac Bodana in front of the small island Ciuai; the Anole, which flows into the sea at Porto Tula and the Burgao, a navigable estuary, municipality of Cimoti and Bubasci in Porto Durnford. Inside the dune area there is a vast plain largely alluvial, and dependent on the Lac Derr, a temporary stream, which dies in the Descec Uama or L. Hardinge. It is inhabited by shepherds of the large group of Ogadēn (Mohammed Zubien, Bartireh, Macabùl): limited crops occur in the interior around Descec Uama (Uardai, Scecal) and along the upper Anola (Bagiuni); intensely cultivated are the floods of Lower Giuba (Goscia), from Uagoscia and Uaboni, and those of middle Juba and Daua from Gobauìn and Gasar Guddà. Further inland is the plateau on the right bank of the Juba, made up of Jurassic limestones, variegated sandstones with gypsum and strips of eruptive rocks. The plateau is covered with scrub and inhabited by Merehàn and Aulihàn shepherds.
The climate, as mentioned, is arid or semi-arid, but, except on the Gulf of Aden, more or less mitigated by the monsoons that blow for about 8 months of the year from NE. in the winter, from Somalia or SW. in the summer. In the coastal area the average annual temperature is around 27 °, in the interior 35 °: seasonal variations are more modest, the warmest and driest season being winter, the coolest and somewhat humid summer; rather marked diurnal variations, especially in the somewhat elevated inland regions; considerable atmospheric humidity, especially along the sea and on rivers. The rains fluctuate between 700 mm. (Brava) and 300 (Lugh) and fall in two seasons, called by the indigenous gu (March-May) and der (September-November); the intermediate seasons are the gilàl (December-February) dry heat and the agaio (June-August) milder and with some drizzle. From the hygienic point of view, the climate is very healthy, except along the rivers where malaria is frequent and there is no lack of forms of amoebic dysentery. Here there is also the nagana who kills animals: the sleeping sickness is fortunately unknown. Rare or very rare, almost unknown in Europeans, are yaws, recurrent fever due to tick bites, tropical ulcers, leprosy, elephantiasis, beriberi.