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Manitoba from the Air
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Description
Erosion and Deposition at the Foot of the Riding Mountain Escarpment

Cretaceous rocks, mainly shales overlain by glacial till, underlie the Riding Mountain Escarpment; the waters of Lake Agassiz that left behind numerous strandlines lapped the base of the escarpment. Many small streams descend the escarpment, dissecting it into steep-sided valleys and depositing the eroded shale in low-angle alluvial fans[i] at the base. Often the streams disappear into the fans before they can reach Lake Manitoba to the east.

In this area, southeast of Dauphin, the escarpment trends southeast/northwest, and the main creek is Crawford Creek 1 which is here incising itself into deposited shale 2 before disappearing into the ground near the northern edge of the photo 3. Another small, unnamed creek in 24/23/18WI[ii] has eroded shale and deposited it across a field cleared for agriculture 4. A similar but less marked effect can be seen in a field near the northern edge of the photo 5. This problem of shale deposition on to agricultural fields is common along the foot of the Riding Mountain escarpment. Poorly developed strandlines can be seen in the southeast 6 and northwest 7.

The area includes part of Riding Mountain National Park; the east/west and north/south cut line in the woodland 8 is the boundary of the park. Land in the park is covered by mixed deciduous/coniferous woodland 9 that extends north and east beyond the park boundary. Land in the east has been cleared for agriculture, and the section lines of the DLS system are obvious 10. A farm sheltered from northerly winds by planted trees can be seen near the northern edge of the photograph 11.

Notes

[i] McGinn, R.A. General Description of the Eastern Slopes of Riding Mountain. Brandon: Brandon University, unpublished manuscript, 1983.

[ii] Short for section 24, township 23, range 18 west of the principal meridian.

Figure 3.20

Erosion and Deposition at the Foot of the Riding Mountain Escarpment