Whirlpool Canyon is a very beatiful spot located on the Liard River that has exposed strata. A lot of the exposed strata at Whirlpool Canyon is shale, but you will see other rock strata also.
In geology, a stratum (plural: strata) is a layer of sedimentary rock or soil was formed at the Earth's surface, with characteristics that distinguish it from other layers. Each layer is generally one of a number of parallel layers that lie one upon another, laid down by natural processes. Strata are typically seen as bands of different colored or differently structured material exposed in cliffs, road cuts, quarries, and river banks. Individual bands may vary in thickness from a few millimeters to a kilometer or more.
Shale is a fine-grained, sedimentary rock, composed of mud that is a mix of clay silt-sized particles, and other minerals, especially quartz and calcite. It is the most common sedimentary rock. Shale is characterized by the ability or tendency of the rock to split along flat planes of weakness less than one centimeter in thickness, called fissility. These planes of weakness are oriented parallel to stratification in sedimentary rocks and occur because of the parallel orientation of clay mineral flakes.
Shales are typically composed of clay minerals and quartz grain, and are typically gray. Black shale results from the presence of greater than one percent carbonaceous material and indicates a reducing environment. Red, brown and green colors are indicative of ferric oxide (hematite; reds), iron hydroxide (goethite; browns, and limonite; yellow), or micaceous minerals (chlorite, biotite and illite; greens).
The process which forms shale is called compaction. The fine particles that compose shale can remain suspended in water long after the larger particles of sand have deposited. Shales are typically deposited in very slow moving water and are often found in lakes and lagoonal deposits, in river deltas, on floodplains and offshore from beach sands.
To log this EarthCache, you must send me the answers to the following questions:
1) Find some shale at this location and describe its colour and texture. How thick is the layer(s) you observed?
2) You will notice that there is some weathered shale strata in areas at this location, find a piece and inspect it, why does the shale break along flat planes like this? (read cache page)
3) Why do you think the strata at this location has been exposed?
4) Take a photo of yourself, your GPS, anything you think is interesting, at this location and upload it with your cache log.
I hope you enjoy this location and the quick lesson on shale.
Sources:
https://en.wikipedia.org/wiki/Shale
https://en.wikipedia.org/wiki/Fissility_(geology)
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