Labels:text | font | black and white | screenshot | white | document OCR: Deserts are made of sand and rock, but they also feature a number of unique regions, including dried up river beds, called wadis in Africa and the Near East, and arroyos in North America. Wadis are dangerous at certain times of the year when they fill with torrents of rainwater which sweep away boulders, pebbles and sand in churning mass. The walls of these channels are steep-sided and are cut back farther with each flood. Seasoned desert travellers know that sleeping in wadis can be a foolhardy practice because rains falling many miles away can
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