Tuesday, October 31, 2017

Finding Peace in the Nation's Most Crowded Park: A Walk Through Yosemite Valley

If you've read my previous couple of posts, you know I was in Yosemite Valley over the weekend. I was guiding my students on a field trip up the Merced River and into the park on Saturday, and I came back on Sunday seeking some better pictures of the recent rockfall at El Capitan.
We can't park a big bus just anywhere on the floor of Yosemite Valley, so I had to let my students loose to find their way to the upper end of the valley using the free trams. There was enough time that I decided to walk the three or so miles from Yosemite Lodge to Happy Isles, picking whatever winding combination of roads, trails, or sandy river shoreline I could find (there's a direct route, but why stick to that?). I was almost immediately awarded with a nice view of Yosemite Falls, which at 2,425 feet is about the seventh highest waterfall in the world. To my surprise, there was a bit of water flowing, kind of unusual this late in the fall.
The fall colors may not match the technicolor splendor that happens in the hardwood forests of the eastern U.S., but then those forests don't have the backdrop of vertical granite walls that Yosemite has. I was reveling in the splash of color here and there. I often think that fall is my favorite time of year here.

I made my way across the meadow trail to Sentinel Bridge. The cliffs of Glacier Point loomed high above. I didn't realize that I'd be up there looking down the very next day (that will be another post).
Half Dome seems to loom over every meadow view in the valley. It rises 4,800 feet above the valley floor. Although glacial ice filled the valley to the rim, Half Dome stood above the frozen rivers. It was shaped by exfoliation sheeting (corners and edges snapping off), as well as a bit of undercutting from the glaciers below. As you will see in a near future post, Half Dome would better be called Four-fifths Dome, but that doesn't flow so well. Actually I prefer the Native American name of Tis-sa-ack ("Crying Girl").
Because people tend to stare at Yosemite Falls when they are flowing, they find it easy to miss the prominent cliff of Yosemite Point and the Castle Cliffs (below).
I crossed the Merced River at Sentinel Bridge, and got a colorful version of the iconic view of Tis-sa-ack reflected in the still water.
It's the funniest thing...the seven square miles of the floor of Yosemite Valley may very well be the most crowded real estate in the national park system. The park doesn't get the highest number of visitors in the system, but it does get five million, and something like 90% of them spend their visit in the valley. And yet, despite the crowds on the day I was there, the moment I got off the road, I invariably found myself alone. Finding peace in the middle of tourist chaos is a precious gift, and I soaked it in.
Approaching the footbridge near the empty Curry Housekeeping Camp, I had a fine view towards Yosemite Point and the Castle Cliffs reflected on the Merced River.
I quickly walked through the gaggle of people at the stores in Curry Village (I'm not a purist; I stopped for a Gatorade at the store). I headed up the trail to Happy Isles. I started to find more and more Dogwood trees turning shades of pink and yellow. I made it to the Nature Center and met with my students to talk about geology, and then we made our way back to Yosemite Lodge.
While I was talking to the students one last time, I happened to turn and saw the Moon rising along the cliffs off to the southeast. I snapped some zoomed pictures, only to find later that I was aiming directly at Glacier Point. If you look closely, you can see the fencing and people gathered on the edge of the precipice. I was pleased with the effect.

We got on the bus and headed home, and despite the hubbub of running around with students all day, it was one of the most serene experiences I've had in a while. And best of all, I would be up there again the next day!

Monday, October 30, 2017

El Capitan Rockfall: Alternate Views, and a Realization That This Wasn't the First TIme

