Paved Coffer to Hells Half Acre — Caribou-Targhee Volcanic Plateau Road
Apollo astronauts trained here. You can drive it.
Most people blow past the Hells Half Acre lava field on US-20 without a second look. Get off the pavement and you’ll find a different world — a 4,000-year-old basaltic flow that looks like it cooled last week, riddled with collapsed tubes, squeeze-ups, and pressure ridges that make cross-country navigation genuinely disorienting. The Caribou-Targhee National Forest roads threading the south side of this flow connect to BLM jeep tracks that push right up to the lava margin, where sagebrush gives way to nothing but black rock. The Snake River Plain stretches flat to every horizon, and the Big Southern Butte punches up to the southwest like a landmark from a different planet.
This is a high-clearance dirt road run, not a hardcore rock crawl — but don’t get cocky. Lava edges are tire-shredding brutal and the tracks are poorly signed. A stock 4WD truck with all-terrain tires handles it fine, but bring two full-size spares. No water out here. Nearest fuel is Idaho Falls, 25 miles east. Best run in May–June or September–October when the Snake Plain heat stays manageable. No permit required. Cell service is nonexistent once you’re in the field. The payoff is a landscape so alien that NASA used it for Apollo crew geology training — that’s not marketing copy, that’s fact.
Trail Specs
| Difficulty | Moderate |
|---|---|
| Trail Type | Backcountry, High Clearance |
| Surface | Dirt, Gravel, Rock |
| Features | Camping, Historic, Remote, Scenic |
| Length (miles) | 18 mi / 29 km |
| Duration | 1 day |
| Max elevation (ft) | 5180 ft |
| Best season | May-June, September-October |
| Minimum vehicle | Stock 4WD high-clearance |
| Nearest town | Idaho Falls, ID |
| Land manager | BLM Idaho Falls Field Office / Caribou-Targhee National Forest |
| Permit required | No |
| Cell service | None |
| Water crossings | No |
| Dispersed camping | Yes |
| Official sources | blm.gov |
| Start coordinates | |
| End coordinates | |
| Copy both for Google Maps directionsClick to copy the directions URL · or open it directly in a new tab | |
| Find on Google | Search on Google → |
Location
Trail Conditions
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Frequently asked questions
Can a stock 4Runner or Wrangler handle this trail without modifications?
Yes. A stock 4WD with genuine high clearance is the minimum — think factory 4Runner, Wrangler, or Tacoma. Lifted rigs have more margin on the rockier lava sections, but this is a moderate trail, not a locker-required situation.
When does this trail open after winter, and is snow a real issue?
Best windows are May–June and September–October. The plateau sits around 5,000 ft and can hold snow or mud into late spring — call the BLM Idaho Falls Field Office before heading out if you're going early May. Summer heat is brutal on this exposed lava field, so avoid July–August if you can.
Do I need a permit or is there a fee to drive this trail or camp at Hells Half Acre?
No permit required to drive the trail. The Hells Half Acre Lava Flow day-use area managed by BLM is free. Dispersed camping on BLM land along the route is also free — standard 14-day stay limit applies.
What's the hardest section of this trail and what does it actually feel like to drive?
The lava rock sections near Hells Half Acre are the roughest — chunky, uneven basalt that demands slow, deliberate throttle. Nothing requires lockers or aggressive lines, but sloppy driving will find your rocker panels. Plan for 2–3 mph through the worst of it.
Is there any water or gas available along the route, and what's the nearest resupply?
There is zero water on this trail — the lava field is completely dry. Fuel up and fill every container in Idaho Falls before you leave; the nearest gas is back there, roughly 18 miles from the trailhead. Cell service is nonexistent the entire route, so tell someone your plan before you go.
Trail track
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