— Photo by Michael Warner

The spectacular tower karst landscape of Guilin Province in China is a geologic wonder that has inspired many generations of Chinese artists.

When I started composing this article in my head, this thought came to me:  “tower  karst” and “Onesquethaw” — two rather obscure terms (to most people) — in one headline.  Might be an attention-grabber!

The Onesquethaw is the stream that originates in Helderberg Lake and flows southeast  — sometimes through impressive canyons and over surging rapids — on its way to the Hudson River.  It passes photogenically through a number of diverse natural preserves, some of which I have written on in the past in this column.

“Karst” is the geologic term for an area of carbonate bedrock — most commonly limestone, but occurring in marble, dolostone, and gypsum as well — with resulting characteristic landscape features.  Each of these rock types dissolves in slightly acidic water, and, given the amount of moisture in Earth’s atmosphere and the carbon dioxide emitted by decaying vegetation on the floors of forests and fields, there is no lack of mild carbonic acid on our planet.

When the acid meets the limestone, sinkholes, caves, underground streams, and bubbling springs are frequently the result.  But, even in the same general areas of the Earth’s surface, outcrops of the same rock type may weather and erode at different rates and leave behind odd and even fantastic remnants of the bedrock — a phenomenon known as differential weathering and erosion.  Think of the great buttes and pinnacles of Monument Valley beloved by Western filmmaker John Ford.


In the Onesquethaw Creek preserve off Rarick Road, Thom Engel stands at the base of one of the karst towers. The Enterprise — Michael Nardacci


Famous Asian landscape

The landscape of Guilin Province in China — commonly pronounced “Guy-lin” — is famous the world over, figuring in thousands of classic Chinese paintings and ubiquitous on the walls and menus of Chinese restaurants: giant limestone towers wreathed in morning mist, often featuring diminutive rice farmers or fishermen dwarfed by the magnificence of the rocky scene.

These towers are the last remnants of ancient limestone layers hundreds of feet thick.  They are laced with enormous cave systems and in some cases have been used by the inhabitants of Guilin as dwelling places and temples for thousands of years.

They have a mystical, otherworldly look to them and their attraction for artist and visitor as well is obvious.  And, though the towers of Guilin are perhaps the best known to travelers, there are many other such sites in Southeast Asia and elsewhere in the world.

Helderberg discovery

As often as I have hiked the hills and forests of the Helderbergs, I am still astounded to find fascinating geologic phenomena in places that — for one reason or another — I have managed to miss in my travels.

Though I have followed the valley of the Onesquethaw Creek through many of its twists, turns, and drops, there is one area off Rarick Road south of Route 32 that had escaped my notice until a long-time friend and fellow caver Thom Engel asked me if I knew that there was a display of tower karst in a natural preserve owned by the Mohawk Hudson Land Conservancy.  It is called the Onesquethaw Creek Preserve; it is a bit tricky to find in the thick forest that borders Rarick Road and there is no clearly defined parking area.

But Thom was able to get his feisty little Honda Fit off the road on what might once have been the beginning of an old logging trail, and, after a short hike, we found the fairly well-defined path that leads into the preserve.  Like many of the forested areas of the Helderbergs, the trees grow thickly, forming a green canopy that keeps the ground relatively free of large, dense shrubs, which obscure the view. 


Erosive action of the Onesquethaw Creek has removed the surface sediment, exposing the jointed rock and potholes formed by rapidly flowing water. Devin Delevan stands on the heavily fractured limestone bedrock that underlies much of the preserve. The Enterprise — Michael Nardacci


The surface undulates and the relatively thin ground sediment is a mixture of soil and glacially deposited pebbles, cobbles, and boulders known as glacial drift.  Tree roots tend to spread out horizontally due to the thinness of the sediment, and walking is a bit precarious.

We had gone only a few hundred feet when we found ourselves confronted by the first of at least a dozen pinnacles of the Coeymans limestone, this one featuring three rounded peaks.  It was highly weathered and covered with mosses, ferns, and other shade-loving plants.

Diminutive compared to the lofty towers of Guilin — 20 feet in height compared to the Chinese towers that soar hundreds of feet — it was definitely an example of tower karst, and scattered around it were others of equal or lesser height.

Exploring the mystery

As it happened, the sky was overcast that day, making the woods rather gloomy, and so I returned on a sunny day a week later with my research assistant, Devin Delevan, to take more photographs and to see if I could come up with some explanation of why these features had formed here.  One tower with a double peak was a particularly striking example, and Devin climbed part way to the top to show scale.

The pinnacles stand close to the edge of the Onesquethaw Creek, which in this stretch usually appears as a dry bed buried in rounded boulders and soil, showing flow only in times of exceptionally heavy spring melt or a storm event such as a tropical storm or hurricane.

But its appearance is misleading, for, in karst lands, streams often are flowing underground.  In many stretches of the Helderbergs, one can drive for considerable distances without seeing a major stream; however, under the surface, extensive cave systems such as the eponymous Onesquethaw Cave near Clarksville as well as Albany County’s Knox Cave and Skull Cave, and Howe Caverns, Secret Caverns, and Ball’s Cave in Schoharie County feature streams that eventually resurge from valley walls or artesian springs to find their ways to the Hudson or Mohawk rivers.

We hiked some distance upstream of the karst towers to the higher area near the edge of the preserve — beyond is private property and farmed land.  Here the ground flattens out for a long distance into a level stretch, which geologists call a bench, likely planed off by the glaciers. We soon heard the sound of flowing water, incongruous given the exceptional dryness of the downstream bed.

Shortly, we came to a portion of the stream bed that was radically different from its downstream character  It is a wide, flat exposure of bedrock limestone, which is obscured by the glacial deposits in lower parts of the preserve:  dimpled with numerous potholes and deeply fractured, with some rifts several feet deep. 


