In southern Somalia the crystalline bedrock outcrops to the south of Baydhabo (Baidoa) in the shape of granite formations called inselbergs. These give way farther south to alluvial plains, which are separated from the coast by a vast belt of ancient dunes stretching more than 600 miles (1,000 kilometres) from south of Kismaayo (Chisimaio) to north of Hobyo (Obbia).

Drainage

The flatness of the Somalian plateaus is interrupted by several deep valleys. Starting in the northeast, these are the Dharoor and Nugaal (Nogal) valleys; both are wadis that, in season, have rivers flowing into the Indian Ocean at Xaafuun and Eyl, respectively. In the southwest are the only permanent rivers in Somalia, the Jubba (Giuba) and Shabeelle (Shebele). Originating in the Ethiopian highlands, these two streams cut deeply into the plateaus before meandering through the alluvial plains toward the coast. Whereas the Jubba flows directly from north of Kismaayo into the Indian Ocean, the Shabeelle veers southwest immediately to the north of Mogadishu and flows into a large swamp before reaching the Jubba. The Jubba carries more water than the Shabeelle, which sometimes dries up in its lower course in years of sparse rainfall in the Ethiopian highlands. During dry seasons, these rivers are a major source of water for people and animals alike.

Because over most of the country the water table is deep or the groundwater has a high mineral content, the conservation of surface runoff is of primary importance.

Soil

The types of soil vary according to climate and parent rock. The arid regions of northeastern Somalia have mainly thin and infertile desert soils. The limestone plateaus of the interfluvial area have fertile, dark gray to brown, calcareous residual soils that provide good conditions for rain-fed agriculture. The most fertile soils are found on the alluvial plains of the Jubba and Shabeelle rivers. These deep vertisols (black cotton soils) have a high water-retention capacity and are mainly used for irrigation agriculture.

Climate

Somalia lies astride the equator and so belongs to the tropics. Unlike typical climates at this latitude, conditions in Somalia range from arid in the northeastern and central regions to semiarid in the northwest and south.

The climatic year comprises four seasons. The gu, or main rainy season, lasts from April to June; the second rainy season, called the dayr, extends from October to December. Each is followed by a dry season: the main one (jilaal) from December to March and the second one (xagaa) from June to September. During the second dry season, showers fall in the coastal zone.

Long-term mean annual rainfall is less than 4 inches (100 millimetres) in the northeast and approximately 8 to 12 inches in the central plateaus. The southwest and northwest receive an average of 20 to 24 inches a year. While the coastal areas experience hot, humid, and unpleasant weather year-round, the interior is dry and hot. Somalia has some of the highest mean annual temperatures in the world. At Berbera on the northern coast the afternoon high averages more than 100º F (38º C) from June through September. Temperature maxima are even higher inland, but along the coast of the Indian Ocean temperatures are considerably lower because of a cold offshore current. The average afternoon high at Mogadishu, for example, ranges from 83º F (28º C) in July to 90º F (32º C) in April.

Plant and animal life

In accordance with rainfall distribution, southern and northwestern Somalia have a relatively dense thornbush savanna, with various succulents and species of acacia. By contrast, the high plateaus of northern Somalia have wide, grassy plains, with mainly low formations of thorny shrubs and scattered grass tussocks in the remainder of the region. Northeastern Somalia and large parts of the northern coastal plain, on the other hand, are almost devoid of vegetation. Exceptions to this are the wadi areas and the moist zones of the northern coastal mountains, where the frankincense tree (Boswellia) grows. The myrrh tree (Commiphora) thrives in the border areas of southern and central Somalia.

Owing to inappropriate land use, the original vegetation cover, especially in northern Somalia, has been heavily degraded and in various places even entirely destroyed. This progressive destruction of plant life also has impaired animal habitats and reduced forage, affecting not only Somalia's greatest resource, its livestock (chiefly goats, sheep, camels, and cattle), but also the wildlife. At present there are still many species of wild animals throughout the country--especially in the far south: hyenas, foxes, leopards, lions, warthogs, ostriches, small antelopes, and a large variety of birds. Unfortunately, giraffes, zebras, oryx, hippopotamuses, rhinoceroses, and, above all, elephants have been decimated, elephants being slaughtered chiefly by ivory poachers. Measures to protect endangered species have been taken by creating a national park in the lower Shabeelle swamp region.

Settlement patterns

Roughly half of the Somali population lives permanently in settled communities, the other half being nomadic pastoralists or agropastoralists. The sedentary population chiefly occupies climatically and topographically favourable regions in southern and northwestern Somalia, where rain-fed agriculture is possible and irrigation agriculture can be practiced along the rivers. Their settlements consist of large, clustered villages near the rivers and in the central interfluvial area, as well as small hamlets farther away. The population is also concentrated in the old trading centres on the coast, such as Kismaayo, Baraawe (Brava), Marka (Merca), Mogadishu, Berbera, and Boosaaso (Bosaso).

The strong influence from Arabia, Persia, and India has shaped the face of the old coastal town centres, and Italian colonial architecture is visible in Mogadishu. Solid constructions of traditional coral limestone and modern concrete brick clearly distinguish the large coastal settlements from the district and provincial capitals of the interior, where traditional wooden houses with thatched or corrugated-iron roofs predominate. There are two main types of traditional house: the typically African round house (mundul), mainly found in the interior, and the Arab-influenced rectangular house (cariish) with corrugated-steel roof, prevailing in the coastal regions and northern Somalia.

Pastoral nomads still live in transportable round huts called aqal. During the dry seasons, the high mobility of these livestock keepers leads to their temporary concentration in the river valleys of southern Somalia and around important water points all over the country.

Heavy migration from rural areas into towns has caused enormous urban expansion, especially in Mogadishu. As a result of increased market-oriented and extrapastoral activities, more nomads are tending to adopt a semi-settled way of life and economy. This has led to a great number of permanent nomad settlements, chiefly along the roads and tracks of the country's interior.

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