Arroyo is the Spanish name for a deep, dry creek bed that is common in the southwest. Semi-arid climates are prone to having short-lived but heavy downpours that run off before the water can soak into the soil. The fast moving water causes erosion that continually deepens and widens these ravines. Typical of far southwestern Oklahoma, this arroyo meanders around sand dunes, under the railroad tracks, and on toward lower ground. A lone coyote bays at the moon from the top of a dune.