Between 110,000 and 12,000 years ago, the majority of Canada was covered in a giant ice sheet, known as the Laurentide ice sheet. (Wikipedia, Dec. 9, 2016, https://en.wikipedia.org/wiki/Last_glacial_period#North_America). The Laurentide ice sheet radically transformed the geography of Canada, creating many of our geographic features and anomolies. Traits that result from a typical ice sheet include abrasions, erratics, morraines, eskers, and drumlins, amongst many other features. At the same time as the Laurentide ice sheet, British Columbia was largely covered by the Cordilleran Ice Sheet, which had similar shaping effect on the terrain of BC.
Image taken By Julie A. Meachen - http://onlinelibrary.wiley.com/doi/10.1002/ece3.2141/full, CC BY 3.0, https://en.wikipedia.org/w/index.php?curid=50396259
Erosion is the stripping of materials by a natural process such as water flowing, wind blowing, or a glacier moving, A glacier erodes the surface either through a process called abrasion, or a different process called plucking (or quarrying). Plucking involves the fracturing and removal of large pieces of material by glaciers, while abrasion is the grinding away of material. Plucking results in much larger pieces of rock being removed from the source, such as erratics, while abrasion results in fine sedimentary particles being picked up and carried in the ice sheet of the glacier. Whatever material the glacier picks up, it will be deposited when the ice melts away. The process of the material coming out of the glacier and being left on the ground is called deposition. Deposition results in adding minerals and sand to the bedrock underneath, which is called glacial till. The Fraser Basin was a sub-glacial lake - a lake formed underneath a glacier - and as the glacier melted, formed a glacial lacustrine deposition. The result of a glacial lacustrine deposition is the entire Fraser Basin, including Crooked River Provincial Park, is covered in a thick layer of glacial till (Metcalfe & Wilkin, 2002, p. 1). An example of the size of typical till is shown below.
By Grabenstedt at the German language Wikipedia, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=5307240
Bear Lake, one of the three lakes within Crooked River Provincial Park, has some of the nicest beaches around. The beaches are the result of the glacial deposition of significant amounts of sand during the last glaciation.
By ScouterWooby. Own Work.
Normally, deposited materials from a glacier reflect the surrounding bedrock (Rutter, 2002, http://www.thecanadianencyclopedia.ca/en/article/glaciation/) . However, "the park consists largely of a glacial sand dune complex which is regional uncommon." (Metcalfe & Wilkin, 2003, p. 1). Walking to nearby Square Lake, much of the roadway is the same fine sand as what makes the Bear Lake beach so appealling to campers.
Sand dunes are formed as glaciers recede. As the glacier melts, the exposed areas contain significant amounts of sand and silt, and can be amassed by wind forces. A loess deposit likewise consists of fine sand and silt, but the sand and silt comes from material that has travelled significant distances within a glacier (David, 2002). Because the sand is so uncommon to the Fraser Basin, the dunes at Crooked River are an example of a loess. The sand must have been transported a great distance to its current location.
Only about 2.5% of sand dunes in Canada are active - an active sand dunes allows the transport of sedimentary materials by wind forces. Desert sand dunes are typically active dunes; however, the high humidity of Canada typically prevents Canadian sand dunes from being transported. The high moisture in the sand creates cohesion, causing the particles of sand to stick together which prevents being moved by wind. The cohesive properties of moist sand are also evident when we use wet beach sand to build sand castles - the cohesion prevents the castles from succumbing to gravity. A typical sand dune in Canada is a concave parabola upwindward (David, 2002).
By Po ke jung (Own work) [CC BY 3.0 (http://creativecommons.org/licenses/by/3.0)], via Wikimedia Commons
Sand dunes resulting from glacial deposition begin with little to no vegetation. Active dunes resist vegetative growth, as the shifting of the sands prevents the formation of strong plant root systems. However, inactive dunes provide opportunities for plant life to grow on the dunes. Looking at the beaches of Bear Lake, there is ample evidence of plant life taking root in the sandy beaches. Plant life that grows in sandy soil provides stabilization for the soil, further discouraging the sand from moving.
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To claim this Earthcache, you must email or message me the answers to the following questions. Do not post your answers in the logs. Logs without answers submitted will be deleted. Once you have sent the answers, you do not have to wait for confirmation to claim the cache.
Question #1) Estimate the height of the beach (dune) from the water level to where the sand appears to stop. This answer will vary with the water level, but you should be reasonably close.
Question #2) Does the sand appear to form a concave parabola? Provide an explanation of how you can tell.
Question #3) What evidence can you see of vegetation moving onto the dune?
Question #4) What has limited the growth of vegetation on the dune? It will help to consider where plants are growing, and where they are not.
Question #5) I love pictures of this lake. They aren't required, but it's such a photogenic lake, and digital photos are cheap, why not take a few? :-)
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References
BC Parks. (no date). Crooked River Provincial Park. Retrieved Dec. 11, 2016 from http://www.env.gov.bc.ca/bcparks/explore/parkpgs/crooked_rv/.
David, P.P. (Jun. 2002). Aeolian Landform. Retrieved Dec. 11, 2016 from http://www.thecanadianencyclopedia.ca/en/article/aeolian-landform/.
Metcalfe, J. & Wilkin, N. (Dec. 2002). Crooked River Provincial Park: Purpose Statement and Zoning Plan. Retrieved Dec. 11, 2016 from http://www.env.gov.bc.ca/bcparks/planning/mgmtplns/crooked/crooked_ps.pdf.
Rutter, N.W. (Feb. 2002). Glaciation: The Canadian Encyclopedia. Retrieved Dec. 11, 2016 from http://www.thecanadianencyclopedia.ca/en/article/glaciation/.
Wikipedia. (Last edited Dec. 09, 2016). Last Glacial Period. Retrieved Dec. 11, 2016 from https://en.wikipedia.org/wiki/Last_glacial_period#North_America.