The probable results of the movement in the crust of the earth are shown in the diagram (fig. 2). Section A represents a cross section of the Glacier Park region, as it most likely appeared, immediately following the long period of sedimentation. The rock strata are horizontal. Section B shows the same region after the rock layers have been slightly wrinkled due to the forces from the southwest, which, although slightly relieved by the bending, still persisted and the folds were greatly enlarged as shown in section C. At this stage the folds reached their breaking limit, and the strata broke in a number of places as indicated by dotted lines in the diagram. As a result of this fracturing, the rocks on the west side of the folds were pushed upward and over the rocks on the east, as shown in section D. The mountain rocks (represented by patterns of cross lines) were shoved over the rocks of the plains (represented in white), producing what is known as an "overthrust fault." It has been estimated that the rocks have moved a distance of at least 15 miles. As the rocks were thrust northeastward and upward they made a greatly elevated region, but did not, however, at any time project into the air, as indicated in section D, because as the rocky mass was being uplifted, streams were wearing it away and cutting deep canyons in its upland portion. The rocks of the mountains, owing to their resistant character, are not worn away as rapidly as the plains formations with the result that great thicknesses of limestone and argillite tower above the plains. Where the older, more massive strata overlie the soft rocks the mountains are terminated by precipitous walls as shown in section E. This explains the absence of foothills that is so conspicuous a feature of this mountain front and one in which it differs from most other ranges. While the region now known as "Glacier National Park" was being uplifted and faulted, the streams were continually at work. The sand and other abrasive material being swept along on the beds of the streams slowly wore away much of the rock. The uplifting gave the streams life and they consequently cut deep valleys into the mountain area. They cut farther and farther back into the mountain mass until they dissected it, leaving instead of an upland plateau a region of ridges and sharp peaks. This erosional process which has carved the mountains of Glacier Park has produced most of the mountains of the world.