Craters of the Moon National Park
Unique Volcanic Formations Highlight this Central Idaho Monument
Craters of the Moon National Monument is operated by the National Park Service. Visitors may see remnants of once live volcanoes in formations throughout the park.
One of the most unique travel destinations in Idaho is Craters of the Moon National Monument. The monument consists of various lava formations left over from an ancient volcano. In 1924, part of the lava field was protected as Craters of the Moon National Monument, under the Antiquities Act by President Calvin Coolidge. The name was first suggested in 1923 by geologist Harold T. Stearns, who found the landscape similar to the surface of the moon as seen through a telescope. Robert Limbert used the name in a 1924 National Geographic article.
The volcanic activity that created the area lasted between 17,000 and 2,000 years ago. The lava field starts from the base of the Pioneer Mountains and flow southeast. Newer basaltic layers are about one-half mile thick, and older rhyolitic layers are about one and a half miles thick. These layers stretch across the Snake River Plains of southern Idaho.
The monument has 83 square miles, though the lava field is much larger. The park includes 53,545 acres. Tourists can take the seven mile loop drive to explore the monument. The northern part of the monument has spatter cones, cinder cones, lava flows, and lava caves. There are several short nature walks to some of the more prominent features. The southern part is mainly wilderness and contains untraveled volcanic features used by serious hikers and explorers.
Though the main features are the volcanic formations, there is plant and animal life here. Pines, cedars, junipers, and sagebrush grow here. There are pikas, woodchucks, and the occasional bear. There are bats, rats, beetles, horned owls, swallows, and ravens. Flora and fauna adapt to the dryness as the wind blows constantly, soils are shallow, and cinders do not hold water. Black lava absorbs summer heat and reaches temperatures of 150 degrees F.
Interesting features along the loop drive include fields of both main types of lava. Pahoehoe lava, a Hawaiian term meaning ropey, hardens quickly into a smooth surface that can be billowy, flat, or sometimes rope like. Aa lava, is a Hawaiian term meaning rough. This lava is much more rugged and is dense and glassy.
There are also lava bombs, pieces blown out of craters that solidify in the air. Tree molds form when lava surrounds a tree and makes an impression of the bark in the lava. Cinder cones form around vents where cinders were thrown into the air. Big Cinder Butte is 700 feet high and is the tallest cone in the park. Other features include North Crater, the Watchman, Sheep Trail Butte, Grassy Cone, Paisley Cone, Sunset Cone, and Inferno Cone. Lava tubes form when the surface starts to harden in the cooler air, while the interior part of the lava flow keeps moving. There are such lava cave systems all over the monument, some of which can be explored. There are also spatter cones, created when pieces of lava coming out of the vent are globs and clots that partially weld together. These cones are less than 50 feet high and 100 feet in diameter.
Though you may be tempted, do not leave the paved drive. Cars crush the cinders and leave an impression that will last for years. Pedestrians should heed the same advice, as the lava is sharp and can cut your shoes and your body if you fall. There is no natural water onsite nor are there any nearby stores. The area is very dry with steady winds. Summers can be hot, but thunderstorms can form at any time. Fall and Spring are better for hiking but the temperature can be very unpredictable. Snow closes the park in winter, though the visitor center is open most of the year. Cross country skiing is allowed in the park with permits. There are also ranger programs during the summer. As with most sites managed by the National Park Service there is a vehicle entry fee. It is worth it to get a first-hand view of the power of a volcano.
(Source: Craters of the Moon Handbook, Handbook 139, published by the National Park Service, 1991)
