Maligne Canyon - Click for more details

 

Understanding the Geology of Canyons

Key Topics

An Introduction to Mountain Canyons

Often overlooked in a landscape of towering peaks, are the rare, yet fascinating mountain canyons. Why are they rare? After all, rivers have been carving canyons for as long as there have been rivers. Although true, we must also remember that rivers have only recently begun to re-sculpt the mountain landscape. When glaciers co-opted the former river beds, they widened and smoothed out most of our canyons, leaving wide u-shaped valleys. With the retreat of the ice, the rivers had to begin anew.

Research suggests that some canyons may have either existed beneath a few large glaciers, or that they may have been subterranean caves exposed by the erosion of their roof by glacial ice. Of particular interest in this theory is Maligne Canyon in Jasper National Park. This canyon is intricately connected with a vast cave system.

Mistaya Canyon, Banff National Park, Alberta, Canada - Click to Learn MoreThe rare nature of our mountain canyons is reflected in their prominence as a focal point for hiking trails, roadside stops, interpretive sites, and even winter guided crampon creeps. Looking into hiking guides youíll find trails leading to locations like Johnston Canyon, Sundance Canyon, Mistaya Canyon, and even Turbine Canyon. Each exhibits a unique character that makes is a worthy hiking destination. In other cases, the canyons are located adjacent to major highways. Marble Canyon, North Saskatchewan Canyon, Sunwapta Falls Canyon and Athabasca Falls Canyons are typical examples. Most are signed and designed to attract roadside visitors. Another roadside canyon, Maligne Canyon, has inspired not only interpretive trails, but an entire gift shop and restaurant.

How Are They Formed?

The formation of canyons can be related to the natural tendency of rivers to reach a base line elevation. This is generally defined as the point at which the river reaches the elevation of the large body of water into which it will drain. Essentially, the larger the difference in height between the river and its inlet into a large lake, the more energy the river will expend in the process of erosion. Much of this energy will be expended towards increasing the efficiency of the drainage system, and facilitating a speedy drop in elevation.

In the case of Maligne Canyon, the river suddenly found itself elevated in a hanging valley as the Athabasca Glacier carved a much deeper valley than its smaller tributary. To facilitate drainage to a now distant valley bottom, the river expended incredible amounts of energy to deepen the channel into the narrow, deep canyon visible today.

Other rivers, like the river flowing down Johnston Canyon, were forced to find new channels when their ancestral streambeds were blocked. A landslide dammed Johnston Canyonís original channel. In other cases, glacial debris may have the same affect.

How Old Are They?

Most of our canyons are very recent additions to the landscape. In most cases, the creation of canyons coincides with the departure of glaciers from their valleys. As the ice began to melt, it not only released ancestral river beds from their icy prison, but it also released immense amounts of water. So much water was released that the rivers were provided with an incredible erosional potential. This extra water supply allowed them to rapidly alter their channels, and the down-cutting may have begun almost instantly. As the glaciers largely, eventually the initial deluge subsided, and the rate of erosion slowed accordingly, but didnít stop. Most of our canyons continue to deepen even today. While you stand at the top of Maligne or Marble Canyon, the valley floor is slowly being etched and scoured. The rate may have slowed, but the process is unrelenting.

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All Material © Ward Cameron 2005