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Crater Rings – Cleft, Idaho
Crater Rings – Cleft, Idaho

A volcanic crater (also A crater (also called a collapse crater or a crater-in-slump crater) is formed when subsurface magma supporting the rock above it drains away for some reason. The unsupported rock cover above the cavity created by the draining magma then collapses. (A similar mechanism is responsible for the formation of caldera craters on mountain peaks, but these are usually larger.)

A subsidence crater can be distinguished from other craters such as maars (e.g. Soda Lakes in Nevada) or impact craters because it does not have a raised rim made of debris ejected from the crater. In addition, they typically have a flat floor, indicating the former existence of a lava lake.

Crater Rings are two collapse craters on a low, broad shield volcano that is thought to be geologically young (less than about two million years old). The eastern crater is about half a mile wide and 300 feet deep, while the western one is slightly smaller and shallower (about 200 feet deep).

This shield volcano is located in the Snake River Plain north of Mountain Home, Idaho, an area that has experienced abundant volcanic activity in the recent geologic past. Despite the ubiquitous volcanism, however, subsidence craters such as this one are rare in these volcanic fields.

Things to know before your trip

The crater rings are located just off Interstate 84 north of Mountain Home, Idaho. Drive north on old US-30 (Old Oregon Trail Highway) 9.1 miles from the intersection with Idaho State Route 51 (American Legion Boulevard) in downtown Mountain Home to an intersection (at approximately 43.21878 N, 115.82268 W) with Cinder Butte Road. Turn left here and follow Cinder Butte Road (which is graded) 1.8 miles to an intersection (at approximately 43.21506 N, 115.85748 W) with a dirt road on the left. Turn left here; the crater rings are located in the low rise that forms the skyline. Drive approximately 1.4 miles and park. This road requires high clearance, but in dry weather, 4WD is probably not necessary. Jeep roads lead around the craters, but they can also be explored on foot.

The ground is all low grass and shrubs. Ryegrass is common, a non-native species whose seeds, when dry, lodge in clothing (such as socks) and also in the fur of pets. Ryegrass is also extremely flammable and has led to more frequent and devastating wildfires in recent years. Be very careful with fire; especially do not park on dry grass as it is easily ignited by a hot catalytic converter.

By Everly