Craters of the Moon: Lava and Cinders

The Earth had been jittery for several days. She shuddered with anticipation. Then, clouds of sulfurous stench hissed out of a widening gape. Fountains of lava shot skyward from the fissure and heaped cinders and blobs around themselves. The prevailing south-westerly wind carried the volcanic dust and skewed the growing cinder cones toward the northeast. Suddenly, as though they had been shut off, the fountains dropped back into the crack. The earth ceased her trembling: only hot hissing remained.

But the earth was not finished. A coal-black cinder cone bulged outward on its flank and broke open a new wound. Lava blood spilled out haltingly. The earth mustered herself and sent lava gushing to the surface. Fragments of the cone broke off, and the torrent rafted them away. As the lava’s crust cooled from incandescent to dark, arteries of lava flowed underneath, pushing the flow along. Like honey, lava spread across the landscape.

Only about two thousand years ago – a mere tick of the geologic clock – an event similar to that just described occurred at Craters of the Moon National Monument in south-central Idaho. But that wasn’t the only incident of volcanism here. A large weakness in the earth’s crust, known as the Great Rift, has permitted molten rock to well up from deep within the earth on several occasions.

The park’s visitor center is an ideal place to start your exploration of this seemingly bleak lava land. The center contains books and exhibits pertaining to the geology, history, and biology of the park. A video displays recent eruptions in Hawaii that were similar to those that occurred at Craters of the Moon centuries ago. Across the road, visitors can camp among the volcanic rock and cinders at the only campground (no hookups) and enjoy an evening campfire program during the summer at the nearby amphitheater.

After you’ve obtained a map, a campsite, and extra water (the visitor center and the campground are the only sources), you can begin your drive along the seven-mile loop road to explore the area. Just past the campground, the road turns abruptly to the right as it reaches part of the young North Crater Flow. Beyond the curve, a paved interpretive trail awaits those wishing to see the lava up close. Along this trail, you’ll see the Triple Twist Tree – an ancient, gnarled limber pine. By counting the number of growth rings in this tree, scientists estimate that this flow may have occurred two thousand years ago, making it one of the youngest flows in the park.

You’ll learn the two types of basaltic lava flows are found at Craters of the Moon. One type is called pahoehoe (pronounced pa-hoy-hoy; a Hawaiian word meaning ropy). A cool yet pliable crust formed on top of this flow, which pushed the crust into pleats. The other kind is aa (pronounced ah-ah; Hawaiian for “hard on the feet”). Aa lava, which is less gassy and more sluggish than pahoehoe, forms spiny chunks on its surface as it flows.

A short distance beyond the parking area is the North Crater Trail. This trail will lead you up the crater where the lava flow originated.

Continuing on, you’ll turn left off of the loop to reach the Devil’s Orchard. Geologists believe that this is the site of an ancient cinder cone that has been reduced to bits and pieces by erosion. You may take a self-guiding trail – which features numbered markers keyed to a booklet – through the chunky remains. You’ll learn about the geology, the bird life, and lichens and other plants. Lichens are an association of fungi and algae that can live on bare rock. Look for the purplish dwarf monkey flowers that carpet the ground here in the early summer season.

If you continue along the loop road, you’ll reach Inferno Cone. A short, steep trail leads to the summit of this mass of cinders. The peak provides a good vantage point for viewing the many cones along the Great Rift to the southeast and northwest. Standing at the summit, you can feel the full brunt of the park’s incessant southwesterly winds. Big Cinder Butte, one of the largest purely basaltic cinder cones in the world, is the tallest cone to the southeast.

From late spring to late summer, many of the more than 200 species of plants native to Craters of the Moon dot the slopes of the cones. Dwarf buckwheat, with its pom-pon-like flower clusters, and bitterroot, whose bright white petals contrasts sharply with the dark centers, are particularly common.

Spatter cones are the next interesting formations along the loop. Nowhere else in the continental United States can you find a better example of spatter cones than at Craters of the Moon. These were formed when the earth threw out blobs of lava that stuck to one another. One of the cones here contains ice year-round. This is because lava rocks nearly always contain gas bubbles, which act as insulators.

A spur road off of the loop leads past frozen cascades of lava to the Tree Molds Parking Area. From here, you’ll take a trail out to the tree molds, which formed when lava flowed over trees and then cooled, often leaving the rock with the impressions of the burning trunks’ bark. You might take the Wilderness Trail from the parking area into the seldom-visited Craters of the Moon Wilderness Area. You’ll need a free permit to enter the wilderness area if you’re backpacking.

The Wilderness Trail branches off of the Tree Molds Trail drops steeply down to a pahoehoe flow and crosses the flow. Rock cairns mark the path across the undulatory, pleated surface. At the far end, you’ll find an old dirt road that extends for about four miles into the wilderness. If you follow this road, you’ll enjoy mild hiking through wide-open scenery with just a little bit of dust and cinders to be concerned about.

