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.
3.10: The Riding Mountain Escarpment
The area shown can be divided into three landform regions: in the west the Riding Mountain Plateau 1; in the centre, the Riding Mountain Escarpment 2; and in the east the Manitoba Lowlands 3.
The plateau has a low amplitude of relief—no more than about 100 feet (30.5 m)—its rolling surface being developed on a thick layer of till overlying Cretaceous age shales. At no place is the bedrock visible. A zone of lakes, from north to south—McKinnon Lake 4, Rowland Lake 5, Campbell Lake 6, Watson Lake 7, and Muskrat Lake 8—follow a line of weakness along the north/south strike of the Cretaceous rocks. Muskrat Lake’s light tone suggests that it contains suspended sediment whereas the others—dark-toned—do not. All the named lakes drain to the west by a series of slow-flowing streams. Most of the plateau is covered by mixed coniferous/deciduous woodland, but poorly drained marshy areas also exist 9, ideal moose habitat.
The escarpment drops over 900 feet (274 m) to the east in less than three miles (five km). It is deeply dissected by many small creeks 10 that have eroded into the shale after removing any overlying till. Bedrock appears as light-toned patches on the valley sides; for example, on both sides of Bald Hill Creek 11. The streams are susceptible to flash floods causing both flooding and the deposition of shale on the fields at the escarpment’s base. Low angle alluvial forms—too low an angle to pick out on the photograph—have coalesced to form an apron between the escarpment and the lowlands. In some cases strong subsequent streams flowing north/south along the strike 12 have captured consequents flowing down the escarpment. Apart from a few steep valley sides the whole escarpment is covered by mixed coniferous/deciduous woodland.
The lowlands are underlain by rocks of Jurassic age overlain by till and glaciolacustrine sediments deposited into glacial Lake Agassiz. Several prominent strandlines can be seen, some of which are named: the Herman 13, the highest, the Norcross 14, and the Campbell 15. They show up principally as a result of land use differences, the Herman, for example, delimiting the eastern edge of the woodland 16. Most lowlands have been cleared for agriculture but fingers of woodland extend along creek courses. It is noticeable that several creeks terminate at the Campbell shoreline 17.
Culturally the area can be divided into two parts. The mainly wooded plateau and escarpment lie within Riding Mountain National Park where woodland clearing is prohibited. In the north the edge of the woodland coincides with the park boundary, but in the south the woodland extends beyond the park 18. In contrast the lowlands have been divided up according to the Dominion Lands Survey (DLS) system. Individual sections (1 square mile) 19 and quarter sections 20 can be seen and gravel roads 21 run east/west and north/south along section lines. The only paved road— PTH 5—diverges from the DLS system in the south 22 but follows section lines further north 23. PTH 19, where it crosses Riding Mountain National Park, is outside the DLS system and includes, what for Manitoba is a rarity, three hairpin bends as it descends the escarpment 24. Forest trails—part of the park’s hiking and ski trail system—can be seen (25 and 26). A CN railway line 27 runs through Kelwood 28, the only nucleated settlement in the area. In contrast to many prairie towns and villages, the orientation of its roads are based not on the railway line but on the north/south and east/west lines of the DLS system.
Figure 3.10: The Riding Mountain Escarpment
Vertical air photograph: A21808-32
Flight height: 24,400 feet a.s.l.; lens focal length: 85.55 mm
Date: August 6, 1970
Scale: 1:81,000 (approx.)
Location: Townships 18 and 19, Range 15 WI and part of Riding Mountain National Park
Map sheets: 1:250,000 62J Neepawa
1:50,000 62J/12 Wasagaming
1:125,000 MCR 207 Riding Mountain National Park