Chapter 3: Geologic Structure and Landforms
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
3.98: Epinette Creek and Sand Dunes East of Shilo: Colour Infrared Photo
This photograph illustrates the usefulness of infrared photographs in identifying vegetation. On infrared photographs,[i] vegetation that is photosynthesizing reflects large amounts of infrared radiation and is imaged as red. On this fall photo, only coniferous trees are growing. These are therefore easily identified on the basis of their red/orange colour and triangular shadow shape.
On the southern dune complex, there are patches of almost white 1 on bare sand; grasses are dark green 2, and coniferous trees—white spruce (Picea glauca)—are orange/red 3. On the northern complex white spruce can be seen in the southeast 4; most of the rest is covered by grasses 5 and dark green patches of deciduous trees 6. The deciduous trees throw short shadows making it possible to differentiate them from grasses. Coniferous trees also occur along the dune ridges (7 and 8).
The vegetation on either side of Epinette Creek is dull green (9 and 10). The colour and the mottled texture suggest a tree cover, probably tamarack (Larix laricina) that enjoys wet conditions. There are also patches of other coniferous trees 11, in this case damp-tolerant black spruce (Picea mariana). East of Epinette Creek, a light-toned area with mottled texture and rounded shadow shapes 12 is probably an aspen (Populus tremuloides) covered area.
Figure 3.98: Epinette Creek and Sand Dunes East of Shilo: Colour Infrared Photo
Vertical air photo (colour infrared): A37130 IR 5870
Flight height: 11,000 feet a.s.l.; lens focal length: 153.12 mm
Date: October 29, 1974
Scale: 1:21,600 (approx.)
Location: Townships 9 and 10; Range 15 WI
Map sheets: 1:250,000 62G Brandon
1:50,000 62 G/14 Carberry
[i] The surface of this old photo is starting to deteriorate which might result in some vertical lines appearing on the screen.