The Oyster River is a small stream that flows northeast from Pearl Lake (near Buttle Lake) and crosses Highway 19 half way between Courtenay and Campbell River (approx. 20km from each town), flowing into the Georgia Basin..
Vancouver Island spans hundreds of millions of years. The island was formed through a combination of processes, including tectonic plate movement, volcanism, erosion and glaciation. Between 29,000 and 15,000 years ago, the most recent glacial period or “ice age” developed; today it is referred to as the Fraser Glaciation. Ice accumulated on the mountain peaks of Vancouver Island and slowly grew into large glaciers. Eventually they joined with other glaciers and formed ice sheets that filled the major valleys. Between 15,000 years before present and today, the climate began to warm and the ice sheets slowly melted and retreated. The release of the weight of ice caused the land to rebound. This exposed areas of land that were previously submerged. For about a thousand years, around 10,000 years ago, the rate of rebounding from the land exceeded the sea level rise caused by the melting glaciers. Eventually the sea reclaimed some of the recently exposed land, and stabilized at its current level. In place of the ice sheets, large deposits of glacial till were left. This was formed from rock that was ground up under the ice sheets, deposited on the surface of the glaciers, or pushed up in front of advancing glaciers. Lakes, streams and rivers formed from melting ice, and rivers transported glacial sediment to new locations.
Rivers and streams are not only conduits of water, but also of sediment. The water, as it flows over the channel bed, is able to mobilize sediment and transport it downstream, either as bed load, suspended load or dissolved load. The rate of sediment transport depends on the availability of sediment itself and on the river's discharge.
These sediments generally consist of well-compacted material that is nonstratified and contains a heterogeneous mixture of particle sizes. It commonly comprises a mixture of sand, silt, and clay that has been transported beneath, beside, on, within, and in front of a glacier and not modified by any intermediate agent
Potholes, or kettles, are cavities or holes which appear to have been drilled in the surrounding rocks by eddying currents of water-bearing stones, gravel and other detrital matter.
The size varies from a few inches to several feet in depth and diameter. The most common occurrence is in shields, where there are ancient rocks (granite, gneiss) with different resistance to erosion, so strong pebbles fall in a small cavity and swirl making this cavity wider and deeper. In areas where there are diamonds and quartz rocks, the hardness of these rocks cave potholes and sometimes remain trapped in the bottom of it. Hardness of pebbles must be the same or higher than the bottom of stream where the kettle is forming.
Some holes are made within riverbeds at the foot of cascades, and under some other circumstances. The term pothole is also sometimes used synonymously with swallow-hole.
To log this cache please email me the following information:
1) Estimate how many feet at the deepest part of the formation and how many feet at the shallowest (riverbed to top of ledge)
2) How many complete (round & closed) potholes can you see
3) Please post a picture of yourself at any point along the railing along the cliff (NOT the Hwy Bridge)(Optional - Not a logging requirement)
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