The Laurentian Upland (or Laurentian Highlands) is a physiographic region which, when referred to as the "Laurentian Region" or the Grenville geological province, is recognized by Natural Resources Canada as one of five provinces of the larger Canadian Shield physiographic division. [1] The United States Geological Survey recognizes the Laurentian Upland as the larger general upland area of the Canadian Shield. [2] [3] [4]
The Laurentian Region, as recognized by Natural Resources Canada, is part of the plateau and dissected southern rim of the Canadian Shield in the province of Québec. It is a western extension of the Laurentian Mountains, and continues across the Ottawa Valley into Ontario as the Opeongo Hills. Viewed from the valleys of the Ottawa and St. Lawrence Rivers, the south-facing escarpments of the Shield give the appearance of mountains 500–800 meters high; looking across the plateau, the relief is more moderate and subdued. These scarps mark the dramatic southern edge of this Upland region, of which Mont Raoul Blanchard is the highest peak. Although the other limits are less well defined, this Laurentian Region in Quebec may be considered to extend 100–200 km northward from the scarps and to stretch from the Gatineau River in the west (mean elevation 400 m) some 550 km to the Saguenay River in the northeast. Here it attains its maximum elevation north of Quebec City in the Réserve faunique des Laurentides (over 1000 m). Individual summits rise above the plateau surface: Mont Sir Wilfrid (783 m) and Mont Tremblant in the west, Mont Sainte-Anne (815 m) at Quebec, Mont Raoul Blanchard (1166 m), Mont Bleu (1052 m) and Mont des Conscrits (1006 m) in Réserve faunique des Laurentides. Cap Tourmente (579 m) and Mont des Éboulements (770 m) are dramatic examples of the scarp face as it drops precipitously to the St Lawrence River.
The more general Laurentian Upland Province may be considered to extend over a larger area of the Canadian Shield, into Northwestern Ontario and parts of Northern Minnesota, Wisconsin, Michigan, and New York State, and is recognized by the United States Geological Survey to include the Superior Upland. [5] As a southern extension of the Canadian Shield, the Adirondack Mountains of New York State might also be considered an extension of the Laurentian Upland. [6]
The Laurentian Upland is primarily made up of ancient Precambrian igneous, metamorphic, and sedimentary rock. [7] With the exception of the river valleys and lacustrine basins, it is a rolling to mountainous peneplain that ranges from 800 to 1400 feet above sea level. [8]
The Superior Upland is the province of the Laurentian Upland which projects into the United States west and south of Lake Superior. [9] This upland, part of the Canadian Shield along with the Adirondacks, is a greatly deformed structure and is composed primarily of igneous and metamorphic crystalline rocks commonly associated with a rugged landscape. At some prehistoric period, this had a strong relief, but today the upland as a whole is gently rolling with the inter-streams surfaces being plateau-like in their evenness. Here they have elevations of 1,400 to 2,300 feet (700 m) in their higher areas, such as the Misquah Hills and Huron Mountains. [10] In this province, we find a part of those ancient mountains regions that were initiated by crustal deformation and then reduced by a long continued erosion to a peneplain of modern relief. A peneplain with the occasional moderately high monadnocks left behind during the peneplanation of the rest of the surface. The erosion of the region must have been far advanced in prehistoric times, even practically completed, because the even peneplain surface is overlapped by fossiliferous marine strata from an early geological date, Cambrian. This shows that the depression of the region beneath an ancient sea took place after a long existence as dry land. [11]
The extent of the submergence and the area over which the Palaeozoic strata were deposited are unknown. Because of the renewed elevation without deformation, erosion in later periods has stripped off an undetermined amount of the covering strata. The valleys by which the uplands are here and there trenched to moderate depth appear to be, in part at least, the work of streams that have been superposed upon the peneplain through the now removed cover of stratified rocks.
