Part 2

From Moonscape to Landscape

Geology of the Craters of the Moon

A 400-mile-long arc known as the Snake River Plain cuts a swath from 30 to 125 miles wide across southern Idaho. Idaho’s official state highway map, which depicts mountains with shades of green, shows this arc as white because there is comparatively little variation here compared to most of the state. Upon this plain, immense amounts of lava from within the Earth have been deposited by volcanic activity dating back more than 14 million years. However, some of these lavas, notably those at Craters of the Moon National Monument, emerged from the Earth as recently as 2,000 years ago. Craters of the Moon contains some of the best examples of basaltic volcanism in the world. To understand what happened here, you must understand the Snake River Plain.

Basaltic and Rhyolitic Lavas. The lavas deposited on the Snake River Plain were mainly of two types classified as basaltic and rhyolitic. Magma, the molten rock material beneath the surface of the Earth, issues from a volcano as lava. The composition of this fluid rock material varies. Basaltic lavas are composed of magma originating at the boundary of the Earth’s mantle and its crustal layer. Rhyolitic lavas originate from crustal material. To explain its past, geologists now divide the Snake River Plain into eastern and western units. The following geologic story relates to the eastern Snake River Plain, on which Craters of the Moon lies.

On the eastern Snake River Plain, basaltic and rhyolitic lavas formed in two different stages of volcanic activity. Younger basaltic lavas mostly lie atop older rhyolitic lavas. This portion of the plain runs from north of Twin Falls eastward to the Yellowstone area on the Wyoming-Montana border. Drilling to depths of almost 2 miles near the plain’s midline, geologists found ½ mile of basaltic lava flows lying atop more than 1½ miles of rhyolitic lava flows. How much deeper the rhyolitic lavas may extend is not known. No one has drilled deeper here.

This combination—a thinner layer of younger basaltic lavas lying atop an older and thicker layer of rhyolitic lavas—is typical of volcanic activity associated with an unusual heat phenomenon inside the Earth that some geologists have described as a mantle plume. The mantle plume theory was developed in the early 1970s as an explanation for the creation of the Hawaiian Islands. According to the theory, uneven heating within the Earth’s core allows some material in the overlying mantle to become slightly hotter than surrounding material. As its temperature increases, its density decreases. Thus it becomes relatively buoyant and rises through the cooler materials—like a tennis ball released underwater—toward the Earth’s crust. When this molten material reaches the crust it eventually melts and pushes itself through the crust and it erupts onto the Earth’s surface as molten lava.

The Earth’s crust is made up of numerous plates that float upon an underlying mantle layer. Therefore, over time, the presence of an unusual heat source created by a mantle plume will be expressed at the Earth’s surface—floating in a constant direction above it—as a line of volcanic eruptions. The Snake River Plain records the progress of the North American crustal plate—350 miles in 15 million years—over a heat source now located below Yellowstone. The Hawaiian chain of islands marks a similar line. Because the mechanisms that cause this geologic action are not well understood, many geologists refer to this simply as a heat source rather than a mantle plume.

Two Stages of Volcanism. As described above, volcanic eruptions associated with this heat source occur in two stages, rhyolitic and basaltic. As the upwelling magma from the mantle collects in a chamber as it enters the Earth’s lower crust, its heat begins to melt the surrounding crustal rock. Since this rock contains a large amount of silica, it forms a thick and pasty rhyolitic magma. Rhyolitic magma is lighter than the overlying crustal rocks, therefore, it begins to rise and form a second magma chamber very close to the Earth’s surface. As more and more of this gas-charged rhyolitic magma collects in this upper crustal chamber, the gas pressure builds to a point at which the magma explodes through the Earth’s crust.

Explosive Rhyolitic Volcanism. Rhyolitic explosions tend to be devastating. When the gas-charged molten material reaches the surface of the Earth, the gas expands rapidly, perhaps as much as 25 to 75 times by volume. The reaction is similar to the bubbles that form in a bottle of soda pop that has been shaken. You can shake the container and the pressure-bottled liquid will retain its volume as long as the cap is tightly sealed. Release the pressure by removing the bottle cap, however, and the soft drink will spray all over the room and occupy a volume of space far larger than the bottle from which it issued. This initial vast spray is then followed by a foaming action as the less gas-charged liquid now bubbles out of the bottle.