In a froth-laden section of one of the ponds, slowly rotating whirlpools show where the water of the Onesquethaw Creek is disappearing into a cave. The Enterprise — Michael Nardacci


Slightly farther upstream, hundreds of gallons of water were pouring over the exposure, forming pools full of clear or froth-laden water, many of which were inhabited by seeming thousands of inch-long tadpoles.  A startled great blue heron interrupted his lunch and took wing when he spotted us but undoubtedly returned after we had left, unwilling to abandon such a fruitful feeding ground.

We then discovered that the ponded areas covered in froth also exhibited small whirlpools, and the rotating water could be heard gurgling as it was sucked downward.  Here the Onesquethaw goes underground much of the time, just as it does in the stretch near Clarksville that parallels Route 443 where Route 85 joins it, only to reappear farther downstream.

And this explained the dryness of the stream in the lower portion of its bed: The water is moving through a subterranean conduit — in common terms, a cave.  The fact that so much water was simply vanishing from the surface hints of the size of that conduit — yet we searched in vain to find an entrance that would admit a human being.

Joints across the universe

But that open expanse of deeply fractured rock offered a tantalizing clue to the existence of the tower karst features.  An examination of the fractures reveals that they occur in straight lines and frequently intersect at something close to ninety-degree angles.  These fractures are referred to as “joints” and they occur everywhere in bedrock.

The Mars Rovers Spirit, Opportunity, and Curiosity have shown joints to be common in Martian bedrock as well.  There are a number of ways in that they may form.  When erosion removes upper layers of rock — or massive glaciers melt at the end of an ice age — the lower layers, free of all that immense weight, are allowed to expand, and their uneven rate of expansion causes the rock to crack. 

 Earth, the violent clashing of the tectonic plates sends shockwaves for many miles beyond their collision boundaries, fracturing the rock often to great depths.  Mars is not believed to have active tectonic plates, but a third possible method of formation is the uneven expansion and contraction of the bedrock due to heating and cooling at different times of day and the year, a process which certainly occurs on Mars and other planets.

Once the joints form, weathering agents such as water and ice can enter them and begin the process of widening and deepening them.  Particularly in a carbonate rock such as limestone, the solution process can go down as far as the water table.  Then, as over the centuries the water table drops, the joints in the rock can continue to widen and deepen.

Due to differential weathering and erosion, some areas will break down faster than others.  In the photograph of Devin on the flat outcrop, note that some stretches are more highly fractured than others, and consequently will eventually disappear faster than the more massive, unfractured stretches.  In centuries to come, these more massive areas could emerge as examples of tower karst.

The limestone strata (layers) in this part of Albany County are around 100 feet thick, so there is a limit to the heights tower karst features can reach — unlike in Geilin and other areas of Southeast Asia where the limestone can be a thousand or more feet in thickness.  But it should be noted that anywhere they appear, the towers have emerged from rock that formed in seas that covered the landscape scores or hundreds of millions of years ago.

And it should not be a surprise that, beneath the mosses, lichens, ferns, and other hardy plants that can grow in the thin soils atop the karst towers of the Onesquethaw Creek Preserve, one might find fossils of trilobites, brachiopods, gastropods, and other shelled creatures that dwelt in the warm and shallow sea that covered this part of New York State a couple of hundred million years before the first dinosaurs ever walked the Earth.


The Enterprise — Michael Nardacci

A gigantic upended fragment of the Helderberg escarpment dwarfs research assistant Devin Delevan. The fragment, partially buried in sediment, was probably brought down by some of the last glacial ice to leave Albany County.

Geologists, I have often told my students, have a name for virtually everything.  For most people, an expression such as “debris that collects at the base of a cliff” would be sufficient to describe debris that collects at the base of a cliff!

But geologists find such an expression rather cumbersome — many of them write astonishingly fine prose — and to avoid that wordy phrase they have coined the term “talus.”  It is a generic term, for when cliffs are as high and massive and diverse in their layered rock types as our Helderberg escarpment is — some layers being soft and thin-bedded and easily weathered, others being extremely hard and massive — they will break down and produce fragments ranging in size from clay particles to gigantic, jumbled slabs.

Then under the force of gravity and the many agents of erosion—ice, water, and wind—they will begin their journeys to lower elevations on the slopes:  journeys that may take moments or days or centuries.

The Helderberg escarpment rises from close to the level of the Hudson River near Ravena and then moves northward on a gradual tilt that lifts it a couple of hundred or so feet per mile, reaching its greatest elevation at High Point above Altamont, where it turns west and gradually diminishes.

Its most prominent cliff is made of two layers of hard limestone — the Lower Manlius and above it the Coeymans — but those layers sit on alternating beds of relatively soft sandstone and shale known as the Indian Ladder beds and are capped by the Kalkberg and the New Scotland limestones, and other beds of shale, sandstone, and limestone.  All of these layers have been subjected to millennia of attack by the forces of nature, and the result is that the escarpment sits on a talus slope hundreds of feet high.

It is a hauntingly beautiful environment, radically different from the orchards and cornfields that border it. The haunt of crows, ravens, pilgrim thrushes, and (in spring) migrating white-throated sparrows, vast forests of deciduous trees and hemlocks on the slopes have had to grow to great heights in order to reach sunlight and have produced a world of perpetual green shade and trickling water.

Since the slopes also face north, whatever sunlight gets through the forest canopy never strikes the ground at a steep angle and the environment tends to be very humid.  Humidity is conducive to weathering and so the bedrock layers are buried under dirt and gravel and larger rock fragments, providing an atmosphere like that of a terrarium, and with similar results.


