Drumlins and Eskers - An Earth Cache EarthCache
Drumlins and Eskers - An Earth Cache
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Guichon Creek flows south through a valley from just south of Tunkwa Lake all the way to the Nicola River near Merritt. The creek was named after Joseph Guichon who moved to the area in the 1870's and one of his descendants (through marriage) is now the Lieutenant Governor of British Columbia. This valley was created by a glacier about 10,000 years ago and it left behind Mamit Lake, Guichon Creek, some eskers, and numerous drumlins.
Near the north end of the valley, a short distance south of Tunkwa Lake, it is quite narrow and the glacier was in a confined in a smaller space and therefore exerted more pressure underneath it, basically eliminating the possibility of the creation of any drumlins or eskers. By the time the valley reaches the Meadow Creek Road, it is wider and the first drumlins start to appear.
Nearby Drumlin.
One theory on the creation of drumlins is that with the now wider valley caused by a wider glacier, there was less pressure underneath the glacier and drumlins were able to be created by the pushing forward and upward of the ground material. As the glacier moves, drumlins are created and they resemble the profile of the top half of a sperm whale. The drumlins’ orientation indicates the movement of the ice flow with the higher blunt ends facing into the glacial movement and the thinner tails tapering off in the down-flow direction. Some drumlins can be as high as 50 metres.
According to Wikipedia, drumlins occur in symmetric, spindle, parabolic, and transverse asymmetrical forms and drumlins are commonly found with other major glacially-formed features and are related on a regional scale to these landforms. The large-scale patterns of these features exhibit spatial organization of the drumlin-forming flows with related tunnel valleys, eskers, scours, and exposed bedrock erosion.
Again, according to Wikipedia, the composition of drumlins varies depending on the area in which they are found, and can consist of similar material to the till of the surrounding moraine or be composed almost entirely of bedrock, sand and gravel or various mixtures thereof.
Two Nearby Small Drumlins.
Mamit Lake was created by deeper gouging of the glacier but unknown to most people there is also a drumlin near the middle of the Lake. This drumlin is more correctly called a shoal because it is under water. I found this drumlin/shoal while fishing and is now one of my "go to" fishing places while most others pass it by not even knowing it is there. There are other smaller drumlins in Mamit Lake that show themselves as islands but they are easily seen as they are out of the water, except at extreme high water levels.
Mamit Lake.
Not far south of Mamit Lake there are other fine examples of drumlins. One in particular is found due west of this earth cache's coordinates on Woodman Road where there is plenty of safe parking. Some of the questions regarding this earth cache refer to this drumlin. The parking coordinates and the cache coordinates are the same ( N 50* 21.019’ / W 120* 48.147’ ). There is plenty of safe parking at those coordinates.
As an extra, a short walk further south along the Mamit Lake Road to N 50* 20.862’ / W 120* 48.204’ will take one to a view location of an esker. Eskers are created through glacial melt wash where melt water streams flow in tunnels along the bottom of a melting glacier. Water seeping through crevasses and cracks in the ice gradually opens these tunnels that run downwards to the end of the glacier, resulting in a narrow ridge of gravel and sand, varying in thickness and length sometimes winding for kilometres parallel with the direction of the movement of the ice. As the glacier retreats, water in the form of a creek forms under the trailing edge and small ridges of ground or eskers form alongside it.
According to Wikipedia, the path of an esker is governed by its water pressure in relation to the overlying ice. Generally the pressure of the ice was at such a point that it would allow eskers to run in the direction of glacial flow, but force them into the lowest possible points such as valleys or river beds, which may deviate from the direct path of the glacier. The concentration of rock debris in the ice and the rate at which sediment is delivered to the tunnel by melting and from upstream transport determines the amount of sediment in an esker. The sediment generally consists of coarse-grained, water-laid sand and gravel, although gravelly loam may be found where the rock debris is rich in clay. This sediment is stratified and sorted, and usually consists of pebble/cobble-sized material with occasional boulders.
Esker.
In order to claim this as a find, please email me the answers to the following questions.
- 1. Estimate the distance due west from the cache coordinates to the drumlin?
- 2. Is the top of the drumlin higher or lower than the ground location of the cache coordinates?
- 3. Why do you think there are so many drumlins in this immediate area?
- 4. After reading the information above and observing the shape of these drumlins, in which direction do you think the glacier was travelling?
Please do not post your answers or any spoilers on this site. The answers must be emailed to me. Thank you.
Please feel free to post any photographs (without spoilers) although none are needed to complete this cache. The drumlins and eskers are all located on private land and there is no need to go onto them. They can all be viewed from public roads.
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(Decrypt)
Ab uvagf ner arprffnel.
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