A shut-in is an Ozark term for a river that's naturally confined within a deep, narrow channel. The river becomes unnavigable even by canoe due to the rapids and narrow channels produced as the stream encounters a more resistant rock that is more difficult to erode. In the Johnson's Shut-Ins State Park in Missouri hard rhyolite and a diabase dike diverts the stream into many little streamlets following a complex joint system "shutting" the river.
Examples can be found in Johnson's Shut-Ins State Park in Missouri, where the Black River has become confined in a shut-in. More than ninety other "shut–ins" occur within and around the St. Francois Mountains region of southeast Missouri.
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.
- Beveridge, p.39 - 62
- Beveridge, T. R., Geologic Wonders and Curiosities of Missouri, Missouri Department of Natural Resources, 2nd ed. 1990, p. 39–62
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