Shut-in (river)

A shut-in is a rock formation that carves through a mountain range, causing a complex of pools, rivulets, rapids and plunge pools. They are found in streams in the Ozarks. Shut-ins are inherently confined to a narrow valley or canyon, with the river valley widening out both above and below the formation. Because the rock resists downcutting, streams typically descend at relatively steep gradient through shut-ins, with the downstream terminus of the formation often marked by a very large plunge pool. The river becomes unnavigable at shut-ins even by canoe due to the rapids and narrow channels.

The term has an origin in Appalachia, where it was used to refer to a narrow river gorge confined by resistant rock layers.^[1]