Getting Under the Skin of a Volcano: Travels in Lava Beds National Monument

What in the world is going on here?? What are these spikes coming out of the ceiling? Is it some kind of deadly trap for Indiana Jones or Lara Croft? Well, no, but they'll hurt like the dickens if you try exploring them without a hardhat. In some of the previous posts in this short series we explored the deep heart of the magma chamber beneath a volcano, and we went both on and above Mt. Shasta to see the dramatic exterior of a volcano. Today we burrow under the skin of a volcano.

Medicine Lake Highland is the biggest volcano in California. It may be barely half as high as Mt. Shasta, but it makes up for the height deficit with broad gentle slopes, giving it a volume of around 130 cubic miles, compared to about 85 for Mt. Shasta. It is classed as a shield or "shield-type" volcano, composed largely of basalt, but with varying amounts of andesite and rhyolite. As such, it displays a wide variety of volcanic phenomena, not the least of which is a dizzying array of lava tubes. A flank of the volcano is preserved as Lava Beds National Monument, and the park has within its borders the highest concentration of lava tubes in the country, if not the world. More than 700 individual caves are known at Lava Beds with a total length of more than 70 miles.

How do lava tubes form? The picture above shows an active lava flow at Pu'u'o'o Crater on the Kilauea volcano on the Big Island of Hawai'i in 2009. The scale in this aerial view is difficult to discern but the skylight (where the red lava is visible) is probably 30 feet across. The tubes develop when river-like lava flows crust over. The lava continues to flow just beneath the surface, sometimes for many miles, being insulated by the overlying crust. The flow in the picture above flowed seven miles to the shoreline and was only a few tens of degrees cooler than it was when it emerged at the vent of Pu'u'o'o. When the eruption ends, the lava drains from the tubes.

The tubes can be quite complex, with bifurcating passageways and multiple levels (one particularly complex cave is called the Catacombs). During our recent visit at Lava Beds we explored Valentine Cave, one of the most accessible in the park. The majority of the tubes are in the Mammoth Crater flow which is around 30,000 years old. Valentine is in a younger flow, around 12,000 years old, so it has less collapse debris than many of the older caves (although it is true that many fallen boulders were removed by CCC workers during the Great Depression). In any case, the passages are easy to negotiate.

Being composed of very dark rock that tends to absorb light, tubes are notoriously hard to photograph. Flash photography tends to produce washed-out photos with little depth. I was using a bright flashlight for illumination and was holding it at arms length to get shadows that provide a sense of depth. I tried using my normal 'sophisticated' camera, but I actually got better results from my Samsung phone!

There are many interesting flow structures in the caves, including the pahoehoe flows on the floor of the caves, and "bathtub rings" on the walls showing that some flows only filled the cave a third full.

The basalt fractured as it cooled, forming the numerous cracks in the roof of the cave. Subsequent weathering in the soils above produced sodium bicarbonate and other chemicals that stain the edges of the fractures.

A lava cascade emerges from a side passage in Valentine Cave.

The lava tubes of Lava Beds National Monument are a fascinating environment to explore. Some of the caves have multiple levels, and some are decorated with permanent ice. One, Fern Cave, has numerous Native American pictographs and also ferns, which is interesting because ferns are not otherwise found in the park; they are a species of the western Cascades. The cool damp environment of the cave provided the right conditions for the plants, which may have arrived on birds feet (I'm guessing here).

There is a lot to do in Lava Beds. The ice cave and Fern Cave can only be visited with a ranger guide, but around twenty caves are open and developed for unaccompanied exploration. One, Mushpot Cave, is lit and has interpretive signs, and even a small amphitheater for ranger talks. On the surface there are lots of hiking trails that allow for the exploration of cinder cones, spatter cones, fault scarps, and the human history of the region (which will be covered in a separate post).

All in all, it's a good place to get under the skin of a volcano!

