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Chapter 3: Geologic Structure and Landforms

3.38: Shell River Valley North of Roblin

Several of the streams flowing from the west side of Riding Mountain and Duck Mountain flow in valleys which are too large for their present discharge; in technical terms, they are misfit streams. The discrepancy between valley size and stream size is explained by the fact that the two highland areas supported ice caps that melted rapidly at the end of the ice age. This produced huge quantities of water that eroded large valleys, possibly in a very short time. Once the ice had melted and the volume decreased, the river channels reverted to their present form.

The photograph shows the Shell River 1 (and valley) 2 that flows southward from the southwest side of Duck Mountain. At the time of maximum ice melt, the channel occupied the area bounded by dashed lines. As the channel was etched into ground moraine—still preserved to east and west—it was free to migrate laterally, and as with all meandering channels, it migrated in the direction of the concave bank as indicated by arrows 3 and left behind scroll bars indicating its former position 4. The banks of the older channel, across which it migrates from one side to another, confine the present channel.

Some of the land has been cleared for agriculture, and as was the practice at the time, much of it has been left fallow. In these fields the dark chernozemic soils produce a very dark tone on the photo 5. The only major transport route in the area is PTH 83 6 leading southwards to Roblin 5 miles south of the photo.

Figure 3.38: Shell River Valley North of Roblin

Figure 3.38: Shell River Valley North of Roblin

Figure 3.38

Vertical Air Photograph: A21085-218

Flight height: 21,500 feet a.s.l.; lens focal length: 152.52 mm

Date: July 17, 1969

Scale: 1:38,400 (approx.)

Location: Townships 26 and 27, Ranges 27 and 28 WI

Map sheets: 1:250,000 62 N Duck Mountain

1:50,000 62 N/6 Burrows Lake