A view of the woods on the steep talus slope of the escarpment reveals a world of perpetual green shade, birdsong, and the trickling of water emerging from the ground. The Enterprise — Michael Nardacci


Every surface is covered with plant life, from the top of small, flat rocks to the massive boulders that moved down the slopes long ago, probably under the influence of the last glacial ice that covered this area.  These are plants that thrive in a wet environment with limited light: violets, trilliums, jack-in-the-pulpits, wild ginger, trout lily, Dutchman’s breeches, and a vast variety of ferns, among others.

They appear soon after the last snow is gone and bloom for a few days and then vanish for another year.  But one in particular is sought after not for its exotic flower but for its odor and taste:  the wild ramp, also known as spring onion, wild garlic, and by other names.

The leaves of wild ramps somewhat resemble those of the lily-of-the-valley, but to the alert eye they signal the presence of a wild onion with a sharp taste that is both sweet and spicy; its odor and flavor can make something very special of an otherwise commonplace dish.

Once their shiny leaves appear, it is a matter of just a couple of weeks before the bulbs swell to half an inch or more in diameter. Then, as they are dug from the ground, their zesty onion odor permeates the air.


Wild ramps, pulled from the ground and scrubbed, their shiny white bulbs releasing their fresh, onion fragrance. The Enterprise — Michael Nardacci


Washed and with their roots cut away, the ramps may be used as flavoring in dozens of dishes; they may be boiled or roasted, or they may simply be eaten raw, giving the tang of spring to salads or plates of raw vegetables.  After a few more short weeks, the leaves wither — among the first of all forest plants to turn yellow as the season progresses — and vanish until the next year’s spring melt and first warm days awaken them again.

An Internet search for “wild ramps” yields upward of 60,000 sites; one quickly learns that wild ramp festivals are held in many Appalachian sites in the spring.  And many of the websites deal with the folklore associated with the plants.

Medieval and early American populations believed the plant to have medicinal qualities — but, of course, onions have long been known to be good for digestion and for the heart.  Probably the more outrageous claims of the ramp’s health-giving qualities are myths, but one can easily understand why the stories have arisen.

For following a cold, snowy, barren winter such as the one we just experienced, suddenly the newly greening forest features a modest-looking plant, which — when drawn from the ground — yields a fragrance as fresh and as invigorating as spring itself.

And what better way to experience the return of the warmer weather than to take a stroll through the forests of the Helderberg talus slopes to enjoy the greenery, perhaps catching a glimpse of the 42 shades of green that it is said every Irishman can distinguish; to listen to the music of the newly-arrived birds and the trickling of the last snow melt; and amid the exhilarating smells of the woods to be fortunate enough to catch the tang of the wild ramp.


— Photo by Mike Nardacci

A polished slab of Becraft limestone shows its numerous Devonian period fossils.

With the Helderberg landscape buried under yet another huge snowstorm in this seemingly endless winter, many of the unique geological features of our area are hidden beneath the drifts.  Fortunately, the subject of this column is fine for the “armchair” geologist — all that is needed being a good imagination!

I put together a number of photos I took with the help of my reliable assistant, Devin Delevan, in the fall and during that warm period we had in mid-December — and voila! — a meditation on the ancient rocks of the Helderberg Plateau and the long-abandoned quarries from which they once were drawn.

And I would like to start with a site which is one of the most accessible — at least when the region is not groaning under the weight of all this snow.


The hamlet of Reidsville is today but a shadow of what it once was.  “Blink and you will miss it” is an apt cliché.  It lies on the Cass Hill Road, a lovely stretch of back road that climbs steeply up onto the hills above Clarksville and passes through miles of forest filled with rambling old stone walls before intersecting with Route 85 just west of Reidsville.

The hamlet consists of a few houses, a barn or two, and a mossy old cemetery whose occupants surely outnumber the current living population.  But back in the first third of the 20th Century, Reidsville was a bustling town of hundreds of inhabitants and featured two churches, a number of stores — and the bustling Reidsville bluestone quarry. 

The quarry today is unimpressive and easy to miss.  A broad depression lying on the north side of Cass Hill Road as one approaches the hamlet’s crossroads, it is filled with stagnant water and cattails, a haven for peepers in spring and bullfrogs in summer.

A couple of abandoned tires have been dumped into it.  Other vegetation has taken hold in the dry areas and only the angular outcrops and low vertical cliffs hint that the depression is not natural.

In the wooded areas surrounding it, piles of the shattered bluestone once quarried there lie covered with weeds and the debris of eight decades of seasonal changes.  According to a 1934 article in The Enterprise, the quarry ceased operations in 1933 due to the arrival on the scene of a building material that, although used extensively by the ancient Romans, had recently become easily-available and relatively inexpensive: concrete.

And, in fact, Portland concrete doomed hundreds of other stone quarries throughout the Northeast and elsewhere in the United States as cut stone — once essential for many building projects — became prohibitively expensive and began to be used more commonly as a luxurious decorative facing stone.  (An old geologists’ joke says that the difference between “rock” and “stone” is that stone is rock you have to pay for!)

And, indeed, looking around the older parts of cities, one notices far more cut stone than would be found in most modern-day building projects.  The massive amounts of white Vermont marble facing the buildings of the Empire State Plaza contributed to the enormous cost of the project.

A television documentary recently revealed that, for a while in the early 1960s, New York State wanted the Albany Catholic diocese to encase the venerable Cathedral of the Immaculate Conception — built from red sandstone — in the same white marble as the plaza so it would “blend in.”  Obviously, the cost of such extravagance was a major factor that contributed to the shelving of that idea — and, one would hope, someone’s sense of historicity and aesthetics did as well.

