ABSTRACT: Howe Lake: a hydrodynamic blowout structure

CGRG Bibliography of Canadian Geomorphology
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Abstract

A field investigation was made of the Howe Lake area in Saskatchewan. The Lake is anomalously circular, with a diameter of 295 meters, and deep, unlike most prairie lakes. The lake is the surface expression of a deep, funnel-shaped depression filled with coarse colluvium at the bottom and finer material near the top. A central pipe extends to a depth of at least 138 meters. Radiocarbon dates and the history of deglaciation in the area given evidence that the structure was formed between 12,000 and 12,500 years ago, shortly after the ice retreated from the area. The structure was probably formed by a hydrodynamic blowout of water from the Mannville Group 400 m below surface. The extreme overpressure of water in the Mannville Group was probably induced by recharge from meltwater of the continental glacier then standing a few kilometers to the north of Howe Lake. The blowout was initiated at Howe Lake by fractures in the subsurface, related to a salt solution-collapse structure. Howe Lake probably served as a valve controlling the artesian pressure in the Mannville Group over a large area until the active ice margin had retreated northeastward, exposing lower elevation discharge areas. Hydrodynamic blowouts provide another process for the orgin of breccia-filled pipes

Bibliography of Canadian Geomorphology