The Hawaiian-Emperor Seamount is a prominent line of underwater mountains in the north-central Pacific Ocean that stretches 4,300 miles from the Aleutian Islands south to the Hawaiian Islands. Key islands in this undersea chain include the Hawaiian Islands, the Midway Atoll, and several smaller uninhabited reefs. A volcanic vein called a hot spot emerged from beneath the Pacific Ocean crust, creating the first mountains. As the Pacific tectonic plate moved in a northwestern direction, the hot spot stayed in the same place, creating a line of volcanoes. Since 1924, the US Geological Survey has operated the Hawaiian Volcano Observatory on Kilauea to monitor the island's four active volcanoes, Haleakala, Hualalai, Kilauea, and Mauna Loa, and the surrounding area. The observatory provides regular updates to the public regarding geologic activity. The frequency of earthquakes along the Hawaiian-Emperor Seamount prompted the US government to install the Pacific Tsunami Warning Center in 1968 to protect residents from sudden, damaging waves.