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 Manitoba are excellent examples of that river form. Several of them have deposited deltas into lakes. The effects of ground water are less easily illustrated, but examples of spring sapping and artesian erosion exist in the south. As all of Manitoba was covered by ice during the latest glaciation, examples of glacial erosion, and especially of glacial deposition, are widespread. Equally impressive are the suite of landforms created by the large glacial lakes that appeared as the ice melted. Glacial spillways, glacial lake deltas, strandlines and flat lake floors are found in many places. Wind action has created dunes on some of the deltas and on glacial outwash deposits. The Hudson Bay coast is rising as a result of isostatic rebound, recovery from the weight of the ice. One result is the existence of strandlines many metres above the level at which they were created. Finally Manitoba’s great lakes are large enough to illustrate many of the landforms normally associated with sea coasts.
[i] Lillesand, T. M. and Kiefer, R. W. Remote Sensing and Image Interpretation (Third Edition). New York: Wiley, 1994, 179.
The Tiger Hills 1, part of the Darlingford end moraine, run in an arc from the northwest corner of the photo to the southeast. Their hummocky form means that they have mainly been left in a wooded state—dark toned on the photo 2. On their proximal side—side in contact with the ice, which advanced from the northeast—is a series of lakes 3, the largest of which is Lloyd’s Lake 4. Lakes further east 5 are shown as being intermittent on the 1:50,000 map (62G/5 Dunrea) of the area, although their dark tone indicates that they were water filled at the time the photo was taken. Northeast of the end moraine is ground moraine 6 with a definite northwest/southeast alignment of ridges and lake-filled furrows 7. Southwest of the end moraine is the Souris-Pembina Spillway 8 that has steep banks and a flat floor, partly occupied by Bone Lake 9, Overend Lake 10, and Pelican Lake 11. Specular reflection produces a light-toned area at the north end of Pelican Lake 12. In the east/west part of the spillway the south bank (north facing) is heavily wooded (dark-toned) 13 because of its wet microclimate, whereas the south-facing slope is only partly tree covered 14. Both the south bank 15 and the north bank 16 are dissected by tree-covered gullies 17.
Three small settlements exist in the area; Dunrea 18 and Ninette 19 are connected by the CN railway line 20, and in the northeast Hilton 21 lies just north of a long abandoned railway line 22. PTH 23 23 runs east/west across the area, south of Dunrea and through Ninette. PTH 18 24 runs north/south.
Vertical air photograph: A21808-67
Flight height: lens focal length:
Scale: 1:79,200 (approx.)
Location: Townships 5 and 6; Ranges 16 and 17WI
Map sheets: 1:250,000 62G Brandon
1:50,000 62G/5 Dunrea