— Photo by Mike Nardacci

The storybook entrance of Spider Cave, newly acquired by the Northeast Cave Conservancy, beckons research assistant Devin Delevan.

Barton Hill looms above Route 146 as it descends to the village of Gallupville and extends north as a series of impressive limestone cliffs along Route 443 to its intersection with Route 30.  From there it stretches to the east with long, gentle slopes and is capped by flat stretches and some of the glacial hills above Routes 7 and I-88.

The name “hill” here is generic, for it is in fact a plateau, an isolated segment of the Appalachian Plateau, cut off millions of years ago from Terrace Mountain (also a plateau), Vroman’s Nose (a mesa), and the Cobleskill Plateau by the respective creeks known as the Fox, the Schoharie, and the Cobleskill.

In addition to the craggy cliffs, its landscape features include broad, fertile farmlands and thick forests — and it also contains numerous karst features: sinkholes, underground streams, and extensive cave systems, not all of which can be entered but which betray their existence through cold springs that burst from the base of the lofty cliffs.  Caboose Cave, Schoharie Caverns, Single X cave, and Gage Caverns (historically and again today known as Ball’s Cave) are some of the caves known to geologists and sport cavers, and enormous occluded sinkholes such as the oddly named Joober Hole indicate there are many more.

Until recently, just two of these caves — Gage and Schoharie caverns — have been accessible to sport cavers with the proper credentials because they are owned and managed by the National Speleological Society, an international society devoted to the science and sport of cave exploration. But recently, through a generous donation, another organization known as the Northeast Cave Conservancy has acquired Spider Cave on the south side of Barton Hill, making it available for both student study groups and exploration.

The Northeast Cave Conservancy is a not-for-profit organization that has been managing and acquiring through purchase or donation a number of caves in this part of the country.  The NCC has thus been able to keep open a number of caves that might otherwise have been declared off-limits by their owners for fear of liability or for other personal reasons.   

For many years, Spider Cave was off-limits to cavers, but the cave with its beautiful entranceway, easily visible from a road, was described in old guide books as having a “storybook entrance but a short story!”  To enter the cave, one must first climb a trail up a precarious slope that borders a stream gushing from the entrance.

The stream tumbles over rocks that are rich with Devonian Period fossils and brilliantly green with mosses and algae.  The picturesque entrance is a shadowy opening in the Manlius Limestone and it leads to a narrow, twisting passageway that can be traversed on foot through the stream for some distance, though squeamish cavers may find themselves contorting their bodies to avoid disturbing the residents of the eponymously-named cave: dozens (sometimes scores) of large black spiders sequestered in nooks and crannies or openly displaying themselves on the cave walls.

But then the walls of the cave begin to pinch inward, the floor rises, and most visitors turn around as it becomes increasingly difficult to move without having one’s clothing caught and torn by the hard fossils and sharp erosional features on the passage walls.  The extent of the cave remains unknown but cavers’ anecdotes tell of intrepid explorers crawling painfully on their sides through pools of icy water, their necessary wetsuits being shredded by the sharp projections from the walls, and turning back after 1,200 feet — or perhaps 1,500 feet — or possibly more, but leaving a small rock cairn to indicate their turnaround point.

Caves with small dimensions can suddenly and without warning open up into caverns of vast proportions — but Spider seems simply to plunge onward into the plateau, guarding well whatever secrets it holds.

The puzzle

And therein lies the puzzle that is Barton Hill.  A topographical map featuring the underground passages shows that the known caves run parallel to each other — following what geologists call the “dip” of the rock layers; the “dip” is nothing more than the angle and direction at which rock layers (called “strata”) are tilted.

In this region, the dip of the strata of Barton Hill is gentle and to the southwest.  For some of the caves, the insurgences — that is, the points at which water enters the caves from the surface, usually through sinkholes and fissures — is known.  For others, the insurgence points have not been identified

This is not unusual, especially in a place like Barton Hill that in many places is covered with layers of glacial deposits, which may obscure features such as sinkholes.  But finding the insurgence point for the water in Spider Cave would give an indication of its length, and might provide a way into the cave’s larger sections — if larger sections exist — through a sinkhole or an enlarged fissure.

And particularly odd are the physics and the chemistry of the water emerging from the springs — or “resurgence points” — along the base of the cliffs.  During times of normal rainfall, some of the springs above Route 146 may be releasing water — and yet others, sometimes only a couple of hundred feet away — may be dry, though during spring snowmelt or following times of excessively heavy precipitation all of the streams may be gushing.  Clearly, something odd is going on underground regarding the flow cycles of the subterranean streams.

