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
3.90: Relict Ice Scour Features Near St. Laurent
In this flat area numerous intersecting lineations, trending in several directions, can be seen. Many are straight 1, but a few have a definite curve 2. Without the benefit of stereovision it is hard to tell whether they are negative or positive features. However, the fact that they are mainly dark-toned 3 due to high soil moisture content suggests that they are furrows. Also, in many cases the availability of water results in tree growth—dark-toned 4. These are minor relief features only a meter (3 ft) or so in depth, and it is suggested that they were scraped into the bottom of
PTH 6 5 crosses the southwest corner with another road joining it from the east 6. The CN railway line 7 is north of, and parallel to, PTH 6. A minor track can be seen in the north 8. Several linear features defy explanation: some southwest/northeast trending lines demarcate areas of different tone 9; also a square feature may be a partially cut field of hay 10.
Figure 3.90: Relict Ice Scour Features Near St. Laurent
Vertical air photograph: A17529-208
Flight height: 8,800 feet a.s.l.; lens focal length: 153.04 mm
Scale 1:16,000 (approx.)
Date: July 27, 1961
Location: Township 17; Range 4WI
Map sheets: 1:250,000 62I Selkirk