Castor
River Shut-Ins, Madison County, MO. Here in Missouri,
most of the rocks are sedimentary rocks - what geologists
sometimes call "soft rocks." Igneous rocks
occur only
in the Saint
Francois Mountains. When rivers cut through
the harder
Precambrian
granites and rhyolites of the St. Francois
Mtns., they form steep sided canyons locally called "shut-ins." The
shut-ins in the photo is 75 miles south of campus. More
info