After you cross the wilderness boundary, you’ll pass between Big Cinder Butte and Half Cone, and then continue on through Trench Mortar Flat. The flat’s name was derived from lava tubes that formed like the tree molds, except that the lava shaped itself around standing tree trunks. After you round Coyote Butte, you’ll come to Echo Crater – one of the better campsites in the area for backpackers.

We camped at Echo Crater on our first and most recent visits to this wilderness. During our first visit, we set up camp on the rim of the crater and day-hiked from there in search of waterholes, fissures, and other features that we noticed on the topographical map. On our last night there, we heard and saw prairie falcons flying around the crater. After we watched them awhile, we discovered that they were a male and female taking turns hunting and guarding their nest on the Echo Crater rim.

On a visit during the 1980’s, we reached Echo Crater around dark. The wind was its normally persistent self, so we camped inside the crater for protection. As it happens, the crater is shaped like a crescent – a high western rim sloping to a lower eastward opening. As we began to cook our dinner, the moon rose a full, flaming, orange-red ball, casting its light across our campsite and into the crater.

In the late 1990’s, we were exploring mapped features that form in lava flows, like lava tube caves and lava bridges. Lava can flow like a river and with the lava on top exposed to the cooler air, a crust can form which solidifies and stops moving. But a lava crust is a good insulator, so the still hot lava underneath can continue to flow. Eventually, the still-liquid lava can drain away leaving a tube behind. If a part of the roof eventually collapses then there is a lava tube cave. If another part of the roof collapses near another collapse, the solid crust overarching the space between them is a lava bridge.

On the Craters of the Moon map, two lava bridges are listed, the Bridge of Tears and the Bridge of the Moon. We went to the Bridge of Tears and camped next to it and also explored Moss Cave and Amphitheater Cave, which formed along the same lava tube as the bridge. We had heard rumors that the Bridge of the Moon might have collapsed and we wanted to go to the area where it should have been and see if we could find it. Not being able to find it could be taken as a sign that it had collapsed.

After camping at Bridge of Tears, we set out on a hiking path that would take us straight toward the Bridge of the Moon’s mapped location. After starting out, we had to skirt around an elliptically shaped depression. We noticed that at the opposite end of the depression, there appeared to be an opening. So we decided to take some time to explore it. It turned out to be a cave with two side-by-side openings. The map didn’t show this feature, so we took notes about it, including its GPS coordinates. We continued on to the Bridge of the Moon’s mapped location, but couldn’t find it. We started back out of the wilderness but spent one more night.

Upon hiking out the next day, we turned in our write-up about the unmapped cave to the rangers at the visitor center and asked if this feature had ever been described before. It turned out that it hadn’t, see we got to name it. Because we are twin brothers and the cave had two openings, we called it Twin Cave. It will never appear on any maps, however, because the Park Service is trying to protect caves from vandalism and doesn’t want to give away their locations.

In August 2016, we went back to the Craters of the Moon wilderness to visit “our” cave after almost 20 years and discovered that one of the openings had gotten larger due to parts of the roof collapsing, but the other seemed to be about the same as before. We took what we call a “twin selfie” by the entrance to post on our social media pages.

The dirt road into the wilderness peters out by the time it reaches two cinder cones situated past Echo Crater – The Sentinel and The Watchman. South of here, in 1879, J.W. Powell and Arthur Ferris of Arco, Idaho, left a marker at Vermilion Chasm during a scouting trip to determine whether the Craters of the Moon area had sufficient water to support livestock grazing. It didn’t. Then, in 1921, Robert Limbert, W.L. Cole, and a dog ventured north from Minidoka to explore this virtually unknown region. During their journey across the aa flows, they could hardly sleep at night because of the sharpness of the lava. The dog cut his feet, so the men had to carry him. After running low on water, they managed to find waterholes by observing the flight of doves. In spite of these hardships, the two men were enthralled with this land, and they gave many of its features the descriptive names that they are known by today. Thanks to Limbert’s reports, photographs, and lobbying, and an article he wrote for National Geographic, Craters of the Moon was declared a national monument in 1924.

Back on the road, after rejoining the loop, you’ll continue on toward the Caves Area. Pahoehoe flows advance via channels or tubes beneath a cooling crust. As the eruption subsides the lava may drain out of the tube, leaving the crust to support itself. Indian Tunnel is an example of a lava tube in which much of the overlying crust has collapsed. Because of this condition, you needn’t carry a flashlight to explore the subway-sized Indian Tunnel. Just outside the tunnel, a ring of rocks is all that remains of a windbreak where the Shoshone Indians once camped while hunting deer and other wildlife of the park. You will need a flashlight to explore the other cave, however. Boy Scout Cave is especially interesting. Throughout the year, this cavern contains a thick layer of ice, which may be covered by a layer of water in the summertime.

Craters of the Moon is also famous for being a part of NASA’s effort to send men to the actual moon. Several of the astronauts came here to study the area as an example of what they might encounter when they landed on the moon.