Arctic Ocean gas reserves, and the Chukchi shelf forms the border between Russian and the United States as stated in the USSR–USA Maritime Boundary Agreement. The whole area is subject to international territorial claims. An underwater ridge, the Lomonosov Ridge, divides the deep sea North Polar Basin into two oceanic basins: the Eurasian Basin, which is between deep, and the Amerasian Basin (sometimes called the North American, or Hyperborean Basin), which is about deep. The bathymetry of the ocean bottom is marked by fault block ridges, abyssal plains, ocean deeps, and basins. The average depth of the Arctic Ocean is . The
Nansen Island (Kara Sea) and some of its larger neighboring islands, such as Taymyra, Bonevi and Pilota Makhotkina, are deeply indented, with many crooked inlets. The sounds between this island and neighboring islands are also somewhat labyrinthic. Geologically all these coastal islands are a continuation of the Nordenskiöld Archipelago which lies further north. And sometimes Nansen Island is considered a part of it. Ostrov Vkhodnoy is a long islet located off Nansena's western end. The sea surrounding Nansen Island is covered with pack ice with some polynias during the long and bitter winters and there are many ice floes even in the summer. Nansen