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Chapter 3: Geologic Structure and Landforms

3.61: The Robertson Esker in Northwestern Manitoba

This image is different from those in figures 3.59, 3.60, and 3.61 in that it is an oblique photograph—technically a high oblique because the horizon 1 is shown. As the name suggests the camera was pointed obliquely rather that straight down as was the case in most photographs shown so far. In some ways an oblique is a more realistic view, more like the view a person gets when looking from a plane window. However, from an interpreter’s point of view obliques have problems. The scale is large in the foreground (in this case about 1:37,500) but decreases progressively away from the camera. This makes it difficult to calculate ground distances and areas.

The photograph was taken looking just south of east and shows another of Manitoba’s named eskers—the Robertson Esker 2, running northeast/southwest across the foreground. It is a very long esker traversing almost the whole of the 1:250,000 map sheet 64K, Whiskey Jack Lake, and extending into the sheet to the south 64F, Brochet. It is recognizable as a discontinuous northeast/southwest ridge running across 80 miles (129 km) of the northern Manitoba landscape. In some places it has a single ridge form 3 as where it forms the southeast shore of Ducharme Lake 4, but both to east 5 and west 6 of that it bifurcates. Eskers are composed of sands and gravels and are characteristically light-toned where they are not covered by vegetation 7. A much smaller esker 8 can be seen on the right of the photo.

This lake-strewn area falls in the open lichen woodland vegetation zone in which “the better drained upland ground cover is dominated by fructose lichens…between…scattered spruce.”[i] This arrangement can be seen in the left foreground 9, but in the background the scale is too small to distinguish details.

Figure 3.61: The Robertson Esker in Northwestern Manitoba

Figure 3.61: The Robertson Esker in Northwestern Manitoba

Figure 3.61

Oblique air photo: T104 R-55

Flight height: 20,000 feet a.s.l.; lens focal length: 6 inches

Date: September 11, 1946

Scale: 1:37,500 (approx.) in the foreground, decreasing towards the rear

Location of centre point: 58° 11'N, 100° 43'W

Map sheets: 1:250,000 64K Whiskey Jack Lake

1:50,000 64K/2 Ducharme Lake


[i] Scott, op. cit., 1996, 51-52.