| Urban geology of the National capital area |
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Natural Resources Canada > Earth Sciences Sector > Priorities > Geological Survey of Canada > Urban Geology
Urban Geology of the National Capital Area Study area
The study area covers approximately 12 650 square kilometres (115 X 110 km), centred on the cities of Ottawa, Hull, and Gatineau. Through user consultations, the study area was expanded beyond the 1970-75 area to include regional municipalities outside the National Capital Region (Bélanger/Moore 1999 [PDF, 60.8 kb, viewer]). The new limits of the study area now include 12 National Topographic Series (NTS) maps at 1:50,000 scale (NTS map). The limits were extended beyond the urban centres to permit planning of regional services such as transportation and energy corridors, waste management, environmental protection, and identification of natural hazards.
The National Capital Area spans over two distinct physiographic-geologic regions: the Laurentian Highlands (Canadian Shield) to the north and west, and the St-Lawrence Lowlands to the south-east. The contrasting landscape of the two physiographic regions is clearly revealed by the digital elevation model (produced from digital topographic values). The hilly relief of the ancient Precambrian rocks of the Canadian Shield (yellow to reddish colours), stands out from the younger flat-lying Paleozoic formations of the St-Lawrence Lowlands (blue to green shades). The precise limits of the two physiographic regions is shown on the Precambrian vs. Paleozoic map (see Geological history and Bedrock geology sections for more details).
Land use and urban development in the National Capital Area are highly controlled by the nature of the underlying bedrock and surficial formations. The landsat image corresponding roughly to NTS map 31G/5, shows clearly the land use pattern: the core of the urban development (reddish colours) is centered at the junction of the Rideau, Gatineau and Ottawa rivers. Both urban and rural (patterned light blue, grey, green, and brown) development correspond to flat-lying Paleozoic rocks and along river valleys in the Precambrian Shield. Forested areas (solid green) are located mainly on the Precambrian Shield, north of the Ottawa River, north of the Carp fault, and in the south-west portion of the map. Other forested areas correspond mainly to bedrock outcrops, where the soil is too thin to support agriculture, or wetlands such as in the Mer Bleue area. The entire Landsat image is also available at a higher resolution.
Author: Robert Bélanger
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