Collectively, the numerous rhyolitic explosions that occurred on the Snake River Plain ejected hundreds of cubic miles of material into the atmosphere and onto the Earth’s surface. In contrast, the eruption of Mount Saint Helens in 1980, which killed 65 people and devastated 150 square miles of forest, produced less than 1 cubic mile of ejected material. So much material was ejected in the massive rhyolitic explosions in the Snake River Plain that the Earth’s surface collapsed to form huge depressions known as calderas. (Like _caldron_, whose root meaning it shares, this name implies both bowl-shaped and warmed.) Most evidence of these gigantic explosive volcanoes in the Snake River Plain has been covered by subsequent flows of basaltic lava. However, traces of rhyolitic eruptions are found along the margins of the plain and in the Yellowstone area.

Quiet Outpourings of Basaltic Lava. As this area of the Earth’s crust passed over and then beyond the sub-surface heat source, the explosive volcanism of the rhyolitic stage ceased. The heat contained in the Earth’s upper mantle and crust, however, remained and continued to produce upwelling magma. This was basaltic magma that, because it contained less silica than rhyolite, was very fluid.

The basalt, like the rhyolite, collected in isolated magma chambers within the crust until pressures built up to force it to the surface through various cracks and fissures. These weak spots in the Earth’s crust were the results of earlier geologic activity, expansion of the magma chamber, or the formation of a rift zone.

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Identifying the Lava Flows

At Craters of the Moon the black rocks are lava flows. The surface lava rocks, basaltic in composition, formed from magma originating deep in the Earth. They are named for their appearances: Pahoehoe (pronounced “pah-hoy-hoy” and meaning “ropey”), Aa (pronounced “ah-ah” and meaning “rough”), or Blocky. Geologists have seen how these flows behave in modern volcanic episodes in Hawaii and elsewhere.

Pahoehoe More than half the park is covered by pahoehoe lava flows. Rivers of molten rock, they harden quickly to a relatively smooth surface, billowly, hummocky, or flat. Other pahoehoe formations resemble coiled, heavy rope or ice jams.

Aa Aa flows are far more rugged than pahoehoe flows. Most occur when a pahoehoe flow cools, thickens, and then turns into aa. Often impassable to those traveling afoot, aa flows quickly chew up hiking boots. Blocky lava is a variety of aa lava whose relatively large silica content makes it thick and often dense, glassy, and smooth.

Bombs Lava pieces blown out of craters may solidify in flight. They are classed by shape: spindle, ribbon, and breadcrust. Bombs range from ½ inch to more than 3 feet long.

Tree Molds When molten lava advances on a living forest, resulting tree molds may record impressions of charred surfaces of trees in the lava.

Upon reaching the surface, the gases contained within the lava easily escaped and produced rather mild eruptions. Instead of exploding into the air like earlier rhyolitic activity, the more fluid basaltic lava flooded out onto the surrounding landscape. These flows were fairly extensive and often covered many square miles. After millions of years, most of the older rhyolitic deposits have been covered by these basaltic lava flows.

The Great Rift and Craters of the Moon. Craters of the Moon National Monument lies along a volcanic rift zone. Rift zones occur where the Earth’s crust is being pulled in opposite directions. Geologists believe that the interactions of the Earth’s crustal plates in the vicinity of the Snake River Plain have stretched, thinned, and weakened the Earth’s crust so that cracks have formed both on and below the surface here. Magma under pressure can follow these cracks and fissures to the surface. While there are many volcanic rift zones throughout the Snake River Plain, the most extensive is the Great Rift that runs through Craters of the Moon. The Great Rift is approximately 60 miles long and it ranges in width from 1½ to 5 miles. It is marked by short cracks—less than 1 mile in length—and the alignment of more than 25 volcanic cinder cones. It is the site of origin for more than 60 different lava flows that make up the Craters of the Moon Lava Field.

Eight Major Eruptive Periods. Most of the lavas exposed at Craters of the Moon formed between 2,000 and 15,000 years ago in basaltic eruptions that comprise the second stage of volcanism associated with the mantle plume theory. These eight eruptive periods each lasted about 1,000 years or less and were separated by periods of relative calm that lasted for a few hundred to more than 2,000 years. These sequences of eruptions and calm periods are caused by the alternating build up and release of magmatic pressure inside the Earth. Once an eruption releases this pressure, time is required for it to build up again.

