View source for Shut-in (river)

{{short description|Type of rock formation found in Ozarks streams}}
{{About|the type of rock formation found in Appalachia|the watercourse in Missouri|Shut-in Creek}}
{{refimprove|date=June 2021}}
[[File:Johnsons Shutins autumn panorama-panini 20130126.jpg|thumb|right|Johnson's Shut-Ins panorama]]

A '''shut-in''' is a type of [[rock formation]] found in streams in the [[Ozarks]], comprising [[stream pool|pools]], [[rivulet]]s, [[rapids]] and [[plunge pool]]s. The term has an origin in [[Appalachia]].

==Description==
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.

==Etymology==
The term has an origin in Appalachia, where it was used to refer to a narrow river [[gorge]] confined by resistant rock layers.<ref name="Beveridge" />

==Examples==
[[Johnson's Shut-Ins State Park]] in Missouri, with its hard [[rhyolite]] and a [[diabase]] [[Dike (geology)|dike]] that divert the [[Black River (Arkansas)|Black River]] into many small streamlets following a complex [[Joint (geology)|joint system]], is the most well known example.<ref name="Beveridge">Beveridge, T. R., ''Geologic Wonders and Curiosities of Missouri,'' Missouri Department of Natural Resources, 2nd ed. 1990, p. 39–62</ref> More than ninety other shut–ins occur within and around the [[St. Francois Mountains]] region of southeast Missouri.<ref name="Beveridge" />  In southern Illinois, the [[Burden Falls Wilderness]] area includes a narrow canyon below a waterfall that is confined by a resistant [[sandstone]] layer; the gorge is referred to as a ''shut–in'', following the Appalachian usage for the term.

==See also==
* {{annotated link|Downcutting}}

==References==
{{reflist}}

{{River morphology}}

{{DEFAULTSORT:Shut-In (River)}}
[[Category:Rivers]]
[[Category:Ozarks]]


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