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.
This high oblique photograph (labeled “high” because the horizon is shown) of the Brandon Hills was taken looking to the southwest. In the foreground is the now abandoned railway line 1 between Brandon and Wawanesa, and running across the middle of the photo is PR 344 2 between the two communities. In the background is the dark-toned tree-covered mass of the Brandon Hills 3 with the light-toned, grass covered, eastern ridge 4. Nearer to the viewer is a complex of ridges 5, the crests of which are grass-covered and the furrows between, wooded. As the photograph was taken in the winter, there is a thin skiff of snow on the agricultural land in the foreground 6 that is traversed by a small intermittent stream 7, frozen at this time of year.
Oblique air photograph
Date: December 6, 1965
Scale: Variable—larger in the foreground and decreasing in the rear
Location: Townships 8 and 9; Ranges 18 and 19 WI
Map sheets: 1:250,000 62G Brandon
1:50,000 62G/12 Wawanesa