rift valley Definition

an elongated valley formed by the depression of a block of the earth's crust between two faults or groups of faults of approximately parallel orientation

an acute, usually epizootic, mosquito-borne disease of domestic animals chiefly of eastern and southern Africa that is caused by a bunyavirus (species Rift Valley fever virus of the genus Phlebovirus), is marked especially by fever, abortion, and death of newborns, and is sometimes transmitted to humans usually in a milder form marked by flu-like symptoms

depression in southwestern Asia and eastern Africa extending with several breaks from the valley of the Jordan River south to central Mozambique