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 (lunar crater) lies across the northern rim of Nansen, and a similar formation is located along the inner southern wall. A merged chain of tiny craters lies across the eastern rim. The interior floor of Nansen is more hummocky and irregular in the northern half, while the southern part of the floor is relatively level. There is a small, bowl-shaped crater in the southeastern part of the floor, and many tiny craterlets lie across the interior and along the inner walls. By convention these features are identified on lunar maps by placing the letter on the side of the crater midpoint that