9. Canada – The Physical Background The Geological Evolution of Canada The Geological Evolution of Canada Physiographic Regions Physiographic Regions Meteorite Craters Meteorite Craters Crustal Movements and Earthquakes Crustal Movements and Earthquakes Climate Climate

Canadian Landscape Variety of landscapes (partly because of country size: 10,000,000 km2 – the 2 nd largest country in the world) Variety of landscapes (partly because of country size: 10,000,000 km2 – the 2 nd largest country in the world) Changes in landscape characteristics reflect: Changes in landscape characteristics reflect: –Differences in surface geology –Differences in climate and related processes

The Main Structural Units of Canada

(a) The Geological Evolution of Canada Landscape in Canada is the product of three major geological developments: formation of Canadian Shield formation of Canadian Shield Formation of mountains from sediments accumulated around the margins of the Shield Formation of mountains from sediments accumulated around the margins of the Shield Deposition of sediments in shallow, intervening areas. Deposition of sediments in shallow, intervening areas.

The Canadian Shield

Canadian Shield A large part of the Shield consists of early Precambrian rocks (at least 2.5 billion years old) – see Table 1.1. in text A large part of the Shield consists of early Precambrian rocks (at least 2.5 billion years old) – see Table 1.1. in text Most of the rocks in the Shield are granite or granite/gneiss (igneous rocks) Most of the rocks in the Shield are granite or granite/gneiss (igneous rocks)

The Main Structural Units of Canada

The Mountains The Cordillera: West Coast; has a long and complex history and is still only partly understood The Cordillera: West Coast; has a long and complex history and is still only partly understood “Formation of the Cordillera resulted form stresses generated by subduction of the Pacific Plate under the Americas Plate” “Formation of the Cordillera resulted form stresses generated by subduction of the Pacific Plate under the Americas Plate” This interaction between the two major plates continues today This interaction between the two major plates continues today

Volcanism in Western Canada

(b) Physiographic Regions (i) Shield - Most of the Shield is rolling and undulating; local relief of the order of 60 to 90 m. More than 25% of land covered by water. - Rock surfaces on Canadian Shield have been “smoothed and abraded” (e.g. by glacial erosion); lakes and glacial deposits

(ii) Interior Plains Prairies composed of three main surfaces, increasing in elevation to the west: Prairies composed of three main surfaces, increasing in elevation to the west: –Manitoba plain (followed by Manitoba escarpment) –Saskatchewan plain –Albertan plain (landscapes in Sask. and Alberatn plains fairly similar)

The Western Interior Plains

Great Lakes – St-Lawrence Lowlands. Glacial deposits cover most of Southern Ontario. Landscape largely a product of last glaciation

(iii) The Mountains The Cordillera and the Appalachians The Cordillera and the Appalachians - Easter part of Cordillera consists of sedimentary rocks (folded – faulted) - Interior system of the Cordillera contains sedimentary, volcanic, and metamorphic rocks (as well as some igneous intrusions)

Physiographic Regions of the Cordillera

Eastern Canada

Meteorite Caters Contribute to shaping of earth surface Contribute to shaping of earth surface Twenty-four impact craters clearly identified in Canada. More could be identified under water Twenty-four impact craters clearly identified in Canada. More could be identified under water Range in size from 10 km to 100 km (diameter) Range in size from 10 km to 100 km (diameter) Erosion and deposition have greatly reduced depth of meteorite craters Erosion and deposition have greatly reduced depth of meteorite craters

Impact craters in Canada

Vertical crust movements and earthquakes Limited data for Canada Limited data for Canada About 2000 earthquakes recorded each year in Canada. About 3/4/ of those are on the West Coast (associated with plate boundaries and tectonic processes) About 2000 earthquakes recorded each year in Canada. About 3/4/ of those are on the West Coast (associated with plate boundaries and tectonic processes) Earthquakes often trigger large mass movements (e.g. landslide, debris flows…) Earthquakes often trigger large mass movements (e.g. landslide, debris flows…)

(c) Climate Diversity of Canadian landscape also the result of climatic variations Diversity of Canadian landscape also the result of climatic variations Differences in climate, in turn, reflect influence of latitude, distance from sea, mountain barriers, etc… Differences in climate, in turn, reflect influence of latitude, distance from sea, mountain barriers, etc… e.g. West facing side of Cordillera characterized by very high precipitation (up to 5 m a year)

Mean temperatures

Climate (ctnd) Most moisture in Cordillera derived from westerly winds coming in from Pacific ocean. Most moisture in Cordillera derived from westerly winds coming in from Pacific ocean. On East side, sources of moisture are Atlantic ocean and Gulf of Mexico On East side, sources of moisture are Atlantic ocean and Gulf of Mexico Low precipitation in Arctic and High Arctic (nut low evaporation) Low precipitation in Arctic and High Arctic (nut low evaporation) Low precipitation and high evaporation is southern Alberta and Saskatchewan. Low precipitation and high evaporation is southern Alberta and Saskatchewan.

Annual Precipitation