Eruptions have been dated by two methods: paleomagnetic and radiocarbon dating. Paleomagnetic dating compares the alignment of magnetic minerals within the rock of flows with past orientations of the Earth’s magnetic fields. Radiocarbon dating makes use of radioactive carbon-14 in charcoal created from vegetation that is overrun by lava flows. Dates obtained by both methods are considered to be accurate to within about 100 years.

A Typical Eruption at Craters of the Moon. Research at the monument and observations of similar eruptions in Hawaii and Iceland suggest the following scenario for a typical eruption at Craters of the Moon. Various forces combine to cause a section of the Great Rift to pull apart. When the forces that tend to pull the Earth’s crust apart are combined with the forces created as magma accumulates, the crust becomes weakened and cracks form. As the magma rises buoyantly within these cracks, the pressure exerted on it is reduced and the gases within the magma begin to expand. As gas continues to expand, the magma becomes frothy.

At first the lava is very fluid and charged with gas. Eruptions begin as a long line of fountains that reach heights of 1,000 feet or less and are up to a mile in length. This “curtain of fire eruption” mainly produces cinders and frothy, fluid lava. After hours or days, the expansion of gases decreases and eruptions become less violent. Segments of the fissure seal off and eruptions become smaller and more localized. Cinders thrown up in the air now build piles around individual vents and form cinder cones.

With further reductions in the gas content of the magma, the volcanic activity again changes. Huge outpourings of lava are pumped out of the various fissures or the vents of cinder cones and form lava flows. Lava flows may form over periods of months or possibly a few years. Long-term eruptions of lava flows from a single vent become the source of most of the material produced during a sustained eruption. As gas pressure falls and magma is depleted, flows subside. Finally, all activity stops.

When Will the Next Eruption Occur? Craters of the Moon is not an extinct volcanic area. It is merely in a dormant stage of its eruptive sequence. By dating the lava flow, geologists have shown that the volcanic activity along the Great Rift has been persistent over the last 15,000 years, occurring approximately every 2,000 years. Because the last eruptions took place about 2,000 years ago, geologists believe that eruptions are due here again—probably within the next 1,000 years.

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Indian Tunnel

Indian Tunnel looks like a cave, but it is a lava tube. When a pahoehoe lava flow is exposed to the air, its surface begins to cool and harden. A crust or skin develops. As the flow moves away from its source, the crust thickens and forms an insulating barrier between cool air and molten material in the flow’s interior. A rigid roof now exists over the stream of lava whose molten core moves forward at a steady pace. As the flow of lava from the source vent is depleted, the level of lava within the molten core gradually begins to drop. The flowing interior then pulls away from the hardening roof above and slowly drains away and out. The roof and last remnants of the lava river inside it cool and harden, leaving a tube.

Many lava tubes make up the Indian Tunnel Lava Tube System. These tubes formed during the same eruption within a single lava flow whose source was a fissure or crack in the Big Craters/Spatter Cones area. A tremendous amount of lava was pumped out here, forming the Blue Dragon Flows. (Hundreds of tiny crystals on its surface produce the color blue when light strikes them.) Lava forced through the roof of the tube system formed huge ponds whose surfaces cooled and began to harden. Later these ponds collapsed as lava drained back into the lava tubes. Big Sink is the largest of these collapses. Blue Dragon Flows cover an area of more than 100 square miles. Hidden beneath are miles of lava tubes, but collapsed roof sections called skylights provide entry to only a small part of the system. Only time, with the collapse of more roofs, will reveal the total extent of the system.

Stalactites Dripped from hot ceilings, lava forms stalactites that hang from above. Mineral deposits Sulfate compounds formed on many lava tube ceilings from volcanic gases or by evaporation of matter leached from rocks above. Ice In spring, ice stalactites form on cave ceilings and walls. Ice stalagmites form on the cave floor. Summer heat destroys these features. Wildlife Lava tube beetles, bushy-tailed woodrats (packrats), and bats live in some dark caves. Violet-green swallows, great horned owls, and ravens may use wall cracks and shelves of well-lit caves for nesting sites.

