Wednesday, October 31, 2012

"I'm not in this race to slow the rise of the oceans or to heal the planet"

Picture from The Message
If there is any justice, this quote by Mitt Romney will hang about his neck like the proverbial albatross until his sad excuse of a presidential campaign is consigned to the dustbin of history. Global warming and climate change have become one of the most profound issues of our history as a civilized society, and it has been all but ignored by the presidential campaigns and most congressional races.

Hurricane Sandy did not result solely from global warming. As climate scientists have made clear, storms and hurricanes are not caused by warming, but they are intensified and strengthened by warmer ocean temperatures. The best analogy I've heard about this subject is the steroid scandal that infected professional baseball a few years ago. No single home run was caused by steroids, but the total number of home runs rose as players juiced up on the drugs. 

It is one thing to disagree about the dilemmas we face concerning global warming, whether we try to change the trajectory of the build-up of greenhouse gases, or whether we simply prepare ourselves for the inevitable effects of the rise of sea level. It is quite another to completely deny the existence of global warming as Senator James Inhofe does, even as his Oklahoma constituents broil in the unprecedented heat waves of the last few years. And it is even worse that presidential candidate Mitt Romney, who once agreed that global warming was a serious concern, pandered to the worst impulses of his political party by mocking President Obama, saying "I'm not in this race to slow the rise of the oceans or to heal the planet". And climate scientists are harassed and threatened by ignorant fools.

Global warming is no longer a prediction of future effects. It is with us now. Many of the projections that were made a decade or more ago are not only coming true, but they are coming true at higher rates than predicted. I'm not here to argue the point; people who have dedicated their lives to the study of our climate have made all the arguments that need to be made. They simply need to be heard, and our politicians need to seek knowledge about issue rather than rejecting it out of hand under the direction of their corporate contributors.

And now this horrific storm has strewn destruction across our eastern seaboard: What will it take to raise awareness, if not this?

Monday, October 29, 2012

Yosemite Reflections and the Answer to the Wee Mystery

Most everyone who tried figured out the trick in yesterday's little mystery. Half Dome in Yosemite was indeed reversed, and it was reversed because we were looking at a water reflection of the iconic rock that looms over Yosemite Valley. One of the reasons I love the fall season in the valley is that the rivers are at their lowest ebb, providing a unique mirrored perspective of the high cliffs. The first and second pictures today are yesterday's mystery pics in their correct orientation.
As I noted in yesterday's post, I was walking from Yosemite Lodge to Happy Isles, and as much as I could I followed the banks of the Merced River. There was no wind, and long stretches of the river were motionless pools. I've been to Yosemite around 70-75 times in the last 20 years, but these scenes were new to me.
So, enjoy the view! The Merced River is the largest river in the valley. It runs all year, but on this day the flow was 23 cubic feet per second, about as low as it can get. Normal spring runoff can produce flows of 1,000-2,000 cubic feet per second, and the worst recorded flood in the upper valley (1997)  reached 10,100 cfs.
As mentioned yesterday, the riverbank environment has been severely impacted by the visits of 4 million people per year. Vegetation has been trampled, leading to sedimentation of the river where soil is not held by the roots of trees and shrubs.
Only two fish species are native to Yosemite Valley, the rainbow trout and the Sacramento sucker. Other species were introduced in the 1870s, and trout were stocked through the 1970s. The fish that remain today are 'feral' populations. The non-native fish have had a profound and negative effect on the other creatures in the riparian ecosystem, especially the amphibians. The endangered Sierra Nevada Yellow-legged Frog is an important example. It has been extirpated in almost every lake and stream where fish have been introduced.
I walked past a very quiet tent camp in Curry Village. This was the most deserted part of my walk, but during the summer, it is a hotbed of tourist activity. I just love this time of year!
I've never really seen Stoneman Bridge before. We always drive or walk over it all the time, but on this day I wandered up to it from downstream to get a different view. Half Dome and Washington Column were reflected in the water. I couldn't help but notice that photographers had piled rocks in the riverbed to form a bridge to the best vantage point.
 In the picture below, North Dome is reflected in the water...
The water in the river was transparent and totally still. At this point, I had to leave the river. It makes a long meander to the north and I was running out of time. I needed to talk to my students about the huge Happy Isles Rock Fall that took place in 1996, damaging the Nature Center, and killing one person. We would also be talking about the catastrophic flooding in 1997. Those violent natural disasters seemed distant and improbable in the peaceful setting along the river on this fall day.
I've enjoyed photographing birds over the years. The water ouzel has proved to be one of my most elusive quarries over the years. I've seen them, but they never seem to stop moving. I saw one this time and I snapped a dozen pictures, but I remain mostly defeated in my efforts towards a sharp picture. This was the best one....
Better luck next time! And I hope it is soon...

