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
3.3: Folded Structures in Precambrian Sedimentary and Metamorphosed Sedimentary Rocks North of Snow Lake
In this area there is a close relationship between structure and topography, the various folds forming a series of ridges and valleys resulting from differential erosion of the various layers.
The tonal variations in the lakes vary from very dark grey (Drysdale Lake 7) to almost white at the south end of Compton Lake, the light tone resulting from the relationship between water surface, sun angle and camera lens, to give specular reflection.
Figure 3.3: Folded Structures in Precambrian Sedimentary and Metamorphosed Sedimentary Rocks North of Snow Lake
Vertical air photograph(s): A13398-129
Flight height: 16,700 feet a.s.l.: lens focal length : 151.65 mm
Scale: 1:32,000 (approx.)
Date: July 8, 1952
Location: Township 70, Range 18 WI
Map sheets: 1:250,000 63N
[i] Mollard and Janes. op. cit., 24.