PLEASE NOTE: The trail may be closed during periods of heavy rain for public safety reasons, so it is recommended to visit this site during nicer weather conditions.
At the posted co-ordinates you will have passed through the first tunnel (walking from the Coquihalla Canyon Provincial Park parking lot) and will have your first glimpse of the canyon. From this spot you will need to answer a few questions posed below and then proceed to the second waypoint to answer a few more questions.
A canyon is a deep ravine between two cliffs that over a long period of time is carved from the landscape by the erosive power of water. The Coquihalla River canyon is an example of that erosive power.
The geology of the Coquihalla River at this spot is composed largely of igneous rock (hard rock formed from volcanic lava) and limestone (softer sedimentary rock composed largely of calcite - CaCO3).
Limestone is easily erodible due to water picking up carbon dioxide (CO2) in solution from the rock which then produces an acidic (low pH) water solution. The acidic solution will dissolve the calcite and eventually wash it away downstream. A gap is then created in the landscape as a result of the acidic action, and over time, as this process continues, deep valleys (canyons) eventually form. The more erosion resistant igneous rock is left in place and eventually forms the walls along the waterway. This is what we see here today.
Rivers have a natural tendency to erode the underlying rock surface to lessen their own pitch slowing their water flow. Over geologic time, their bottoms will gradually reach a baseline elevation which is the same elevation as the body of water it will eventually drain into. The Coquihalla canyon is located about 8 km upstream from where the Coquihalla River empties into the Fraser River just north of Hope.
To log this cache you must answer a few questions that can be found by visiting the site. Please email me your answers. Do not post your answers with your log otherwise it will be deleted.
1) From the posted co-ordinates estimate the height of the canyon walls from the bottom of the canyon.
2) Tell me the structure of the canyon walls (smooth, blocky, broken?). Why do you think it looks the way it does?
3) How wide do you estimate the canyon is at this point.
4) From the second waypoint tell me the differences you notice compared to the first waypoint.
5) How wide to you estimate it is from side to side at this point.
Fun Fact. Several movies have been filmed using this canyon as a backdrop.