Buckskin Gulch.  Rising above a sand wash are the towering walls and narrow passageways of Buckskin Gulch, a dramatic slot canyon forged by centuries of erosion through sandstone.  Buckskin Gulch is the worlds longest accessible slot canyon, running from the Paria River toward the Colorado River.  Flash flooding is a serious danger in the narrows where there is no escape. Buckskin Gulch, Paria Canyon-Vermilion Cliffs Wilderness, Arizona, USA, natural history stock photograph, photo id 20724