This earthcache takes you to Vittrekwa Pass, one of many scenic locations along the Dempster Highway. Here, the highway enters an old glacial waterway. As you drive through this area, you can see deformed (folded or distorted) rocks of the Devonian Imperial Formation. The pass is the transition of the Richardson Mountains to Peel Plain to the northeast.
The rocks in Vittrekwa Pass are approximately 360 to 420 million years old. They have a two-phase history of deformation. The first deformation occured during the Ellesmerian Orogeny, about 350-370 million years ago. Further tilting and folding occured during the Laramide Orogeny, about 70-80 million years ago.
An orogeny is a geological process or event in which mountains are formed through folding and faulting of the earth's crust. An orogeny tends to occur in smaller areas or linear belts over a shorter time period, and often results in dramatic folding. The long chains of mountains often seen on the edges of continents form through orogeny. For example, the Laramide Orogeny was a period of mountain building in western North America which contributed to the raising of the Rocky Mountains.
Geological folds occur when one or a stack of originally flat and planar surfaces, such as sedimentary strata, are bent or curved. This can be a result of temperature, pressure, or other stresses such as volcanic intrusions. Folding may also occur due to slumping of sedimentary material before it turns to rock.
Folds in rocks can vary in size from microscopic to mountain-sized. They can occur as a single fold or in extensive fold trains. Often, not only are the rock layers folded, they are also inclined or tilted from horizontal. Faults may also be present. A fault is a crack or fracture in the earth's crust resulting from the displacement of one side with respect to the other. The diagram below shows several different types of folds.
Logging Requirements:
1) At the posted coordinates, you can see the rock layers on the eastern side of the road:
a) Can you see any tilting, folds, or faults?
b) If present, what type of fold can you see here?
c) Estimate the angle and thickness of the layers.
2) At the additional waypoint on the south side of the road:
a) Can you see any tilting, folds, or faults?
b) If present, what type of fold can you see here?
c) Estimate the angle and thickness of the layers.
3) Analyze the information from both locations:
a) Which waypoint do you think has the older rocks, and why?
b) In what direction do you think the earth's crust was moving to create these angles?