Cinder Cones and Spatter Cones

Cinder Cones When volcanic eruptions of fairly moderate strength throw cinders into the air, cinder cones may be built up. These cone-shaped hills are usually truncated, looking as though their tops were sliced off. Usually, a bowl- or funnel-shaped crater will form inside the cone. Cinders, which cooled rapidly while falling through the air, are highly porous with gas vesicles, like bubbles. Cinder cones hundreds of feet high may be built in a few days. Big Cinder Butte is a cinder cone. At 700 feet high it is the tallest cone in the park. The shape develops because the largest fragments, and in fact most of the fragments, fall closest to the vent. The angle of slope is usually about 30 degrees. Some cinder cones, such as North Crater, the Watchman, and Sheep Trail Butte, were built by more than one eruptive episode. Younger lava was added to them as a vent was rejuvenated. If strong winds prevailed during a cinder cone’s formation, the cone may be elongated—in the direction the wind was blowing—rather than circular. Grassy, Paisley, Sunset, and Inferno Cones are elongated to the east because the dominant winds in this area come from the west. The northernmost section of the Great Rift contains the most cinder cones for three reasons: 1. There were more eruptions at that end of the rift. 2. The lavas erupted there were thicker, resulting in more explosive eruptions. (They are more viscous because they contain more silica.) 3. Large amounts of groundwater may have been present at the northern boundary of the lavas and when it came in contact with magma it generated huge amounts of steam. All of these conditions lead to more extensive and more explosive eruptions that tend to create cinder cones rather than lava flows.

Spatter Cones When most of its gas content has dissipated, lava becomes less frothy and more tacky. Then it is tossed out of the vent as globs or clots of lava paste called spatter. The clots partially weld together to build up spatter cones. Spatter cones are typically much smaller than cinder cones, but they may have steeper sides. The Spatter Cones area of the park (Stop 5 on the map of the Loop Drive) contains one of the most perfect spatter-cone chains in the world. These cones are all less than 50 feet high and less than 100 feet in diameter.

Life Adapts to a Volcanic Landscape

Two thousand years after volcanic eruptions subsided, plants and animals still struggle to gain toeholds on this unforgiving lava field. Much of the world’s vegetation could not survive here at all. Environmental stresses created by scant soil and minimal moisture are compounded by highly porous cinders that are incapable of holding water near the ground surface where plants and other organisms can make ready use of it. Scarce at best—total average precipitation is between 15 to 20 inches per year—rainwater and snowmelt quickly slip down out of reach of the plants growing on cinder cones. Summer’s hot, dry winds rob moisture from all living things exposed to them. Whisking across leaves and needles the winds carry away moisture precious to plant tissues. On the side of a cinder cone, summer day temperatures at ground level can be more than 150°F.

The secret to survival here is adaptation. Most life forms cope by strategies of either resisting or evading the extremes of this semi-arid climate. To resist being robbed of moisture by winds and heat, a plant may feature very small leaves that minimize moisture loss. To evade heat, wind, and aridity, another plant may grow inside a crevice that provides life-giving shade and collects precious moisture and soil particles. Another plant may spend about 95 percent of the year dormant. It may rush through the germination, sprouting, leafing out, blooming, and fruiting stages and return to the dormancy of its seed stage in just two weeks. The dwarf buckwheat has adapted to life on porous cinders by evolving a root system that may spread out for up to 3 feet to support its aboveground part, which is a mere 4 inches high. This buckwheat only looks like a dwarf because you can not see its roots.

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Plants Adapt to a Volcanic Landscape

Water is the limiting factor in plant growth and reproduction both on the lava fields of Craters of the Moon and on the surrounding sagebrush steppe. Plants have developed a combination of adaptations to cope with drought conditions. There are three major strategies:

1. Drought tolerance Physiological adaptations leading to drought tolerance are typical of desert plant species. The tissues of some plants can withstand extreme dehydration without suffering permanent cell damage. Some plants can extract water from very dry soils. Sagebrush and antelope bitterbrush exemplify drought tolerance.

