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.
3.46: Glacial Grooving in the Interlake and Westlake Regions
This is a LANDSAT I colour composite made using bands 4 (0.5-0.6 micrometres: green), 5 (0.6-0.7 micrometres: red), and 7 (0.8-1.1 micometres: infrared); consequently infrared radiation is represented in addition to some parts of the visible section of the electromagnetic spectrum. The data was recorded on April 23, 1974 before the leaf-on stage of deciduous trees, but coniferous trees were reflecting infrared radiation producing an orange tinge over much of the image.
At this date Riding Mountain 1 is still snow covered, and most of the water bodies are still ice covered with a surface layer of snow and consequently appear white on the image. Within Riding Mountain National Park, Whirlpool Lake 2, Clear Lake 3, Shoal Lake 4, Lake Audy 5, and Whitewater Lake 6 can be seen. North and east of the park are Dauphin Lake 7, Lake Mantitoba 8, Dog Lake 9, Ebb and Flow Lake 10, Lonely Lake 11, Portage Bay (part of Lake Manitoba) 12, Lake St. Martin 13, Sturgeon Bay (part of Lake Winnipeg) 14, Spence Lake 15, Long Island Bay 16, and Sagemace Bay 17 (part of Lake Winnipegosis 18); and Waterhen Lake 19. All these water bodies are ice and snow-covered, but there are some areas of open water, dark blue in colour, for example, Jackfish Lake 20, the south end of Dauphin Lake 21, and Pineimuta Lake 22. Also there is open water where there is a strong current between water bodies; for example, at the Narrows on Lake Manitoba 23 and just to the south of that 24, south of Peonan Point 25, at Crane Narrows 26, at the Narrows on Lake St. Martin 27, and where the Fairford River flows into Portage Bay 28.
There is also a lot of open water—dark blue—east of Lake Winnipegosis and Waterhen Lake 29 and west of Lake Manitoba 30. The water lies in north/south trending grooves, mapped as intermittent water bodies and marshy areas on topographic maps. The grooves were etched into the Devonian bedrock of the area by southward moving ice, the ice exploiting minor variations in resistance to erosion. These grooves should not be confused with similar features trending generally southeast/northwest along the east and north side of Riding Mountain 31 and Duck Mountain 32. These are Lake Agassiz strandlines deposited after ice had retreated from this area.
In addition to the natural features observed, some land has been cleared for agriculture, for example, at the base of the Riding Mountain escarpment 33, around Dauphin Lake 34, and in the fertile Swan River Valley 35. In these areas the characteristic checkerboard pattern of the DLS is seen.
Figure 3.46: Glacial Grooving in the Interlake and Westlake Regions
Landsat I image
Date: April 23, 1974
This is a colour composite of bands 4—wavelength 0.5-0.6 micrometres (green), 5—wavelength 0.6-0.7 micrometres (red), and 7—wavelength 0.8-1.1 micrometres (infrared)
Scale: 1:1,000,000 (approx.)