Table of Contents
2: Location, Borders, and Lakes
3: Geologic Structure and Landforms
6: Pre-historic and Early Historic Settlements
7: Survey Systems
8: Southern Hamlets, Villages, and Towns
9: Mennonite and Hutterite Settlements
10: First Nations Settlements
11: Northern Settlements
12: The Southern Cities
13: Mining and Oil Extraction
15: Industry / Manufacturing
16: Water Resources
17: Parks, Recreation, Sports
18: Transport and Communications: Past and Present
19: Legal Issues and Law Enforcement
3: Geologic Structure and Landforms
Click for chapter introduction
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.
3.58: An Esker in Northwestern Manitoba
Eskers are linear ridges deposited by water in tunnels in or under ice sheets. Although they are not particularly high—heights are in metres or tens of metres—they are striking features of the landscape of northern Manitoba often running for tens of kilometres across the land seemingly heedless of the underlying topography on to which they have been superimposed.
This photograph taken near the northern border (60°N) of Manitoba is of an area of drift-covered bedrock. An esker 1 runs the whole width of the photo from north to south. This makes it 8 miles (12.9 km) long, but inspection of the 1:250,000 map of the area (64N Kasmere Lake) reveals that it is 20 miles (32 km) long. In the north, the esker forms the western shore of Putahow Lake 2 into which drains the Putahow River 3 after traversing a series of rapids 4 which are bypassed by Husky Portage 5. This esker is not a single ridge; in two places (6 and 7) it splits into two or more ridges. Another smaller esker 8 runs across part of Putahow Lake. In this area and to the north and west the land has a drumlinized appearance 9, several of the mounds poking above the lake level 10.
This area lies within the forest sub-zone of the forest/tundra transition vegetation zone.[i] The vegetation consists of open lichen woodland; dark areas 11 are patches of woodland, whereas light-toned patches 12 are lichen-covered ground.
The dark area in the southeast 13 is a technical defect, either in taking or in printing the photo.
Figure 3.58: An Esker in Northwestern Manitoba
Vertical air photograph: A15707-15
Flight height: 30,000 feet a.s.l.; lens focal length: 152.56 mm
Date: July 23, 1957
Scale: 1:57,900 (approx.)
Location of centre point: 59° 53'N, 100° 43'W
Map sheets: 1:250,000 64 N Kasmere Lake
1:50,000 64 N/15 Putahow Lake
[i] See Scott, G. A. J. “Manitoba’s Ecoclimatic Regions” in Welsted, Everitt and Stadel. op. cit. 1996, figure 4.2, 45.