2. Drought avoidance Certain structural modifications can enable plants to retain or conserve water. Common adaptations of this type include small leaves, hairiness, and succulence. The small leaves of the antelope bitterbrush expose less area to evaporative influences such as heat and wind. Hairs on the scorpionweed reduce surface evaporation by inhibiting air flow and reflecting sunlight. Succulent plants such as pricklypear cactus have tissues that can store water for use during drought periods. Other plants, such as wire lettuce, avoid drought by having very little leaf surface compared to their overall volume.

3. Drought escape Some plants, such as mosses and ferns, escape drought by growing near persistent water supplies such as natural potholes and seeps from ice caves. Many other drought escapers, such as dwarf monkeyflower, simply carry out their full life cycle during the moist time of the year. The rest of the year they survive in seed form.

Plant Microhabitats

Lava flows Most plants cannot grow on lava flows until enough soil has accumulated to support them. The park’s older volcanic landscapes, where soils are best developed, are clothed with sagebrush-grassland vegetation. On younger lava flows, bits of soil first accumulate in cracks, joints, and crevices. It is in these microhabitats that vascular plants may gain footholds. Narrow cracks and joints may contain desert parsley and lava phlox. Shallow crevices will hold scabland penstemon, fernleaf fleabane, and gland cinquefoil. Deep crevices can support the syringa, various ferns, bush rockspirea, tansybush, and even limber pine. Not until full soil cover is achieved can the antelope bitterbrush, rubber rabbitbrush, and sagebrush find suitable niches. On lava flows soils first form from eroded lava and the slow decomposition of lichens and other plants able to colonize bare rock. These soils can be supplemented by wind-blown soil particles until vascular plants gain footholds. As plants begin to grow and then die, their gradual decomposition adds further soil matter. These soil beginnings accumulate in cracks and crevices, which also provide critical shade and wind protection. Deep crevices provide lower temperatures favoring plant survival.

Cinder gardens Compared to the lava flows, cinder cones are much more quickly invaded by plants. Here, too, however, volcanic origins influence plant growth. Compared to the relatively level lava flows, steeply sloping cinder cones introduce a new factor that controls the development of plant communities: topography. Here you find marked differences in the plant communities between the north- and south-facing slopes. South-facing slopes are exposed to prolonged, intense sunlight, resulting in high evaporation of water. Because of the prevailing winds, snow accumulates on northeast sides of cones, giving them far more annual water than southwest-facing sides receive. The pioneering herbs that first colonize cinder cones will persist on southwest-facing slopes long after succeeding plant communities have come to dominate north-facing slopes. It is on these north-facing slopes that limber pine first develops in the cinder garden. South-facing slopes may never support the limber pine but may be dominated by shrubs. Unweathered cinder particles range in size from 3 to 4 inches in diameter down to very small particles. They average about ¼ inch in diameter.

Ecological conditions at Craters of the Moon are generally so harsh that slight changes can make the difference for the survival of a plant or other organism. Life thrives in many rock crevices that are surrounded by barren exposed lava rock of the same physical composition. These microhabitats provide the critical shade and increased soil and moisture content required for plant survival. Over the years, particles of soil will naturally collect in rock crevices, which also have the effect of funneling precipitation into their depths. Their shade further protects these pockets of soil and water from wind erosion, excessive heat, and evaporation and leaching by direct sunlight.

At Craters of the Moon, crevices are of such importance to plants that botanists differentiate between narrow, shallow, and deep crevices when studying this phenomenon. Narrow crevices will support dwarf goldenweed or hairy goldaster. Shallow crevices support scabland penstemon, fernleaf fleabane, and gland cinquefoil. Deep crevices give rise to syringa, ferns, bush rockspirea, tansybush, Lewis mockorange, and even the limber pine tree. Complete soil cover and then vegetative cover can develop on these lava flows only after crevices have first become filled with soil.

Plants exploit other means of protection to survive in this harsh environment. Shaded and wind-sheltered, the northern side of a cinder cone can support grass, shrubs, and limber pine trees while the cone’s southern face supports only scattered herbs. Most cinder cones in the park show distinct differences of plant cover between their northern and southern exposures. Northern exposures are cooler and more moist than southern exposures, which receive far more direct sunlight. In addition, here at Craters of the Moon, the prevailing southwesterly winds compound the ability of the dry heat to rob porous cinder cone surfaces and their living organisms of precious moisture.

