Hell's Half Acre Volcano — United States

Hell's Half Acre, the easternmost of the young basaltic lava fields of the Snake River Plain, covers an area of about 400 km2 SW of Idaho Falls. Basaltic lavas forming the broad, low shield are dominantly pahoehoe flows that were erupted from a 3-km-long, NW-SE trending vent system at the NW part of the field during a brief eruptive episode about 5,200 years ago. The summit vent area contains an irregular, elongate 300 x 800 m central depression where a former lava lake fed late-stage flows. About 10 circular pit craters are present in the lava lake surface, and two prominent lava tube systems are located near the summit vent complex. Two major flow lobes, each about 5 km wide and 10 km long, extend to the S and SW along the flood plain of the Snake River and surround Morgans Pasture, a large kipuka.