Spatter Cones and North Crater Area Regulations

National Park Service
U.S. Department of the Interior

Superintendent's Compendium
Of Designations, Closures, Permit
Requirements and Other Restrictions
Imposed Under Discretionary Authority.

James A. Morris, Superintendent

Craters of the Moon
National Monument
18 m SW of Arco, Hwy 93
P.O. Box 29
Arco, ID 83213

208-527-3257 phone
208-527-3073 fax

CRMO Superintendent's Compendium

Determination based upon 36 CFR 1.5 (a)(1), 1.5(c) Closures and Public Use Limits and 1.6 (a) Permits

Off-trail travel is prohibited in the Spatter Cones/Big Craters area and in the North Crater Flow Trail area.

Spatter Cones: The spatter cones are the icons of the monument, but by their very nature of formation are fragile and vulnerable to damage. Comparison of modern photographs with historic photographs shows a loss of elevation of approximately two feet as a result of anthropogenic disturbance. The spatter cones are steep sided and poorly consolidated, which not only makes them vulnerable to human damage, but also makes them hazardous for humans to climb on because individual globs of ejecta being used for hand or foot holds can break loose easily. In addition, the spatter cone vents have connections to the Great Rift in the subsurface. But, these passages can be blocked by snow, rock fall, or snow and rock fall plugs (like usually seen at snow cone), which can fail resulting in a precipitous fall of 75 ft. or more. Also, some of the deeper vents are lined with delicate mineral encrustation and vulnerable to damage by climbers. Both because of the vulnerability of the monument's icon geologic features to damage and also because of safety concerns the spatter cones area is closed to off-trail use.

Big Craters: The northeast rim of Big Craters represents a significant falling hazard. Parts of the rim are fairly well agglutinated, while other parts are loose cinder. It is not hard to picture someone starting to slide on the rim and not being able to stop before the precipitous drop into the crater. Most of the sides of the cone complex are at the normal angle of repose and some zones armored with spatter are above the normal angle of repose. This makes them particularly vulnerable to downslope movement, the passage of a single person can generate a trail and puts the hiker at physical risk. For protection of the cinder cone and human safety the cone complex is closed to pedestrian traffic with the exception of the southwest rim trail.

North Crater Flow Trail: This trail is one of the most highly used trails in the monument, seeing tens of thousands of visitors per year. It showcases pahoehoe ropes, which are fragile and vulnerable to destruction. It also showcases a pressure ridge with outstanding squeeze-ups of lava that came up along the tension fracture in the top of the ridge and poured down the side. In the past there was a squeeze up in this area know as the "Devil's Sewer", but it was lost due to human vandalism. Glassy surface crusts on the pahoehoe are also vulnerable to damage from foot traffic. To protect these resources, the North Crater Flow Trail area is closed to off trail use.

map of closed area

map of closed area


Last updated: February 28, 2015

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Mailing Address:

Craters of the Moon National Monument and Preserve
P.O. Box 29

Arco, ID 83213


(208) 527-1300

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