Glaciation has strongly scoured away the deeply weathered soils that presumably existed here in preglacial time. It left behind firm and rugged ledges in the low hills and swells of the ground and spread an irregular drift cover over the lower parts, whereby the drainage is generally disordered being deposited in lakes and swamps and elsewhere rushing down rocky rapids.
The Canadian Shield, also called the Laurentian Plateau, is a large area of exposed Precambrian igneous and high-grade metamorphic rocks that forms the ancient geologic core of the North American continent. Glaciation has left the area with only a thin layer of soil, through which the composition of igneous rock resulting from long volcanic history is frequently visible. As a deep, common, joined bedrock region in eastern and central Canada, the Shield stretches north from the Great Lakes to the Arctic Ocean, covering over half of Canada and most of Greenland; it also extends south into the northern reaches of the United States. Human population is sparse and industrial development is minimal, but mining is prevalent.
The Appalachian Mountains, often called the Appalachians, are a system of mountains in eastern to northeastern North America. The Appalachians first formed roughly 480 million years ago during the Ordovician Period. They once reached elevations similar to those of the Alps and the Rocky Mountains before experiencing natural erosion. The Appalachian chain is a barrier to east–west travel, as it forms a series of alternating ridgelines and valleys oriented in opposition to most highways and railroads running east–west.
Missouri, a state near the geographical center of the United States, has three distinct physiographic divisions:
The Intermontane Plateaus of the Western United States is one of eight U.S. Physiographic regions (divisions) of the physical geography of the contiguous United States. The region is composed of intermontane plateaus and mountain ranges. It is subdivided into physiographic provinces, which are each subdivided into physiographic sections.
The Boston Mountains is a Level III ecoregion designated by the Environmental Protection Agency (EPA) in the U.S. states of Arkansas and Oklahoma. Part of the Ozark Mountains, the Boston Mountains are a deeply dissected plateau. The ecoregion is steeper than the adjacent Springfield Plateau to the north, and bordered on the south by the Arkansas Valley. The Oklahoma portion of the range is locally referred to as the Cookson Hills.
The Laurentian Mountains are a mountain range in southern Quebec, Canada, north of the St. Lawrence River and Ottawa River, rising to a highest point of 1,166 metres (3,825 ft) at Mont Raoul Blanchard, northeast of Quebec City in the Laurentides Wildlife Reserve. The Gatineau, L'Assomption, Lièvre, Montmorency, Nord and St. Maurice rivers rise in lakes in this mountain range.
The richly textured landscape of the United States is a product of the dueling forces of plate tectonics, weathering and erosion. Over the 4.5 billion-year history of our Earth, tectonic upheavals and colliding plates have raised great mountain ranges while the forces of erosion and weathering worked to tear them down. Even after many millions of years, records of Earth's great upheavals remain imprinted as textural variations and surface patterns that define distinctive landscapes or provinces.
The Cumberland Mountains are a mountain range in the southeastern section of the Appalachian Mountains. They are located in western Virginia, southwestern West Virginia, the eastern edges of Kentucky, and eastern middle Tennessee, including the Crab Orchard Mountains. Their highest peak, with an elevation of 4,223 feet (1,287 m) above mean sea level, is High Knob, which is located near Norton, Virginia.
Superior National Forest, part of the United States National Forest system, is located in the Arrowhead Region of the state of Minnesota between the Canada–United States border and the north shore of Lake Superior. The area is part of the greater Boundary Waters region along the border of Minnesota and the Canadian province of Ontario, a historic and important thoroughfare in the fur trading and exploring days of New France and British North America.
The geology of Minnesota comprises the rock, minerals, and soils of the U.S. state of Minnesota, including their formation, development, distribution, and condition.
The Geology of Pennsylvania consists of six distinct physiographic provinces, three of which are subdivided into different sections. Each province has its own economic advantages and geologic hazards and plays an important role in shaping everyday life in the state. They are: the Atlantic Coastal Plain Province, the Piedmont Province, the New England Province, the Ridge and Valley Province, the Appalachian Plateau Province, and the Central Lowlands Province.
