Geography Topography and Climate

The Middle East and North Africa occupy that part of the Earth's crust where three tectonic plates converge, causing great ranges of high-fold mountains to be thrust up, notably in western North Africa and in the northern tier states of Turkey and Iran. Peaks in the high Atlas Mountains of Morocco and the Taurus range in Turkey exceed 12,000 feet, whereas Mount Damavand, in Iran's Elburz mountains, exceeds 18,000 feet. Running north and south, the Hijaz, Asir, and Yemen ranges are high escarpments in the southwestern Arabian Peninsula, paralleling the anticlinal highlands that form the Lebanon and Anti-Lebanon mountains and the Judean Hills of Palestine.

The Middle East and North Africa lie roughly between latitudes 20° and 40° north in a transitional climatic zone between equatorial and mid-latitude climates. Because of general atmospheric circulation patterns, a characteristic of these latitudes is prevailing aridity - the "Mediterranean Rhythm" of winter rain and summer drought. Only westward-facing coasts and mountain ranges receive the 250 millimeters (about 10 inches) rainfall considered the minimum necessary for cultivation. The lack of cloud cover is a major factor influencing temperature, for clear skies and intense solar heating of the land cause very high temperatures during the day although temperatures fall considerably at night. Another characteristic of the region is scanty water supply. Except for the Nile, Tigris, and Euphrates, the majority of rivers are short streams with a rapid and intermittent course down rugged mountain sides. The lack of wooded land is another serious deficiency. Long occupation has meant prolonged exploitation of the land over millennia, almost total deforestation, and removal of ground cover, resulting in uncontrolled water runoff and soil erosion. Aggravated by overcultivation and unrestrained grazing, especially by goats, soil erosion has led to extensive desiccation and desertification. Hence, at mid-twentieth century, it was estimated that only 5 to 7 percent of the total area is cultivable naturally.

The implications of prevailing aridity and great expanses of mountainous or desert terrain have been significant for human survival: Population has been relatively sparse and discontinuous in distribution; until recently, nomadism was widespread; and settled argiculture most often has required irrigation and complex infrastructures to govern the allocation of scarce water resources.

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