In terms of tectonics, the Arctic realm of the Earth represents a mosaic consisting of blocks of the old Pre-cambrian continental crust amalgamated by belts of the younger (Late Proterozoic-Mesozoic) crust and separated by basins with the newly formed Late Jurassic-Cenozoic oceanic crust. The largest Precambrian North American (with associated Greenland representing an element of the former Laurentia), East European (Bal-tica), and Siberian cratons occupy peripheral positions. The central Arctic region includes fragments of another continental massif that are exposed in the Northeastern Land of Spitsbergen (Svalbard), Franz Josef Land, Northern Island of Novaya Zemlya, Severnaya Zemlya, the New Siberian and De Long archipelagoes, and Peary Land of the Canadian Arctic Archipelago, as well as in the underwater Lomonosov, Mendeleev, and Chukchi ridges. In integrity, this massif was named Arctida in .
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