A 1935 geologic map of the Berne Quadrangle shows that the Reidsville quarry was one of numerous bluestone quarries once active in the Helderbergs, and a drive around some of the back roads of the area will reveal them to be in a state similar to the one at Reidsville.  But for many years they provided work for hundreds of laborers, and their products are visible in areas such as downtown Albany and Troy where sidewalks were frequently constructed from the stone.

Helderberg “bluestone”

In this part of New York State, “bluestone” is a common term for a hard sandstone of late Devonian age — roughly 360 million years old.  It is not really blue — in its freshly-cut stage, it is a rich, attractive dark shade of gray sometimes tinged with green and it tends to weather to black or brown depending on its iron content.

Helderberg bluestone originated in what is known as the Catskill Delta that emerged during the Acadian Orogeny (mountain-forming episode) as the landmass that would one day be called Europe collided with proto-North America and threw up a series of lofty mountains to our northeast.  The sediments that washed down from those mountains filled in the shallow tropical sea in which our local limestone layers formed and produced a series of interlocking deltas, creating environments in which forests of some of the earliest large land plants would emerge.  The Gilboa Petrified Forest is a well-known example.

In the Helderberg area, the rock does not typically show many fossils, though in other locations it may feature trilobites and brachiopods and other typical Devonian marine fauna, most of which are extinct today.  In Oneonta and the upper Catskills, the fern tree fossils and fragments of some of the other early land plants become common, evidence that the strata in which they occur formed in non-marine environments.  

Today, much of the bluestone that is still quarried commercially is sold from outlets such as the eponymous Helderberg Bluestone on Route 443, which takes the stone from but a single active quarry.  Since it easily separates or is cut into flat slabs, it is used widely in retaining walls, just as it has been used for hundreds of years in the Helderbergs for walls and foundations.

The historic cemetery on Peasley Road near Rensselearville features a beautifully constructed example.

Oriskany sandstone

Another somewhat less commonly used Helderberg building stone is known as the Oriskany sandstone, named for what geologists call its “type location” at Oriskany Falls in Oneida County.

The Oriskany is what is known as a “calcareous” sandstone, meaning that it has a high content of calcium carbonate in addition to quartz sand and it is believed to represent both near-shore and on-shore ancient beach deposits. Such beaches are found in many tropical areas of the world today and Acadia National Park’s famed “Sand Beach” is a temperate-zone example of the type.  

It is a relatively thin layer — averaging no more than 2 to 4 feet in most areas of the Helderbergs though it thickens greatly to the south of the area.  The Oriskany is widely prized as a decorative facing stone because it contains enormous quantities of large brachiopod fossils, which stand out impressively as the rock weathers.

A currently inactive quarry near the village of Knox on Route 156 — formerly known as the “Knox Fossil Rock Quarry” — was used for years as a source of the Oriskany.

A wonderful display of its fossils may be seen in the fireplace of the old Hofbrau Restaurant on Warner’s Lake (now the Maple Inn) and exterior walls of the Western Diner on Route 20 in Guilderland where the large — sometimes fist-sized — shells of the ancient creatures appear in the thousands, some in fragments but many intact, just as they would have been found on a Devonian-Period beach.

When the Oriskany is exposed to years of weathering, the carbonate materials tend to dissolve away, often leaving the sea shells — with a high silicate content — easily visible.

Limestone layers

The Helderberg escarpment that rises to the west of Albany is composed of three major limestone layers.  The thin-bedded Manlius limestone and the massive Coeymans limestone above it make up the more prominent cliffs, visible from many miles away on a clear day as a stark gray band, tilting gently to the south. The two are believed to have formed from the carbonate-rich ooze at the bottom of a relatively warm, shallow sea during the Devonian Period. 

Many Helderberg and Schoharie area caves are formed in these limestone units, which dissolve readily in naturally occurring acids.  In the stretch of countryside between Altamont and New Salem, the two layers have a combined thickness approaching one hundred feet, maintaining a similar thickness as they stretch south along the Vly Creek Reservoir

Approximately 140 vertical feet higher is a second, slightly less prominent line of cliffs composed of the Onondaga limestone, also a major former of caves. The Onondaga is light gray and in its lower reaches contains layers and nodules of chert, a hard silicate rock commonly known as flint.

Above Thacher Park, the upper Onondaga forms an extensive flat landscape known as a “bench” on which the northern stretch of the Beaverdam Road was constructed, and along which numerous small sinkholes and some short caves have formed.

None of these three limestone units has been widely sold as a commercial building stone, but the relative purity of all three layers made them valuable in the making of Portland cement in years past.  The limestone was harvested from now-abandoned quarries such as the one found on Rock Hill Road near the Vly Creek Reservoir and smashed into jagged boulders, which were then burned in wood-fired lime kilns to drive off the volatiles.

Ruins of many of these kilns lie scattered throughout the Helderbergs, often covered with mosses and lichens and calling to mind the so-called “Beehive” buildings constructed by the ancient Celts and scattered throughout western parts of the British Isles and France.  Locally, Callanan Industries and the extensive quarry in the village of Howes Cave continue to quarry limestone for this purpose.

All three of the units also found use in the construction of foundations for houses and sometimes entire buildings, as testified to by the beautiful stone dwellings in the Onesquethaw Valley south of Clarksville and the handsome Onesquethaw Reformed Church, all of which were built from the Onondaga.

And, of course, the hundreds of miles of old stone fences that lace the woods of the Helderberg and Cobleskill plateaus were built of these and other types of rock found locally and constitute some of the best places to collect Devonian period fossils.