Sunday, October 28, 2012

Up a Creek in Yosemite Valley, and a Wee Mystery For You......

I was in Yosemite Valley yesterday, and it was just gorgeous. I was conducting a field trip for my earth science class (oh, the torture; a required field Yosemite!), but had a few moments as the class was making their way from one end of the valley to the other to see the effects of the 1996 Happy Isles rock fall. I decided to do something new, and follow the Merced River as much as I could from Sentinel Bridge to Happy Isles.
Following the banks of the river is not as easy as it might seem. Not so much from inaccessibility, since the valley is flat, but because decades of overuse has severely impacted the bank vegetation, and the national park service is trying to limit the trampling of grasses and saplings by closing off parts of the river to foot traffic. The problem isn't as severe in the river channel itself (the gravel and rocks are rearranged every time the river floods), so I was able to see quite a bit of new territory by staying next to the water. And...I practically had the river to myself. There were only a few photographers about.

It's not like I was exploring a virgin wilderness, mind you. The picture above was the wide beach in front of the Curry Village canvas tent village. Had this been a summer day, this spot would have resembled a crowd on southern California beach. But today it was deserted; the village is closed down, either for the season or for the hantavirus scare.
The beach is not so much sandy as it is pebbly. I enjoyed getting on hands and knees to see the plutonic rocks up close and personal. Although the rocks of the Sierra Nevada are described as "granite", it would be more correct to say that they are "granitic". A look at a geologic map of the region shows a variety of rocks that formed the same way that granite does (magma cooling slowly deep in the crust), but which have a variety of names based on the proportions of feldspar, quartz and dark iron-bearing minerals like biotite mica: diorite, quartz monzonite, granodiorite, tonalite, and gabbro. The "average" Sierra rock is more like granodiorite than granite. The area upstream of Curry Village is dominated by the Half Dome granodiorite, which at 86-88 million years is one of the younger intrusive rocks of the Sierra Nevada.
I promised a wee mystery. And it is "wee"...

What is wrong with the following two images???

How it was: Today in Yosemite Valley

It was one of those treasured kind of days, the chance to explore Yosemite Valley. I was on the road with my students, and we got a great day of sun and fall colors (and quite a bit of geology, too). I lead with a picture of Half Dome along with one of the most beautiful trees in the world, an old elm in the meadow between the visitor center and Lower Yosemite Falls.
On a geology field trip, one does not just march into Yosemite (shades of Sean Bean and Mordor?). One has to be properly prepared. A trip from the Great Valley to Yosemite Valley involves passage through the Sierra Nevada Metamorphic Belt and a journey through time, back as far as the latest Proterozoic. We stopped along the Merced River several times, first to look at gold dredging tailings (and an osprey tending to a nest), and then to look at some incredibly contorted ocean-floor cherts of the Calaveras Complex. What a great mapping exercise for structural geology students! Of course, accessibility is a problem...these rocks are completely underwater for most of the year.
Then a stop at the famed Tunnel View, which is close to the spot where the first European-Americans discovered the valley in 1851. The local Miwok people discovered the valley thousands of years ago, of course, but that somehow seems to escape the attention of the historians (and really, why do we still celebrate Columbus Day?).
 Fall is just getting going in Yosemite Valley. We had a rainstorm last week, so the air was clean and crisp. I often think that fall is my favorite time of year in Yosemite, with the vivid colors and sparse crowds (but then I visit in spring...or winter...or summer, and change my mind).
I gave the students a bit of free time with an appointment to meet at the upper end of the valley in a couple of hours. I set off across the meadows and over to the Merced River to have a look...
The Royal Arches and North Dome seemed little changed. This is not so true of Half Dome since the Ahwiyah Rock Fall in 2009 permanently changed the appearance of the iconic rock.
 The deer were out in force, distracting my students, and me too...
I walked across Sentinel Bridge to take in a view of Half Dome from a perspective that no one in the world has ever thought to photograph (ok, ok, everyone who visits Yosemite Valley takes this picture; but really, who can resist?). But it did give me an idea, after a moment's reflection. I set off towards Happy Isles along a new route...more on that next time.
It was a beautiful day.

