29geology

Trent Workman

Note top left image: ‘Map of the beaches and deltas of the glacial Lake Agassiz in southern Manitoba’. In Of Exploration of the Glacial Lake Agassiz in Manitoba. Geological and Natural History Survey of Canada,1890. p 74.

Projecting Lake Agassiz on chalk

The Plan of the Dead Glacier expands the scope of Upham’s work to include the area covered by the ice sheet that melted or died in its place over millennia. Contemporary representations of the prairie region often focus on political boundaries, reinforcing the idea of a neutral, divided landscape. The Plan neglects these boundaries, shifting to a view of the land as a field of relations. The base of this map emphasises the snow cover that is characteristic of the region. On this aerial sketch, snow cover reveals the underlying geologic condition by the subtle differentiation of the soft soils of the interior, and the exposed bedrock of the surrounding Canadian Shield.

In 1890 American mineralogist Warren Upham combined his first-hand field observations of end moraines, beaches and fluvial channels as comprehensive evidence of the existence of glacial Lake Agassiz 1 . At the time, the glacial lake was still a contested theory. Upham superimposed the outline of the pro-glacial lake on the most accurate image of Manitoba of the time, a 1890s survey map, which included lakes and rivers as well as the recently administered quarter-section grid. Upham’s approach of layering the former glacial lake onto a contemporary map compressed the deep time of Lake Agassiz with the present, confronting the current landscape with its shaping forces.

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