20 Mile Rock

Idaho Falls, Idaho 83402

20 Mile Rock

20 Mile Rock Professional Review and Guide

"Hike and explore a lava/desert playground close to Idaho Falls. The Hell’s Half Acre lava flow is one of several lava flows in Idaho’s Snake River Plain that erupted about 4,100 years ago. It’s 222 square miles, or 162,000 acres.

The loop trail through this unusual terrain is marked by blue-tipped poles. Enjoy the abundant wildflowers such as evening primrose, Indian paintbrush, wild onions, penstemon, geraniums, and prickly pear cactus in May and early June. Since there is no actual trail other than following markers, you can take your time exploring the cracks and crevasses in the lava rock."

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Trail Information

Idaho Falls
Nearby City
Trail Type
Easy to Moderate
Skill Level
Best March through December
Upper Snake Field Office BLM, (208) 524-7524
Local Contacts
Hike and explore a lava/desert playground close to Idaho Falls.
Local Maps

Activity Feed

Jul 2018