Chilliwack's Jellyroll EarthCache
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One of several upcoming earthcaches in this unique area featuring
sites demonstrating the everchanging valley we live in!
To begin, we need to define some of the terms used in this earth cache:
• Limestone – a rock type consisting of sediment from small marine animals which is deposited on the bottom of seas and salt water areas.
• Metamorphic – an earth process where rock is transformed due to extreme heat and/or pressure.
• Plate tectonics – a geological theory that explains the movement of “plates” on our earth’s surface. This movement is responsible for earthquakes, tsunamis and volcanic activity.
• Syncline – This is a fold which is created in stratified rock layers, caused by weaknesses, or “faults” in the rock strata. As uplift of buried rock layers occurs, stresses caused by these weaknesses will cause the layers to buckle. These layers will buckle in towards the center of the rock layers. In contrast, an “anti-syncline” will fold upwards towards the top of the rock layers.
• Stratification – layers of sediment on top of one another, usually occurring from the oldest layer to the youngest in earth history.
• Subduction – As one “plate” moves over another, the one which is forced below is referred to as the subduction layer. This layer may be responsible for volcanic activity and uplift of the plate above it.
• Uplift – a term referring to the process which creates mountains and volcanoes at the earth’s surface. When a subducted plate is forced upwards by natural processes, the layer above rises, creating hills and mountains in a process called “orogeny”.
This earth-cache is meant to bring you to a place where you can see an example of a syncline fold. As the rock face seen here was uplifted, the stresses and fractures in the layers caused this unique formation. This rock face is representative of stratified limestone. Limestone occurs in marine environments, so the fact that it can be witnessed here demonstrates the tectonic upheaval which has created much of this landscape.
As the Juan de Fuca Plate off of the coast of British Columbia has subducted under the continental plate over time, the marine sediments from the Pacific Ocean and Coastal Mountains have been subjected to severe heat and pressure. Further uplift in the Chilliwack Valley has brought these once again to the surface as metamorphic and folded limestone.
This area is unique in its formation, as the bedrock witnessed here predates glacial influence. The uplift and metamorphism seen here occurred in the late Palaeozoic Era (Saunders, "Late Quaternary Geology and Geomorphology of the Chilliwack Valley, 1985).
In order to claim this earth-cache, please email the owner via our profile link at the top of the cache page. Do not post your answers on the cache page! Please feel free to post a picture of your or your group at the site!
1.) What evidence of glaciations do you find at the cliff site?
2.) What differentiates the rock found here from the granite found in the same area?
3.) What, in your opinion, could have caused the folding seen high in the cliff face?
4.) In what direction does the fold in the cliff face?
While in the area, be sure to check out the nearby caches, such as Rock Climber and Slesse Cave; all within walking distance :)
We hope you have fun learning some of our area’s wonderful history!
Additional Hints
(No hints available.)