Craters of the Moon National Monument and Preserve is a national monument and national preserve located in the Snake River Plain in central Idaho, near the small town of Arco. The protected area's features are volcanic and represent one of the best preserved flood basalt areas in the continental United States.
The Monument was established on May 2, 1924. In November 2000, a Presidential proclamation greatly expanded the Monument area. The National Park Service portions of the expanded Monument were designated as Craters of the Moon National Preserve in August 2002. It lies in parts of Blaine, Butte, Lincoln, Minidoka, and Power counties. The area is managed cooperatively by the National Park Service and the Bureau of Land Management (BLM).
The Monument and Preserve encompass three major lava fields and about of sagebrush steppe grasslands to cover a total area of . All three lava fields lie along the Great Rift of Idaho, with some of the best examples of open rift cracks in the world, including the deepest known on Earth at . There are excellent examples of almost every variety of basaltic lava as well as tree molds (cavities left by lava-incinerated trees), lava tubes (a type of cave), and many other volcanic features.
The Craters of the Moon Lava Field spreads across and is the largest mostly Holocene-aged basaltic lava field in the lower 48 U.S. states. The Monument and Preserve contain more than 25 volcanic cones including outstanding examples of spatter cones. The 60 distinct lava flows that form the Craters of the Moon Lava Field range in age from 15,000 to just 2,000 years. The Kings Bowl and Wapi lava fields, both about 2,200 years old, are part of the National Preserve.
Craters of the Moon Lava Field reaches southeastward from the Pioneer Mountains. This lava field is the largest of several large beds of lava that erupted from the south-east to north-west trending Great Rift volcanic zone—a line of weakness in the Earth's crust created by Basin and Range rifting. Together with fields from other fissures they make up the Lava Beds of Idaho, which in turn are located within the much larger Snake River Plain volcanic province. The Great Rift almost extends across the entire Snake River Plain.
The rugged landscape remains remote and undeveloped with only one paved road across the northern end. Craters of the Moon is located in south-central Idaho midway between Boise and Yellowstone National Park and its elevation at the visitor center is above sea level. Combined U.S. Highway 20-26-93 cuts through the north-western part of the monument and provides access to it.
Total average precipitation in the Craters of the Moon area is between 15 to 20 inches (400 to 500 mm) per year. Most of this is lost in cracks in the basalt, only to emerge later in springs and seeps in the walls of the Snake River Canyon. Older lava fields on the plain have been invaded by drought-resistant plants such as sagebrush, while younger fields, such as Craters of the Moon, only have a seasonal and very sparse cover of vegetation. In fact, from a distance this cover disappears almost entirely, giving an impression of utter black desolation. Repeated lava flows over the last 15,000 years have raised the land surface enough to expose it to the prevailing southwesterly winds, which help to keep the area dry. Together these conditions make life on the lava field difficult.
Pioneers traveling in wagon trains on the Oregon Trail in the 1850s and 1860s followed an alternate route in the area that used old Indian trails that skirted the lava flows. This alternate route was later named Goodale's Cutoff and part of it is located in the northern part of the monument. The cutoff was created to reduce the possibility of ambush by Shoshone warriors along the Snake River such as the one that occurred at Massacre Rocks, which today is memorialized in Idaho's Massacre Rocks State Park.
After gold was discovered in the Salmon River area of Idaho a group of emigrants persuaded an Illinois-born trapper and trader named Tim Goodale to lead them through the cutoff. A large wagon train left in July 1862 and met up with more wagons at Craters of the Moon Lava Field. Numbering 795 men and 300 women and children, the unusually large group was relatively unmolested during its journey and named the cutoff for their guide. Improvements to the cutoff such as adding a ferry to cross the Snake River made it into a popular alternate route of the Oregon Trail.
United States Army Captain and western explorer B.L.E. Bonneville visited the lava fields and other places in the West in the 19th century and wrote about his experiences in his diaries. Washington Irving later used Bonneville's diaries to write the Adventures of Captain Bonneville, saying this unnamed lava field is a place "where nothing meets the eye but a desolate and awful waste, where no grass grows nor water runs, and where nothing is to be seen but lava.
