On one level, the Canadian Rockies’ geological story seems rather obvious. At some point in time, long before the earliest man was even glint in Mother Nature’s eye, some great force thrust great big hunks of rock up from the depths below toward what was probably a pretty dust-filled sky. But where did they come from, you ask? From the sea, of course.
With the exception of a few isolated pockets of igneous, formerly molten rocks, the Rockies are comprised almost entirely of layered sedimentary rocks, including limestone, dolomite, shale and sandstone. Sedimentary rocks form as sediments layer one on top of another on the bed of a large body of water. Depending on the parent material and how forces such as weathering, erosion, transportation and deposition affect them, the layers form as either inorganic or organic rock. Inorganic rocks consist of minerals and individual grains left behind after older rocks erode. Organic rocks originate from either chemical or organic origins. They include rocks formed from the remains of living organisms and those created as a result of various chemical processes, including the Rockies’ limestones, dolomites and natural resources such as coal. As mountains form however, the neatly stacked layers shatter as rocks are bent, folded, cracked and eroded and older layers end up settling over younger ones. Once the raw materials exist, they can become mountains. This happens when the continental plates shift and the resulting forces transform a level plain into a towering mountain range. According to the plate tectonics theory, the earth’s surface is comprised of a series of plates, each one moving in relation to the others. When and where these plates collide, mountains are born.
As you drive through the Rockies, from Mount Yamnuska on the eastern edge, west past Castle Mountain and Lake Louise and north along the Icefields Parkway all the way through Jasper to Mount Robson, you may notice the Rockies come in a variety of shapes and sizes. Castellate Mountains, composed of horizontal lying layers, resemble their name and often have vertical towers resembling ancient castle-style turrets – as Banff’s Castle Mountain does. Mountains cut in dipping layered rocks result from rocks being thrust upward at a 50 or 60 degree angle to create peaks such as Mount Rundle, next to Banff townsite, that exhibit one continuous, sweeping, smooth face on one side and one sharp, steep face on the other that reveals the uplifted layers. Dogtooth Mountains – such as Banff’s Mount Louis – form when masses of almost vertical layers erode, leaving behind very hard rock layers that sometimes jut straight into the sky in jagged points. A long ridge of almost vertical rock layers that erodes into a jagged ridge resembling a saw blade is called a Sawtooth Mountain. The Canadian Rockies also include Matterhorn Mountains, formed when glaciers scour a summit’s four different sides to create a square-topped peak similar to the European mountain of that name – like the Rockies’ own Mount Assiniboine. Other mountain shapes include Anticlinal, where compressed rock that doesn’t crack forms into smooth domes and depressions and Synclinal, mountains formed in dipping troughs and Complex mountains, which are simply mountains that defy classification with a combination of upfolds and downfolds that result in very complex structures.
