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Geo Notes

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Western University
Geography 2010A/B
Suzanne Greaves

Geo Notes Oct/12 Canadas Physical Geography - The physical geography varies across Canada. There are interactions between people and the physical world, and favourable physical conditions can make a region more attractive for human settlement. The physical geography of Canada and the US are very different and this has limited the area suitable for settlement in Canada and its economic potential. Regional geographers are concerned about the effect of human activities on the natural environment. - Physical geography has distinct and unique regional patterns across Canada. Physiographic regions are one aspect of this physical diversity. Climate, soils, and natural vegetation are another aspect and they provide the basis for biodiversity. The impact of human activity is changing the natural environment and, in the case of air, soil, and water pollution, there are long-term negative implications for all life forms. Physical geography has a powerful impact on Canadians by making certain areas more attractive for settlement and urban/industrial development. This relationship between the natural environment and the human world forms the basis of the core/periphery model. - There are five basic elements of the physical geography: geology physiography, climate, vegetation, and soil. Physiography is the study of landforms, their underlying geology, and the processes that shape these landforms. Vegetation has a large impact on soil and climate impacts them both. - The earths surface features a variety of landforms (mountains, plateaus, lowlands) that are subject to change by various physical processes. The process of denudation gradually wears down mountains by erosion and weathering. Weathering is the decomposition of rock and particles. Erosion is the displacement of loose material by wind, water, and ice in a downward movement. Denudation is constantly happening and can change the shape of the earths surface over long periods of time. - Geology Rock type: The earths crust consists of three types of rocks igneous, metamorphic, and sedimentary. All three types are subject to erosion (transport of sediments) and weathering (breaking rock down into smaller pieces). Igneous rocks were formed 3.5 billion years ago when molten rock cooled. Igneous rock well up from the interior of the earth and if they cool above the earth, they are called extrusive. Sedimentary rocks are formed from particles of pre-existing rock. Denudation caused rocks to be broken down, transported, and then deposited in a body of water. The sediments are deposited in horizontal layers (strata) and over time they are compacted/compressed to form hard rock. Metamorphic rocks are igneous or sedimentary rocks that have been transformed or changed into metamorphic rock by the application of extreme heat and pressure. Metamorphic rocks are often produced when the earths crust is subjected to folding (bends and deforms earths crust) and faulting (fractures earths crust). A fault line is a crack or break in the earths crust. Continental drift is also called plate tectonics and it is the movement of earths crust. Fossil fuels can only be found in sedimentary rock, but not all sedimentary rock has fossil fuels. Igneous and metamorphic rocks contain minerals (copper, gold, zinc). The Alberta Badlands contain lots of sedimentary rock. The Canadian shield is composed of igneous and metamorphic rock (oldest rock in Canada, mostly underground). Platform rocks (sedimentary) are found in the interior plains. Folded belts (igneous and metamorphic) are found in mountains. The coastal plain is the most recently deposited material and it is found on the arctic coastline near the mouth of the Mackenzie river. - The earths surface can be classified into different physiographic regions. A physiographic region is a large geographic area characterized by a single landform. It has three key characteristics it extends over a large, contiguous (adjoining) area with similar relief features, its landform has been shaped by a common set of geomorphic processes, and it possesses a common geological structure and history. Canada has seven physiographic regions and they are cordillera (formed during Cenozoic era), interior plains (formed during Mesozoic era), Canadian Shield (largest, formed during Precambrian era), Great Lakes-St. Lawrence Lowlands (smallest, formed during quaternary era), Hudson Bay lowland, Appalachian uplands (formed during Paleozoic era), and arctic archipelago (formed during Paleozoic era). The Appalachian uplands are the oldest mountains in Canada, the Innuitian are the second oldest mountains, and the western mountains are the youngest. Each physiographic region