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Chapter 5: Vegetation

5.30: Palsas in Wet Fenland South of Churchill

In this area a surficial layer of marine silt overlies silty till.[i] It lies within the area of discontinuous permafrost; i.e., there are areas where water below ground is continually frozen. A series of creeks including Alston Creek 1 and Wakworth Creek 2 drain northward ultimately into the Churchill River just off the photo to the west. Palsas—ice-filled peat mounds—are light-toned and circular to oval 3. The surrounding fen is lower, wetter, and darker 4. The fen is also darker along drainage ways 5 where the permafrost is thawed and the active layer—the layer in which ice melts during the summer—is thicker. In the area, marked 6 ridges and ponds display a reticulate pattern, giving rise to the term "net fen." There are vestiges of raised strandlines 7, now about 100 feet (30.5 m) above sea level. Above the general level of the strandlines are numerous lakes, some of which are darker-toned 8, whereas others are very light 9 due to specular reflection.

The thin white line in the west 10 is the Hudson Bay Railway leading north to Churchill. The whistle point Bylot 11 is located at the bend in the line. Construction began at The Pas in 1910 and was completed on March 29, 1929. The total distance from The Pas to Churchill is 510 miles (816 km), much of it over spongy muskeg and discontinuous permafrost. The building of the line was a remarkable engineering feat, but maintenance costs over discontinuous permafrost have been high and in recent years the existence of the line has been constantly threatened. It is now owned and run by an American company.

Figure 5.30: Palsas in Wet Fenland South of Churchill

Figure 5.30: Palsas in Wet Fenland South of Churchill

Figure 5.30

Vertical air photograph: A17406-57

Flight height: 30,000 feet a.s.l.; lens focal length: 88.28 mm

Scale: 1:105,000 (approx.)

Date: July 31, 1961

Location of lake 8: 58° 24' North, 93° 54' West

Map sheets: 1:250,000 54L Churchill

54K Cape Churchill

1:50,000 54K/5 Warkworth Creek



[i] Interpretation from Mollard and Janes op cit., 1984,132.