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The Finlayson Point area has a magnificent array of glacial features. You are going to be asked to identify and photograph three... Roche Moutonnee, crag-and-tails, and striations.
Between 30,000 and 10,000 years ago, the southern Vancouver Island area was covered in a sheet of ice that originated in the coast mountains on the lower mainland and slowly flowed down what is now the Strait of Georgia and out Juan de Fuca strait. In this region, this period of glaciation is called the Fraser Glaciation. There were other periods of glaciation prior to that, but the Fraser Glaciation is responsible for almost all of the glacial features on southern Vancouver Island.
Finlayson point is a very popular intertidal area with access from Dallas Road; the glacial features you'll explore are most easily accessed at low tide. The coast line here is beautiful and a little rugged. Use the steps and paths provided to get to the beach areas, DO NOT go down the cliffs!
WARNING! Stay away from this EarthCache if there are strong winds and/or waves blowing on shore in this area OR if there are icy conditions. The terrain is rough and may be slippery... it is suitable for dogs and children IF the weather is nice.
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What you need to know:
When a glacier advances, it pushes along rock and gravel and anything else that is in its path. Under the ice, rock and gravel act like sandpaper and scrape the surface of the bedrock. Any hard, bigger rocks that are being dragged along will gouge out long channels in the bedrock. These scrapes and gouges are called "striations" and will be aligned with the direction of movement of the glacier. At Finlayson Point, the ocean waves have exposed the bedrock along the waterfront and these striations are clearly visible. There are other places in Victoria where you can see striations (Mount Tolmie, Bear Hill, Lone Tree Hill for example).
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Above and Below: Striations in the direction of the glacier
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Roche Moutonnee, note the jagged downstream end... plucked off by the glacier.
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Roche Moutonnee (translated from french... Rock Sheep) are areas where a glacier rides up over a hard rock area and chips off rock on the downstream slope, leaving a jagged downstream edge. On land, a field of Roche Moutonnee may look like small hills with a jagged end all oriented in the same direction. In 1776, a Swiss Scientist named Saussure used the name Moutonnee (french for fleecy, ruffled) to describe them and the name evolved into the popular "rock sheep" name they have today. At Finlayson point, the jagged downstream end are all that is clearly visible, but they are excellent example of such erosion. |
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Crag-and-tail formations are formed when a glacier rides up and over a hard piece of rock that is embedded in softer rock. On the upstream side of the hard rock, the soft rock will have been eroded completely away. The downstream side, being somewhat protected by the hard rock, will gradually slope back down to the surrounding rock level. These formations may be tiny (few centimeters long) to massive (few kilometers long). A famous Crag-and-tail is the hill on which Edinburgh Castle sits. At Finlayson Point, the smaller variety is present in abundance.
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Small hard rocks protect elongated downstream areas. These are crag-and-tails. |
Your Task:
Within a two or three minute walk from the listed coords you can see examples of all of the features described above. In order to show that you have learned what these features are, and can recognize them in the field, you must take four photographs and post them.
1. Photograph a Roche Moutonnee
2. Photograph striations on the rock with a stick or a person pointing in the direction of ice flow.
3. Photograph a crag-and-tail.
4. Photograph yourself with your GPS at (or close to) the posted coords.
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