Midway Atoll is part of a chain of volcanic islands, atolls, and seamounts extending from Hawaii up to the tip of the Aleutian Islands and known as the Hawaiian-Emperor seamount chain. It consists of a ring-shaped barrier reef nearly in diameter and several sand islets. The two significant pieces of land, Sand Island and Eastern Island, provide a habitat for millions of seabirds. The island sizes are shown in the table above. The atoll, which has a small population (approximately 60 in 2014, but no indigenous inhabitants), is designated an insular area under the authority of the United States Department of the Interior.