On the Hells Half Acre lava flow near Blackfoot, Idaho
Copyright © Ralph Maughan
The Hells Half acre lava flow, which emerged from a shield volcano, is one of many basalt flows on the Snake River Plain. It is relatively young, and it has only been partially colonized by vegetation. It is also a very large and mostly roadless flow. Nevertheless, it is near the population centers of Idaho Falls and Blackfoot, and Shelley, Idaho (less than ten miles). Interstate highway 15 cuts through a small portion of the flow. At rest stops on the Interstate, there are short paved walks providing an interpreted trail across the very rough surface.
The Idaho Falls District of U.S. Bureau of Land Management (BLM) administers the area, and it has recommended about 100,000 acres to Congress for wilderness designation. The recommended designation has languished, perhaps because no threat is perceived, although a cell tower tall enough to generate criticism was recently erected on a scenic, but non-roadless part of the flow.
The best time to explore the flow is probably May and late September when the temperature is comfortable. After winter's moisture, much of the basalt is bulging with well-hydrated moss, and the lichens are almost luminescent. Exploration during the time of snow is so difficult to be almost impossible.
The hiker should have very good boots, carry water, and have a good sense of direction. A compass will not work properly on the flow and there are few landmarks to guide you. This is a place you won't have to worry about encountering terrain-destroying all terrain vehicles. There are a fair number of rattlesnakes. Watch where you step to avoid them and so you won't fall in one of the many deep cracks. This is a very good place to break some bones.
Moss in May on the Hells Half Acre lava flow
© Ralph Maughan
Rattlesnake. Hells Half Acre
copyright © Ralph Maughan
Telephoto view to the west across the Hells Half Acre flow.
The buttes are old volcanoes.
© Ralph Maughan
Hells Half Acre Lava Flow roadless area/ Email Ralph Maughan May 27, 2006