In 1901 and 1903, Israel Russell became the first geologist to study this area while surveying it for the United States Geological Survey (USGS). In 1910, Samuel Paisley continued Russell's work and later became the monument's first custodian. Others followed and in time much of the mystery surrounding this and the other Lava Beds of Idaho was lifted.
The few Caucasians who visited the area in the 19th century created local legends that it looked like the surface of the Moon. Geologists Harold T. Stearns coined the name "Craters of the Moon" in 1923 while trying to convince the National Park Service to recommend protection of the area in a national monument.
Limbert set out on his third and most ambitious foray to the area in 1924, this time with W.C. Cole and an Airedale Terrier to accompany him. Starting from Minidoka, Idaho, they explored what is now the monument area from south to north passing Two Point Butte, Echo Crater, Big Craters, North Crater Flow, and out of the lava field through the Yellowstone Park and Lincoln Highway (now known as the Old Arco-Carey Road). Taking the dog along was a mistake, Limbert wrote, "for after three days' travel his feet were worn and bleeding".
A series of newspaper and magazine articles authored by Limbert were later published about this and previous treks, which increased public awareness of the area. The most famous of these was an article that appeared in a 1924 issue of National Geographic where he called the area "Craters of the Moon," helping to solidify the use of that name. In the article he had this to say about the cobalt blue of the Blue Dragon Flows:
In large part due to Limbert's work, Craters of the Moon National Monument was proclaimed on May 2, 1924 by U.S. President Calvin Coolidge to "preserve the unusual and weird volcanic formations". The Craters Inn and several cabins were built in 1927 for the convenience of visitors. The Mission 66 Program initiated construction of today's road system, visitor center, shop, campground and comfort station in 1956 and in 1959 the Craters of the Moon Natural History Association was formed to assist the monument in educational activities. The addition of an island of vegetation completely surrounded by lava known as Carey Kipuka (Carey Kipuka.jpg) increased the size of the monument by in 1962.
Since then the monument has been enlarged. On October 23, 1970 the United States Congress set aside a large part of it——as Craters of the Moon National Wilderness, protecting that part under the National Wilderness Preservation System.
Much later NASA visited the real Moon through the Apollo program and found that its surface does not closely resemble this part of Idaho. NASA astronauts discovered that real Moon craters were almost all created by impacting meteorites while their namesakes on Earth were created by volcanic eruptions; both are desolate. Apollo astronauts performed part of their training at Craters of the Moon Lava Field by learning to look for and collect good rock specimens in an unfamiliar and harsh environment.
For many years, geologists, biologists and environmentalists have advocated for expansion of the monument and its transformation into a national park. Part of that goal was reached in 2000 when the monument was expanded 13-fold from to its current size in order to encompass the entire Great Rift zone and its three lava fields. The entire addition is called the Backcountry Area while the two older parts are called the Developed Area and Wilderness Area. Opposition by cattle interests and hunters to a simple expansion plan led to a compromise of having the addition become a national preserve in 2002 (which allows hunting, not ordinarily permitted in national parks and monuments in the U.S.). Craters of the Moon National Monument and Preserve is co-managed by the National Park Service and the Bureau of Land Management.
The Snake River Plain is a volcanic province that was created by a series of cataclysmic caldera-forming super-eruptions which started about 15 million years ago. A migrating hotspot thought to now exist under Yellowstone Caldera in Yellowstone National Park has been implicated. This hot spot was under the Craters of the Moon area some 10 to 11 million years ago but 'moved' as the North American Plate migrated southwestward. Pressure from the hot spot heaves the land surface up, creating fault-block mountains. After the hot spot passes the pressure is released and the land subsides.
Leftover heat from this hot spot was later liberated by Basin and Range-associated rifting and created the many overlapping lava flows that make up the Lava Beds of Idaho. The largest rift zone is the Great Rift; it is from this fissure system that Craters of the Moon, Kings Bowl, and Wapi lava fields were created.
In spite of their fresh appearance, the oldest flows in the Craters of the Moon Lava Field are 15,000 years old and the youngest erupted about 2000 years ago, according to Mel Kuntz and other USGS geologists. Nevertheless the volcanic fissures at Craters of the Moon are considered to be dormant, not extinct and are expected to erupt sometime during the next thousand years. There are eight major eruptive periods recognized in the Craters of the Moon Lava Field. Each period lasted about 1000 years or less and were separated by relatively quiet periods that lasted between a 500 to as long as 3000 years.