Friday, October 26, 2012

Geological Excursions in the Sonora Pass Region now available at Sunbelt!

Our field guide to the geology of the Sonora Pass region and the eastern Sierra Nevada region is now available for sale at Sunbelt Publishing for $24.95 (here is the link)! This was the roadguide for our recent meeting of the Far Western Section of the National Association of Geoscience Teachers. There are quite a few geological road guides out there for the eastern Sierra Nevada, especially around the Mono Lake area, but there have been fewer guides for the area to the north. It is a fascinating region, with widespread Miocene volcanism, faulting and Pleistocene glaciations (the largest glaciers of the eastern Sierra Nevada traversed the West Walker River gorge).
One of California's most intriguing ghost towns can be found at Bodie (above), and one can also find a strange "fluvial forest" in the West Walker River, a group of long-dead Ponderosa pines that provide evidence of a century-long mega drought only a thousand years ago (below).
The western slope of the Sierra along the Stanislaus River hides some geological treasures as well, including the Columns of the Giants and the Natural Bridges in the cave country north of Columbia State Park (below).
Here is the table of contents...

A Geographical Sketch of the Central Sierra Nevada
A Brief Overview of the Basement Rocks of the Central Sierra Nevada

Trip 1: The Sierra Crest Graben: A Miocene Walker Lane Pull-Apart in the Ancestral
Cascades Arc at Sonora Pass
by Cathy Busby, Alice Koerner, Jeanette Hagan, and Graham Andrews at the University of California, Santa Barbara
Trip 2: A Guide to the Geology of the Eastern Sierra Nevada between Sonora Pass
and June Lake, California
by Garry Hayes, Modesto Junior College
Trip 3: Geology and Climatology of the Saddlebag Lake Region near
Tioga Pass
, CA by Laura and Ryan Hollister
Trip 4: Sword Lake Debris Flow by Jeff Tolhurst, Columbia College
Trip 5: Unique Geology along the Stanislaus River, Western Central Sierra Nevada by Noah Hughes, Modesto Junior College
 Appendix A: The Flora of Central California: Central Valley to the Great Basin by Mary Cook

A reminder: Sales of this guide will fund the scholarship program of the Far Western Section of the NAGT, which supports geology majors throughout California, Nevada and Hawaii. The book can also be purchased directly from the Far Western Section at this link. Check it out!

Thursday, October 25, 2012

Geopoetry: Accretionary Wedge #51

It's already almost the deadline for the Accretionary Wedge #51. Where does the time go? This month's wedge is hosted by Matt Herod at Geosphere, and the topic of the month is geology and poetry. Specifically: "In this wedge I encourage people to wax poetic about anything geological they would like, in any poetic style. Be it limerick, haiku or sonnet. Of course, you don’t have to write your own poem if that is not your thing. Find a geology/earth themed poem that already exists and explain why you like it and what about it moves you. So lets all connect to the bard hidden within us and slam out some great poetry!".

Geology and poetry aren't usually associated with each other, although the word "poetry" played a big part in one of the more important research papers of the 1960s: the Harry Hess paper that laid out the basics of sea-floor spreading and divergent boundaries ("History of Ocean Basins"). In his introduction, he referred to his work as "geopoetry", in that his ideas were speculative, but based on science just the same. He expected the confirming evidence would emerge later on, as it in fact did.

I'm not much of a poet, but my students have put together some great stuff over the years. One of my favorites appeared on my desk in my second year of teaching, back in 1990. I offer it as my contribution to this month's Accretionary Wedge...

The Ballad of Historical Geology by Vicki

Winding our way through geologic time
Has been quite an experience
Learning about critters long ago dead
from fossil evidence

Crumping, crunching orogenies
Adventure beyond compare
Transgressions, regressions, climatic extremes
If we could only have been there!

Or better yet, time lapse photography
To show us what occurred
From way back when in the Cambrian
When life forms were so absurd

Our list for field trips has expanded
We're poised, rock hammers at our side
Let's go find that Burgess shale
And some giant trilobites

Archimedes, archaeopteryx,
Let's go from A to Z
And collect all that we can carry
of every fossil family

Let's check out that iridium layer
In our search for ultimate truth
Or did the dinosaurs really die
From drinking tainted vermouth?