The build-up of successive lava flows has so raised the landscape that it now intercepts wind currents that operate higher above surrounding plains. Limber pine trees find footholds on the shaded and sheltered northern exposures of cinder cones. Bitterbrush and rabbitbrush shrubs that can barely survive on the lower skirts of a cinder cone’s southern side may grow two-thirds of the way up its protected northern face. For many species of plants the limits of habitability on this volcanic landscape are narrowly defined. Very small variations in their situations can determine success or failure.

Travelers often ask park rangers whether or not some of the park’s plants were planted by people. The plants in question are dwarf buckwheats and grow in cinder gardens. It is their incredibly even spacing that creates an orderliness that is easy to mistake for human design. The regular spacing comes about because of the competition for moisture, however. The root systems of these plants exploit the available water from an area of ground surface much larger than the spread of their foliage. In this way, mature plants can fend off competition by using the moisture that would be required for a potentially encroaching plant to become established. The effect is an even spacing that makes it appear, indeed, as though someone had set out the plants on measured centers.

Craters of the Moon abounds with these surprising plant microhabitats that delight explorers on foot. The bleak lava flows separate these emerging pockets of new life, isolating them like islands or oases within their barren volcanic surroundings.

Scientists have studied Carey Kipuka, an island of plantlife in the most southern part of the park, to find out what changes have occurred in the biologic community. _Kipuka_ is a Hawaiian name given to an area of older land that is surrounded by younger lava flows. Recent lava flows did not overrun Carey Kipuka, so its plant cover is unaltered. Shortage of water protected it from livestock grazing that might have changed its character. Its vegetation is a benchmark for comparing plant cover changes on similar sites throughout southern Idaho.

For the National Park Service and other managers of wildlands, kipukas—representing isolated and pristine plant habitat unchanged by human influence—provide the best answer that we have to the important question, “What is natural?” Armed with a satisfactory answer to that question, it is possible to manage the land ecologically. Park managers can seek to restore natural systems and to allow them to be as self-regulating as possible. It is ironic that Craters of the Moon, a volcanic landscape subjected to profound change, should also protect this informative glimpse of what remains unchanged.

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Wildflowers

Wildflowers carpet Craters of the Moon’s seemingly barren lava fields from early May to late September. The most spectacular shows of wildflowers come with periods of precipitation. In late spring, moisture from snowmelt—supplemented now and then by rainfall—sees the blossoming of most of the delicate annual plants.

Many of the park’s flowering plants, having no mechanisms for conserving moisture, simply complete their life cycles before the middle of summer. This is particularly true of those that grow on the porous cinder gardens into which moisture quickly descends beyond reach of most plants’ root systems.

As summer continues and supplies of moisture slowly dwindle, only the most drought-resistant of flowering plants continue to grow and to bloom. With the onset of autumn rains, only the tiny yellow blossoms of the sagebrush and rabbitbrush remain.

Mule Deer

Brad Griffith could be called the mule deer man. In 1980, this wildlife researcher began a three-year study of the mule deer herd that summers in the park. The immediate concern was that the deer, protected inside the park, might be overpopulating their range and endangering their habitat. Griffith set out to find out just how the deer use the area, what their population level is, and how certain factors—production, mortality, and distribution—affect their population dynamics. The mule deer use the park April through November only, because winter brings snows too deep for the deer to find food here. The most striking finding of Griffith’s research is that the mule deer at Craters of the Moon—unlike mule deer studied elsewhere—have a dual summer range. Put simply, the mule deer have had to undergo behavior modification to live here. The deer move back into the southern park in mid-April, living in the protected wilderness area there. While in the wilderness area, the park’s deer routinely live up to nearly 10 miles from open water, getting their water from food, dew, fog, and temporary puddles. This area has higher quality forage for these deer than any other part of their annual range. The trade-off is that the wilderness area has almost no open water. When the moisture content of their forage decreases in summer, usually in July, the deer move up to the northern part of the park where there is open water. Their habits in the northern part of the park are unusual, too, Griffith says, because there the deer live in much closer quarters than other herds are known to tolerate on summer ranges. They live in this wildlife equivalent of an apartment complex until the fall rains come. Then they move back down to the wilderness area. The deer make this unusual summer migration, Griffith suggests, to avail themselves of the high quality forage in the southern park. “The park serves as an island of high quality habitat for mule deer,” he wrote in his report. It is now known the deer will leave the wilderness area for the northern park after 12 days with daytime highs above 80°F and nighttime lows above 50°F in summer. “We can’t really predict this,” Park Ranger Neil King says, “but the deer know when this is.” What is happening is that the percentage of water in their forage plants falls below what is necessary to sustain the deer with increasingly hot weather. As you would expect, does nursing two fawns leave a couple days earlier than does with only one fawn. The rate at which their fawns survive to the fall of the year is astonishing. “This is an incredibly productive herd,” Griffith says, “right up there with the highest fawn survival rate of any western mule deer herd.” Park rangers continue Griffith’s studies by taking deer census counts.