Kings Bowl Lava Field erupted during a single fissure eruption on the southern part of the Great Rift about 2,250 years ago. This eruption probably lasted only a few hours to a few days. The field preserves explosion pits, lava lakes, squeeze-ups, basalt mounds, and an ash blanket. The Wapi Lava Field probably formed from a fissure eruption at the same time as the Kings Bowl eruption. More prolonged activity over a period of months to a few years led to the formation of low shield volcano in the Wapi field. The Bear Trap lava tube, located between the Craters of the Moon and the Wapi lava fields, is a cave system more than long. The lava tube is remarkable for its length and for the number of well-preserved lava cave features, such as lava stalactites and curbs, the latter marking high stands of the flowing lava forever frozen on the lava tube walls. The lava tubes and pit craters of the monument are known for their unusual preservation of winter ice and snow into the hot summer months, due to shielding from the sun and the insulating properties of basalt.
A typical eruption along the Great Rift and similar basaltic rift systems in starts with a curtain of very fluid lava shooting up to high along a segment of the rift up to long. As the eruption continues pressure and heat decrease and the chemistry of the lava becomes slightly more silica rich. The curtain of lava responds by breaking apart into separate vents. Various types of volcanos may form at these vents; gas-rich pulverized lava creates cinder cones (such as Inferno Cone – stop 4) and pasty lava blobs form spatter cones (such as Spatter Cones – stop 5). Later stages of an eruption push lava streams out through the side or bottom of cinder cones, which usually ends the life of the cinder cone (North Crater, Watchmen, and Sheep Trail Butte are notable exceptions). This will sometimes breach part of the cone and carry it away as large and craggy blocks of cinder (as seen at North Crater Flow – stop 2 – and Devils Orchard – stop 3). Solid crust forms over lava streams and lava tubes (a type of cave) are created when lava vacates its course (examples can be seen at the Cave Area – stop 7).
Geologists feared that a large earthquake that shook Borah Peak, Idaho's tallest mountain, in 1983 would restart volcanic activity at Craters of the Moon, though this proved not to be the case. Geologists predict that the area will experience its next eruption some time in the next 900 years with the most likely period in the next 100 years.
All plants and animals that live in and around Craters of the Moon are under great environmental stress due to constant dry winds and heat-absorbing black lavas that tend to quickly sap water from living things. Summer soil temperatures often exceed 150 °F (65 °C) and plant cover is generally less than 5% on cinder cones and about 15% over the entire monument. Adaptation is therefore necessary for survival in this semi-arid harsh climate.
Water is usually only found deep inside holes at the bottom of blow-out craters. Animals therefore get the moisture they need directly from their food. The black soil on and around cinder cones does not hold moisture for long, making it difficult for plants to establish themselves. Soil particles first develop from direct rock decomposition by lichens and typically collect in crevices in lava flows. Successively more complex plants then colonize the microhabitat created by the increasingly-productive soil.
The shaded north slopes of cinder cones provide more protection from direct sunlight and prevailing southwesterly winds and also have a more persistent snow cover (an important water source in early spring). These parts of cinder cones are therefore colonized by plants first.
Gaps between lava flows were sometimes cut-off from surrounding vegetation. These literal islands of habitat are called kipukas, a Hawaiian name used for older land surrounded by younger lava. Carey Kipuka is one such area in the southernmost part of the monument and is used as a benchmark to measure how plant cover has changed in less pristine parts of southern Idaho.
A common plant seen on the lava field is the Dwarf Buckwheat (Drawf Buckweat at Craters of the Moon National Monument.jpeg), a flowering plant tall with a root system wide. The root system monopolizes soil moisture in its immediate area, resulting in individual plants that are evenly spaced. Consequently, many visitors have asked park rangers if the buckwheat were systematically planted.