El Capitan and the September rockfall from Taft Point on Oct. 29, 2017
Yosemite Valley changed geologically on September 27 and 28, and as I noted in my previous post, the valley will never look the same again. A series of rock falls resulted in a new scar on the east face of the east wall of the El Capitan cliff that can be seen from many points within the valley, including the iconic Tunnel View.
September rockfall from Taft Point on Oct. 29, 2017
I finally got to Yosemite Valley on Saturday, and got a few photos from the Tunnel View that I posted yesterday, but I was with students on a bus. Buses aren't allowed to stop just anywhere in the valley, so I was anxious to get back to the valley in my own car, and Mrs. Geotripper was all for visiting the valley, so we went back up there yesterday. The question, of course, was where to go for a good look? I definitely wanted an aerial view, so we headed up Glacier Point Road, the only route that allows for views from the rim of Yosemite Valley. Glacier Point offers views beyond belief, but only of the upper end of the valley. For a view of El Capitan, the "easy" choices are to hike to the top of Sentinel Dome, or to hike to Taft Point. Both hikes are about a mile and are not overly difficult. Sentinel is farther to the east and doesn't provide as good an angle on the cliff face that fell, so I headed out to Taft Point as the sun approached the western horizon.
The view is striking. The rocks let loose from well over a thousand feet over the valley floor. According to Greg Stock, geologist for Yosemite National Park, the biggest slab (out of seven total), was 394 feet long, 148 feet wide, and between 8 and 28 feet thick. That's bigger than a football field. It had a volume of 10,250 cubic meters, and weighed about 27,675 metric tons. If these numbers and dimensions seem incredibly exact, there's a reason. As Greg Stock explains, in an informative research paper, the walls have been mapped in three dimensions by a form of radar (lidar), and in the aftermath of the rockfall, the walls at the site of the fall were mapped again. The difference in volume could then be calculated.
El Capitan from Taft Point in 2005
I was at Taft Point in 2005, taking pictures of course, and one can compare the appearance of the cliff prior to the event in September.
Horsetail Falls area and future site of rockfall in 2005
The rockfall is also apparent from many spots on the valley floor. We headed to El Capitan Bridge, which offers an excellent straight-on view with the Merced River in the foreground. The white scar is unmistakable.
The Horsetail Falls cliff on Oct. 29, 2017
The difference between before and after couldn't be clearer. It's easy to miss the scale on cliffs this grand...remember, the missing slab of rock was bigger than a football field.
The cliff near Horsetail Falls in 2016
Another way to get a sense of scale is to add the 3,000 foot cliff of El Capitan to the scene...
El Capitan and the Horsetail Falls cliff on October 30, 2017

As I was going through my old pictures, I came to realize that slides have come off this particular cliff in the past. I actually witnessed one of them in 2010 when I was lounging on the granite near the top of Sentinel Dome across the valley. When I say "witnessed" I mean I heard the commotion first, took a moment to realize what I was hearing, jumped up, scanned up and down the valley, and finally thought to turn on the camera and take a few pictures of the rising dust plume.
Dust plume from the 2010 rockfall east of El Capitan
My account of that event can be found here: http://geotripper.blogspot.com/2010/10/rock-fall-near-el-capitan-in-yosemite.html. One can see in the picture below that the 2010 fall was just below the slab of rock that came down in 2017. One can imagine that the stresses on the cliff above were complicated by the event several years earlier.

Saturday, October 28, 2017

You Can Never See This View Again. Ever.

The title isn't as ominous as it sounds, but it is true. This is the panorama seen from Tunnel View at the west end of Yosemite Valley, one of the most famous viewpoints in the world, in 2013. But the specific scene above can never be experienced by anyone ever again. Geological forces, instead of acting at a slow incremental pace, moved things tragically fast late last month. A chunk of granitic rock the size of a football field came off the cliff just east of El Capitan (cliff on the left), and the scar will be visible for centuries. The picture below is how it looked today.

The view is fundamentally the same, but the changes are occurring, and the appearance of Yosemite changes with it. See below for a zoom of the cliff near Horsetail Falls, first in 2013, and then how it was this afternoon.
There were a total of seven rockfalls from the site on September 27-28, 2017. One person was killed and two were injured. One report mentions the largest of the falls as weighing 30,000 tons. This wasn't the biggest rockfall in Yosemite's history, not even close. The largest in recorded history was the Middle Brothers slide of 1987, which totaled about 1.4 million tons. Prehistoric rockfalls in the Mirror Lake area were larger still.
Actually, if we were to look at photographs from a decade ago, there would be an additional difference. The 2009 Ahwiyah Point rockfall scar can be seen just right of center, in both of the pictures above (but especially in the upper one). It totaled 115,000 tons, but thankfully injured no one. Check below for a 2009 view of the same spot to compare the difference.

Although partly hidden in shadow, the rock face at the bottom, just right of center (below the snow) is composed of darker weathered rock instead of the white scar seen in the photos above. Geologic change is constant only in that fact that it happens. Sometimes it is imperceptible, and sometimes is rapid and tragic.