Complex questions

The chemistry of these streams also raises complex questions.  Cave waters are often saturated with calcium carbonate, and so a cave’s ceilings, walls, and floors may exhibit stalactites, flowstone, stalagmites, and curious dam-like structures in the streambeds themselves called “rimstone pools.”

These form as the water flowing through the cave or entering through cracks in the ceiling “de-gasses” —   that is, it loses its carbon dioxide that makes the water acidic and causes the dissolved calcium carbonate to be deposited on ceiling, wall, or floor.

But Barton Hill has some springs known as “tufa” springs: These occur when for some reason the cave water retains its carbon dioxide and calcium carbonate as it flows underground, perhaps in a very small aquifer without any air space, preventing the saturated water from “de-gasing.”

In these situations, as the stream resurges from the cliff base into the open air, the sudden pressure release will cause the water to “de-gas” much as a carbonated beverage de-gases when its bottle cap is removed.  Now the dissolved calcium carbonate will be deposited on whatever is in the path of the stream: rocks, twigs, or masses of moss or plant fragments, making the materials appear to be coated with light-colored paint or forming a spongy-appearing rock known as “tufa.”

Calcium carbonate can also form a natural cement and bind together enormous quantities of what geologists call “glacial till,” the mixture of rock fragments and soil left by the retreating glaciers.  An extensive area of the hill slope between Gallupville and Shutter’s Corners has been cemented together into a kind of conglomerate by this process;  here mineral-saturated water from ancient springs in the cliff far above the slope deposited so much of their dissolved calcium carbonate that they eventually sealed themselves up.  This particular outcrop is heavily fractured and appears poised at some point to slump down the hillside onto Route 443.

The stretch of Route 146 approaching Gallupville has several other springs besides Spider Cave, but only one is easily recognizable as a tufa spring and at various times of the year when there is heavy precipitation or snowmelt, the underground stream feeding the spring produces great quantities of tufa that end up tumbling down the stream bed as cobbles or boulders.

Yet, oddly enough, the stream cascading down from Spider Cave also has a mass of algae-and-moss covered tufa in a small area its bed, but not in the stretch above or below it. Clearly, there is something unusual occurring in the chemistry of the stream flowing through Spider Cave that is seasonally altering the acidity of the stream — what chemists call “pH.”

Finding the stream’s insurgence point and examining the terrain under which the water flows on its way through Spider Cave might help to explain its curious behavior.

Numerous studies have been done of the geology and the known caves on Barton Hill; perhaps the best known among cavers and professional geologists is contained in Prof. John Mylroie’s doctoral thesis, “Speleogenesis and Karst Geomorphology of the Helderberg Plateau, Schoharie County, New York,” published in 1977.

But the occluded sinkholes, the shadowy fissures, the numerous bubbling springs, and the still-unexplored stretches of caves both known and unknown tell us that the beautiful forested plateau yet holds many secrets.


Sand Beach, Maine, geology

— Photo by Mike Nardacci

Sand Beach, Acadia National Park's most popular attraction, is a "pocket beach" sheltered by a rocky shoal and by the rocky peninsula known as "Great Head," featuring popular hiking trails.

My first experience with Acadia National Park on Mount Desert Island in Maine was in the summer of 1987 when I went as a graduate student to the College of the Atlantic in Bar Harbor for a course in the island’s geologic foundations.  I was assigned a dorm room in a refitted mansion from Bar Harbor’s Victorian heydays, one of several on the college’s campus.

With the enigmatic name of “Seafox,” the building sat on a low cliff right above Frenchman Bay and had a view out over the cluster of fir-tree crowned, rocky islands known as the Porcupines to the far shore of the Schoodic Peninsula and the Gulf of Maine beyond it.

It is a stunning view, and it evoked in me a line from John Denver’s ballad “Rocky Mountain High”:  “…Comin’ home to a place he’d never been before.”

Mount Desert Island — the locals insist on pronouncing the middle word “dessert,” as in baked Alaska — is roughly 12 by 17 miles and shaped like a huge lobster claw.  Its interior is rugged:  30 or so named peaks with steep slopes and barren, wind-blasted summits that belie their fairly low elevations, making them seem far higher than they really are and posing a challenge to even experienced climbers.

The glacially-sculpted valleys between them are thick with deciduous trees — oaks, maples, and birches — as well as balsams, spruces, and other conifers.  One mountain-bordered valley called Somes Sound is a deep, briny body of water with an uncanny resemblance to Lake George; it is Maine’s only fiord, a U-shaped glacially-cut valley filled with sea water.