Indians, Early Explorers And Practicing Astronauts

Not surprisingly, archeologists have concluded that Indians did not make their homes on this immense lava field. Astronauts would one day trek about Craters of the Moon in hopes that experiencing its harshly alien environment would make walking on the moon less disorienting for them. No wonder people have not chosen to live on these hot, black, sometimes sharp lava flows on which you must line the flight of doves to locate drinking water.

Indians did traverse this area on annual summer migrations, however, as shown by the developed trails and many sites where artifacts of Northern Shoshone culture have been found. Most of these archeological sites are not easily discerned by the untrained eye, but the stone windbreaks at Indian Tunnel are easily examined. Rings of rocks that may have been used for temporary shelter, hunting blinds, or religious purposes, numerous stone tools, and the hammerstones and chippings of arrowhead making are found scattered throughout the lava flows. Some of the harder, dense volcanic materials found here were made into crude cutting and scraping tools and projectile points. Such evidence suggests only short forays into the lavas for hunting or collecting by small groups.

The Northern Shoshone were a hunting and gathering culture directly dependent on what the land offered. They turned what they could of this volcanic environment to their benefit. Before settlement by Europeans, the vicinity of the park boasted several game species that are rare or absent from Craters of the Moon today. These included elk, wolf, bison, grizzly and black bear, and the cougar. Bighorn sheep, whose males sport characteristic headgear of large, curled horns, have been absent from the park since about 1920.

Military explorer U.S. Army Capt. B.L.E. Bonneville left impressions of the Craters of the Moon lava field in his travel diaries in the early 1800s. In _The Adventures of Captain Bonneville_, which were based on the diaries, 19th-century author Washington Irving pictures 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.” Irving is perhaps most famous for _The Legend of Sleepy Hollow_, but his _Adventures_ is considered a significant period work about the West and provided this early, if brief, glimpse of a then unnamed Craters of the Moon.

Pioneers working westward in the 19th century sought either gold or affordable farm or ranch lands so they, like the Northern Shoshone, bypassed these lava wastes. Later, nearby settlers would venture into this area in search of additional grazing lands. Finding none, they left Craters of the Moon substantially alone.

Early pioneers who left traces in the vicinity of the park did so by following what eventually came to be known as Goodale’s Cutoff. The route was based on Indian trails that skirted the lava fields in the northern section of the park. It came into use in the early 1850s as an alternate to the regular route of the Oregon Trail. Shoshone Indian hostilities along the Snake River part of the trail—one such incident is memorialized in Idaho’s Massacre Rocks State Park—led the emigrants to search for a safer route. They were headed for Oregon, particularly the Walla Walla area around Whitman Mission, family groups in search of agricultural lands for settlement. Emigrants traveling it in 1854 noticed names carved in rocks and trees along its route. It was named in 1862 by travelers apparently grateful to their guide, Tim Goodale, whose presence, they felt, had prevented Indian attacks. Illinois-born Goodale was cut in the mold of the typical early trapper and trader of the Far West. He was known to the famous fur trade brothers Solomon and William Sublette. His name turned up at such fur trade locales as Pueblo, Taos, Fort Bridger, and Fort Laramie over a period of at least 20 years.