Wildflowers bloom from early May to late September but most are gone by late August. Moisture from snow-melt along with some rainfall in late spring kick-starts the germination of annual plants, including wildflowers. Most of these plants complete their entire life cycle in the few months each year that moisture levels are good. The onset of summer decreases the number of wildflowers and by autumn only the tiny yellow flowers of sagebrush and rabbitbrush remain. Some wildflowers that grow in the area are the Arrow-leaved Balsamroot, Bitterroot, Blazing Star, Desert Parsley, Dwarf Monkeyflower, Paintbrush, Scorpionweed, Scabland Penstemon] and the Wild Onion.
Most desert animals are nocturnal, or mainly active at night. Nocturnal behavior is an adaptation to both predation and hot summer daytime temperatures. Nocturnal animals at Craters of the Moon include woodrats (also called packrats), skunks, foxes, bobcats, mountain lions, bats, nighthawks, owls, and most other small desert rodents.
Animals that are most active at dawn and dusk, when temperatures are cooler than mid-day, are called crepuscular. The subdued morning and evening light helps make them less visible to predators, but is bright enough to allow them to locate food. Some animals are crepuscular mainly because their prey is. Crepuscular animals in the area include mule deer, coyotes, porcupines, Mountain Cottontails, jackrabbits, and many songbirds.
Many animals have a specific temperature range where they are active, meaning the times they are active vary with the seasons. Snakes and lizards hibernate during the winter months, are diurnal during the late spring and early fall, and become crepuscular during the heat of summer. Many insects and some birds also alter their times of activity. Some animals, like ground squirrels and marmots, have one or more periods of estivation, a summer hibernation that allows them to avoid the hottest and driest periods.
Several animals are unique to Craters of the Moon and the surrounding area. Subspecies of Great Basin Pocket Mouse, pika, Yellow-pine Chipmunk, and Yellow-bellied Marmot are found nowhere else. Lava tube beetles and many other cave animals are found only in the lava tubes of eastern Idaho.
The deer arrive in the southern part of the pre-2000 extent of the monument mid-April each year once winter snows have melted away enough to allow for foraging. Griffith found that by late summer plants in the area have already matured and dried to the point that they can no longer provide enough moisture to sustain the deer. In late July after about 12 days above and warm nights above the herd migrates 5 to 10 miles (8 to 16 km) north to the Pioneer Mountains to obtain water from free-flowing streams and shade themselves in aspen and Douglas-fir groves. Rain in late September prompts the herd to return to the monument to feed on bitterbrush until snow in November triggers them to migrate back to their winter range. This herd, therefore, has a dual summer range. It is also very productive with one of the highest fawn survival rates of any herd in the species.
Afternoon winds usually die down in the evening, prompting behavioral modifications in the herd. The deer avoid the dry wind by being more active at night when the wind is not blowing. In 1991 there was a three-year average of 420 Mule Deer.
A series of fissure vents, cinder cones, spatter cones, rafted blocks, and overlapping lava flows are accessible from the Loop Drive, long. Wildflowers, shrubs, trees, and wild animals can be seen by hiking on one of the many trails in the monument or by just pulling over into one of the turn-offs. More rugged hiking opportunities are available in the Craters of the Moon Wilderness Area and Backcountry Area, the roadless southern and major part of the monument.
Craters of the Moon Campground has 51 sites – none of which can be reserved in advance. Camping facilities are basic but do include water, restrooms, charcoal grills, and trash containers. National Park Service rangers present evening programs at the campground amphitheater in the summer.
Backcountry hiking is available in the Craters of the Moon Wilderness and the much larger Backcountry Area beyond (added in 2000). Only two trails enter the wilderness area and even those stop after a few miles or kilometers. From there most hikers follow the Great Rift and explore its series of seldom-visited volcanic features. All overnight backcountry hikes require registration with a ranger. No drinking water is available in the backcountry and the dry climate quickly dehydrates hikers. Avoiding summer heat and winter cold are therefore recommended by rangers. Pets, camp fires, and all mechanized vehicles, including bicycles, are not allowed in the wilderness area.
Skiing is allowed on the Loop Drive after it is closed to traffic in late November due to snow drifts. Typically there are 20 inches (50 cm) of snow by January and 25 in (60 cm) by February. Cross-country skiing off of Loop Drive is allowed but may be dangerous due to sharp lava and hidden holes under the snow. Blizzards and other inclement weather may occur.