NASA sent astronauts to train in central Idaho — and you can walk the same lava fields

It’s Where Fire Met the Moon

Central Idaho has a place where the ground turned to black glass thousands of years ago, and NASA thought it looked enough like the moon to send astronauts here.

Craters of the Moon National Monument and Preserve covers 1,117 square miles of hardened lava flows, cinder cones, and volcanic cracks along the Snake River Plain.

You can climb inside caves carved by molten rock, hike up a cinder cone with views into three mountain ranges, and stargaze under some of the darkest skies in the lower 48. The road in starts easy.

What you find along it gets stranger with every stop.

A 52-mile crack splits the earth 800 feet deep

The Great Rift runs 52 miles through the park, a volcanic crack that drops as deep as 800 feet in places. That makes it one of the deepest open rift cracks on Earth.

Between 15,000 and 2,000 years ago, at least 60 lava flows oozed out of fissures and vents along the rift. No single volcano did this.

The lava came from the ground itself. President Calvin Coolidge established the monument in 1924, calling it a “weird and scenic landscape.”

Those volcanoes below the surface are dormant, not extinct, and geologists expect new eruptions within the next 1,000 years.

The seven-mile loop connects every major stop

A paved seven-mile loop road links all the trailheads and viewpoints in the park.

You can drive the whole thing in 30 minutes, but most people spend three to five hours pulling over to explore cinder cones, lava flows, spatter cones, and cave entrances. Every vehicle can handle the road during the open season.

Snow closes it from roughly November through April, so plan your visit between late spring and early fall.

Inferno Cone gives you views for 100 miles

Inferno Cone is a half-mile round trip, short but steep.

You climb a barren hill of dark cinders to a summit at 6,181 feet, and from the top, you get a full 360-degree view.

The Great Rift stretches below you, the Snake River Plain spreads to the horizon, and the Pioneer Mountains rise to the north. On clear days, you can pick out the Teton Range about 100 miles to the east.

There’s no shade, and those black cinders soak up heat, so bring sun protection.

Walk 800 feet inside a lava tube cave

The park’s lava tube caves formed when flowing lava cooled and hardened on top while molten rock kept moving underneath, then drained away and left hollow tunnels.

Indian Tunnel is the most popular, stretching about 800 feet with collapsed ceiling sections that let in daylight. You need a free cave permit from the visitor center before you go in.

Rangers will check that your clothes and shoes haven’t been worn in other caves, a rule that protects bats from white-nose syndrome.

Cave access changes through the year to protect bat colonies, so check at the visitor center when you arrive.

Lava swallowed trees and left their hollow shapes behind

More than 25 volcanic cones dot the park, including spatter cones you can walk right up to and peer inside. These formed when blobs of molten lava shot into the air and stacked up around a vent.

The Tree Molds Trail, a two-mile round trip, takes you to a place where lava swallowed a forest thousands of years ago. The trees burned away but left hollow molds in the hardened rock.

Some captured trees still standing upright. Others show trunks knocked flat by the flow.

Broken Top Loop packs every volcanic feature into 1.8 miles

This loop trail gives you almost everything the park has in under two miles.

You walk across lava flows, through cinder fields, and past lava bombs, chunks of molten rock that eruptions tossed into the air and that cooled before they hit the ground.

Interpretive signs along the way break down the geology in plain language, so families with kids get a lot out of this one. You pick up the trail at the Tree Molds parking area.

Wildflowers push through lava that hits 170 degrees

The lava fields look lifeless at first glance, but over 700 species of flowering plants grow here.

Dwarf monkeyflower, Indian paintbrush, bitterroot, and dwarf buckwheat push color through the black rock from early May into late September, with peak bloom around mid-June.

The plants survive by sending roots deep through cracks in lava that can reach 170 degrees on the surface. Pockets of older land called kipukas sit surrounded by younger lava flows.

Carey Kipuka preserves some of the only undisturbed natural grassland left on the Snake River Plain.

Three species live here and nowhere else on Earth

A Great Basin pocket mouse, an American pika, and a yellow-pine chipmunk each evolved into subspecies found only in this park.

Down in the lava tubes, beetles and other cave-dwelling invertebrates exist nowhere else in eastern Idaho. Above ground, pronghorn migrate about 100 miles each way through the area between summer and winter ranges.

The park has recorded over 200 bird species, and you might spot mule deer, bobcats, golden-mantled ground squirrels, or prairie falcons on any given visit.

Apollo astronauts learned to read rocks right here

In 1969, NASA sent Apollo astronauts Alan Shepard, Edgar Mitchell, Eugene Cernan, and Joe Engle to Craters of the Moon for geological field training.

Pioneering geologist Eugene Shoemaker guided them, turning test pilots into field geologists who could identify and collect rock samples in rough terrain.

The moon’s craters come from impacts, not volcanoes, but the surface texture and ground conditions were close enough to be useful. NASA scientists still study the park’s lava tubes today.

A 2022 study found they closely resemble lava tubes on Mars.

The Milky Way fills the sky over black lava

Craters of the Moon earned its International Dark Sky Park certification in 2017, and it sits in one of the darkest areas in the continental United States, far from any major city light.

In summer, rangers lead astronomy programs, constellation tours, and Star Parties where volunteer astronomers set up telescopes for public viewing.

The black volcanic landscape in the foreground makes the sky feel even bigger. Star Parties draw hundreds of visitors and typically run from summer through fall.

Devil’s Orchard shows how plants reclaim the rock

This half-mile paved trail loops through a field of lava fragments where native plants have slowly taken hold.

Interpretive signs explain how life gains a foothold in what looks like impossible ground and how human activity has shaped the area over time.

The path is flat and accessible for all ages and ability levels, making it a good first stop if you want a quick look at the landscape before heading deeper into the park. You can finish it in about 20 minutes.

Visit Craters of the Moon in Central Idaho

You can reach Craters of the Moon along US Highway 20/26/93, about 18 miles southwest of Arco, Idaho. Idaho Falls is 84 miles to the east, and Twin Falls sits 90 miles to the south.

Stop at the Robert Limbert Visitor Center first for displays, a park film, ranger info, and your free cave permit. The 51-site Lava Flow Campground sits just past the visitor center if you want to stay the night.

Entrance runs $20 per vehicle, good for seven days, and the America the Beautiful pass gets you in.

This article was created with AI assistance and human editing.

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