As a result, one can reach most summits in the Rockies with little or no climbing, and rappel descents can be avoided from most summits. Mt. Louis and Mt. Alberta are notable exceptions and therefore involve long rappel descents. The other chief factor in Rockies mountain formation is glaciation, which has been responsible for carving mountains, creating hanging valleys, and steepening many north-facing walls. Since limestone and quartzite are harder than the intervening strata of shale, they present themselves as steep cliffs. Brewer's Buttress,Castle Mountain Limestone Most of the climbing in the Rockies is on limestone.
Limestone varies from astoundingly good to astoundingly bad.
The slabs at the Guide's Rock, just north of Banff, for example, are as clean and solid as the best granite. On the other hand, many alpine routes, especially those which see little traffic, can be frighteningly loose. Limestone frequently appears in alternating bands of hard and soft rock, which explains the classic nature of cliff alternating with rubble ledges as seen on Rundle, Castle, Alberta, Temple, etc. Quartzite tends to be steep, blocky, and split by clean horizontal and vertical cracks. Climbing is typically on clean, in-cut holds or good jam cracks, and protection is easy to come by.