A dry valley is a valley once created by a ﬂowing stream that now has little or no running water. Some dry valleys are relatively minor indentations, others much deeper chasms. Possible reasons for the disappearance of the initial stream include lack of rainfall and a consequent lowered water table. Or the stream may have been beheaded—diverted at its source, perhaps by another stream. Another possibility is that a signiﬁcant climatic shift dried up the ﬂow of water over time. A dry valley in limestone karst could have lost its stream down a joint in the rock or to a collapsed underground cavern. The name Dry Valley has been given to valleys across the United States, from California to Tennessee, Idaho to Georgia, Alabama to Arizona.