The Wapi Lava Field, SE of the Craters of the Moon, covers about 325 km2, and consists of a low shield volcano formed during an eruption around 300 BCE that produced ~6 km3 of pahoehoe lava flows. The small King's Bowl rift immediately to the north was also formed at about the same time along a central eruptive fissure flanked by two parallel non-eruptive fissures. This eruption produced a phreatic explosion that created Kings Bowl, an 80-m-long, 30-m-deep explosion crater. Eruptions overlapped with the last eruptive period of the Craters of the Moon lava field. The vent area lies along the Great Rift of the Craters of the Moon and consists of five major and a half-dozen minor vents covering an area of 0.5 km2. The largest of the vents contains several pit craters truncating lava lakes that filled the crater. Pillar Butte, a mass of layered lava flows and agglutinates, forms the high point of the lava shield. The Split Butte maar to the west is partially overlapped by flows of the Wapi field.