Diagrams showing normal fault resulting in landscaping drop and the stages in the fault development
The Rocky Mountain Trench Fault is considered to be a major normal fault or system of connected faults. The floor of the trench dropped several kilometers due to this faulting and the trench floor was subsequently covered by glacial outwash till. Near Skookumchuck this northwest trending fault, turns north and up the Lussier River Valley where it dissipates.
The 1,500 meter high eastern wall of the trench, that can be seen from the Norbury Lake parking area is called the Steeples. The steep east wall of this valley is the fault scarp on which sedimentary rocks as young as the Miocene age have been down dropped against mid Proterozoic Belt-Purcell rocks to the east. This is a classic fault-line scarp where resistant rock is exposed. The youngest movement took place in the last 5 million years ago.
Steeples from Eager look out. Note no foothills!
The Rocky Mountains were created approximately 85 million years ago mainly by thrust faulting which is the opposite of a normal fault. In a thrust fault the landscape is compressed whereas in a normal fault the landscape is stretched. Thrust faults push older rock up over younger rock. whereas in a normal fault younger rock slides down next to older rock..
Thermal Springs are very rare along this fault however a significant hot spring can be experienced near the terminus of the fault along the Lussier River. see http://www.geocaching.com/seek/cache_details.aspx?wp=GCQV3F coordinates are N 50 08.090 W 115 34.625.
Near Canal Flats a north trending thrust fault dominates and does not run under the trench floor but runs northward up the Stanford Range toward Radium and slightly beyond. It is the Redwall Fault. Other than the 210 km Rocky Mountain Trench Fault, no other fault is in the southern trench, however numerous east/west transverse faults cross the trench floor at various locations. In the northern section of the trench 50 km north of Golden, or about 220 km from the terminus of this fault, another fault picks up and underlies the trench floor for about 370 km.
For more information about the Redwall Fault go to GC3TM6J http://tinyurl.com/merqphd
Acknowledgements to: B.C. Pearce (Geological Field Guide to The Southern Rocky Mountain Trench; E Swanson, College of the Rockies; Mathews and Monger, Roadside Geology; Ben Gadd, Handbook of the Canadian Rockies; Wikipedia, Kootenay Hulio for Sunset on the Steeples picture.
To log this Earthcache, please email the owner with the following: a) Although this a major fault how come there are no visible signs. b) comment on how many peaks can be seen of the Steeples and why they are referred to as the Steeples. c) Describe the difference between a normal fault and a thrust fault.
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