Getting Oriented
The monument sits on the Snake River Plain in central Idaho, off US-20/26/93 about 18 miles southwest of Arco. The lava belongs to the Great Rift, a fissure system that runs northwest to southeast across the plain for roughly 45 miles. The U.S. Geological Survey counts eight eruptive periods here between about 15,000 and 2,000 years ago, each separated by a quiet stretch averaging around 2,000 years. The youngest flows are roughly 2,000 years old. The present quiet interval has run about that long, so USGS considers another eruption likely within the next thousand years.
About 25 cinder cones stand along the rift, some up to 800 feet high, and the Loop Drive threads between them.
The Drive
The Loop Drive is a seven-mile paved one-way loop with seven main stops, starting from the visitor center at the monument entrance. It is easy driving suitable for any vehicle, and most stops have a short paved path to the feature. An entrance fee applies. The road is open to vehicles from about mid-April through mid-November and closed by snow the rest of the year, when it is groomed for cross-country skiing from roughly mid-December through February.
Give the loop two to three hours if you walk the short trails. There is no fuel, food, or reliable cell service on the loop, so arrive fueled and carrying water.
Points of Interest
- North Crater Flow. A short trail crosses one of the field's younger aa flows and passes crater-wall fragments that the lava rafted away from their vent.
- Devils Orchard. An accessible half-mile loop through cinder islands stranded in the flow.
- Inferno Cone. A steep walk up a bare cinder cone for a view across the whole lava field and the line of the Great Rift.
- Spatter Cones. Small, steep-sided cones built from clots of pasty lava, with vents you can look down into.
- Big Craters and Tree Molds. A cluster of larger craters, plus casts left in the rock where lava surrounded and burned standing trees.
- Caves Area. A short spur reaches a group of lava tubes, including Indian Tunnel and Dewdrop Cave. Entering any cave requires a free permit from the visitor center, part of the Park Service's white-nose-syndrome screening for bats.
Where to Camp
The Lava Flow Campground sits near the loop entrance, first-come first-served, with vault toilets and no hookups. It usually opens in spring and closes once water is shut off in fall. Dispersed camping is available on the surrounding BLM ground off the monument.
Tips for a Safe and Enjoyable Trip
- Summer sun is the main hazard. The black lava radiates heat, shade is scarce, and there is no water on the loop. Carry more than you think you need.
- Aa lava is sharp enough to shred skin and tires. Stay on established trails and pullouts.
- Get the cave permit before you plan on the Caves Area, and bring a light and closed-toe shoes.
- Fill up in Arco or Carey. There is no fuel at the monument.
- The loop closes to cars in winter. Check the monument's conditions page before a shoulder-season trip, since opening and closing dates move with the snow.
Fuel and Water
The last fuel and full services are in Arco, about 18 miles northeast, or Carey, about 24 miles west. Water is available seasonally at the visitor center and campground; there is none along the Loop Drive itself.
Nearby
Arco bills itself as the first town in the world lit by atomic power, and the EBR-1 Atomic Museum sits just east of it on US-20/26. Big Southern Butte rises off the plain to the northeast. Sun Valley and the Wood River Valley are about an hour and a half west via Carey.