The last and perhaps rarest of the Helderberg area stone used decoratively is the beautiful Becraft limestone.  The Becraft is not widely exposed on the plateau, and in most places it has a thickness of only 12 or 13 feet, though, according to the well-known New York State geologist Winifred Golding, in its type locality — Becraft Mountain near Hudson — it reaches a thickness of 45 feet and was also once quarried in the making of Portland cement.

It is described as an example of “coquina,” made up almost entirely of variously-sized shell fragments cemented together — in this case by calcite.  Coquina tends to form in what are called “high energy” environments: areas in which powerful waves remove very small fragments but leave behind enormous quantities of whole or partial medium-sized shells that then get naturally cemented together.

The Becraft is thus a very hard rock and, when broken, it tends to have a great many jagged edges — the protruding shell fragments.  The only quarry I am aware of in the Helderberg area where the Becraft was cut commercially is again the old Knox Fossil Rock Quarry.

Due to its hardness, the stone will take a high polish and was used for decorative counters and tabletops.  An example is on an antique dresser that I refinished a number of years ago and for which I purchased a polished slab from Helderberg Bluestone to replace its damaged top.

Strata with evocative names

There are a number of strata of other rock-types found in the Helderbergs which have evocative names but have found less commercial use:  the New Scotland limestone, the Brayman shale, the Rondout waterlime, the Esopus grit.

These strata, along with those discussed above, form a gigantic layer cake, some of which is visible in natural outcrops, much of which is buried under layers of glacial sediment and luxuriant forest growth.  To the geologist, the strata indicate episodes of ancient seas rising and falling, of continents colliding, of ecosystems changing, of strange creatures evolving and flourishing or going extinct.

And, for the inhabitants of the Helderberg area, they have long provided stone for purely practical purposes, of course, but they have also provided materials for decoration that are not only beautiful but tell of diverse worlds, gone forever into the labyrinths of the ages.


Caves are mysterious places even for those of us who have spent decades in exploring and trying to understand the agents of nature that formed them, and it should be noted that for a large percentage of the world’s population, caves are “terra incognita.” Someone once called the subterranean world “The Eighth Continent,” and it is probably far less familiar to most people than anything they might have learned about Antarctica.

Think of the number of stories, novels, films, and TV shows that are set wholly or partially in caves, often wildly — even hilariously — inaccurately portrayed to those who are knowledgeable about them, but undoubtedly appealing to some aspect of the human subconscious that has a fear of dark, unknown chambers that exist in what is melodramatically — but not inaccurately — described as the “bowels of the earth.”

It is therefore not surprising that visitors to caves often ask questions that, due to the questioners’ innocence, might seem pretty silly to those among us whose avocation — and sometimes vocation — involves the sport and science of caving.

When I first started teaching a high school earth science course to freshmen and a geology and astronomy survey course for seniors, I still harbored a remnant of a notion instilled in me in one of those education courses required of aspiring secondary-school teachers, sometimes taught by a professor who seemingly has never been within a mile of a classroom filled with adolescents (said Mike cynically): that notion being that the only dumb question is the one that is not asked.

But that got kicked out of me after a couple of years when I was finishing up a two-week unit on stars and stellar evolution with my seniors.

We had talked about the birth of the universe — old beyond imagining — and we had analyzed the Hertzsprung-Russell diagram; we had compared the sun with red dwarf stars and massive blue giants, discussed the formation of red giants, neutron stars, and black holes; and we had looked at dozens of slides of open clusters of blazing stars arrayed about a nucleus like swarming bees; spectacular nebulae spangled with gases and dust of every color of the spectrum; spiral galaxies, barred spirals, elliptical galaxies, irregular galaxies, all of them fantastically huge and beautiful beyond belief — and all of them sufficient to make one wonder in the silence of one’s bed at night if those folks who believe in intelligent design might just be on to something.

I was wrapping up our discussion in preparation for a test on the unit the next day when I remarked that, in spite of all the discoveries made by wondrous instruments such as the Hubble Telescope, there were still many things that we do not know about stars.

At that moment, a rather sleepy-looking student who shall remain nameless and who — as I recall — had not shown much more than tentative signs of life during his weeks in my classroom, raised his hand.  When I called on him, he asked, “When the astronauts go up in the space shuttle, can they go outside?”

Confused by the seeming irrelevance of the question I replied, “Yes, of course.  But what does that have to do with the test tomorrow?”

The look on his face suggested he had hit on something that had evaded all those amateur astronomers like Steven Hawking and Neil DeGrasse Tyson and he said smugly, “Well, next time they go up there, why don’t they just go outside and get a couple of stars, and bring them back down to Earth?”

Needless to say, the reaction of some of the more knowledgeable students in the class was — shall we say — less than charitable toward the student’s question and they showed it, while I tried not to crack a smile at this young man’s total cluelessness and gently explained what he should have known weeks before: Stars are a bit too large and hot to fit into the cargo bay of a space shuttle.

How much of a cave is underground?

Anyone who has ever guided a group of tourists through a commercial cave or taken a group of wet-behind-the-ears novices on their first “wild” cave trip has, of course, heard many, many preposterous inquiries — and it requires the patience of Job not to roll the eyes, sigh like a spouting whale, and say, “That is a seriously silly question.”

Years ago, when I had taken another group of students on a week-long trip to Mammoth Cave, we were on what was called the Historic Tour, and our guide — all decked out in his Park Service uniform and Smokey-the-Bear hat — told the crowd of about a hundred that the only dumb question was the one they didn’t ask.

After a couple of fairly intelligent questions that had to do, as I recall, with the age of the cave and the great size of the passageways, the ranger pointed to an anonymous hand waving above the crowd and said, “Sir?”  At which point came the question, “Is all of this cave underground?”