Exploring a Volcanoe's Insides: The Tubes of Lava Beds National Monument

Lava Beds National Monument is a special place, one of my favorite spots to visit in California. It's so different than what people expect of a California park: where are the beaches, the mountains, the Redwood trees? It's way out in the hinterlands of northeastern California, about 30 miles south of Klamath Falls, Oregon. In the previous two posts, we mentioned the historical value of the park as a monument to the memory of the Modoc People, and as a great place to see basalt flows. But one of the other big reasons the monument was established can be seen in the picture below.

What? You don't see anything except piles of boulders? They actually actually reveal a bit of the inside of a volcanic system. Not the really deep stuff, but the plumbing system that allowed molten basalt to flow many miles without solidifying. The picture below is of a collapsed lava tube system. The park has many others that haven't yet collapsed.

Lava Beds has a startlingly large number and variety of lava tubes. In a small park, perhaps no wider than a dozen miles at any point, there are more than 700 individual caves with something like 75 miles of passageways. And a large number of them are open and accessible for exploration.

We paid a visit to four of them during our teaching day, and the students visited another half dozen in the evening after the academic day was done (it doesn't really matter in a cave whether it is day or night, after all). We hiked first to Symbol Bridge Cave, a short cave on the main Mammoth Crater lava flow system. The tube, which is collapsed in many areas, is around 12 miles long, extending across the park. Modocs or other Native Americans left pictographs on large basalt boulders at the entrance.

Big Painted Cave is just a short distance away on the same tube system. It also has some pictographs (hence the name), but in the bottom it also has an interesting sight: an ice pool, down inside a second level. Open water of any kind is rare in the park. Basalt flows tend to fracture while cooling, so water tends to seep into the ground and disappear, later emerging from large springs around the margins of the volcano (Medicine Lake Highland). If you have a plastic water bottle next to you, you probably are drinking some of the volcanic water from MLH. They bottle it and sell it.

In some rare instances, the fractures are blocked and water accumulates in the bottom of the cave. During the winter, cold sinking air freezes the water, and the cold air remains in the bottom of the cave all through the summer. The ice persists all year.

Our next exploration took us to Skull Cave, the largest cave opening in the park, at about 60 feet high and 60 feet wide. It somehow feels bigger as you walk into the darkness. It also has a sinister aspect, one that earned the cave's name. Just at the point where the darkness becomes complete, the cave drops off into a deeper chamber, a fall of about 20 or 30 feet. Numerous bones were discovered there, including those of two humans. Luckily, today there is a trail and metal ladders that avoid the dangerous drop-off. There is a large ice pool in the depths of Skull Cave as well.

Somehow I keep mentioning Star Wars things; in the last post in was a Sarlaac. In this one, I couldn't help but feel like I was walking through the belly of the giant worm cave in the asteroid field of "The Empire Strikes Back", where the Exogorth lived.

Our next stop was Valentine Cave. It is different than the others. The majority of caves in the park are part of the Mammoth Crater Flow, which emerged around 30,000 years ago. Valentine's flow (called the Valentine flow, by incredible coincidence), erupted only about 11,000 years ago. The cavern passages have far fewer collapsed sections, and many of the collapse blocks that were in the cave were removed by the CCC during the Depression years. The cave is clean and easy to stroll through.

Many typical lava tube features can be viewed in the passages, which total around 1,600 feet. They include terraces and benches that represent the drop in the flow level during the waning stages of the eruption. The ceilings are covered with thousands of lavacicles, where lava was dripping from the roof of the tubes. They make a good argument for wearing helmets whenever exploring the caves. The spiky rocks can put a real dent in someone's skull.

Lava tubes, like all caves, can be notoriously hard to photograph. The dark basalt tends to absorb light. Camera flashes wash out the scenes and leave no shadows to provide depth. I experimented with time exposures to varying success, using my flashlight to paint the walls. The white material is sodium bicarbonate and soluble salts that have seeped through the fractures from the ground above. One can see the popcorn-like surface of the last lava to flow through the tube.

I was happiest with the shot below. It shows best the three dimensional aspect the cave.

