When you think about volcanoes and lava flows, you might think of lush, tropical Hawaii. You probably wouldn't think of Idaho. Yet, beginning millions of years ago and ending a few thousand years ago, lava flowed periodically over a vast area of what is now high-desert southern Idaho. Hot molten rock oozed from deep fissures in the earth and spread like molasses over the Snake River Plain in southern Idaho.
Location of Hell's Half Acre Trail
Soil covers the oldest lava, but Interstate 15 between Blackfoot and Idaho Falls, Idaho, traverses an exposed 222-square-mile section of 4100-year-old lava called Hell's Half Acre. North or southbound motorists on I-15 can access paved, concrete walkways into the lava bed from the parking lots at the Blackfoot Rest Area about 20 miles south of Idaho Falls.
"We wanted to have visitors who stop to experience what it's like on a lava field," says Bill Boggs, Outdoor Recreation Planner for the Bureau of Land Management in Idaho's Upper Snake Field Office. The BLM in cooperation with the Idaho Transportation Department installed the Hell's Half Acre Trail and interpretive signs over the lava bed. The trail on each side of I-15 is divided into loop sections. On the northbound side, each of three loops is .5-mile or less, and one loop is wheel-chair accessible. A walk on the paved trail refreshes travel-weary motorists.
The Lava: a Harsh Environment
When you're traveling 65 mph in your vehicle, you can't see the life that exists in what appears to be a barren wasteland, says Boggs. But atop the rough, cracked black surface of the lava bed you'll see that a variety of life has adapted to the harsh habitat. "The lava gets very hot in summer and very cold in winter, and things don't grow easily," says Boggs. "We only have about ten inches of rain a year."
Plant and Animal Life on the Lava
Yet, dark green juniper trees and pale green sagebrush soften the hard landscape in places where there's enough soil for their roots. Grasses and prickly pear cactuses grow where they can gain a foothold. In the deep lava cracks that hold moisture, ferns flourish. "Snow stays in the cracks into June," says Boggs. Rust, chartreuse and green splotches of lichens colonize the pocked black lava and steadily break it down into soil.
While the plants can't hide, the animals can. So trail walkers will be lucky to spot a mammal or reptile. The animals shelter in caves throughout Hell's Half Acre. Among others, coyotes, cottontail rabbits, sage grouse and several snake species, including rattlesnakes, live in the lava. You may see birds.
If you're planning to drive through southern Idaho on I-15, plan to stop at the Blackfoot Rest Area and stretch your legs on the Hell's Half Acre Trail. A walk through the lava landscape on the easy trail will refresh you and teach you a little geology and ecology of the unusual habitat. You could even make Hell's Half Acre a destination.
Pamela Crowe - Pamela Crowe
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