The Enterprise — Mike Nardacci
An outcrop of tilted bedrock shows the ongoing tectonic interaction of the Indian subcontinent with China.
For those of us “of a certain age,” our images of China probably derive from the late 1960s and early 1970s: scenes of grim-looking Beijing with thousands of stern-faced, androgynous-looking Red Guards marching, chanting, and waving Chairman Mao’s little Red Book, the images looking even grimmer for having been shot in black-and-white.
But the Chairman’s call for China to be in a state of “permanent revolution” has come full circle: Most modern Chinese find the whole Mao era to be at least an embarrassment if not a collection of horrible memories.
China has become a market economy and tourist guides talk openly of Mao’s atrocities; they tell of swirling rumors that his mummified body will be removed from exhibit in Tiananmen Square, and that his gigantic mausoleum that Ramses II might have envied will be torn down.
The Chinese people dress fashionably, markets in the big cities are overflowing with food and consumer goods, and private businesses are exploding. China still has many problems, among them serious air pollution and a government that permits a certain amount of economic freedom but far less political freedom.
But visitors to China cannot help but be aware that the winds of change are blowing as surely as those that sometimes carry thick clouds of dust from the Gobi desert over Beijing. And they become aware quickly of something else, too: China is an awesomely beautiful country.
I recently returned from a trip that took some friends and me to China, and our travels will be the subject of this and future “Back Roads Geology” columns. Our itinerary took us to Cambodia as well, and might easily be described in such clichéd terms as “eye opening” and “life-changing” — but in this case the clichés are true and they are not hyperbole.
Vast country
The world seems a much bigger and more fascinating place to anyone who has seen China. It is a vast country, with landscapes as diverse and spectacular as any in the United States.
Its high mountains result from the ancient collision of the Indian subcontinent with Southeast Asia, and exposures of distorted bedrock and China’s sometimes catastrophic earthquakes indicate that the collision is ongoing. Elsewhere are more lofty mountains and wilderness, the lair of the giant panda, and to the west lie the Gobi Desert and occupied Tibet and the Himalayas.
And much of China is karst terrain: thick limestone bedrock in which the agents of weathering and erosion in the humid stretches of China have carved out craggy pinnacles, hollowed out caves, pockmarked the surface with giant sinkholes, and formed gushing springs.
The great Yangtze River flows down from the Himalayas through some of the most stunning scenery in China, in particular the legendary stretch known as the Three Gorges where millions of years of river erosion have carved out a spectacle to rival — and in stretches exceed — our own Grand Canyon.
Downstream is the eponymous Three Gorges Dam — a technological wonder of the world but also a source of great controversy. While it has allowed the production of enormous amounts of electrical energy, it has also raised the river’s water level over a hundred feet, displacing 1.3 million Chinese and in the process flooding towns and archeological sites and causing much ecological change.
One thinks of the similar effects of the Egyptian High Dam at Aswan, the building of dams by the TVA — and the loss of villages and farmland behind the dam at New York’s Great Sacandaga Lake. Nonetheless — the stretches of the river from Chongoing (familiarly known as “Chun-king”) down to the dam itself have become prime areas for the visitor to China — and a few hours on a cruise ship through the region demonstrate why.
Even before reaching the magnificent vistas of the Three Gorges themselves, the scenery is evocative — one might accurately describe it as mystical. Though the landscape exhibits enormous pinnacles and buttes, as in Arizona’s Grand Canyon, the climate here is very humid and the walls of the gorge are thick with vegetation.
The Yangtze is brown as the Mississippi, partly due to the heavy sediment load it bares from locations as far away as the high Himalayas, and partly due to effluent from riverside villages and sediment from mines drowned as the water rose behind the great dam. The river cuts steeply through verdant hills and mountains dotted with small villages — some reachable only by boat — and temples and pagodas from China’s past, often situated on slopes that are so steep as to appear inaccessible.
A land out of legend
The beautiful Shibaozhai Taoist pagoda rises surrounded by lush gardens near the peak of a precipitous limestone promontory reachable only by a hike up a steep incline and a harrowing traverse of a swaying suspended bridge. The wooden structure was built over 400 years ago, 12 levels tall and constructed without a single nail.
Inside it are narrow, twisting passages and shadowy alcoves, within which reside over-life-sized statues of Taoist deities and heroes. Their presence is disorienting, but in a pleasing way — telling visitors that they have entered a world parallel to their own but governed by unfamiliar figures.
That the pagoda and so many other relics of China’s past survived the barbarity of Mao’s Cultural Revolution is often a tribute to the wisdom of numerous local officials and citizens; alerted to the destructive intentions of the Red Guards, the locals papered the walls of many pagodas, temples, and other ancient relics with posters of Chairman Mao. This made the structures sacrosanct and untouchable by the mindless mobs.
This is a land out of legend. The channel of the river becomes narrow, and the buttes and pinnacles become higher and more precipitous. Waterfalls burst from hidden caves and gush down steep, narrow passes, not unlike those in the Hawai’ian islands, showing as many shades of green as it is said that a true Irishman can distinguish.
