Hell's Half Acre covers an area of about 400 km2 (150 sq mi) of Bingham County and Bonneville County it is south-west of Idaho Falls. The field is the second largest of the Snake River Plain fields. The lava is basaltic in nature which formed a broad, low shield volcano with dominantly pahoehoe flows that were erupted from a 3-kilometer (1.9 mi) long, north-west to south-east trending vent system at the north-west part of the field during a brief eruptive episode about 5,200 years ago. Interstate 15 crosses the south-east edge of the lava field south-west of the city of Idaho Falls.
Hell's Half Acre lava field is a National Natural Landmark.