I have made it a point whenever I am taking a tour through a commercial cave to ask the guide — when I can catch him or her out of earshot of the rest of the tourists — what is the silliest question they have ever been asked.  As it happens, that question about whether all of the cave is underground is a fairly common one.

If the guide can resist the temptation for sarcasm, he or she might say simply, “All that we know of it is.”  A guide once told me he had replied, “All of it except for the gift shop and cafeteria” — and drew not a smile from the questioner who seemed to accept those areas as, indeed, being parts of the cave.

Compendium of questions

And, so what follows is a compendium of questions that either I have been asked or questions I have acquired from commercial cave guides.  

—  1. How long did it take the Indians to carve this cave out?

This is also a surprisingly common question asked of cave guides.  People who have no understanding of erosion and chemical weathering are bound to be mystified and awed by the great size of some cave passages — Mammoth Cave’s Main Passage has room for a modern jetliner to fly through it.

But caves form because surface water has picked up carbon dioxide from the atmosphere or from decaying plants and becomes mild carbonic acid.  When this acid comes in contact with calcium carbonate — the main constituent of limestone and marble — it dissolves it to a solution of calcium bicarbonate, which then washes away.

Given the right conditions and enough time, the process can form out huge cave passages.  And as for that silly question: If Native American Indians had carved the cave — what on Earth did they do with all that rock they hauled out?

— 2. How thick are the walls of the cave?

The sedimentary rock from which most caves are dissolved forms in layers, which often cover thousands of square miles.  In the Helderberg area, most of our large caves (including commercialized Howe Caverns and Secret Caverns) have formed in one of three types of limestone:  the Manlius, the Coeymans, or the Onondaga.

The Manlius limestone is found as far west as Syracuse and as far south as Port Jervis;  the Coeymans stretches from New York to Virginia;  and the Onondaga stretches as far west as Detroit.  Each of these areas consists of thousands of square miles, so trying to figure how thick the walls are would be a monumental task, but a good answer would be, “Really, really thick

— 3. How much of the cave hasn’t been discovered yet?

One would think that the response to this question would be something flippant, such as, “We won’t know until we discover it.”  But, in fact, it is sometimes possible to come up with an intelligent answer.

If the known passages in a cave have formed in a geographic region throughout which the same geologic conditions exist, there is a good possibility that many more passages have formed under sections that have not been surveyed.  By measuring the length of passages in a set area, one might by inference conclude that a lot more of the cave has not yet been discovered and perhaps even extrapolate a rough estimate of how much.

At Mammoth Cave in Kentucky, for example, the same geologic conditions exist for hundreds of square miles, beneath some of which are over 400 miles of explored cave. But, by extrapolation, geologists have concluded that there could be in excess of one thousand miles of the cave when — or if — Mammoth is ever fully explored.

— 4. Is any of the light down here natural?

Since caves are roofed by solid rock that can be many hundreds of feet thick, with rock walls that can be hundreds of miles thick, and with bedrock floors that may literally stretch to the Mantle of the Earth, it is highly unlikely that any natural light could enter beyond what cavers romantically but accurately call the “Twilight Zone.”

This is the region near a natural entrance to a cave into which dim sunlight may reach, and that may have unusual ecologies, featuring both plants and animals that exist in a world of feeble light and perhaps wildly changing seasonal temperatures.

Sport cavers carry their own lights  (a minimum of three is the requirement) and commercial caves have complex and often expensive electrical systems for lighting.

— 5. How many undiscovered entrances to the cave haven’t been found yet?

When asked such a question, cave guides must be tempted to say, “We’ll know when they have been discovered.”

But again, what seems to be a no-brainer actually can have a rational, scientifically based answer.  Caves form in regions of limestone or marble bedrock known as “karst.”  Karst areas usually are characterized by mainly subterranean drainage of runoff into extensive cave passages, numerous springs, streams that tend to go underground shortly after they get started, and a surface pock-marked with the depressions known as “sinkholes,” which permit surface waters and sometimes human explorers to enter the caves below them.

But sinkholes can become occluded: wholly or partially blocked up by sediments and other natural debris that may effectively cut off everything but water from entering the cave systems.

Scientists known as hydrogeologists who study the effect of local geological conditions on water flow — above as well as below ground — have developed a technique known as “dye tracing” to permit following the flow of water to places humans cannot go.  This process involves placing harmless dyes in water that is sinking into the ground and then watching the suspected resurgence points to see if the dye-laced waters emerge, indicating there has been a connection.

My young research assistant Devin Delevan is pictured standing at the brink of a vertical sinkhole near the village of Clarksville, an area known to have extensive cave systems.  Though in the photograph the sinkhole is dry, in times of heavy precipitation dye could be added to water, pouring into it and a connection might be determined.

Karst areas often have hundreds of such sinkholes, many of which could be hooked into a cave system through this method, even if a human could not physically enter the cave.  Numerous previously “unknown” entrances could thus be identified.

— 6. What happens if there is a fire while we are in there?                                               

This question was actually asked of me some years ago when I was guiding a group of students from a downstate New York college through Clarksville Cave.

One young man took a look at the cave’s tight, intimidating entrance and a vision must have passed through his head of a dozen students madly fleeing from flames and battling each other to get out of the cave. His question elicited a burst of laughter from several of his fellow students who were clearly aware that there was nothing within the cave that would be capable of a conflagration.

I assured him of that fact and his face turned red and I expect his question went the rounds through the dorm that night, much to his embarrassment.

— 7. How much does it cost to air-condition (or heat) this cave?

Since limestone and marble and other kinds of dense rock are good insulators, beyond its Twilight Zone a cave will remain pretty much the same temperature all the year around. Caves generally will assume the average ambient temperature of the area in which it is located, making caves seem cool in summertime and warm in winter — everything being relative to temperatures outside the cave at a given time.

