The Aleutian Islands (; possibly from Chukchi "aliat", "island") are a chain of more than 300 small volcanic islands. They are in the Northern Pacific Ocean. They are spread out over an area of 6,821 sq mi (17,666 km²) and go out about west from the Alaska Peninsula toward the Kamchatka Peninsula. They mark a line between the Bering Sea and the Pacific Gulf of Alaska. Crossing longitude 180°, they are the furthest West part of the United States Nearly all the islands are part of Alaska but at the extreme western end are the Commander Islands which are in Russia. The islands, with their 57 volcanoes, are in the northern part of the Pacific Ring of Fire. The Alaska Marine Highway passes through the islands.