Canada Geology

Geology, tectonics and morphology present, in the territory of the Dominion, even more marked simplicity than in the rest of the continent, if they are considered in their general lines. The overall evolution hinges on a very ancient fundamental architecture, whose detail forms were determined in recent periods, so that even where the archaic and paleozoic soils prevail, which constitute the main nucleus of Canada, the morphology presents characteristics of youth.

The best-defined structural unit is the so-called Canadian or Laurentian shield (or, as it would seem more appropriate to call it in harmony with what we will say below, the Hudsonian Penepian), which extends over about half of the Dominion (4.2 mil. sq., 1 / 5of the entire continent) from the Atlantic to the Glacial Sea, from S. Lorenzo to the lower Mackenzie. On this immense surface of crystalline rocks (granites, gneisses, schists), intensely corrugated, but subjected for a very long time (from the upper Devonico) to a no less intense denudation that reduced them to penepian, the Quaternary glaciations, which operated there by dilating by two main centers (Keewatin, Labrador), engraved the base plate in various ways: large surfaces of bare and rounded rock alternate with higher remains of ancient reliefs, moraines, fluvio-glacial formations, characteristic being above all the indetermal. the neatness of the dividing lines between the different basins, and the irregularities of the longitudinal profile of the watercourses that run through them. In the boundless solitude the line of horizon, always the same, is lost among the mists of the plain, which the forests cover for more than half of its surface: the average height usually remains below 500 m., but the glacial incisions, leaving cavities that waters have transformed into lakes, they give the landscape a certain movement of lines, which locally attenuates the monotony of the whole. The woodland covering, limited to the north by the climate conditions (frozen ground), marks, with its extreme edge, the boundary of the two large areas into which the penepian can divide: that of conifers and the belt of barren grounds, which essentially continues in the islands of the North American archipelago. Differences in level, even not very pronounced, take on great importance locally (watershed), but above all remarkable are on the south-eastern edge of the penepiano, where it rises steeply on the San Lorenzo valley, which traces a fracture line. Geologically, the valley still belongs to the shield, of which it retains the hydrographic characteristics, but it is partly hollowed out in the selvedge of undisturbed Paleozoic deposits (essentially Ordovician), which fringes the expanse of crystalline assizes towards mid-cloud, reaching as far as the great lakes, while it forms the term of passage between these and the last offshoots of the Appalachians. Due to their geological characteristics, the isolated Anticosti torpedo block and the vast clod of Ordovician-Devonian land that forms a triangle between lakes Huron, Erie and Ontario, and is the most economically advanced region of Canada; morphologically this looks like a series of terraces, delimited by a more or less clear line of escarpments (Niagara) and also crisscrossed by troughs and glacial furrows (Algonchino Park).

Most of the province of Quebec, which extends to N. del S. Lorenzo, like the peninsulas or islands that continue towards the E., falls within the area affected by the Caledonia-Armorican fold systems, which assumes the greatest width beyond the border: it essentially results from plates which, already reduced to penepian in the Jurassic and Cretaceous periods, were then raised, eroded and also subjected to the action of glaciers. The Canadian section includes the last beams of the White Mountains and the Green Mountains (distinguished from each other above all by the prevalence, respectively, of igneous and metamorphic soils), and the so-called Notre-Dame Mountains, which of the former can be considered the continuation along the right bank of the lower S. Lorenzo. Where this seems to flex towards the NE. the group of Schick-shocks rises massively, forming the squat peninsula of Gaspé; tabular block untouched by the great Labrador glacier (M. Table Top, 1219 m), evidence of the oldest penepian, which descends to the ocean with postglacial marine terraces.

New Brunswick is made up of a vast plate, on average a few hundred meters high, inclined towards S., where the St. John valley opens up; with the northern part, mainly granite-gneissic, the extension of the Carbonic, which assumes greater importance (mines) in the contiguous portion of Nova Scotia and in the Cape Breton Island, contrasts with S. Morphologically, the easternmost, or outer, strip of this peninsular fragment, which the Coquebid Range unites with the continent, stands out quite well from the area facing the Bay of Fundy and San Lorenzo. On the mainly granite base, glacial erosion has spread a minute lace of furrows, while a recent movement of submersion fringed the coast of rias and islands, extreme offshoots of the drowned valleys.

According to simplyyellowpages, the western edge of the Canadian shield is marked by the contact between the crystalline-paleozoic rocks and the large band of cretaceous soils that stretch without interruption from Kansas to the mouth of the Mackenzie. The stratigraphic arrangement of the complex is here undisturbed: in S. the transition from the penepian to the Rocciose is accomplished by means of successive steps, of which the easternmost, which dominates the bottom of the Quaternary lake of Agassiz (in the region around Winnipeg), is marked by so-called Coteau des Prairies, which continues in Canada with the Pembina Mountains, Riding Mountains and the Duck, Porcupine and Pasquia Hills, all less than 800 m. in height. On the plateau, which can be named after its major demographic center (Regina), more than the glacial modeling, attested by the moraine apparatuses, the large number of closed basins (salt lakes) is noteworthy: to the West it is delimited by a second step, the edge of which rises over 1000 m. (Coteau du Missouri), while towards S., not far from the border line, the watershed between Saskatchewan and Missouri runs, in Canadian territory, over a series of tabular reliefs, culminating in the Cypress Hills (m. 1131) and in the Wood Mount (1013). Better identified, also geologically, is the highest step of the prairies (Calgary) to the west: apart from the greater extent of the disturbances suffered during the uplift, the not very resistant Cretaceous and Paleogenic sandstones that characterize it appear energetically affected by the ‘normal erosion already in a period prior to the Pleistocene glaciation, which attenuated, without erasing them, the traces, coulées) that separate the various clods in which the region is fragmented.

The breadth of the prairie region, between the foot of the Rocks and the shield, is on the 49 ° of about 1300 km., But gradually decreases towards the N. in Upper Alberta and in the lower Mackenzie, the latter still imperfectly known: the great forest of the Canadian penepian is linked here without interruption to that which covers the northern part of British Columbia. The middle basin of the River of Peace, from which the upper Alberta region takes its unit, is covered by lake depositions similar to those that characterize the plains of lower Manitoba, distinguishing itself from the area that continues it towards the north also for the greater extension of the areas free from the forest and suitable for cultivation.

All the remaining territory, between the western edge of this undisturbed strip of deposits and the shores of the Pacific, is a region in itself, both geologically, because it is raised and corrugated (after the end of the Cretaceous period), and orographically, due to its greater elevation and the character impressed by the surface modeling. Overall, it covers approximately 1.5 mil. of sq. km., extending from NO. to SE. for a length of about 2500 km. and with an average width of 600, which gradually decreases from the international border to the Arctic glacial ocean. In the great variety of forms and characters that come from its own breadth, and despite the many gaps that still make our knowledge imperfect, the structural elements allow us to recognize a few clearly identified major units.

Canada Geology