Angola has three principal natural regions: the coastal lowland, characterized by low plains and terraces hills and mountains, rising inland from the coast into a great escarpment and an area of high plains, called the high plateau (planalto), which extends eastward from the escarpment (see fig. 3). The coastal lowland rises from the sea in a series of low terraces. This region varies in width from about 25 kilometers near Benguela to more than 150 kilometers in the Cuanza River Valley just south of Angola's capital, Luanda, and is markedly different from Angola's highland mass. The Atlantic Ocean's cold, northwardflowing Benguela Current substantially reduces precipitation along the coast, making the region relatively arid or nearly so south of Benguela (where it forms the northern extension of the Namib Desert), and quite dry even in its northern reaches. Even where, as around Luanda, the average annual rainfall may be as much as fifty centimeters, it is not uncommon for the rains to fail. Given this pattern of precipitation, the far south is marked by sand dunes, which give way to dry scrub along the middle coast. Portions of the northern coastal plain are covered by thick brush. The belt of hills and mountains parallels the coast at distances ranging from 20 kilometers to 100 kilometers inland. The Cuanza River divides the zone into two parts. The northern part rises gradually from the coastal zone to an average elevation of 500 meters, with crests as high as 1,000 meters to 1,800 meters. South of the Cuanza River, the hills rise sharply from the coastal lowlands and form a high escarpment, extending from a point east of Luanda and running south through Namibia. The escarpment reaches 2,400 meters at its highest point, southeast of the town of Sumbe, and is steepest in the far south in the Serra da Chela mountain range. The high plateau lies to the east of the hills and mountains and dominates Angola's terrain. The surface of the plateau is typically flat or rolling, but parts of the Benguela Plateau and the Humpata Highland area of the Huíla Plateau in the south reach heights of 2,500 meters and more. The Malanje Plateau to the north rarely exceeds 1,000 meters in height. The Benguela Plateau and the coastal area in the immediate environs of Benguela and Lobito, the Bié Plateau, the Malanje Plateau, and a small section of the Huíla Plateau near the town of Lubango have long been among the most densely settled areas in Angola. Data as of February 1989
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