The ocean water surrounding Mount Desert Island — MDI for short — is achingly cold, and even at the climax of a hot summer it is unusual for it to get above 55 degrees; tourists visiting an MDI beach for anything more than a very brief, bracingly cold dip are usually well-advised to head inland to one of the island’s numerous ponds and lakes which commonly reach 70 degrees by August.

Waves meet bedrock

But most visitors to the island’s ocean beaches are not there for swimming: They are there to take in the stunning scenery that results when the powerful waves come in off the Gulf of Maine and crash into the hard bedrock of the island.  It is mostly granite, but in a few places it is made up of hard sedimentary rock and a metamorphic rock called schist.

All of these rock types are very ancient, the youngest being from the Devonian period — roughly 400 million years old, while the oldest — the schist — dates from the Cambrian and Ordovician times, roughly 550 million years in age.  When the powerful Atlantic waves meet the bedrock of Mount Desert Island, the results are what the tourist brochures call “eye-popping.”

And fortunately, some of the most spectacular are easily viewed from Acadia’s Park Loop Road, which skirts a long section of the coast before heading into the fragrant forest of interior Mount Desert Island.

Every high school student is familiar with the diagram in the Earth Science Reference Tables showing the relationship between the velocity of water and its consequent ability to move rock particles.  To describe it simply, the higher the yearly average velocity of a stream or a wave, the larger the particles it can move.

Very slow-moving water — a meter (roughly one yard) per second or less — can transport tiny particles such as silt, clay, and sand, and some diminutive pebbles; but as the water’s average velocity increases to 4 or 5 meters per second or higher, it develops the ability to transport increasingly huge boulders, and sometimes to hammer away at bedrock, leaving nothing but sheer cliffs rising from the sea.

“Sand Beach”

Given the island’s location off the coast of Maine, exposing much of it to the full power of the ocean, it is not surprising that sandy beaches are uncommon on MDI.  In fact, there are just two, and one is artificial, with truckloads of sand required every few years to keep up with the ocean’s erosive power to take it away.  But the other is natural, and it affords one of the most breathtaking views on the island.

Named perhaps a bit too literally “Sand Beach,” it sits on the side of the island that faces directly east making it a tempting target for the huge waves that roll in off the Atlantic all the year around.  But Sand Beach is what geographers call a “pocket beach.”

It sits tucked back into a broad, shallow valley, protected partially on its east side by the craggy peninsula called “Great Head” and to its south by a large rocky shoal known as “Old Soaker.” Against both of these features, powerful waves break and lose much of their power.

Thus they are unable to blast away completely the sand that ends up on the beach, either washed down from higher areas on the island or transported along the coast by off-shore currents.  Probably the singular most popular visitor draw on the island, it offers in summer a gorgeous place to sunbathe, picnic, and perhaps to test one’s ability to withstand the numbing but bracing waters without fear of the ocean’s ability to create crushing waves and rip currents.

Safe haven

The picturesque village of Bar Harbor is located on the edge of Frenchman’s Bay, named for the explorer Samuel De Champlain.  The bay has been known since the days of sailing ships as a safe haven from the wild Atlantic waves.

Several small beaches at Bar Harbor village face open water, and wave action washes away small sediments, leaving them covered in pebbles.


Still, not far off the coast the surrounding waters are very deep, and in spite of the existence of a scattering of islands and an artificial breakwater, relatively strong waves frequently break against Bar Harbor’s shores, washing away small sediments such as silt and sand but leaving larger ones such as pebbles in place.

The village sits on the sedimentary sandstone and siltstone bedrock known as the “Bar Harbor formation.”  When the rock is eroded by waves, it tends to break down in layers, which in turn weather into small, flat fragments, resulting in what is known as a “shingle beach.”

During times of accelerated wave velocity, such as in a storm, the fragments clatter against each other, becoming smooth from the grinding and producing a haunting sound.  Those who remember Matthew Arnold’s beautiful poem “Dover Beach” from their school days may recall that it was just such sounds on an English beach that inspired his philosophical musings.

Given the fact that vast stretches of Mount Desert Island have harder bedrock than underlies Bar Harbor and are exposed to waves more powerful than those at the village, it follows that many of the island’s beaches are scenically rugged, especially along the east coast of MDI, both north and south of Sand Beach.   In these locations, waves are on average powerful enough the year around to wash away all but the largest sediments.

Little Hunter’s Beach

A number of cobble beaches have formed, with some of the sediments produced directly from their underlying bedrock, and vast quantities were transported there by the great glaciers that covered the island 20,000 years ago.  A particularly photogenic example is Little Hunter’s Beach, named for a stream that spills down and into the ocean from the high forest looming above the beach.

