1. When tectonic forces compress rock they cause it to bend. Sometimes if the rock bends too much it will crack. This happened to many beds of local limestone rock.
2. The landscape in the areas we've been biking through was formed, and continues to be formed, by the movement of glaciers. When these glaciers begin to melt the water needs to go somewhere. Deep cracks in the limestone rock are a natural place for the water to flow- downhill.
3. The glacial water is full of 'rock flour,' bits of sand and rock that the glacier has eroded from the surrounding landscape. This rock flour works like sandpaper, rounding and smoothing the sides of the canyon walls.
The result is a deep canyon with both jagged and rounded features. The jagged 'ripped' features are the result of ancient plate tectonics; the smooth features a result of past and current glacial water flow.
Marble canyon- Kootenay National Park
Geology in action!
Please note- this is a basic explanation of how these canyons formed. For more detailed information please consult additional sources.