has a different geological structure and these structural differences have produced unique mineral resources in each region, and as a result, different regional economies. Each physiographic region has its own topography and varies according to its surface material. The Pleistocene epoch began 2MYA and the last glacial/ice advance of this epoch was the Wisconsin glaciation, which ended 11,000 years ago. The late Wisconsin ice advance consisted of two ice sheets, the laurentide and the cordillera. As the global climate began to warm, the ice sheet weakened and ice retreated. Glaciation from these ice sheets changed the geography of Canada. The great lakes were formed by glacial scouring (scrubbing) and then filled with meltwater from the receding ice sheet. Today, the largest glaciers in Canada are in the mountains of ellesmere island. Glaciation is a major shaping force. The retreat from Southern Ontario occurred 10,000-15,000 years ago. Alpine glaciers form in the western mountains and continental glaciers covered Canada. A moraine is a hill created by glaciation. - An ice age is a geological period of severe cold accompanied by the formation of continental ice sheets. - The Canadian Shield: Is the largest physiographic region in Canada. It forms the ancient geological core of North America. Molten rock solidified into the Canadian Shield 3BYA. During the last ice advance, the surfaces of the Canadian shield and other physiographic regions were subjected to glacial erosion and deposition, which are caused by ice sheets grinding over the earths surface. During the movement of an ice sheet, loose materials (sand, gravel, boulders) are trapped in the ice. As the ice sheet reached its maximum extent, the edge of it melted, depositing rocks, soil, and debris. This debris is called till (unsorted glacial deposits). Drumlins and eskers are depositional landforms common to the Canadian Shield. Drumlins are long, low hills composed of till. Eskers are long, narrow mounds of sand and gravel deposited on the bottom of a stream flowing under a glacier and they appear on the land surface after the glacier has retreated. Glacial striations, scratches or grooves in the bedrock caused by rocks embedded in the bottom of a moving ice sheet, are also found here. The Canadian shield consists of a rugged, rolling upland and is shaped like an inverted saucer. Areas/towns here tend to be industry/resource towns. - The Cordillera: Is a region of mountains, plateaus, and valleys, and it extends from Yukon to BC. It was formed 40-80MYA. The North American tectonic plate moved westward and collided with the pacific plate. This collision compressed sedimentary rocks into mountains and plateaus. During the late Wisconsin ice advance 18,000 years ago, glaciers grew and eventually covered the cordillera. Cirques were formed. They are large, shallow depressions found in mountains at the head of glacial valleys that are caused by the plucking action of the alpine glaciers. As the glaciers grew, they spread downward into the main valleys, creating arretes. Arretes are ridges formed between two cirques. As the glaciers advanced, they eroded the sides of river valleys and created U-shaped glacial valleys called glacial troughs. - The Interior Plains: Is a region of sedimentary plain that is located between the Canadian shield and the cordillera. Most the population lives in the southern part, where grain farming and cattle ranching occur. A sea once occupied the interior plains, and over time, sediments were deposited into the sea and sedimentary rocks were eventually formed. The oldest sedimentary rocks were formed 500MYA during the Paleozoic era.Tectonic forces have had little effect on the geology of this region, so it is described as a stable geological region. Rivers have cut through this sedimentary rock and exposed Cretaceous rock strata (Alberta Badlands). Beneath the surface of the interior plains are fossil fuel deposits located in sedimentary structures called basins. Fossil fuels are the result of the capture of suns energy by plants and animals in earlier geologic time. Fossil fuels are non-renewable sources. As the Laurentide ice sheet melted and retreated from the interior plains 12,000 years ago, the surface of the region was covered by a lot of debris deposited by the ice sheet. Lake Agassiz was the largest glacial lake in North America. Glacial spillways were formed, and they are valleys formed by the flow of water originating from a melting ice sheet or from water escaping from glacial lakes. There are changes in elevation that create three sub-regions within the prairies Manitoba lowland, Saskatchewan plain, and Alberta plateau. The Cypress hills are located in southern AB and SK. The Cypress hills were enclosed by the Laurentide ice sheet
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