Friday, October 27, 2017

Trump Demonstrates the Need for the Antiquities Act: Fighting for the Bear's Ears and Grand Staircase-Escalante

It's not complicated. It's called the Antiquities Act, and the law has but four sections, and no subsections. You can read it in its entirety below. It lays out the process by which the president of the United States can establish a national monument to protect endangered historic landmarks, historic and prehistoric structures, and other objects of historic or scientific interest that are situated upon the lands owned or controlled by the Government of the United States. The law was passed in 1906 because of the wholesale destruction of archaeological sites taking place across the western United States at that time.

American Antiquities Act of 1906 

Be it enacted by the Senate and House of Representatives of the United States of America in Congress assembled, That any person who shall appropriate, excavate, injure, or destroy any historic or prehistoric ruin or monument, or any object of antiquity, situated on lands owned or controlled by the Government of the United States, without the permission of the Secretary of the Department of the Government having jurisdiction over the lands on which said antiquities are situated, shall, upon conviction, be fined in a sum of not more than five hundred dollars or be imprisoned for a period of not more than ninety days, or shall suffer both fine and imprisonment, in the discretion of the court.

Sec. 2. That the President of the United States is hereby authorized, in his discretion, to declare by public proclamation historic landmarks, historic and prehistoric structures, and other objects of historic or scientific interest that are situated upon the lands owned or controlled by the Government of the United States to be national monuments, and may reserve as a part thereof parcels of land, the limits of which in all cases shall be confined to the smallest area compatible with proper care and management of the objects to be protected: Provided, That when such objects are situated upon a tract covered by a bona fide unperfected claim or held in private ownership, the tract, or so much thereof as may be necessary for the proper care and management of the object, may be relinquished to the Government, and the Secretary of the Interior is hereby authorized to accept the relinquishment of such tracts in behalf of the Government of the United States.

Sec. 3. That permits for the examination of ruins, the excavation of archaeological sites, and the gathering of objects of antiquity upon the lands under their respective jurisdictions may be granted by the Secretaries of the Interior, Agriculture, and War to institutions which the may deem properly qualified to conduct such examination, excavation, or gathering, subject to such rules and regulation as they may prescribe: Provided, That the examinations, excavations, and gatherings are undertaken for the benefit of reputable museums, universities, colleges, or other recognized scientific or educational institutions, with a view to increasing the knowledge of such objects, and that the gatherings shall be made for permanent preservation in public museums.

Sec. 4. That the Secretaries of the Departments aforesaid shall make and publish from time to time uniform rules and regulations for the purpose of carrying out the provisions of this Act. Approved, June 8, 1906 