Soon our cruise ship docks and we disembark at a confluence where a narrow tributary called the Shennv Stream joins the river, and, like the Yangtze, the Shennv flows brown with suspended sediment from the high terrain above it.
Here we shuffle into small, elegant boats, painted in the traditional colors of red and gold. The boats are motorized but surprisingly quiet as they glide upstream — as are we, its passengers — for we glide into a stunning landscape of steep green slopes, reaching upward to sheer faces of limestone rock.
Springs burst from the dense forests and here and there an ancient rock staircase ascends from the river shore and vanishes mysteriously into the dense growth high above. A cloudburst a few hours before has fed a number of waterfalls that resolve into fine spray before they reach the river shore.
The high peaks of the Shennv valley are draped in low-lying clouds and before us is the inspiration for thousands of Chinese scroll paintings, depicting mystical landscapes in which human constructions disappear into the drifting fog.
The evocation of the hidden valley of Shangri-la in James Hilton’s romance “Lost Horizon” is inevitable. Here in the valley of the Shennv is a world green beyond belief, appearing untouched by any human presence, far removed from the noise, the pollution, and the human turmoil of the world outside
Through centuries of Chinese history in which ruthless dictators and benevolent despots built their fortresses and walls and fomented revolutions and waged wars, the Shennv has flowed beneath towers of ancient rocks and dense forests of trees that seem never to have known an ax.
But soon it is time for our quietly moving tour boat to return us to our cruise ship on the Yangtze, time to return to a world of schedules and obligations and technology. And, in the days and weeks that follow, we are left to ponder: Did we, or anyone, really enter — if ever so briefly — that hidden, primeval valley?
And yet, in our thoughts remain those mysterious, mossy staircases, rising from the rocky banks of the Shennv and vanishing into the misty wilderness above.
— 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.
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— 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.
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.
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.
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.
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— 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.
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.
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.
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.
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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.
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.
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.
Location:
— 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.
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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.
The Enterprise — Mike Nardacci
A “doorway to nowhere” in Penasco Blanco is part of ruins that have stood unoccupied for nearly a thousand years.
The Enterprise — Mike Nardacci
From a distance, the ruins of Penasco Blanco resemble natural rock outcrops protruding from the top of the mesa.
The Enterprise — Mike Nardacci
Fragments of Anasazi pottery: In some areas, they lie in thick layers, evidence of centuries-long occupation of the ruins.
The Enterprise — Mike Nardacci
This ancient pictograph is believed to show the supernova of 1054 A.D. with a crescent moon and what may be the artist’s handprint above it.
Bordered by sagebrush and other sparse desert vegetation, the washboard-surfaced road to Chaco Canyon traverses a barren, waterless landscape.
The Enterprise — Mike Nardacci
Huge boulders, like this one, exhibiting honeycomb weathering, are common in arid landscapes.
The Enterprise — Mike Nardacci
A barren talus slope is topped by sheer cliffs along Highway 550 in New Mexico.
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!
Location:
The Enterprise — Michael Nardacci
Damoiselles: A pair of sunglasses shows the size of the tiny structures near the entrance to a Clarksville area cave. Pebbles in the clay matrix have protected the sediments beneath them, forming little columns.
The Enterprise — Michael Nardacci
Hoodoos eroding out of a glacial drift on the Normanskill at “Ghost Fire Bend.” These structures change radically from year to year because of heavy precipitation.
The Enterprise — Michael Nardacci
A sweeping view over Tent Rocks State Park stretches to Sandia Mountain near Albuquerque.
The Enterprise — Michael Nardacci
A sweeping view over Tent Rocks State Park stretches to Sandia Mountain near Albuquerque.
The Enterprise — Michael Nardacci
A few stubs are all that remain of some very old hoodoos. Others show the classic shape while newly forming hoodoos emerge slowly from the surrounding slopes.
The Enterprise — Michael Nardacci
A massive boulder compressed the sediment below it, protecting it from erosion — a textbook example of hoodoo formation.
A point I have always tried to make with my students or participants in one of my field trips is that geologists have a name for absolutely every natural process involving the rocky sphere that is Planet Earth. And one of the wonderful things that has happened in recent decades is that scientists have sent robot probes to examine the surfaces of other planets, as well as asteroids and comets, and have found not only that many of the same processes occur on worlds as alien as the Moon, Venus, and Mars, but have discovered exciting evidence of other geologic phenomena unknown on Earth and waiting to be explained.
Over the past few days, the Internet has been sizzling with reactions to a rock photographed by the Curiosity Rover that has a passing resemblance to a thighbone. Given the fact that not one of the robots sent there has yet found persuasive evidence that anything as large as a microbe ever lived on Mars, the curiously shaped rock is unlikely to be anything but that: a curiously shaped rock.