In the Helderberg/Schoharie area, yearly average temperatures are about 50 to 52 degrees Fahrenheit, and that tends to be the temperature of our caves.  No artificial cooling or heating is required.

Two truly preposterous queries

There are undoubtedly many more Seriously Silly questions that cave scientists and guides have to deal with, but then there are the ones that are truly preposterous or totally incoherent, and I will end with two of these.

Not long ago, I was touring a commercial cave with a group of students and popped my question to the guide, a young woman college student.  She did not hesitate for even a moment.  Last year, she told me, she and several other guides had been asked a question that was the talk of their crew for several weeks: People on tours were asking, in all seriousness, “Is this the cave that was moved from New Jersey?”

Understand: The visitors’ portion of this cave is over half a mile in length and in places 60-feet high.  How and from where the idea had circulated that it had been moved from another state no one seemed to know, but, not wanting to risk losing her job over a condescending reply, the guide had answered simply, “No, it’s been right here in Schoharie for thousands of years.”  The guide reported that no one in her group had even cracked a smile.

At the same cave the year before, I had posed my question to a young man who was majoring in geology at a local college.  He told me that some weeks before, while his group was standing on the banks of the cave’s gurgling underground stream, a visitor had asked “Is the water in this stream real?  Or is it natural?”

Aware that the man’s question was absolutely serious — but unable to decipher its meaning and unwilling to prolong the issue by asking the man to explain what he meant — the guide replied, “Actually, we have both in the cave.”

The man nodded and seemed satisfied.

And that stunner and the one my student asked me about packing up stars in the space shuttle and bringing them back to Earth have permanently put an end in my mind to the notion that the only dumb question is the one you don’t ask. Professors of education, take note.

The Enterprise — Mike Nardacci

From a distance, the ruins of Penasco Blanco resemble natural rock outcrops protruding from the top of the mesa.

By Mike Nardacci

The term “geopoetry” seems to have been coined by Scottish poet Kenneth White to describe geologic writing that shows “the relationship of the Earth and the opening of a world.”  The idea is that the few known facts of a situation are combined with intelligent speculation to evoke its mystery and wonder — but not necessarily to provide definitive answers.

I have always believed that anyone who aspires to an understanding of geology needs to have a vivid imagination: To stand, for example, on Route 156 between Voorheesville and Altamont and look at the Helderberg escarpment rising above you and envision it 20,000 years ago buried under the mile-plus-thick continental glacier.  Or to project your mind farther back into the Devonian Period 400 million years ago when this part of New York lay under a warm shallow sea dotted with low coralline islands that, through the fantastic processes of plate tectonics, would rise up into the looming, fossil-rich plateau we see there today.

Over the past decade, I have made several trips to Chaco Canyon in New Mexico, a spectacular preserve about a hundred miles northwest of Albuquerque off of Route 550, but often described by visitors as being “a hundred miles west of Nowhere.”

The highway passes through some of the bleakest terrain in the United States, though some of it is starkly beautiful, as arid landscapes tend to be, bordered by miles of desert plants: sagebrush, cactuses, and cholla, towered over by angular mesas and buttes formed of dusty, pastel-colored rock.

Chaco is then accessed by a truly horrendous 13-mile-long washboard-surface dirt road, which surely is intended to discourage all but the most determined of visitors.   Although designated as a National Historical Park, Chaco has no facilities beyond a campground that offers rather primitive camping (though it does feature flush toilets), and a visitor center, which is, as they say, “under renovation.”

It is air-conditioned and has a small shop selling a variety of books that theorize about Chaco’s human history, but had — as of this past June — no exhibits at all, which is a shame considering that a few years back it had a museum featuring fascinating displays and presenting information about Chaco’s spectacular Anasazi ruins and the ancient people’s stunning architecture and pottery.

Mystery and miracle of water

In June of this year, I was again hiking in Chaco with a friend, Mike Whalen, who is a filmmaker living in Boulder, Colorado. The temperatures were somewhat lower than we had expected: mid-80s in the late afternoons but relatively cool and dry early in the days, and so we chose one particularly clear morning for a hike to a pueblo ruin known as “Penasco Blanco,” the most remote in the immediate vicinity of Chaco and one that we had never managed to visit on previous trips.

It lies atop a mesa at the end of a relatively flat three-and-a-half mile trail that leads out over the dusty floor of Chaco Canyon through vast stretches of sagebrush and cactuses, some of which were late blooming in exuberant shades of red and yellow and orange in the wake of the spring rains.  The path at first follows the base of the canyon’s North Mesa and has some shady stretches, but the last mile-and-a-half or so are out in the open.

Frequent examples of honeycomb weathering may be found in the boulders at the base of the cliffs.  This phenomenon — fairly common in extremely arid environments — seems to occur when salts within the rock migrate toward the surface and form crystals that shatter it.  The shady recesses undoubtedly provide respite from the blistering sun for desert birds and reptiles. Though the temperature was still in the 70s, the high sun shining through a cloudless sky soon became oppressive and we found ourselves gulping down our water faster than we had planned.   

And it is true that, among the great mysteries of Chaco Canyon, one of the most perplexing revolves around the subject of water.

The people of many ancient cultures thought of water as something spiritual — even sacred. Temples were built over springs, which must have been regarded as connection points between the world of the gods and that of humans.

It is not hard to see why and it is on the subject of water that this essay ventures into geopoetry. Consider the appearance of the landscape on the road from Albuquerque to Chaco: Much of it consists of plateaus and mesas composed largely of shale and siltstone but capped by hard sandstone forming steep escarpments above the crumbly talus slopes.