It might be hard to believe, but there was a time when certain people thought the Grand Canyon was not worthy of preservation as a national park. There was a time when the protection of Zion Canyon was controversial. It was the same for Olympic National Park. Arches National Park. Death Valley National Park. Joshua Tree National Park. It may be hard to believe, but it took the actions of a president to save these crown jewels of our national park system from destruction by using the Antiquities Act. It sometimes took time for it to dawn on people that these lands were national treasures and worthy of protection. At a more mercenary level, it took time for some people to realize that more money could be made by protecting the land than could be made by consumptive uses like logging or mining. Eventually Congress named these monuments as national parks, and they are the most precious parts of the American landscape.
The history of the Antiquities Act has thus been controversial at times, but in the end, the monuments that have been established by presidents, both Democrat and Republican, have ultimately been recognized as important parts of our national heritage. These lands are the best of what our country has to offer. And that is what makes developments in the last few months so distressing. Our country has been hijacked by robber barons who think only in terms of personal profit from public lands at the expense of our citizens. Ground Zero lies in southern Utah and northern Arizona at Grand Staircase-Escalante National Monument, and Bear's Ears National Monument. We have a president who is illegally trying to undo the declarations of earlier presidents.
Grand Staircase-Escalante National Monument was established by President Bill Clinton in 1996, It was controversial because it was established in part to preclude strip-mining for coal on the Kaiparowits Plateau. The park protects 1.8 million acres of spectacular plateaus and slickrock canyons, and has come to be recognized as one of the most important paleontology parks in the nation. New dinosaur species continue to be discovered within lands protected by the monument. It seems ironic to me that towns and villages adjacent to the park have prospered because of tourism in this park. If they had built the coal mine, the coal itself would be giving out by now, and the towns would be in decline. Instead, as long as there is a monument these towns will do well. Given the issue of rampant overcrowding in nearby Zion National Park, Grand Staircase-Escalante provides a lot of wide-open space and recreational opportunities.
Bear's Ears National Monument is a special place. It had been proposed for decades, as it has the largest concentration of archaeological sites in the Four Corners region. Negotiations had gone on for years, and local tribes were unified in asking protection of the region, as were numerous environmental organizations. Grazing and certain other historical activities were to be allowed to continue. But greed won out and the negotiations faltered. President Barack Obama stepped in and established the monument, which was smaller than the most ambitious proposals, but which still included 1.4 million acres.
Cedar Mesa, the central feature in the southern part of the monument, was a critically important part of the "fertile crescent" that supported Ancestral Pueblo communities for more than a thousand years. Earlier cultures have lived in the region for thousands of years, and archaeological investigations have only scratched the surface of the stories to be told here. This land is sacred to the Native Americans who live in the region today, and many of their cultural activities take place in the monument.
Unfortunately, many of the present-day inhabitants of the region have no appreciation or respect for the cultural value of this region other than the price that they can get on the black market for pottery, fabrics, and other artifacts that they are stealing on an ongoing basis throughout the monument. The rangers of the Bureau of Land Management and Forest Service have been threatened with violence for doing their job of protecting these lands, and they are overextended. Trump and his Interior Secretary Zinke don't care that this is going on. They are now working to undo the work of decades of negotiation and compromise, and are trying to open these lands to even more exploitation and damage with their efforts this week. Most residents of Utah are in support of the monument, but they are being ignored by their own government.
I have a personal connection to the Bear's Ears. I have been bringing students into this region for thirty years, guiding them to understand the geology, archaeology, and natural history of this incredible region. All of these pictures were taken on these trips. Besides the cultural and archaeological value of this region, it is also a land of incredible vistas and spectacular scenery. With parks like Arches, Zion and Grand Canyon bursting at the seams with visitors, we need more protected lands, not less.
The president's actions are clearly illegal, and I hope that anyone who loves this country will oppose him in this terrible venture. I cannot accept that this land will be given back to the pothunters and grave robbers. The local people who argue that these lands should be given over to the state because they and their ancestors have lived there for a whole century rarely note the irony of their attitude. The local people whose ancestors lived here for thousands of years want this land protected.

Even more, I hope that more people from other parts of the world will visit, explore, and make their own personal discoveries. People who love a land will fight to protect it from exploitation. If these issues concern you, please consider contacting your own representatives in Congress, and if they don't listen to you, consider working hard to replace them in coming elections. Government officials in Utah should also be hearing from us. They need to know that losing tourism dollars may hurt more than any short-term profits to be gained by destroying the monuments.
Yes, I'm angrier than usual tonight. These lands that I love more than almost any other are under attack, and I fear that greed and money will win out over what is right and good. Trump and Zinke are proving the wisdom of the Antiquities Act, as they the exploiters the act was meant to stop.