Now the semester has drawn to a close
We're all ready to go
But there is one thing we haven't addressed
That I'd still like to know

The text mentioned Lucy
But it did not discuss
Fred and Wilma, Barney and Betty
And their importance to us!

And where the heck is Bedrock
On Pangea I or II?
Could I get a map to go there?
If so I bid you adieu!

Well, Vicki...I found Bedrock for you in 2011. It's in the borderlands between Colorado and Utah in the Paradox Basin. The picture is above...

Wednesday, October 24, 2012

Ghosts of the Gold Miners - The Kennedy Mine

As a geologist, I understand the attraction that historians have for history. Geologists are historians in their own way, although our "history" covers, oh, just a few billion years more than that of students of human history. On the other hand there is a certain distance between ourselves and our subjects. I can't exactly feel an emotional kinship with a trilobite or tyrannosaur, but I can look at pictures like these, and see something in the eyes and lives of the people who stood together in 1914 in front of the Kennedy Gold Mine in Jackson, California. The picture hangs in the museum at the mine. If this had been a picture of a Pennsylvania shipyard at almost the same time, one of the young men could have been my grandfather.
These were the miners, millers, muckers, and mechanics who ran the gold mining operation. Even though it ceased operations in 1942, much of the mining complex still remains, and is open for tours. We were there for our field trip to the Mother Lode last weekend.
Looking at pictures like this, and looking at the artifacts from that time, one quickly realizes that there was nothing romantic about being a gold miner. If such "romantic" lives ever existed, it was during the first heady years of the Gold Rush in 1848, but it didn't last long, and few people actually became rich. Most of the miners were the farm laborers of their day. Pay was low, and conditions were appalling. A diagram at the museum shows that with the exception of the Depression years, the miner's pay was much lower than other related positions in the workforce.
Imagine working in a place where the management required that all workers had to change their clothes and shower in front of observers, to make sure they weren't trying to walk out with gold samples. Safety regulations didn't exist. There were no hard hats. Mining accidents were a fact of life; exhibits at the mine note that accidents took 36 lives between 1887 and 1942. In 1922, one horrible tragedy (an underground fire) took 47 lives in the adjacent Argonaut Mine. Statistics don't record how many miners led shortened lives from breathing the quartz dust ("miner's phthisis", or silicosis).
The miners and muckers worked in the dark, with a single candle for illumination in the early years (carbide lamps came later). The work was backbreaking. Early on, holes for explosives were drilled with hand tools. Steam operated drills came along later, but they produced far more dangerous silica dust.
Still, the mine was an impressive operation. From 1860 to 1942, the mine produced around 1.4 million ounces of gold. The underground workings exceeded 130 miles in length, and reached a depth of 5,912 feet, the deepest mine of its day. The site had a 100-stamp mill for crushing the gold-bearing rock (about 1/4 ounce per ton) that ran 24 hours a day. The noise had to be deafening.
The present day metal headframe is 125 feet high. The earlier wood headframe (visible in the historical photo above) burned in 1928. The fire actually burned all of the above-ground buildings except for the stampmill and the mine/milling office (below).
The most jarring building on the property is the mine office. It looks totally out of place given the harsh industrial nature of the other surviving buildings at the mine. Despite the Victorian appearance, there was a foundry on the left side of the building where the gold ingots were forged. The mine offices and walk-in safe were on the right bottom floor. Offices took up the second floor, and the top floor included accommodations for investors and VIP visitors.
The mine produced a lot of gold and yet it also produced mountains of toxic waste (they were polluting the town water supply and were eventually forced to put the acid-rich tailings in another valley entirely, using a unique set of waterwheels). It was a critical part of the town's economy, and yet broke lives. It is an interesting conflict of priorities. The last owner of the mine site desired that mine be preserved, and yet she also hoped that the property could preserve the natural environment as well (there are far more trees on the mine property today. The Kennedy Mine Foundation attempts to fill that role, and they have done a good job at presenting the story and the history of the operation.

Monday, October 22, 2012

I Successfully Predicted Four Earthquakes This Week! And Why Events in Italy Today are Chilling

Before anyone gets excited about today's headline, read the following disclaimer:


Allow me to repeat myself...


