Two billion years ago volcanos erupted in southeastern Missouri, spewed forth lava and clouds of volcanic dust, and formed the St. Francois Mountains, the first rocks in Missouri's geological column.
It is a region of rugged knobs and hills and deep valleys. Here rivers and streams run through shut-ins, small canyons, where running water has eroded the soft sedimentary rocks down to the hard Precambrian Igneous Rocks, grey rhyolite and pink granite.
The later rocks in Missouri's geological column, the sedimentary rocks deposited as the inland seas washed in and out of Missouri, never covered the St. Francois Mountains. Taum Sauk Mountain is the highest point in Missouri at 1,772 feet.
The ecosystems they support are protected in the Mark Twain National Forest, in state parks--Elephant Rocks, Sam Baker, Taum Sauk Mountain, and Johnson's Shut-ins, and in natural areas--Hughes Mountains. |