Monday, October 23, 2017

Ghosts of the Empty Lands East of the Sierra Nevada: The Town of Bodie

The Matterhorn Crest of the Sierra Nevada from Bridgeport. Bodie is another twenty miles to the east.
Central California is almost literally a "land flowing with milk and honey". The Great Valley (called by those who live elsewhere the Central Valley) is one of the richest agricultural regions on planet Earth, producing most of the nation's nuts, and a significant portion of its vegetables and fruits. And lots of honey, from the bee colonies used to pollinate the crops, and milk from the hundreds of dairy farms. The rich harvest is made possible by the imposing wall of the Sierra Nevada, a 400-mile-long mountain range that wrings out practically all the moisture in the storm systems that roll in from the northwestern Pacific Ocean. It is in so many ways a gentle land where extreme weather events are relatively rare (recent floods and droughts notwithstanding). The fault lines for which California is famous are relatively far to the west, so earthquakes don't often affect the towns and cities of the valley (although the possibility is certainly there).
But...rise above the valley floor and into mountains, and over the crest to the lands beyond to the east, and things change. The storms that bring so much richness to the west slopes are used up by the time they cross the crest, and often all they bring to the east is bitter cold dry winds. The forests, if they exist at all, are scraggly Pinon Pines and Utah Junipers. Most slopes are covered with drought tolerant sagebrush and rabbit brush. The growing season is measured in weeks, not months. Agricultural efforts in a harsh land like this are generally doomed to failure. In fact, the written history of the region is generally one of failure and disaster (the indigenous peoples of this land tell a different story of course; there is a difference between imposing one's will on a landscape versus surviving on the resources available).
In 1848, gold was discovered in the Sierra Nevada foothills, and hundreds of thousands of hopeful people converged on the Mother Lode with their dreams of avarice, or at least dreams of a better life. A few of them got rich, some of them barely got by, and many failed. Many of them walked and rode from Mexico and Central America, others came from the east coast by ship, and some courageous, but perhaps foolhardy people walked across the vast desert between the Rocky Mountains and the Sierra Nevada. Mere survival was the challenge for many of them, and a fair number didn't. Imaginative minds could hear the cries of those lost in the howling winds.
The damage at the top of the brick building was from a 5.7 magnitude earthquake last year. It closed the park for several months.
The Gold Rush lasted for half a decade before the rivers were depleted of their riches, and most of the gold that remained could only be mined by methods that required vast amounts of money from investors. There wasn't much left for the individual prospector to search for, and thousands of hungry miners began to consider the barren lands east of the Sierra Nevada that they had traversed years earlier. Men began to creep back over the Sierra Nevada and began searching the empty lands beyond. As usual, most failed in their efforts, but others found riches. One man managed both. W.S. Bodey found a ledge of gold ore in the barren hills north of Mono Lake in 1859, but before he could enjoy his discovery, he froze to death in the harsh winter. A few others worked the ledges in the years that followed, but it wasn't until 1876 that a truly rich lode was found. Investors were brought in, a series of mines, including the Standard Mine, were established, and by 1880, a town of 10,000 people had risen from the sagebrush. The city was called Bodie (Bodey's name was apparently altered to make the pronunciation clearer).
The town developed a fearsome reputation. In the harsh climate, there were few amenities besides drinking, and deadly conflicts were a constant part of life. One legend stated that a young girl, upon finding that she would be moving there wrote "Goodbye God, I'm going to Bodie" (a town has pride, and an editor for the local paper said the punctuation was wrong; she had actually said "Good, by God, I'm going to Bodie").

The mines were successful for a few decades, producing perhaps 2 million ounces of gold, but by 1913 the Standard Mine shut down, and people drifted away. 2,000 buildings were scattered across the valley, occupied by perhaps a few hundred people. A fire in 1932 destroyed most of the buildings, but 167 of them survived. Concerns about vandalism led to the establishment of Bodie Historical State Park in 1962, and efforts were made to stabilize what buildings remained. What's left is one of the most picturesque ghost towns to be found in the American West. The only residents today are a few rangers, and the ghosts. I'm not usually superstitious, but I would be just a little creeped out living there. I see the signs that say that all visitors must be gone by nightfall, and I wonder...why?
We visited the park at the end of September during our fall field studies trip, and the day was comfortable, not too warm, not too windy, but I found out later that overnight Bodie had been the coldest spot in the entire United States at 16 degrees (the hottest spot at 104 degrees was Death Valley; we were halfway between the two that night). Snow had fallen less than a week earlier, and snow fell again a few days later. And this was the "nice" time of year.
The Standard Mine mill and the once-proposed open pit mine on the hill beyond.

The Bodie Hills are the remains of four stratovolcanoes that were active 8-14 million years ago. Hydrothermal activity around hot springs associated with the volcanism was responsible for the emplacement of the ores. Gold resources certainly remains, and because the gold claims were still valid, efforts were made in the 1990s to mine the hill above the town by way of open pit mining. Millions were expended in exploration and public relations, but eventually the lands were withdrawn from mineral speculation, and the ghosts of Bodie will be able to rest in relative peace.

If you want to visit, information about the park can be found here: http://www.parks.ca.gov/?page_id=509.

Sunday, October 22, 2017

How Does a Pristine Cavern Look? Black Chasm Provides a Clue

Some things can only be experienced once. The discovery of a new plant or animal that no one has ever seen, a new mineral, a new planet in space, to see a vista that no one has witnessed before. Exploration of new things is one of the great joys of being human. One of the saddest lines I've ever seen in a move was from The Truman Show (1998):

Young Truman: I'd like to be an explorer, like the great Magellan.
Teacher: [rolling down a map of the world] Oh, you're too late. There's really nothing left to explore.
Entrance room of Black Chasm cave. The dirt on the decorations is from soil seeping in from above, but many of them are broken from early explorers and visitors.

