Last updated: April 4, 2024
Article
Life Among the Lava Flows
NPS Photo
Rocks from recent volcanic eruptions dominate the landscape of Craters of the Moon. The Great Rift, a 52 mile long series of volcanic fissures, is responsible for these eruptions that occurred between 15,000 and 2,100 years ago. The eruptions are stacked on top of each other which creates a patchwork of lava flows of different ages, types, and surface textures. While seemigly barren at first glance, this lava field that spans 618 square miles hosts an amazing variety of organisms that occupy every niche.
After each eruption, plants and animals began to return to the area while the lava fields were still cooling. Some species, like bighorn sheep and grizzly bears, have been gone for almost 100 years, but most continue to thrive. Windblown soils provide an important habitat for the plant communities that thrive here including the once widespread sagebrush steppe. In addition to large areas of sagebrush steppe, the park also contains numerous kipukas, isolated islands of vegetation protected by surrounding lava flows that act as small, undisturbed havens for native plants and animals.
Rugged terrain and a lack of water have discouraged people from altering the area with the roads, buildings, farms, and powerlines that occupy much of the present day Snake River Plain, so Craters of the Moon remains largely untouched.
NPS Photo
Lava Flows
Lava flows can vary greatly from one another at Craters of the Moon. Some lava flows are very dense and have a surface of angular blocks referred to as block lava. Others have a rough, jagged surface called a'a lava. Still others have a smooth, ropy, or billowy surface called pahoehoe lava. Most lava seen in the park is pahoehoe.
Unlike places where the climate is warmer year-round and more predictable like Hawai'i, it takes thousands of years for plants to cover lava flows in the Snake River Plain. The short growing season combined with frequent, gusty winds and hot summers makes this a harsh environment for many organisms. The summer sun can heat the surface of the black rocks to 150°F or more.
Lichen are one of the first organisms to colonize these areas after an eruption, growing at most 1-2 mm in diameter per year. These small but mighty patches of algae and fungi color rocks and trees in nearly every part of the park and are easiest to spot on bare rocks.
Plants usually begin finding places to grow in between the cracks and gaps in the lava flows. Pahoehoe flows that have more cracks and spaces for soil and water to collect create more hospitable habitats than a'a, which does not retain water well. Some lava flows produced small mounds called tumuli or elongated pressure ridges which can have cracks large enough to support water-loving ferns. Eventually, these plants will break down the rocks and create a more suitable habitat for other organisms.
Pikas are an unusual animal to find in this environment, but a unique population of them has adapted to make a living among the lava flows at Craters of the Moon. These small relatives of the rabbit take shelter from the elements in piles of a'a and broken pahoehoe and feed on the plants that grow in these areas. Like chipmunks, marmots, and mice, they benefit from the cooler temperatures and shelter the lava flows provide.
NPS Photo
Lava Tubes
The lava flows along the Great Rift also created lava tubes, a type of cave. During eruptions, hot lava will sometimes continue to flow beneath the surface of cooling lava to create a tunnel. Openings in lava tubes can be created when the roof of the lava tube collapses due to weathering or gravity.
Hundreds of lava tubes have been found at Craters of the Moon, with thousands more remaining unexplored. These tunnels create refuges for life away from the harsh elements of the Snake River Plain. The temperature inside most caves changes very little and basalt makes a good insulator. Some lava tubes contain water or even ice year round, creating underground water holes with natural air conditioning. Water is a precious resource in the high desert, so lava tubes attract a variety of wildlife.
Some insects like lava tube beetles and mites spend their entire lives in these caves. Bats are some of the park's most famous lava tube residents. Craters of the Moon is home to at least 11 species of bats, many of which use lava tubes to hibernate in the winter. Like bats, birds also use lava tubes for shelter. Ravens, pigeons, and violet-green swallows are a few that are often seen near cave entrances. Other small animals like lizards, rodents, weasels, and pikas may make use of lava tubes the same way they use piles of a'a lava.
USFWS Photo / Tom Koerner
Sagebrush Steppe
Sagebrush steppe, the most common vegetation type in the intermountain west, has many names including sagebrush grassland, shrubland, cold desert shrub, and western rangeland. Although there are slight differences in these terms, the common component among them is the presence of shrubs.
As its name suggests, sagebrush dominates many of these communities and occurs in combination with complex mixtures of other shrubs, grasses, and forbs. Factors like climate, soil conditions, parent material, and the shape of the landscape determine the characteristics of shrubland communities. The dominant species of sagebrush in the northern part of Craters of the Moon is mountain big sagebrush. Mountain big sagebrush is widespread throughout the park and is found alongside several types of grasses. Five other species of sagebrush are also found in the park. Other common shrubs are antelope bitterbrush and rubber rabbitbrush. Both of these are common on cinder cones. Sagebrush is common in areas with older geology and where better soils have developed.
The sagebrush steppe ecosystem provides a valuable habitat for wildlife at the park, including sage-grouse, mule deer, pronghorns, songbirds, and small mammals. Protection from both natural barriers and park management help keep many of the park's plant communities in pristine condition.
NPS Photo
Kipukas
Like islands in an ocean of black rock, kipukas dot the lava fields at Craters of the Moon. Kipuka is a Hawaiian term that describes pockets of older, more vegetated lava surrounded by younger lava flows. More than 500 kipukas are found in the park.
A kipuka begins as a slight rise in elevation, a bump in the landscape. During an eruption, high points like hills or older volcanoes may be cut off and separated by the lava flows. Relatively lush with plant life compared to the younger surrounding flows, kipukas are often easy to spot.
In the volcanically active Snake River Plain, this cycle has played out repeatedly over millions of years. Lava erupts to form a gently-sloped shield volcano. The volcano weathers with age, captures wind-blown soil, and develops plant life. Nearby volcanoes unleash rising tides of new lava flows that surround the vegetated summit of the older volcano. Eventually, the sagebrush island is covered by younger flows and the cycle begins again.
More than 500 kipukas are found in the park and range in size from less than one acre up to tens of thousands of acres. Laidlaw Park is the park's largest kipuka at 84,400 acres. Ringed by a narrow, passable strip of lava, this massive kipuka has been altered by roads, grazing, and invasive plants for more than a century. More common are less disturbed kipukas like Carey Kipuka, only a few hundred acres in size and embedded deeper within the protective barrier of rugged lava.
In 1962, John F. Kennedy added Carey Kipuka to the monument with the stroke of his presidential pen. Isolated from the disturbances common in Laidlaw Park and the rest of the Snake River Plain, its unaltered ecosystem became rare and valuable. Biologists today use the kipuka's healthy community of sagebrush and grasses as a model guiding restoration of native vegetation in the monument and beyond. Some of the park's kipukas are also home to some of the oldest juniper trees in Idaho. Carey Kipuka and several other kipukas are now further protected as Research Natural Areas for long-term scientific study. Additional protection came in 2000 when President Clinton expanded the monument, citing the rarity and scientific importance of kipukas among other considerations.
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