The situation is rather comparable to the stratigraphy of the Helderberg plateau, where the shale- and soft-sandstone talus slopes towering above Voorheesville and Altamont are capped by the hard Manlius and Coeymans limestone layers that form the vertical cliffs of Thacher Park.  But the Helderberg area is a very wet climate and the slopes — and indeed, every fissure and hollow in the cliffs — are green with massive amounts of vegetation.  As the song says, “The hills are alive….”

The New Mexican talus slopes show signs of the occasional turbulent movement of water — but then, so does the surface of dry and dusty Mars.  Yet, aside from pinyon pines and junipers on the valley floor that somehow manage to find enough moisture to thrive, the slopes in the New Mexican scene are nearly devoid of life, whether plant or animal, and the changes brought by abundant water verge on the miraculous.

Doors to nowhere

The trail to Penasco Blanco crosses a small dry wash just before it makes the final steep ascent of the mesa, and in a sheltered alcove above the trail is an ancient pictograph — one of the most remarkable ever discovered.  It seems to record the appearance of a crescent moon and next to it a supernova that was observed in other parts of the world as well in 1054 A.D.

Clearly, the ancient inhabitants of Chaco Canyon took a keen interest in the stars and one of them made the effort to record the stellar explosion; the handprint may well be that of the artist.

On this mid-June day, the wash was indeed very dry and probably had not had any flow since the sparse spring rains following the melting of whatever light snow cover had fallen on the canyon. Beyond the wash a series of exposed switchbacks led to the top of the mesa, and, as we climbed up to the crest, we were presented with a view of the Penasco Blanco ruin a thousand or so feet away.

The ruin is immense; ovular and greater in area than a football field, it was subdivided into hundreds of rooms and passages and courtyards — home, it is believed, to perhaps many hundreds of puebloan people.

A dozen or more of the sunken, circular pits known as kivas — which served as places of worship and socialization — are scattered about it.  The ruin is mostly unexcavated, so the tumbled-down walls and doors to nowhere stand picturesquely on the windy mesa as they have for centuries, and in places the ground is littered with fragments of the Anasazi people’s beautifully decorated pottery.

The low hills around it reveal the partially exposed walls of other, smaller “satellite” pueblos that were built as Penasco Blanco grew and expanded.

Questions persist

Surveying the ruins, built so deftly from millions of rock fragments, we were confounded by a number of questions. The first had arisen a year ago when Mike and I hiked to another ruin called Pueblo Alto, remotely situated on Chaco’s North Mesa: What was the source of all the rock fragments from which the ancient pueblos were constructed?

The landscape around the ruins is covered with shattered rock, though it is likely that the vast majority of these have weathered from the walls of the ruins themselves.  Undoubtedly many more lie buried in the dry soil, but excavating them in that sometimes scorching heat would have been agonizing.

The bases of the various mesas are littered with innumerable fragments of the needed sizes — but transporting them up the cliffs to the building site in the thousands of tons needed would be an appalling task even with modern technology.  From all evidence, the ancients had nothing to rely on but arm- and leg-muscle power — and this fact is one of the major aspects of the Chaco Canyon mysteries.

But, as we stood there draining our canteens under the glaring New Mexican noon sun, another even more provocative question arose in our minds: How did the ancient people supply the builders with water?

We tried to envision great teams of workers engaged in construction activities that in some ways must have posed many of the same challenges that faced the builders of the Egyptian pyramids. But the pyramid builders had the Nile River at their feet — an endless supply of water for drinking, cooking, washing, and probably bathing when the heat became unbearable.

Southwestern museums often display hollowed-out gourds and huge ceramic pots that are believed to have been used by the ancient people for water storage.  But to store water, one must first obtain it, and, here in the vast dry stretches of Chaco Canyon, the only source of water other than rare precipitation is the Chaco Wash — a narrow streambed incised into the compacted soil of the canyon floor that, except for brief periods in spring and the occasional August gulley-washer, is never more than a sluggish, muddy trickle, and it is over a mile from Penasco Blanco.

Clearly, it could never have provided enough water for this pueblo’s builders let alone the construction teams raising the other pueblos of Chaco Canyon.

And that fact raises another major question: How were the workers and the inhabitants of the pueblos fed?

The builders of the great Egyptian monuments had the well-watered and incredibly fertile fields of the Nile Valley to provide their food.  But, although for millennia the inhabitants of the Southwest have been expert at what is called “dry farming” to raise the “three sisters” crops of corn, beans, and squash, one can only wonder how the ancients managed to produce enough food for the teams of workers building Penasco Blanco as well its inhabitants — and one must keep in mind that Chaco Canyon holds over a dozen other large pueblos and innumerable smaller ones.

But even “dry farming” requires essential amounts of water, so once again the question arises: What was its source?  And how was it transported to the top of the mesa in sufficient quantities to allow Penasco Blanco to expand and flourish?

A survey of the literature both popular and more technical on the subject of Chaco Canyon shows researchers with wildly differing interpretations of the reasons for the construction of the pueblos of Chaco Canyon, of estimates of its population, and of the enormous problems that revolve around the source and quantities of food and water.

But one fact is critical: Water is life.

Hence, scientists today are excited by the discovery that, in the far reaches of our solar system, the moon Europa, orbiting Jupiter, and the smaller satellite Enceladus, orbiting Saturn, show evidence of being the repositories of gigantic quantities of water in both liquid and solid states: beckoning targets for future exploration.

And yet here in one of the most hostile environments in the United States, a thousand years ago a great culture grew and flourished, reaching startling technical and artistic heights that evoke admiration and even awe today.

What made it possible was water.  But where that water came from and how the ancient people obtained and transported it are questions that science is nowhere near answering.  “Geopoetry” indeed!