The caves of Lava Beds are fascinating. Some provide micro-climates where ferns and other unusual biota survive, despite aridity of the high desert environment. Others are full of ice (and are so fragile that tours are only offered in winter, since the warmth of people can cause melting). Quite a few have multiple levels, as one lava flow followed another. Post Office Cave has at least five of these levels, and Skull Cave has three. A large number of animals and insects live in the caves, including several endangered bat species (all bat species in the country are endangered by White-Nose Syndrome, which is spreading west from caves back east).

The park service has provided a pleasant campsite among the juniper trees, and a newly constructed visitor center. They sell cheap bump hats, and loan out flashlights for visitors to explore caves.

We emerged from Valentine Cave, and returned to our base at the Research Center. Tomorrow we would be going over Medicine Lake Highland.

A Convergence of Wonders: Day 2, Lava Beds and Newberry Caldera

A Convergence of Wonders is a chronicle of our recent journey through the Pacific Northwest and Northern Rocky Mountains. This the second day's story...

What is that blazing orange light interrupting my slumber?? June 16 dawned very early, with twilight beginning around 4:30 AM, and sunrise about 5:20. I was up for good at that point. There was no sleeping in the brightness; tents don't insulate you from the outdoors as well as solid walls. I've always loved dawn at Lava Beds National Monument, though. The sky is as big there as any place I know, with far-off horizons and clear air.

Our day was going to be spent on the two largest volcanoes of the Cascades, and hardly anyone has heard of either of them: Medicine Lake Highland, and Newberry Caldera. Crater Lake was slated to be on the day's menu, but 10-12 feet of snow still coated the rim, and we just weren't going to see it this time around. Both Medicine Lake and Newberry have been called basaltic shield volcanoes, but they are more complicated than "normal" shields with a variety of lava and magma compositions and are described as "shield-shaped volcanoes". We started the day on the flank of Medicine Lake Highland, but we couldn't actually see the volcano until mid-day, when we were far enough away. It is the largest single volcano in the Cascades with a volume of around 130 cubic miles (Shasta has around 85-100 cubic miles).

The best known part of Medicine Lake Highland is Lava Beds National Monument, where we spent the night. The park preserves a series of basalt flows that developed a network of lava tubes, underground conduits that allowed the basaltic lavas to flow for miles before cooling. The tubes drained at the end of the eruption, leaving a series of caves. Lava Beds preserves the largest concentration of lava tubes in North America, in excess of 700, with a combined length of more than 30 miles.

The students had explored a few of the lava tubes the previous night, so we sampled just two in the morning. Valentine Cave is in a separate younger flow, and is remarkably clear of debris and easy to walk through (the CCC cleared much of the talus in the 1930s). It has most of the interesting cave features such as lavacicles, bathtub rings (lava benches), rafted boulders, lava falls, and pahoehoe flows on the cave floor.

Outside the caves, there were an unusual number of wildflowers in evidence, given the long spring and cooler temperatures. This is an Indian Paintbrush on the flank of Mammoth Crater, the source for more than two-thirds of the lava flows in Lava Beds.

After a visit to the Visitor Center, where we were certified as free of white nose syndrome (this is a horrific bat disease, not a human one), we went to the more ominous sounding Skull Cave. The name is like something out of a campy adventure movie, and the reality is also kind of frightening. Skull is a cave with multiple levels, and the first drop to the second level down is just within the zone of total darkness. Animals and a few humans without sources of light would move into the cave, looking for water maybe, and just as it got dark they would step over the side into the abyss (literally and figuratively). Today there is a metal stairway to negotiate the dropoff, and we explored the icy depths (literally icy; water sinks into the cave in the winter, freezes, and stays there, even in summer).

Skull has the largest opening of any cave in the park because it is part of the main feeder tube that transported the lava for 10-15 miles. Unlike the smaller caves, the main tube is relatively unstable, and huge blocks of basalt have broken off the ceiling and littered the cave floor to the extent that few original flow features are visible. It was so large I half-expected to see Han Solo, the Millenium Falcon, and a giant space worm in there.

