Lava Formations

The sign never names the lava it describes. This is the edge of Hells Half Acre, a flow of about 162,000 acres that poured from a fissure vent to the northwest and reached as far as the interstate, which crosses its southeast corner. Its age is less settled than its size: the BLM gives about 4,100 years on one of its own pages and about 5,200 on another. Loop trails leave both rest areas into the flow. The northwest part became a National Natural Landmark in 1976, and more than 66,000 acres are managed as a wilderness study area.

What the plaque says

Lava Formations Molten rock, forced upward for 30 to 50 miles through fissures in the earth, has cooled into the hard lava found here. Continued pressure from below has made great cracks in the contorted surface. This lava solidified only a few thousand years ago, and not very much soil covers it yet. But vegetation is getting a start, and unless new flows intervene, windblown soils will cover these rock layers. Then the surface here will look the same as the surrounding plains, which also are layers of lava and windblown soils. 287 Text prepared by the Idaho Academy of Science and the Idaho State Historical Society. Marker made and installed by Idaho Transportation Dept.

Where it stands

Worth the stop nearby

• Shoshone-Bannock Tribal Museum — 20 mi
  Fort Hall told from the other side of the trade counter, by the tribes whose reservation now surrounds the site of the post.

More markers nearby

• Elephant Hunters — 17 mi
• Taylor's Bridge — 17 mi
• Eagle Rock Ferry — 17 mi
• Three Buttes — 27 mi