Halema'uma'u Crater lies at the heart of Kilauea, one of the two active volcanoes at Volcanoes National Park. The other is Mauna Loa, the world's largest active volcano. Halema'uma'u Crater is the home of Madame Pele, Goddess of Hawaiian Volcanoes. The crater is about 3,000 feet across and almost 300 feet deep. With its white walls, it looks like a moon crater. The Crater expels about 300 tons of sulfur dioxide daily both within the crater and along the rim. Lava boiled in this crater from 1823 to 1924. The most recent eruption within the crater occurred for less than a day in 1982.

Today scientists believe that the top of the underground reservoir of hot molten rock that feeds the volcano lies about two miles below Halema'uma'u. When pressure in the reservoir builds, lava may erupt here or at vents or fissures along the sides of the volcano.