Hell's Half Acre (south trails)
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GeologyHikingRock Formation
Overview
Hell's Half Acre Lava Field is a basaltic lava plain located on the Snake River Plain of Idaho in the United States. It is the easternmost of the basaltic lava fields on the Snake River Plain, located about 25 miles (40 km) west of Idaho Falls, Idaho and 30 miles (48 km) north of Pocatello, Idaho. In 1976, the National Park Service designated the northwestern portion of the site a National Natural Landmark.
Practical Info
Every dayOpen 24 hours
Suggested Duration1-2 hours
Best TimeSpring (April to May) or autumn (October) is highly recommended, as this vast basaltic lava plain lacks any shade and gets dangerously hot in summer. Start hiking at 7:00 AM; the cool morning air is ideal for the uneven terrain, and early sunbeams cast long shadows across deep fissures, emphasizing the dramatic topography before intense sun hits.
Getting TherePrivate vehicle transit is required. The South Trails trailhead is uniquely located directly off Interstate 15, between Idaho Falls and Blackfoot. Drive along I-15 and pull into the official Blackfoot Rest Area (accessible from both directions); dedicated trailhead parking and informational kiosks are situated inside this rest stop, allowing direct access to the loops.
Travel Tips
- South trails start off the I-15 rest area; the field is cut by unstable volcanic rifts and deep open cracks, requiring strict adherence to the marked trail poles.
- This Wilderness Study Area has no potable water or infrastructure; each hiker must explicitly pack a minimum of 2 liters of water during summer to prevent dehydration.
- The vast basalt flow loses landmarks at night making navigation impossible even with illumination; return before dark and stay alert for prairie rattlesnakes.
Reviews
Positive
- The vast basalt lava field features jagged fissures and rugged craters, offering a surreal, outer-space visual that claims its fame.
- Hiking the South Trails deep into the primitive wilderness ridges delivers an exceptional, thrill-packed volcanic adventure fun.
- Positioned right off Highway 20 with zero entry fees, featuring paved parking, clean accessible restrooms, and clear trail maps.
- The pedestrian density is exceptionally sparse, escaping tourist crowds to let you fully embrace the quiet Shoshone geology.
Heads up
- Summer heat is brutal as the black lava rock bakes in intense sunlight, holding zero shade trees or trail shelters.
- The wild lava tracks are intensely rugged, sharp, and fractured, ruining light sneakers and completely stopping strollers.
- The inner loops feature zero public trash cans or water fountains, forcing hikers to pack out all individual waste wrappers.
- While plastic markers outline the trail, the uniform black terrain makes it easy to get disoriented during heavy dust storms.