Now...let's read this together out loud in unison...


Good. Let's move on...
Last week was Earth Science Week, and on Thursday we in California did emergency drills for earthquakes in the Great Shakeout. In conjunction with the Shakeout, I revised a previous post about the myths and misconceptions about California and earthquakes. It was quite long, so you may have missed that I predicted a couple of earthquakes in one of the later paragraphs. They were as follows:
  • 200 earthquakes will occur in California,
  • Of these, there will be a magnitude 4 quake in southern California, most likely in the Colorado Desert near Salton Sea.
  • There will be a magnitude 3 earthquake in northern California, most likely north of the Bay Area, somewhere around Clear Lake.
  • There will be a larger quake at the Vanuatu Islands in the Pacific Ocean, quite possibly in the magnitude 6 range.
  • There will be a magnitude 5 earthquake offshore of Japan.
So, how did I do?

How about that? Five for five. 100%. So I am an earthquake predictor par excellence, eh? No. Not at all. I did what any charlatan or fake psychic (and they're all fake) would do: I played the odds. Take a bit of geologic knowledge and set the parameters wide enough, and you will almost never get an earthquake "prediction" wrong. Earthquakes happen in particular regions, and the "background" seismicity will always include some slightly larger temblors.  "Psychics" have been predicting quakes for years to pad their scores on the yearly list of predictions for the new year. They are depending on getting enough easy predictions right so they sound like they have those "special powers" even though they get practically everything else wrong.

Here's what's wrong with this...they act with impunity, knowing they will never pay a price for being wrong. They will scare people without fear of arrest for causing worry and panic.

So what was the chilling news out of Italy today? It was this: six geologists were convicted of manslaughter for failing to predict a terrible quake that killed 309 people. They were scientists who were convicted for not foreseeing the unforeseeable.

This is a huge issue. Self-styled psychics and con artists can act with impunity without fear of punishment, while responsible seismologists and other scientists are put on trial for not being able to predict something that has never been successfully predicted. Something is very, very wrong in Italy, and I hope the geologists are cleared on appeal.

People who are caught in tragedies will always need some way of understanding what has happened to them. They will often turn to a scapegoat as a way of avoiding tragedy in the future. In ancient Israel, a goat (a "scapegoat") was symbolically loaded with the sins of the people and banished to the wilderness. In the culture of the day, when the gods ruled the heavens and controlled the natural disasters that affected society, it almost made sense to do this. In this modern era, it makes no sense at all to make scapegoats out of the scientists who are doing all they can to protect lives by understanding the patterns and probabilities of earthquakes.
We can't make short-term predictions, but we can certainly make long-term ones. This is a map of the probabilities of damaging earthquakes in California over the next 30 years. Should we arrest the geologists if a quake on this map turns out to be bigger than predicted?

Sunday, October 21, 2012

The Sierra Nevada Underground: Into the Black Chasm

California is full of delightful geological surprises. Mention "caverns" and most Americans will think of places like Mammoth Cave, Kentucky, or Carlsbad Caverns in New Mexico. Not too many people will think of California, but California does have an unexpected number of world-class cavern systems.

The state has such a complex geologic history involving granite intrusions, volcanic eruptions and earthquakes that it is easy to forget that for vast stretches of geologic time, California was stunningly boring passive continental margin. In Paleozoic time, the region was a shallow sea, slowly collecting mud and lime deposits in a tropical environment. In some cases, the tropical islands and shorelines were elsewhere, but the rocks were transported to California on the giant conveyor belt of the Pacific and Farallon tectonic plates. As the Farallon plate was subducted beneath the continental margin, the limestone sequences were scraped off and added to the metamorphic sequences of the western Cordillera.

The limestone was baked and transformed into marble, and a great deal of marble was preserved in a tract of crust (or terrane) in the western Sierra Nevada Metamorphic Belt called the Calaveras Complex. The Calaveras hosts many of the caverns found in the state; there are hundreds of them. Unless I lost count somewhere along the line, six caverns in the Sierra Nevada have been developed for public tours: Crystal Cave in Sequoia National Park, Boyden Cave in Kings Canyon, and four caves in the Mother Lode: Moaning Cave, Mercer Cavern, California Caverns, and today's destination, Black Chasm Cavern.
I was at Black Chasm yesterday with twenty of my students, on a field studies trip through a portion of the Mother Lode. The cave is privately owned, but it has been granted National Landmark Status, a designation that recognizes the geologic or historic importance of the cave, and encourages the preservation of the feature. The owners have done an good job at Black Chasm. It is one of the best places I know of that gives the casual visitor the experience of seeing a cave that is close to pristine condition, much as when it was first discovered.