The Misquah Hills are a range of mountains in northeastern Minnesota, in the United States. They are located in or near the Boundary Waters Canoe Area Wilderness within Superior National Forest. Eagle Mountain, the highest point in Minnesota at 2,301 feet, is considered to be part of the Misquah Hills.
The Duluth Complex, the related Beaver Bay Complex, and the associated North Shore Volcanic Group are rock formations which comprise much of the basement bedrock of the northeastern part of the U.S. state of Minnesota in central North America. The Duluth and Beaver Bay complexes are intrusive rocks formed about 1.1 billion years ago during the Midcontinent Rift; these adjoin and are interspersed with the extrusive rocks of the North Shore Volcanic Group produced during the same geologic event. These formations are part of the Superior Upland physiographic region of the United States, which is associated with the Laurentian Upland of the Canadian Shield, the core of the North American Craton.
The Great Lakes-St. Lawrence Lowlands, or simply St. Lawrence Lowlands, is a physiographic region of Eastern Canada that comprises a section of southern Ontario bounded on the north by the Canadian Shield and by three of the Great Lakes — Lake Huron, Lake Erie and Lake Ontario — and extends along the St. Lawrence River to the Strait of Belle Isle and the Atlantic Ocean. The lowlands comprise three sub-regions that were created by intrusions from adjacent physiographic regions — the West Lowland, Central Lowland and East Lowland. The West Lowland includes the Niagara Escarpment, extending from the Niagara River to the Bruce Peninsula and Manitoulin Island. The Central Lowland stretches between the Ottawa River and the St. Lawrence River. The East Lowland includes Anticosti Island, Îles de Mingan, and extends to the Strait of Belle Isle.
The proglacial lakes of Minnesota were lakes created in what is now the U.S. state of Minnesota in central North America in the waning years of the last glacial period. As the Laurentide Ice Sheet decayed at the end of the Wisconsin glaciation, lakes were created in depressions or behind moraines left by the glaciers. Evidence for these lakes is provided by low relief topography and glaciolacustrine sedimentary deposits. Not all contemporaneous, these glacial lakes drained after the retreat of the lobes of the ice sheets that blocked their outlets, or whose meltwaters fed them. There were a number of large lakes, one of which, Glacial Lake Agassiz, was the largest body of freshwater known to have existed on the North American continent; there were also dozens of smaller and more transitory lakes filled from glacial meltwater, which shrank or dried as the ice sheet retreated north.
The Innuitian Region is a physiographic division of Canada's far north. It is one of three physiographic divisions of the Arctic Lands physiographic region, along with the Arctic Coastal Plain, and the Arctic Lowlands.The Queen Elizabeth Islands comprise most of the region, which is also considered to be part of the Arctic Archipelago.
The North Shore Highlands are a physiographic and ecological region of the U.S. state of Minnesota in central North America. They were formed by a variety of geologic processes, but are principally composed of rock created by magma and lava from a rift about 1.1 billion years ago, which rock formations are interspersed with and overlain by glacial deposits. Their ecology derives from these origins, with thin, rocky soils supporting flora and fauna typical of their northern, inland location.
The geology of North America is a subject of regional geology and covers the North American continent, the third-largest in the world. Geologic units and processes are investigated on a large scale to reach a synthesized picture of the geological development of the continent.
The sub-Cambrian peneplain is an ancient, extremely flat, erosion surface (peneplain) that has been exhumed and exposed by erosion from under Cambrian strata over large swathes of Fennoscandia. Eastward, where this peneplain dips below Cambrian and other Lower Paleozoic cover rocks. The exposed parts of this peneplain are extraordinarily flat with relief of less than 20 m. The overlying cover rocks demonstrate that the peneplain was flooded by shallow seas during the Early Paleozoic. Being the oldest identifiable peneplain in its area the Sub-Cambrian peneplain qualifies as a primary peneplain.
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