Geology

Caves

12 destinations along 11 roads

Caves are what water writes underground. Rain turns faintly acidic, seeps into limestone, and over ages dissolves the rock from within — the same slow chemistry behind the decorated chambers of Timpanogos, the ice pocket at Mossy Cave, and Lehman Caves under Great Basin's peaks. Homestead Crater went warm instead, a geothermal spring domed in its own mineral crust; Grand Canyon Caverns went bone-dry, the largest dry cavern in the country. That one is also a Hualapai burial place, not a curiosity — the ground beneath the road keeps its own meaning.

MT-21

Lewis and Clark Caverns State Park

Whitehall

A limestone cave the Civilian Conservation Corps spent six years making walkable, by the steps, lights and tunnel visitors still use.

Scenic Byway 121

Mossy Cave Trail

Tropic

A hidden waterfall and ice cave just off the highway

SR-171

Lake Lenore Caves

Soap Lake

Shallow shelters in a coulee wall that people used for thousands of years, where the archaeologists who arrived in 1958 found that collectors had dug them over first.

OR-461

Oregon Caves

Cave Junction

A cave of marble rather than limestone, found in 1874 by a hunter who followed his dog in by matchlight and found his way out by the sound of a stream.

US-501

Great Basin National Park

Baker

Nevada's only national park — caves below, the oldest trees on earth above, the darkest skies overhead

NM-531

El Malpais National Monument

Grants

The badlands south of Grants: lava 3,900 years old from McCartys Crater, a tube system at least seventeen miles long, and an old trail across four lava flows between Zuni and Acoma.

US-621

Carlsbad Caverns National Park

Carlsbad

The way into the cave has changed four times: a guano miner's bucket, a wooden staircase, a 750-foot elevator, and now a timed ticket and a switchback trail down the natural entrance.

Historic Route 661

Grand Canyon Caverns

Peach Springs

The largest dry cavern in the country, 210 feet under Route 66 — a Cold War fallout shelter, the deepest hotel room in America, and a Hualapai burial place the tourists once mistook for a sideshow.