The rounded cobbles that bury the bedrock several meters deep here come from numerous  points to the beach’s north, many from inland Maine.  They are of many kinds and brilliant colors:  granite, basalt, schist, and other rock types, rounded and polished by centuries of wave erosion.


Little Hunter's Beach is an example of a "pocket beach," tucked back into the coastline but in this case facing unobstructed wave action.


There is a direct relationship between the force of the waves and the steepness of a beach surface, so traversing Little Hunter’s is a challenge, akin to walking on an enormous, slanted pile of billiard balls. Like Sand Beach, Little’s Hunter’s is also a pocket beach, tucked back a couple of hundred feet into the landscape — but Little Hunter’s faces open ocean, and only the distant Cranberry Islands somewhat lessen the waves’ power to remove sediments.

Hence the beach is made largely of cobbles, with smaller pebbles visible only at the waterline at low tide, when wave energy is often much lower. The beach is bordered by woods filled with balsam firs, spruces, and bayberry, and the cold breeze that blows over it carries their fragrance for great distances.

Powerful waves

A few miles north of Little Hunter’s is a section of coast open to the full fury of the Atlantic and here are found what geologists call “high energy” beaches. In these areas, the waves have sufficient energy to leave behind nothing but boulders or have blasted away all sediments and left massive cliffs rising starkly from the raging ocean waters.

A boulder-strewn beach that is easily visible from the Park Loop Road is called “Monument Cove,” a recess cut back a couple of hundred feet into the bedrock, which consists of the beautiful deep-pink Cadillac Mountain Granite, forming 60-foot cliffs that tower above a jumble of boulders, some a meter or more in diameter.

Monument Cove with its sheer cliffs and massive boulders is easily accessible from Acadia's Park Loop Road.


It can take waves moving 1,000 centimeters per second — over 30 feet — to move rocks of that size; but the rounded and smoothed appearance of the rocks testifies to waterflow of that power, providing a spectacle of furious waves and foam and the roar of the sea during the occasional off-shore hurricane or one of the many winter storms that pound the Maine coast.

And yet — areas of Maine’s coast can be subjected to even greater wave velocities, and the stretch near Anemone Sea Cave is a sobering example. Anemone Cave harbors a population of sea anemones, in addition to sea stars, sponges, and other delicate life, and to protect it the National Park Service has long stopped publicizing its location.

However, that location makes it hazardous to humans as well.  The water immediately off the shore here plunges to great depths, permitting enormous waves to blast away at the coast with very little frictional drag from the bottom.  The result is that, in this stretch of Mount Desert Island, there is no beach in the conventionally understood sense of the word at all.

Instead, there are high cliffs rising directly out of the sea, featuring precipitous drops, and a combination of the relentless forces of frost action in winter and the rhythmic, endless surges of giant waves have blasted out a sea cave.  Such caves are relatively rare on the east coast of the United States, but common farther north and on the west coasts of both the United States and Canada where waters tend to be deeper and waves more powerful the year around.

Great diversity

Mount Desert Island has long been known to naturalists and oceanographers as a tremendous outdoor laboratory where creatures ranging in size from tiny ones such as plankton to far larger ones such as whales and a spectacular variety of plants may be studied; to geologists, it offers beautiful examples of all of the major rock types and the forces that from ancient times have created and weathered and eroded them.

But the island has also for many centuries drawn a great diversity of visitors as well:  Native American Indians fishing the rich waters, sailing ships seeking a safe harbor during storms, and city-dwellers looking to escape summer heat. But it has also drawn lovers of the island’s natural beauty and artists seeking to capture the astounding landscapes created when the angry ocean meets rock.


— 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.

— Photo by Mike Nardacci

The Knox Fossil Rock Quarry is now inactive.  The subject is standing on an outcrop of Becraft limestone right at its contact with the overlying Oriskany sandstone.

— Photo by Mike Nardacci

A dilapidated lime kiln in Joralemon Park near Ravena is one of dozens scattered throughout the Helderberg region

— Photo by Mike Nardacci

The stone wall in the historic cemetery on Peasley Road near Rensselaerville is constructed of Helderberg bluestone.

— Photo by Mike Nardacci

The abandoned Helderberg bluestone quarry in the formerly bustling village of Reidsville is quiet now.

— Photo by Mike Nardacci

The Rock Hill Road limestone quarry, the products of which were once used in the manufacture of Portland cement, has long since been abandoned.

— Photo by Mike Nardacci

An exterior wall of the Western Diner in Guilderland shows numerous brachiopod fossils found in the Oriskany sandstone.

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.