Then followed a general uplift of the entire region. Drainage courses traversed the newly formed rocks and the principal streams carved broad valleys with sweeping curves or meanders. The wind and other forces of weather chiseled away at the rocks to form “slick rock” surfaces and the dome-shaped hills called whalebacks and baldheads. A large mass of molten rock pushed outward from the interior, arching the earth’s crust to form Navajo Mountain. This local uplift caused small streams to furrow canyons across the soft cross-bedded Navajo sandstone. It also caused the large streams to deepen their channels; those with broad valleys, through necessity, followed the former meandering course. This frequently gave rise to blocks of solid rock, called “fins” and “necks,” standing between entrenched meanders. It was one of these “necks” from which Rainbow Bridge was formed. When the “neck” was once formed, running water laden with cobbles and sand scoured at the sides. Frost action and expansion and contraction, due to temperature changes, loosened great slabs of rock as well as particles. Gravity helped to remove them. Eventually, an opening was worn through the “neck.” This gave the stream a direct course through the “neck” rather than around it. Continuing erosion enlarged the opening and deepened the gorge. Thus, the canyon spanned by Rainbow Bridge came into being. Mother Nature used the less severe forces of weathering for shaping and polishing the outline of Rainbow Bridge. For example, when moisture freezes within a crevice it exerts pressure on the surface of a rock and causes the outer portion to shell off, forming a relatively smooth surface. The Navajo sandstone is particularly subject to this type of weathering. It is porous and the curved layers of the cross-beds are held together with weak, natural cement that is easily removed by percolating water. Dissolving of the cementing materials and prying action by frost are the chief agents for carving the rock. The cross-bedding is important in controlling the shape. Thus, the combination of several factors, over a long period of time, developed for us the arch as we now see it. In the words of J. B. Priestly “How do we know that the Rainbow Bridge is not itself a kind of symphony, no more to be completely explained by geology than Beethoven is by acoustics?” [Illustration: RAINBOW BRIDGE TRAIL FROM RAINBOW LODGE, ARIZONA, TO RAINBOW BRIDGE NATIONAL MONUMENT, UTAH] Horse and Foot Trail RAINBOW BRIDGE NATIONAL MONUMENT EL. 3880′ Echo Spring Camp EL. 3860′ RAINBOW BRIDGE CANYON EL. 3840′ REDBUD PASS SPRING EL. 4280′ CLIFF CANYON EL. 6480′ EL. 6600′ Rainbow Lodge EL. 6280′ November 1950 RB-N.M. 7001 Vertical Cliff