Along the flanks of the Front Range, the eroded edges of the sedimentary rocks which once covered the range are exposed. These rocks are usually tilted sharply against the mountains, as at Garden of the Gods, Denver’s Red Rocks Park, and the Flatirons near Boulder. The Rocky Mountain Association of Geologists has erected a plaque explaining the geology of the Red Rocks area; look for it about half a mile northeast of the Red Rocks Amphitheater. Tilted layers of Paleozoic and Mesozoic sandstones form hogback ridges along the mountain front, and stand out clearly on aerial photographs. In some areas, particularly near Boulder, Coal Creek, and Golden, the tilting of the sedimentary layers has been so extreme that the layers are upside down. Basement rocks may even be thrust out above them. [Illustration: Sandstones and conglomerates of the Pennsylvanian Fountain Formation dip steeply toward the plains along the eastern edge of the Rockies. Near Denver, erosion has carved these rocks into a natural amphitheater, now the site of Red Rocks Amphitheater. Precambrian granite forms the hill in the background. (Jack Rathbone photo)] Further north, near Loveland and Lyons, as well as further south at Colorado Springs, irregularities in the uplift have caused abrupt breaks in the generally smooth eastern edge of the range. Folds and faults in these areas trend northwest, cutting across and offsetting the mountain front. [Illustration: South of Colorado Springs, between Fort Carson and the NORAD installation in Cheyenne Mountain, Mesozoic rocks are faulted against the mountain front. Paleozoic rocks are deeply covered by as much as 3000 feet of Mesozoic sediments. They come to the surface about 10 miles further south.] RAMPART RANGE Garden of the Gods Ute Pass Fault MANITOU SPRINGS PIKES PEAK MASSIF CHEYENNE MOUNTAIN COLORADO SPRINGS CROSS SECTION Ute Pass Fault Rampart Fault Tertiary Mesozoic Paleozoic Precambrian [Illustration: West of Boulder, several intersecting sets of joints pattern the Precambrian rocks above Boulder Creek. (John Chronic photo)] The west margin of the Front Range is not as sharply defined as the eastern margin. Prominent faults edge North, Middle, and South Parks, however. The northern end of the range merges with the Medicine Bow Mountains, where dips of sedimentary rocks seldom exceed 30 to 40 degrees. At its southern end, the Front Range plunges into the plains, although a southwest-trending ridge connects it with the Wet Mountains. Within the Precambrian core of the Front Range, many economic mineral deposits have been found. These are discussed in Chapter III. Glacial features of the Front Range are discussed in Chapter II in the section on the Quaternary Period. Wet Mountains