Bentonite Hills

Bentonite Hills

Natural Attr
Last Updated: July 2026

Type

Geological Formation

Accessibility

High-clearance 4-wheel-drive vehicle required

Best Season

Spring (April-May) and fall (September-October) offer ideal combinations of reliable road access, comfortable temperatures, and excellent photography conditions.

Busiest Season

Summer months (June-August), though this remote location never experiences heavy crowds.

Features

Softly rounded, multicolored banded hills in shades of gray, red, purple, maroon, brown, and green. Composed of Brushy Basin shale member of the Morrison Formation from the Jurassic period.

Elevation

5,500 ft

Overview

About This Attraction

The Bentonite Hills display softly-contoured, banded ridges in shades of gray, red, purple, maroon, brown, and green—layers within the Jurassic Brushy Basin shale member of the Morrison Formation. These ancient mudstones were deposited as mud, silt, fine sand, and volcanic ash in warm, shallow lakes and swamps approximately 150 million years ago. The distinctive popcorn-like surface texture results from bentonite clay (altered volcanic ash) repeatedly absorbing water, swelling, and then cracking as it dries—a weathering process still active today. Access requires high-clearance 4-wheel-drive vehicles via Hartnet Road, and the fragile surface is easily damaged; every footprint and tire track leaves scars that take years to heal.

Quick Facts

Type

Geological Formation

Elevation

5,500 ft

Access

High-clearance 4-wheel-drive vehicle required

Main Features

Softly rounded, multicolored banded hills in shades of gray, red, purple, maroon, brown, and green. Composed of Brushy Basin shale member of the Morrison Formation from the Jurassic period.

What You'll See

Softly-contoured, banded hills with visible color gradations in gray, red, purple, maroon, brown, and green. The distinctive popcorn-like surface texture created by bentonite clay (altered volcanic ash) expanding and contracting through water-absorption cycles.

What Makes It Special

Composed entirely of bentonite clay (altered Jurassic volcanic ash) from the Morrison Formation. The distinctive fine popcorn-like surface texture develops from ongoing cycles of clay absorbing water, swelling, and then cracking as it dries. This weathering process is geologically active today.

Best Time to Visit

Spring (April-May) and fall (September-October) offer ideal combinations of reliable road access, comfortable temperatures, and excellent photography light. Summer heat is intense and afternoon thunderstorms frequently render clay roads impassable. Winter is generally passable but less reliable after snow.

Safety Considerations

Bentonite clay becomes extremely slick and gummy when wet—travel becomes difficult or impossible. Roads are impassable during and after rain. Never venture off the main road; the surface is easily damaged and scars take years to heal. High-clearance vehicles only. No services or emergency help nearby. Afternoon thunderstorms are common in summer. Call 435-425-3791 before visiting for current road conditions.

Visitor Tips

  • Call 435-425-3791 (press 1 for information, then 4 for road conditions) before visiting—access is highly weather-dependent.
  • Roads become impassable when wet; bentonite clay turns extremely gummy and slippery. Always check the weather forecast.
  • High-clearance 4-wheel-drive vehicle required; standard vehicles risk getting stuck or damaged.
  • Drive slowly to minimize dust and preserve the fragile clay surface.
  • Bring plenty of water and supplies; no services are available.
  • Stay on the main road; footprints and tire tracks scar the surface for years.
  • Visit early morning or late afternoon for best photography light and cooler temperatures.
ℹ️ Data Sources
🏞️ National Park Service 📝 YourNPGuide Editorial

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