Our next stop was more sobering. California was never kind to the hundreds of native cultures that existed prior to the Mission era and the Gold Rush. Many were slaughtered or sickened to extinction without leaving any kind of record. The Modoc culture was destroyed, but not without a fight. Lava Beds was the site of the last battles between the U.S. military and native peoples in California, in 1872-1873. Despite being outnumbered as much as 10-1, the Modoc people held out for five months.

I've provided a detailed commentary on the battles that took place in my Other California series about Lava Beds. In short, the Modocs held the advantage of knowing the territory, and of taking shelter at Captain Jack's Stronghold, a natural fortress that was almost impossible to take as long as there were a few armed defenders. Pressure ridges and schollendomes provided the trenchs and "castle" walls that made the stronghold practically impregnable.

A fire swept through the Stronghold and much of the northern part of Lava Beds a few years ago, leaving just a few Junipers unscathed. Being the only trees for some distance, a lot of birds were in evidence, including a pair of juvenile Great Horned Owls.

Why do owls always look so perturbed? I suppose a bunch of tourists with cameras had something to do with it...

We moved on to an outlier of the park, a deeply eroded tuffaceous cone called Petroglyph Point. The cone had erupted in the midst of Tule Lake, and the yellow layers of tuff had been deeply eroded by waves on the lake, forming a striking west-facing cliff punctuated by tafoni, hollows formed by weathering. One can see the wave-cut notches running along the base of the cliff behind the chain-link fences. Why are the fences there? Oh yeah, petroglyphs. Petroglyph Point is the largest panel of petroglyphs in the country...

Most of the rock carvings in the cliff predate the Modocs. The lake lapped at the base of the cliff, and the artists would have required rafts or canoes to reach the site. Because the lake has been mostly diverted and dried up for agricultural purposes, blowing sand and dust threatens the integrity of the rock art. See more info on the panel here.

We were finally far enough away to see the full extent of the Cascade's largest volcano, by volume. Medicine Lake Highland is the broad gently sloping dome on the horizon. Mt. Shasta can be seen on the right skyline (click on the photo for an enlarged view).

Then came one of the dreaded "pushes". We had to put about 170 miles between us and our next destination, Newberry Volcano. Oregon has some pretty volcanoes, including Mt. Theilsen and Mt. McLaughlin, but they were only occasionally visible between stretches of dense forest. The road was very straight and monotonous after Klamath Lake. Eventually though, we arrived at Newberry Caldera, a shield-like volcano similar in many respects to Medicine Lake Highland. We also found a wall of snow. The bathrooms were unavailable, the camp we had reserved months earlier was not open yet (fortunately I knew this and had made alternate arrangements), and there was no official parking available to see our main site, the obsidian dome. We made do, and most of the students hoofed it over the snowbanks to see the obsidian up close (more than a few snowballs were launched as well).

I crossed the highway and climbed the hill to get a better perspective on the dome. Mountains like Newberry and Medicine Lake have multiple magma sources, probably because very hot deep mantle source basalts melt some of the more silica-rich continental crust. The volcanoes spew out plenty of highly fluid basalt flows, but also occasionally produce much stickier rhyolite flows, forming small plug domes. The rhyolite lava often forms obsidian and pumice, as it did here.

We were in the midst of a caldera on the summit of Newberry. A caldera forms from the collapse of the top of a volcano due to the withdrawal of magma during eruption sequences. Paulina Peaks on the rim of the caldera loomed high above us while we hiked through the snow. Crater Lake (which we were not able to visit) is one of the world's best examples of a recently formed caldera. The catastrophic explosion that accompanied Crater Lake's origin probably did not happen at Newberry. The caldera development was more gradual and less explosive.

We were ready to get to camp, and traveled the final 30 miles as quickly as we could. We set up in the group site at Tumalo State Park, a pleasant site just outside Bend, Oregon. The evening was nice enough, but somehow overnight, the temperature dropped to 28 degrees. This is summer??

On day three, we head for the coast and for great disappointment (this sentence has multiple meanings, as you will see).

The Other California: Exploring the Volcano Underground

Continuing our series of where to go in California once you've seen all the places on the postcards....

