The Hawaiian Volcano Observatory (HVO) is an agency of the U.S. Geological Survey, with temporary offices located in Hilo on the Island of Hawaiʻi. The former volcano observatory clifftop facility and HVO offices, closed due to structural damage in 2018, is located at Uwekahuna Bluff on the rim of Kīlauea Caldera. The observatory staff and equipment monitors four active Hawaiian volcanoes: Kīlauea, Mauna Loa, Hualālai, and Haleakalā. Because Kīlauea and Mauna Loa are significantly more active than Hualālai and Haleakalā, much of the observatory's research is concentrated on the former two mountains.