Marble Canyon EarthCache
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Marble Canyon - Kootenay National Park -
(A geological study in the effects of erosion in the formation of Marble Canyon.)
Marble Canyon
In simple geological terms, erosion is the process of wearing or grinding something down (as by particles washing over it). It is the way in which the earth's surface is worn away by the action of water and wind.
I have been coming to Marble Canyon since my parents first brought me here as a child more than half a century ago. A lot has changed in me in that time but, apart from the 2003 fire, little has changed in the formation of the canyon. Many tons of rocks have been washed downstream through the canyon over those years but, in the lifetime of mountains, half a century a miniscule amount of time.
Marble Canyon started out at the bottom of a shallow tropical sea more than 500,000,000 years ago. Sea creatures fell to the bottom of the sea and their shells helped to form the limestone and dolomite rocks that we see in the canyon today.
Over time, the movement of the earth’s surface pushed the seabed up to form the Rocky Mountains and created the area we see here today. As the rock bent and folded, it cracked and formed faults. Tokumm Creek has worked its way into a fault and has continued to erode it over the centuries.
However, it was not only the movement of the earth’s surface that created Marble Canyon; ice also helped to shape the valley.
Two glaciers, each more than a kilometre thick - higher than the peaks around you, met at this point and carved their way through the mountains gouging out the two valleys in which you are standing. One glacier was slightly smaller than the other and, as it retreated, it created the smaller Prospector Valley which was left hanging high over the deeper Vermillion Valley. As it melted, the Prospector Valley glacier released floods of meltwater that poured down through the faults in the valley floor and cascaded in a massive waterfall into Vermillion Valley.
The rocks and mud and dirt that flowed through the faults acted in the same way that sandpaper works on wood. Instead of sawdust, “rock dust” has continued to grind away at the sides and bottom of the creek. Ice also acts to break down the rock. As water freezes into cracks in the rocks, it expands and breaks away pieces of rock which then fall into the creek and are swept downstream scraping the canyon walls as they pass. The sides of the faults were eroded and smoothed and carved into the shapes we see today by these rock chips, pebbles, and dirt. Where the water swirled around and around in whirlpools, you can find the beautiful curved bowl-shaped “pothole” features in the walls of Marble Canyon. Where softer rock lay beneath harder stone, natural arches (bridges) were formed as the softer rock wore away from underneath the harder stone allowing the water to surge underneath.
In 2003, a forest fire raged for 40 days through Kootenay National Park and created the devastation that you see on the mountains around you. It burned 170 square kilometres of the park. This is also as natural a part of the park as the erosion of Marble Canyon. It is estimated that such a fire will burn through this area every 200-300 years. The result of the fire is an increase in the diversity of the plants and animals that live here. It will also result in an increase in the amount of soil that is eroded into the creek by rainstorms and snow-melt. This contributes to the continued erosion of the canyon rock until plants can, once again, stabilize the surface soil around the creek with their roots to prevent further erosion.
(Credit: Parks Canada - The geological and historical information above is taken from the Parks Canada sign-posts placed along the trail and has been edited for this cache.)
The walking trail from the parking lot (at the listed co-ordinates) to the upper falls takes about half an hour round-trip. It is well worth the stroll but, please, stay on the path. The path, though steep in places, has stone stairs and hand-rails all along it. It is not difficult and is easily walked by a child or person of average health. It is sign-posted along the way with information concerning the creation of the canyon and geological and natural features to observe.
Questions/photo instructions
1. E-mail the cache owner (do not post) the difference (in thousands of years) between the first signpost at the beginning of the trail (N 51 11.174 W 116 07.387) and the last sign post before the upper falls.
Clue: The geological time-line for the formation of the canyon is shown at the top of the information signs with “You are here” and a little person standing on a cliff near a waterfall.
2. E-mail the cache owner (do not post) the depth (in feet or metres) of the canyon below the upper bridge at the base of the falls. (Guesstimate)
3. This is Marble Canyon. E-mail the cache owner (do not post) the name of the rock (mineral) most prominent in the canyon.
4. Post a picture of the creek and mountains from the upper bridge at N 51 11.391 W 116 07.644. (It will be interesting to see how the forest and vegetation changes in the photos over the seasons and the years.) Logs without photos will be deleted.
WINTER CAUTION: The walking trail may be impassable to the top bridge in the winter depending on the snow conditions. Please exercise caution and discretion.
Additional Hints
(No hints available.)