alluvial plain – area built up by rich fertile soil left by river floods silt – small particles of rich soil

sedimentary rock – type of rock formed when layers of sediment or dirt from the ocean floor are compressed are compressed together and harden refineries – facility that turns petroleum into gasoline and other products

wadi – dry riverbed that fills with water when rare rains fall in the desert steppe – partly dry grassland often found on the edges of the desert

nomad – a person who lives by moving from place to place to lead herds of grazing animals to fresh pasture dry farming – agriculture that conserves water and uses crops and growing methods suited to semiarid environments

aquifer – underground layer of rock through which water flows rationing – making a resource available in limited amounts

desalinization – process of treating seawater to remove salts and minerals and make it drinkable irrigation – process of collecting water and distributing it to crops

polytheism – belief in more than one god theocracy – form of government in which the leader claims to rule on behalf of a god

monotheism – belief in one god covenant - agreement

prophet – messenger of God anti-Semitism – hostility or discrimination against Jews because of their religion or race

caliphs – successor of Muhammad terrorism – violence used against the people or government in the hopes of winning political goals