Craters of the Moon National Monument and Preserve

Lore & Background

Craters of the Moon National Monument and Preserve is located in south-central Idaho, on the Snake River Plain, along U.S. Highway 20 between the towns of Arco and Carey. The area consists of three major lava fields and sagebrush steppe grasslands, covering over 400,000 acres across five counties. These lava fields are part of the Great Rift of Idaho, a long zone of crustal weakness. The landscape features numerous volcanic cones, including well-preserved spatter cones, and more than 60 distinct solidified lava flows that range in age from 15,000 to about 2,000 years old. Among the volcanic features are basaltic lava varieties, tree molds left by incinerated trees, lava tubes, and open rift cracks, one of which is the deepest known on Earth. The younger lava fields support very sparse, seasonal vegetation, appearing from a distance as a black, desolate expanse. Most precipitation is lost into cracks in the basalt, later emerging as springs in the Snake River Canyon. The monument and preserve are managed jointly by the National Park Service and the Bureau of Land Management.

Reader's Guide

Craters of the Moon National Monument and Preserve is significant as a well-preserved example of basaltic volcanic activity in the contiguous United States, with lava fields, cones, tubes, and tree molds. The area was visited by Paleo-Indians about 12,000 years ago and later used by the Northern Shoshone during summer migrations. Emigrants on the Oregon Trail used an alternative route called Goodale's Cutoff, which skirts the lava flows. The area remains remote and undeveloped, with only one paved road across the northern end. Its harsh conditions—dry, with sparse vegetation—make it a unique landscape for studying volcanic geology and adaptation.

Did You Know?

• The Northern Shoshone created trails through the lava field during summer migrations and built stone circles visible near Indian Tunnel.

Volcanic Architecture and the Great Rift

The landscape at Craters of the Moon is the product of repeated eruptions along a 53-mile line of crustal weakness known as the Great Rift of Idaho. Stretching from southeast to northwest across nearly the entire Snake River Plain, this volcanic zone has produced multiple large lava beds that together form the broader Lava Beds of Idaho. The Craters of the Moon Lava Field alone spans 618 square miles, making it the largest predominantly Holocene-aged basaltic lava field in the contiguous United States. Within its boundaries, more than twenty-five volcanic cones rise from the terrain, with particularly striking examples of spatter cones. Sixty distinct solidified lava flows, ranging in age from roughly 15,000 years to just 2,000 years, layer across the surface. The Kings Bowl and Wapi fields, both approximately 2,200 years old, add further volcanic diversity. Among the site's most remarkable features is the deepest known open rift crack on Earth, plunging 800 feet into the ground. Visitors encounter basaltic lava in varied forms, tree molds where ancient trunks were incinerated and left hollow cavities, and lava tubes that function as natural caves.

Indigenous Presence and Oral Memory of Fire

Paleo-Indians moved through this region roughly 12,000 years ago, though they left behind very little in the way of archaeological traces. The Northern Shoshone, a hunter-gatherer people, later carved trails through the lava field during their seasonal summer migrations from the Snake River toward the camas prairie lying to the west. They never established permanent settlements here, but their connection to the land was deep and practical. They gathered edible plants, nuts, roots, and berries, and hunted a wide spectrum of game. Larger animals such as elk, mule deer, pronghorns, bison, bears, cougars, and bighorn sheep provided meat and hides for shelters and windbreaks. Smaller species—squirrel, red fox, coyote, river otter, raccoon, pine marten, rabbit, and various birds—supplied delicate furs for clothing. Stone circles still visible near Indian Tunnel mark their presence. Perhaps most poignantly, the most recent eruptions, ending around 2,100 years ago, were almost certainly witnessed by the Shoshone. Ella E. Clark recorded their oral account: a serpent dwelling on a mountain, enraged by lightning, coiled its body around the peak and squeezed until liquid rock burst forth, fire erupted from cracks, and the mountain exploded.

From Presidential Proclamation to Dual Stewardship

The site's protected status began on May 2, 1924, when it was established as a national monument. For nearly eight decades it remained a relatively modest unit, but in November 2000 President Clinton issued a presidential proclamation that dramatically expanded the boundaries. The following year, in August 2002, the 410,000-acre National Park Service portions of the enlarged area received the formal designation of Craters of the Moon National Preserve. The monument alone encompasses 343,000 acres, and together the monument and preserve stretch across five counties—Blaine, Butte, Lincoln, Minidoka, and Power—covering a combined 1,117 square miles. Governance is a cooperative arrangement between the National Park Service and the Bureau of Land Management, reflecting the mixed federal and public lands within the boundary. Geographically, the site sits in south-central Idaho, roughly midway between Boise and Yellowstone National Park, at an average elevation near 5,900 feet. Access runs along the combined US 20–26–93 corridor between the small towns of Arco and Carey, yet the interior remains rugged and remote, with only a single paved road crossing the northern end.

A Landscape Shaped by Aridity and Wind

The ecology of Craters of the Moon is defined by scarcity. Total annual precipitation in the area falls between 15 and 20 inches, but the fractured basalt surface swallows most of that water into its cracks, where it eventually resurfaces as springs and seeps far away in the walls of the Snake River Canyon. The result is a landscape where water, though technically present, is largely unavailable to surface life. Older lava fields scattered across the Snake River Plain support drought-resistant vegetation such as sagebrush, but the younger flows at Craters of the Moon—some only 2,000 years old—host merely a seasonal and extremely sparse cover of plants. Viewed from a distance, that thin green layer vanishes almost entirely, leaving an impression of utter black desolation stretching to the horizon. Repeated eruptions over the past 15,000 years have also raised the land surface enough to expose it fully to the prevailing southwesterly winds, which sweep across the plain and keep the air dry. The combination of porous ground, relentless wind, and limited moisture makes survival on the lava field genuinely difficult for most organisms.