The Snake River Plain sprawls across southern Idaho, a volcanic terrain built over millions of years. In places, this plain is 60 miles wide, with basalt lava deposits plunging more than 10,000 feet deep. The Great Rift volcanic rift zone cuts through the monument and preserve, a fracture in the Earth's crust that has produced eight major eruptive periods over the past 15,000 years. The most recent activity at Craters of the Moon and the nearby Wapi lava fields occurred roughly 2,000 years ago. Geologically speaking, this is practically yesterday. The landscape tells the story: cinder cones, spatter cones, lava tubes, and multiple types of lava flows frozen in time, waiting for the next chapter.

Despite appearances, this seemingly barren landscape supports more than 660 types of plants and 280 animal species. The key lies in the kipukas, islands of older vegetation surrounded by newer lava flows. When molten rock poured across the landscape, it sometimes flowed around higher ground, leaving pockets of untouched soil and plants. These refuges now protect the last intact sagebrush steppe communities on the Snake River Plain. Within this harsh environment, unique subspecies have evolved: a Great Basin pocket mouse, a pika, a yellow pine chipmunk, and a yellow-bellied marmot found nowhere else on Earth. Lava tube beetles and other cave-dwelling creatures exist only in the lava tubes of eastern Idaho.

Over 212 bird species have been sighted on or above the monument. Many are rocky area or shrubland specialists rarely seen in such numbers elsewhere. Small ponds formed by spring rains and snowmelt attract surprising numbers of waterbirds: ducks, geese, shorebirds, herons, and gulls. Swans pass through regularly during spring migration to Canada. The shrublands support Brewer's Sparrows, Sage Sparrows, Sage Thrashers, and Sage Grouse. Even during harsh winters, when temperatures plunge well below freezing and blowing snow blankets the black lava, birds remain. Ravens, nutcrackers, and chickadees live here year-round. Some winters bring arctic visitors: Snowy Owls and Gyrfalcons hunting above the frozen flows.

Weather at Craters of the Moon runs to extremes. The monument spans from the foothills of the Pioneer Mountains to near the Snake River, and conditions vary dramatically across this range. Annual precipitation drops from 16 inches at the Visitor Center to under 10 inches at the southern boundary. Summer sun bakes the black lava until surface temperatures exceed what most thermometers can measure, while air temperatures climb into the 90s. Drying winds of 15 to 30 miles per hour are daily occurrences. Yet delicate wildflowers burst through the cinder slopes each May and June: pink monkeyflowers, yellow dwarf buckwheats, white bitterroots. The monument was certified as a Dark Sky Park, and at night, far from city lights, the Milky Way arches over lava formations that look appropriately lunar.

The monument's lava tube caves offer some of its most fascinating exploration. Formed when the outer surface of flowing lava cooled and hardened while molten rock continued flowing beneath, these tubes now provide pitch-black corridors into the volcanic underworld. Exploring them requires preparation: at least three light sources per person, sturdy thick-soled shoes, and a hard helmet to protect against rough, sharp surfaces above and below. The 7-mile Loop Road connects the park's major attractions above ground, but below the surface lies another world entirely. Echo Crater in the backcountry draws the adventurous, though hikers must carry at least a gallon of water per person per day. The black cinder ground absorbs heat rapidly, and there is no water source in the wilderness.