Page:History of Southeast Missouri 1912 Volume 1.djvu/16

x stream nor covered with sediment as would have been the case if this part of the stream bed were as old as most of it. A part of this ridge extends into the alluvial section and is known as the Scott county hills. Other ridges make off from the central dome of the upland to the southwest extending into Arkansas and Oklahoma.

Within recent years the name St. Francois mountains has been applied to the hills in St. Francois, Iron, Wayne, and Washington counties. These hills are not only among the highest in the Ozark region of Missouri, but they are perhaps the only true mountains found within the state. They seem to have been formed not by the wearing down of the plain as is the case with most of the Ozark hills, but to have been thrust up from beneath by forces within the earth and thus are true mountains in their origin. In these mountains are exposed the only Azoic rocks in Missouri. The granites which form the primordial base on which this Ozark region was built have been thrust up in the formation of these mountains until they are now at the surface: Iron Mountain, Shepherd Mountain, Pilot Knob, and others in their vicinity are some of the best known of these St. Francois mountains. The hill just west of Knob Lick in St. Francois county in the vicinity of the granite quarries known as Syenite, is a good example of these mountains formed by uplift. The name St. Francois mountains is peculiarly appropriate to them since most of them are found in St. Francois county and since also they form the source of the St. Francois river. The name because it is appropriate and describes a distinct formation will probably come into general acceptation and use. The upthrust which created these mountains brought the hard granite and basalt to the surface or near it in many places, and in places dikes of these rocks were formed crosswise of the ridges previously existing. The streams of the section occur for the most part in the folds in the ridges formed within the