in britanica we read, Although the detail of the terrain in many parts of the is directly attributable to the Pleistocene glaciations, the major physiographic divisions reveal close correlation with geologic structure. The two largest shield areas, the Canadian and the , have developed similar landscapes. West of Hudson , in southwestern Baffin Island, and in Karelia the is low and rocky with countless lakes and disjointed drainage. Uplands, generally 1,000 to 2,000 feet above level and partially covered with glacial deposits, are more widely distributed. They form the interior of Quebec-Labrador and parts of the Northwest Territories in , and the Lapland Plateau in northern Scandinavia. The eastern rim of the Canadian Shield in Canada from Labrador to Ellesmere Island has been raised by crustal changes and then dissected by glaciers to produce fjords that separate mountain peaks more than 6,000 feet high. The surface of the shield in Greenland has the shape of an elongated basin, with the central part, which is below sea level, buried beneath the Greenland ice cap. Around the margins, on the east and west coasts, the mountainous rim is penetrated by deep troughs through which local and inland-ice glaciers flow to the sea. The mountains are highest in the east, where they exceed 10,000 feet. In shield areas where sedimentary mantle the crystalline variety, as in north-central Siberia, the southern sector of the Canadian archipelago, and Peary Land, the topography varies from plains to plateaus, with the latter deeply dissected by narrow valleys. Far beyond the margins of the shields, extensive plains have evolved on soft sedimentary rocks. In North America these form the Mackenzie Lowlands, Banks and Prince Patrick , and the Arctic Plains section of northern ; in northern Europe they form the Severnaya Dvina and Pechora Plains. In Siberia the Ob delta, its northeastern extension to the Laptev Sea, the North Siberian Lowland, the West Siberian Plain, and farther east the Lena-Kolyma plains (including the New Siberian Islands) have also developed on sedimentary rocks. Although there are differences in degree, these terrains are essentially flat, occasionally broken by low rock scarps, and covered with numerous shallow lakes. The plains are crossed by large rivers that have laid down deep alluvial deposits. The strongly folded rocks associated with the two orogenic periods in the Arctic form separate physiographic regions. The original mountains of the older, Paleozoic folding were long ago destroyed by erosion, but the rocks have been elevated in recent geologic time, and renewed erosion, often by ice, has produced a landscape of plateaus, hills, and mountains very similar to the higher parts of the shields. In Ellesmere Island the mountains are nearly 10,000 feet high. In Peary Land and Spitsbergen maximum elevations are about 6,000 feet, while in eastern and on Novaya Zemlya and Severnaya Zemlya the uplands rarely exceed 2,000 feet. The younger groups of fold mountains of northeast Siberia and Alaska are generally higher. Peaks of 10,000 feet are found in the…

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