Anyone who likes antiques or other "old stuff" and also has a yearning to visit the wild outdoors should investigate a natural antique: the St. Francois Mountains Natural Area. This natural area, including parts of Ketcherside Mountain Conservation Area and Taum Sauk Mountain and Johnson Shut in's state parks, is part of the oldest landscape in Missouri and one of the oldest in the Midwest.
Located in Reynolds and Iron counties, these rugged mountains, with their unique geologic formations and plant and animal communities, are prize antiques in Missouri's natural world.
The St. Francois Mountains Natural Area is one of the most recently designated state natural areas recommended by the Missouri Natural Areas Committee (see sidebar on page 9). This designation protects and recognizes one of the best examples in the state of a large, wild igneous (volcanic) landscape that includes forests, savannas, open glades, an outstanding Ozark creek, the largest waterfall in the state and rare plants and animals. To top it all off, these features are located on and near the highest mountain in the state, which reaches 1,772 feet in elevation.
The formation of the St. Francois Mountains started over a billion years ago in the late Precambrian Geologic Era, long before the notion of dinosaurs, primitive amphibians, trees and trilobites. Great explosions of volcanic ash and gases blasted through the earth's crust. Ash flows blanketed miles of earth. Periods of uplifting, folding and deformation of the earth's surface were followed by more eruptions and deposition of volcanic materials.
In no other natural setting is the geologic story of these mountains so clearly presented. Rock exposures in today's natural area provide evidence of past volcanic activities and allow an observer to view the geologic history of this most ancient part of the Ozarks. At least six different igneous rock formations are exposed within the area.
The formations mostly are composed of rhyolite porphyry-brittle rock that formed from over-land ash flow that cooled and solidified rapidly, forming fine grains. In contrast to rhyolite porphyry, granite, which is found infrequently on the area (but is important in the overall St. Francois Mountain region), formed from liquid molten magma deposited below the ground surface. It cooled and solidified slowly while still underground, forming coarse grains with large crystals of feldspar (a mineral group of silicates of aluminum and potassium, sodium or calcium) and quartz.
Basalt is visible as black bands of rock throughout the rhyolite exposures. Basalt