The problem is that many Sierra caves were discovered by miners in the 1850s, and they became well-known and well-visited. It was not at all unusual for the cave owners to encourage their visitors to take a stalactite as a memento of their visit, and the caves were stripped of their decorations (speleothems would be the proper term for the stalactites and other features of caves). The early explorers often used torches for light, and the soot left its mark on the remaining speleothems.
Black Chasm was discovered early on, but it was the cave's namesake that protected it from the worst damage. The entrance into the cave is very steep, and after clambering down the steep slope, probably hanging onto a rope, the early visitors passed through one interesting room, but then found themselves perched on the brink of an eighty foot cliff that ended in the darkness below. Without technical equipment there was no going forward or going down. The interior passages of the cave were protected from vandals by inaccessibility.

When the owners of Black Chasm decided to open the cave for tourism, they constructed a walkway that clings to the wall of the Black Chasm and passes into the rooms beyond. The contrast between the first room of the cave and the last room is striking. Many of the stalactites and other speleothems are broken off, and the remaining ones have a patina of orange-red mud that comes from seepage of iron oxides from soils above, but also from soot and dirt from the early visitors. The room is still pretty, but not exceptional to anyone who has visited other caverns.
Then you pass through the namesake chasm. The walls on both sides are vertical, and in the inky darkness below there is a deep lake. The cave is host to a unique species of amphipod, which I hope is immune to the effects of fallen eyeglasses, cameras and other paraphernalia dropped by visitors. The owners clean up what they can, but cave diving is a seriously dangerous business, and I don't think they do it casually for cleaning things up.They warn you to hold onto your valuables...
And then you start to see what an undamaged and pristine cave is really like...the parallel fins are referred to as cave bacon.
The natural color of most speleothems is a pearly shade of white. It's truly hard to resist touching these decorations, especially since they are so close to the walkway. I trust you won't do it if you visit. It is far too easy to cause damage or mar the appearance. It is such a privilege to be able to see things like this without a plastic screen blocking the way...
The cavern has some nice examples of soda straws (above), which are very thin stalactites that are among the first speleothems to disappear in unprotected caverns. One touch would be enough to break them off. I've seen some in Kartchner Cavern in Arizona that broke off without being even touched. The just broke off, maybe from something as weak as wind currents or the shaking of a distant earthquake (the effects of quakes are muted in caves, as they are much less affected by surface wave shaking).
The draperies in the far room of the tour are nothing short of fantastic. The lighting is nicely placed to allow for back-lighting. Flash photography from handheld cameras almost never works in caverns. The flash washes out any contrasts in color, and without shadows, the features lack depth. I get a lot of non-flash pictures that I have to delete because I shake too much, but the few I get with the back-lighting are far more satisfying.

The final room of the tour is exceptional because of one particular kind of speleothem: helictites. Helictites can be characterized as stalactites that refuse to recognize the law of gravity, or by some descriptions, stalactites on acid. They have grown in random directions, perhaps because the water that formed them was driven as much by capillary action as it was by gravity.
From a distance, the wall looks fuzzy with white "stuff"...
Up closer, the fuzz resolves into thousands of individual helictites.
I can almost imagine them wiggling about and forming into a tourist-eating cave monster...
The complexity of the helictites is just stunning. I never get tired of trying to get another shot. Shawndee, the manager at the cave, probably thinks I'm ignoring her while she is talking to my students, but I do listen. I'm just multitasking, trying to get the perfect shot!
I always see something new whenever I go into Black Chasm. This time it was the dogtooth spar crystals in an obscure cavity along the walkway. Dogtooth spar is a crystal form of calcite, which along with aragonite is the mineral that makes up most of the speleothems in the cave.
Black Chasm Cave, as noted before, is a privately owned business. They are there to make a profit, but they have done a good job of protecting their cave, and I recommend a visit. They offer discounts for educational groups (they can accommodate up to 22 people at a time, so large classes would need to split into two tours). More information about the cave can be found here. Tell them Geotripper sent you!