After the discovery of gold in Idaho’s Salmon River country, a party of emigrants persuaded Goodale to guide them over the route they would name for him. Goodale was an experienced guide: in 1861, he had served in that capacity for a military survey west of Denver. The large band of emigrants set out in July and was joined by more wagons at Craters of the Moon. Eventually their numbers included 795 men and 300 women and children. Indian attacks occurred frequently along the Oregon Trail at that time, but the size of this group evidently discouraged such incursions. The trip was not without incident, but Goodale’s reputation remained sufficiently intact for his clients to affix his name to the route. Subsequent modifications and the addition of a ferry crossing on the Snake River made Goodale’s Cutoff into a popular route for western emigration. Traces of it are still visible in the vicinity of the park today.

Curiosity about this uninhabitable area eventually led to more detailed knowledge of Craters of the Moon and knowledge led to its preservation. Geologists Israel C. Russell and Harold T. Stearns of the U.S. Geological Survey explored here in 1901 and 1923, respectively. Taxidermist-turned-lecturer Robert Limbert explored the area in the early 1920s. Limbert made three trips. On the first two, he more or less retraced the steps of these geologists. On his third and most ambitious trek, Limbert and W. L. Cole traversed what is now the park and the Craters of the Moon Wilderness Area south to north, starting from the nearby community of Minidoka. Their route took them by Two Point Butte, Echo Crater, Big Craters, North Crater Flow and out to the Old Arco-Carey Road, then known as the Yellowstone Park and Lincoln Highway. These explorations and their attendant publicity in _National Geographic Magazine_ were instrumental in the proclamation of Craters of the Moon as a national monument by President Calvin Coolidge in 1924.

Since Limbert’s day, astronauts have walked both here and on the moon. Despite our now detailed knowledge of the differences between these two places, the name—and much of the park’s awe-inspiring appeal—remains the same. It is as though by learning more about both these niches in our universe we somehow have learned more about ourselves as well.

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Early Explorers and the Limbert Expedition

The first known explorations of these lava fields were conducted by two Arco, Idaho, cattlemen in 1879. Arthur Ferris and J.W. Powell were looking for water for their livestock. The first scientific explorations were carried out by Israel C. Russell, surveying the area for the U.S. Geological Survey in 1901 and 1903. Beginning in 1910, Samuel A. Paisely, later to become the park’s first custodian, also explored these lava fields. In 1921, the U.S.G.S. sent two geologists here, Harold T. Stearns and O.E. Meinzer, with a geologist from the Carnegie Institute. Based on this field work, Stearns recommended that a national monument be created here. Also during the early 20s, the explorations of Idaho entrepreneur Robert W. Limbert caught the public’s fancy. A report of the explorations of “Two-gun” Bob Limbert was published in the March 1924 _National Geographic Magazine_. Limbert was a Boise, Idaho, taxidermist, tanner, and furrier. He was also an amateur wrestler and quick-draw artist who later performed on the national lecture circuit. Reportedly, Limbert once challenged Al Capone to a pistol duel at 10 paces. Evidently Capone declined. Limbert made three treks into the lava fields between 1921 and 1924. He first explored the more easily accessible northern portion of the lava fields. Limbert’s third expedition crossed the area from south to north, however, starting from Minidoka.

The Limbert Trek

With Limbert were W.L. Cole and an Airedale terrier. Taking the dog along was a mistake, Limbert wrote, “for after three days’ travel his feet were worn raw and bleeding.” Limbert said it was pitiful to watch the dog as it hobbled after them. The landscape was so unusual that Limbert and Cole had difficulty estimating distances. Things would be half again as far away as they had reckoned. In some areas their compass needles went wild with magnetic distortions caused by high concentrations of iron in the lava rock. Bizarre features they found—such as multi-colored, blow-out craters—moved Limbert to write: “I noticed that at places like these we had almost nothing to say.” Limbert and Cole discovered ice caves with ice stalactites. They found water by tracking the flights of mourning doves. They found pockets of cold water (trapped above ground by ice deposits below the surface) covered with yellowjackets fatally numbed by the cold. They drank the water anyway. In desert country, said Limbert, one can’t be too picky. Between Limbert’s lively article in the _National Geographic Magazine_, and the reports of geologist Stearns, President Calvin Coolidge was induced to designate part of the lava fields as Craters of the Moon National Monument on May 2, 1924.