As discussed in the previous post, California has a place with possibly the greatest concentration of lava tubes in the continental United States, some 700 of them, with around thirty miles of passageways: Lava Beds National Monument, on the flanks of California's biggest volcano, Medicine Lake Highland. Today's post is a brief photo essay on some of the kinds of things you can see underground at Lava Beds.

Two lava flows produced essentially all the lava tubes in the park. The first of these is the basalt of Mammoth Crater, which erupted around 30,000 years ago. Most of the caves occur in this unit. Mammoth Crater is a 1/4 mile wide, 340 foot deep pit at the south edge of the park which produced lavas that traveled as far as ten miles, producing a complex, multi-pronged tube system, shown on this map from the previous post. The Heppe Caves, above, are found just a few hundred yards from Mammoth Craters. The collapse pit in the picture is 168 feet across and 68 feet deep.

One oddity about Lava Beds is the total lack of open water in the monument: no creeks, no rivers, no lakes. Basalt flows become highly fractured as they cool and contract, and any water on the surface sinks quickly into the subsurface. Heppe Cave is one of the few exceptions, in that it often has a small pool at the bottom, probably maintained and sealed by underlying ice layers (the pool had disappeared when we visited in September).

The largest opening in the park is found at Skull Cave, near Schonchin Butte. The opening, seen above, is 60 feet in diameter. Though relatively short, the cave has one unfortunate attribute: just at the point where it turns totally dark, it drops into a second underlying tube system. This natural trap led to the cave's name, as early explorers found numerous skeletons of animals and two humans who had fallen in the darkness to their deaths. A metal stairway makes for a safer journey today.

These tubes-over-tubes have another interesting feature. In the frigid winter, cold air sinks into the caves. When the surface over the caves warms during the summer, the cold air stays put, so some of the caves in the monument maintain ice all year long. The deepest part of Skull Cave contains a frozen pond and a number of icicles (the ice in the photo below was taken in September). Another cave in the park, Crystal Ice Cave, is renowned for complex ice formations it contains. Special arrangements must be made to visit the cave, and it has some challenging passages.

The basalt of Mammoth Crater covers two-thirds of Lava Beds, but another flow about 10,000-11,000 years ago produced some fine lava tubes as well. This is the basalt of Valentine Cave. Valentine Cave itself is one of the cleanest and easiest caves to explore, with high ceilings and few breakdowns. It has about 1,600 feet of accessible passageways and displays many of the typical features of underground lava flows, including branching passageways, lava pools and cascades, pahoehoe flows, lava benches, pillars, and lavacicles.

Photographing lava tubes is a challenge. Dark colored rock in total darkness does not show well when you use a flash. For amateurs like myself, the best results come from photographs near entrances (as above), or by using a time exposure, and "painting" the walls with flashlights as seen below (pros use strobes of course). I like the cave ghosts in the picture below; several people walked through the scene during the 30 second exposure.

This other photo doesn't include ghosts, but shows the pahoehoe floor of the final lava flow in the tube, and some lavacicles on the ceiling. They can form as part of the ceiling melts while lava flows below.

Below are some sharktooth stalactites (lavacicles) in another cave. They are one to two inches long. They are also a really good reason to wear a helmet when exploring these caves. Your head can damage these by breaking them off, but I fear a great deal more damage can happen to your skull (the park sells some nice "bump caps" for a couple of dollars).

Tickner Cave (below) is also formed in the basalt of Valentine Cave, and is found close to the flows source at the south boundary of the park. It has a great many nice cave features, including a natural bridge.

Lava Beds tubes are full of surprises. One special example is Fern Cave, in an isolated section of the park. The monument lies within the rain shadow of the Cascades and is classed as semi-arid. The tube openings sometimes provide humid micro-climates, and a lush growth of ferns native to the other side of the range is found just inside (below). The interior contains numerous pictographs from the original human inhabitants of the region. The site is sacred to the Modoc People, and special arrangements must be made to explore the cave.

So there you have it...you've explored five lava tubes at Lava Beds National Monument! Less than one percent...looks like you will simply have to visit the park if you want to see more!