Arctic land

Conditions typical of Arctic lands are extreme fluctuations between summer and winter temperatures; permanent snow and ice in the high country and grasses, sedges, and low shrubs in the lowlands; and permanently frozen ground (permafrost), the surface layer of which is subject to summer thawing.Motion of plates in the Paleogene and Neogene periods (about 65.5 million to 2.6 million years ago) led to igneous activity in two regions. One was associated with mountain building around the North Pacific, and active volcanoes are still found in Kamchatka, the Aleutian Islands, and Alaska.