Mauna Loa, an active volcano on the island of Hawaii, in Hawaii Volcanoes National Park. Mauna Loa (“Long Mountain”) is considered one of the largest mountains on earth. It rises 13,677 feet (4,169 m) above sea level, extends more than 18,000 feet (5,490 m) underwater, and covers some 2,000 square miles (5,200 km2) at sea level. Eruptions, averaging one every three or four years, occur in the summit crater, Mokuaweoweo, and along a great northeast-southwest fissure that splits the crater and the mountain. Mauna Loa is one of the most abundant lava producers on earth. On several occasions lava flows have threatened the city of Hilo on the island's east coast.