Lava River Cave: Exploring Arizona’s Subterranean Lava Tube

Beneath the ponderosa pine forests of northern Arizona, a hidden tunnel stretches through the earth—a remnant of a fiery past frozen in time. Known as the Lava River Cave, this natural underground corridor was carved not by water or ice, but by molten lava, making it one of the most accessible and striking lava tubes in the American Southwest.

Located in the Coconino National Forest, about 14 miles northwest of Flagstaff, the Lava River Cave offers a unique opportunity to walk inside a geologic phenomenon that began nearly 700,000 years ago.

The Birth of a Lava Tube

The Lava River Cave formed during a volcanic eruption in the San Francisco Volcanic Field, a region dotted with more than 600 volcanic cones and other igneous features. As lava spewed from a vent, it flowed down the slope in a molten stream. The outer layer of the lava cooled and solidified quickly, while the inner lava continued to flow—insulated by the hardened shell around it.

Eventually, when the eruption subsided and the lava source stopped, the still-molten interior drained away, leaving behind an empty tube: a lava cave over 0.75 miles (1.27 kilometers) in length.

This kind of lava tube is rare in the continental United States, and even rarer to find one so intact and open to the public. Inside, the cave maintains a steady temperature of about 40°F (4°C) year-round, creating a cool escape from Arizona’s summer heat.

Inside the Tunnel of Fire

Visitors to the Lava River Cave must come prepared—there’s no artificial lighting or paved walkways. Entry is via a rocky opening in the forest floor, and the interior terrain is rugged, with uneven surfaces, low ceilings, and spots where crawling is required. Headlamps, sturdy shoes, and layered clothing are essential.

Once inside, explorers are greeted by a world of darkness and basalt. The walls and ceiling bear the frozen ripples of flowing lava, with patterns that reveal the speed and movement of the ancient molten river. In some areas, the cave’s ceiling is over 30 feet high; in others, it narrows to just a few feet.

There are no stalactites or underground rivers here—only silence, stone, and the echo of ancient volcanic activity.

Scientific Significance and Public Access

For geologists, the Lava River Cave offers a rare opportunity to study volcanic processes, particularly the way basaltic lava behaves during eruptions. The tube preserves features such as lavacicles (lava drips from the ceiling), benches (indicating changing flow levels), and shelving, all of which contribute to our understanding of igneous geomorphology.

The cave is managed by the U.S. Forest Service and remains open to the public, though entirely undeveloped—meaning it retains its raw, natural condition. While this allows for a true wilderness experience, it also places responsibility on visitors to respect and preserve the cave.

Graffiti and vandalism have posed challenges in the past, prompting calls for greater stewardship and education.

A Journey into Arizona’s Fiery Past

The Lava River Cave is a tangible reminder that Arizona’s landscapes were once forged in fire and upheaval. Walking its path is like stepping backward into a time when lava flowed freely across the land, reshaping everything in its path.

Unlike the sandstone canyons and sunbaked deserts typically associated with the state, this underground corridor reveals another side of Arizona—cool, dark, volcanic, and deeply ancient.

It’s not just an adventure—it’s an immersion in geologic history, where every twist and ripple in the stone marks a moment in the Earth’s restless evolution.