Geology and landforms
Geology and Landforms
© Parks Canada
One thing geology isn't, is stationary. Forces, past and present, shaped and reshape the land into the unique forms found in Waterton and throughout the Crown of the Continent ecosystem.
Massive thrust sheets, ancient seas, glaciers, wind, rain and ice, rivers and streams all influence the landforms we see.
Some of these forces like wind, rain and ice are seasonal, even daily occurances, others like thrusts and glaciation occur over long periods of time. The landforms we see reflect A Brief History in Time: where the past meets the present.
The rock layers in Waterton are primarily eroded sediments laid down particle by particle at the bottom of an ancient sea which existed 1,500 million years ago. Evidence of this ancient seabed is provided by fossilized ripple marks and salt crystal casts. These rock layers make up the park's geological foundation.
The rocks were formed at a time before the development of complex animal life on earth, so only fossils formed by primitive cyanobacteria are found. Some developed into impressive cabbage-like fossils called stromatolites.
The park's unusual red and green rocks are shaly siltstones called argillite. The red rocks contain oxidized iron; the green rocks contain unoxidized iron. Beige/grey/brown rocks are limestone or dolomite. A noticeable black band seen on the face of some park mountains, called the Purcell Sill, is igneous rock.
In most of the front ranges of the Canadian Rockies, mountains were built of overlapping, tilted thrust sheets. In Waterton, the main movement was a single, flat-lying thrust sheet originating about 100 km/65 miles southwest of the mountains' present position. For millions of years it slid northeast, more or less horizontally over younger 70 million year old Cretaceous rock. This fault is called the Lewis Thrust.
Erosion and Deposition
Since the mountains were built, glaciers and other forms of erosion sculpted them then deposited the pieces at their feet. Glacial and fluvial deposits blanketed the area east of the moutains, creating Waterton's unique 'Where The Mountains Meet The Prairie' landscape.
Most of this landscape sculpting was done by mountain (cordilleran) glaciers. There are presently no glaciers in Waterton, just snowpatches. Glacier National Park has several snowfields and about 50 small glaciers, which are retreating rapidly. At current rates of recession, they may be gone by mid-century.
However, the effects of glaciation are still obvious - deep, U-shaped and hanging valleys (eg. Upper Waterton and Akamina); arêtes (e.g. Citadel Peaks); cirques (e.g. Cameron Lake); kames (e.g. where the Prince of Wales Hotel sits) and eskers (e.g. in the bison paddock).
Every day, erosion continues to tear down mountains then deposits their fragments to create new landscape features. It does this using water, ice, gravity, weathering and avalanches. Post-glacial features include the alluvial fans of Blakiston Creek and the townsite ( Tale of Two Fans ); and the water eroded Red Rock Canyon.
A Brief History In Time
Trying to imagine the age of the earth is a daunting task. The 1,500 million year old story of Waterton's landforms presents only one chapter of our planet's 4,600 million year history!
We can form an idea of the relative duration of the earth's past by thinking of it compressed into one year [1 day = 12.6 million years]: