Chapter 3: Geologic Structure and Landforms
Geologic interpretation of images begins with the identification of lineaments, “regional linear features caused by linear arrangement of regional morphological features such as streams, escarpments, and mountain ranges and tonal features that in many areas are the surface expressions of fractures or fault zones.”[i] The emphasis in this section is on geologic structures and landforms, both of which can be easily identified on air photographs and other images.
The sequence followed here is that often found in geomorphology books. Geologic structures and structurally controlled landforms are illustrated first, followed by images of mass wasting and of the results of the agents of erosion—running water, ground water, ice, wind and the sea. The meandering rivers of southern
3.39: The Little Saskatchewan River Valley Northeast of Newdale
The Little Saskatchewan River 1 flows south from Riding Mountain, and at the location shown occupies a meander belt about 1500 feet (457 m) across 2. In the past, when ice over
This is a spring photo, and patches of snow can still be seen in the valley 6. Also at this time of rapid snow melt, parts of the floodplain are inundated resulting in a dark tone 7. Three gullies enter the main valley from the north; one is clearly occupied by a stream 8, but the others 9 appear dry. Similar dry gullies enter from the south 10. Outside the valley the surface is underlain by ground moraine with numerous hollows that in the spring are lake filled; however, the topographic map of the area shows many of these lakes as intermittent 11.
The land is divided according to the DLS system with roads following north/south and east/west section lines even across some lakes 12. However, in some places the topography determines road direction as, for example, down the valley side 13 and along the valley side 14. The east/west road 15 is, judging by its light tone, newly constructed.
Figure 3.39: The Little Saskatchewan River Valley Northeast of Newdale
Vertical air photograph: A15225-27
Flight height: 20,000 feet a.s.l.; lens focal length: 152.26 mm
Date: May 24, 1956
Scale: 1:35,200 (approx.)
Townships 16 and 17, Ranges 19 and 20 WI
Map sheets: 1:250,000 62K Riding Mountain
1:50,000 62K/8 Newdale