And there are things that can be destroyed only once. The extinction of a species, a beautiful canyon marred by a poorly-planned development, the destruction of a culture or a people.
If there is anything I have learned as a scientist and a teacher, it is that there is never an end to exploration. I was reminded of this as I took a group of students on a field studies journey on Saturday. Ostensibly the trip was about caverns and karst topography in the Sierra Nevada Mother Lode, although it included a great deal of information about the 1848 Gold Rush as well. We toured Highway 49 between Jackson and Columbia, but included an excursion through Black Chasm Cave near the village of Volcano.
Helictites in Black Chasm Cave
So many caves that are known today were discovered in previous centuries, and have been explored and vandalized to a shocking degree. My opening point about a single moment of discovery and a single final moment of destruction applies in many ways to caverns. A cavern can only be discovered and explored once. From that time on, in human terms, it is moving inexorably towards destruction. Caverns cannot recover from the damage inflicted by human visitors in any kind of time frame that people would recognize.
Helictites in Black Chasm Cave
Non-cavers are often confused or bemused by the nearly maniacal lengths that cavers take to prevent causing damage to pristine caves. But the cavers themselves understand. Many experienced cavers have watched some of their favorite places turn from a mystical underground fairyland to a dark dirty troll's den in the space of a few years. Research literature documents the destruction of caves as their location becomes known to the public at large. For this reason, the location of the vast majority of caverns is a closely held secret. A pristine cave is a rare and precious resource that is too easily lost to vandals. As a consequence, most casual cave visitors will never know the experience of a newly discovered cave. But there is a way that they can come close.
Helictites and stalactites in Black Chasm Cave
There are around a thousand known caves in the Sierra Nevada, and six are open for tours: Crystal (in Sequoia National Park), Boyden (just outside Kings Canyon National Park), Moaning (near Columbia), California (outside San Andreas), Mercer (near Murphys), and Black Chasm. Each of them have their charms and educational value, but Black Chasm stands out. It is one of the few that has the feel of an undefiled cave, at least once you've crossed the "chasm".
The "Dragon", mascot of Black Chasm. That's not the normal color...the guide was using a laser pointer on it.
The miners who discovered most of the Sierra caves explored them with smoky torches or candles, and they as well as those who followed over the years had no compunctions about touching and breaking off the speleothems (cave decorations) found in the caves. Owners even encouraged visitors to take a souvenir, thinking that the stalactites would grow back within a few years. These caves ended up with dirty walls and ceilings, and the only stalactites left were those that were out of reach of visitors. This also happened at Black Chasm.
But a short distance into the steep cave entrance the rocks drop off into the inky darkness of the chasm itself. It's around 90 feet deep with sheer walls and a series of small lakes or ponds at the bottom. Getting to the rooms beyond required technical climbing skills that weren't practical until the 1960s and 1970s. Those who were then able to explore deeper into the cave were careful spelunkers, not vandals, and the rooms they found were spectacular.
When the owners decided to develop the cave, they constructed a series of stairs and bridges that provided access to the back rooms of the cave, but the stairwells also prevent tourists from getting too close to the pristine decorations. And what wonderful decorations they are! The first thing I always notice is the pearly white color of the dripstone and flowstone features. They don't have any soot or dirt on them at all. The next thing that comes to my attention is the total lack of broken features. They quite literally look the way they did when they were first discovered except for the lighting. Because the flowstone and other features are translucent, the owners were able to place the lighting behind the features so the light could glow through. The photographic results sans flash are wonderful. Flash pictures always seem to make the speleothems look flat and featureless.
The crowning feature of Black Chasm Cave is the number and variety of helictites. They can be thought of as stalactites on drugs. They don't believe in gravity and have instead grown in all kinds of directions, almost as if someone took handfuls of spaghetti noodles and tossed them onto the wall. They are rare in caves, especially those open to tourists, in part because of their incredibly fragile nature. A single touch would be more than enough to snap them off. But it hasn't happened at Black Chasm. The sheer number on some walls (thousands of them) have resulted in the cave being declared a National Natural Landmark, a federal program that encourages owners of outstanding natural features to protect their resource (of course it doesn't hurt their public relations).
The owners of Black Chasm Cave have done a great job of protecting their resource, and their tours are done well. In addition, they encourage educational groups by offering steep discounts, so I have no problem recommending them to my fellow educators. Information about visitation and tours can be found on their website at https://caverntours.com/black-chasm-cavern-national-natural-landmark/. They also have an excellent nature trail on the property (that will be in the next post), plus a curio shop with some surprisingly sophisticated speleology texts for sale, along with the usual geodes and t-shirts.

Don't ever stop exploring!