But the various chat rooms that dwell on such things are buzzing with charges that NASA (the National Aeronautics and Space Administration) is once again concealing evidence of macrobiotic life on Mars and those who disagree are denounced in vitriolic (and often hilariously ungrammatical) language.
Yet the fact is that the natural processes which change the shape of Earth’s surface are sometimes capable of producing very curious results: hence, the chess-piece shapes of the rocky towers of Bryce Canyon, the elegantly sculptured mesas and buttes of Monument Valley, and the granite profile of New Hampshire’s Old Man of the Mountains that collapsed ignominiously some years ago into a heap of rubble due to frost-wedging.
A few weeks back, on emerging from a trip with some students through one of the caves near the village of Clarksville, I noticed some odd, miniscule features on a pile of muddy debris at the cave’s entrance. The debris was glacial drift, deposited on the Clarksville area by one of the streams pouring off the melting Ice Age glaciers thousands of years ago: hundreds of penny-sized and smaller pebbles in a matrix of packed clay.
But many of the pebbles stood atop a small, thin column of that clay, forming tiny structures geologists call by the French term “damoiselles”— which loosely translates as “little maidens.” Evidently, to the French-speaking geologists who coined the name, the pebbles resembled broad bonnets perched atop the slender structures below.
This happens when rain water or melting snow cascades down an exposure of soft sediment, washing away anything that is not protected by the tiny pebbles; their weight has slightly compressed and hardened the materials on which they sit.
In many places in the world, these structures appear on a much larger scale. Chimney Bluffs State Park on Lake Ontario features enormous examples, which are often given the name “hoodoos” when they form such massive structures. A somewhat smaller display of hoodoos appears on the mysteriously named “Ghost Fire Bend” of the Normanskill, though these are currently not accessible by car with the closing of Grant Hill Road due to road work.
In June of this year, while on a hiking trip to New Mexico, I had the opportunity to visit Tent Rocks State Park on the reservation of the Cochiti Pueblo, southwest of Santa Fe. The preserve was originally given the Keresan language name Kasha-Katuwe, which is usually translated as “rocks that resemble teepees.”
Here, between 6 million and 7 million years ago, the land was buried under the debris from an incredibly violent volcanic eruption that formed the Jemez Caldera, a giant bowl-shaped depression to the north. Layers of the soft, spongy-looking rock known as pumice, compacted rock fragments called tuff, and volcanic ash buried the region in layers hundreds of feet thick.
The weight of all of that air-borne sediment compacted the strata into a crumbly matrix rock that weathers easily due to the wildly varying seasonal temperatures and is poorly resistant to erosion by the occasional rainfall or melting snow. But mixed in with the smaller rock fragments are boulders, some the size of an automobile, and these had the effect of compressing and compacting the sediments that lay beneath them. Thus the sediments were protected from the raging, highly erosive waters that flow during those occasional periods in arid climates when sudden torrential rains fall.
The results are the hoodoos of Kasha-Katuwe, and they are marvels to behold.
Those found near the parking area for the preserve’s trailheads gave Tent Rocks its name. There are a dozen or more of them, ranging in height from a couple of yards to 20 or 30 feet, but these represent the last stage in the erosion cycle of the hoodoos. They have lost their protective boulder caps and, in respect to geologic time, they are not long for this world.
Though this part of the Southwest is currently experiencing a severe decade-long drought, every drop of rain that does fall is washing them down to ground level, the eventual fate of all hoodoos.
To get a better idea of nature’s inventive sculpting talents, one must hike up one of the two major trails that head into the park. They are easy for the experienced hiker, though the lack of shade and the unforgiving summer sun make it mandatory to carry a couple of quarts of water. In addition, signs warn of poisonous snakes lurking in the underbrush — sufficient cause for those inclined to bushwhack to stay on trail.
A textbook example of the formation of the hoodoos lies on the edge of the eroding mesa around which the trail meanders. Rising some 20 feet from the middle of a dry wash, the structure is crowned by a large boulder of pumice.
Farther along the trail, the hoodoos become larger and more varied in shape and one particularly steep slope offers a view of their entire life cycle: some eroded down to mere stubs, some proudly displaying their protective caps, and others just beginning to emerge from the eroding cliffs.
They derive their weird shapes from the varying hardness of the rock strata from that they form. A slot canyon cut into the rock by raging waters offers a shady respite from the heat and climaxes in a hair-raisingly steep and exposed series of switchbacks leading to a jaw-dropping view out over the canyon to Sandia Mountain above Albuquerque.
The American Southwest — particularly in New Mexico and Arizona — features some spectacular geology due to its diverse rock types; its wildly varying elevations; and its climate, which tends to be arid but is subject to sudden intense flooding.
Terms such as “weathering,” “erosion,” “resistance,” “strata,” “frost wedging,” and other prosaic expressions may seem lifeless on the page of the textbook. But, in an environment such as Tent Rocks State Park, these dry words describe nature’s endlessly varied talent to create wonders in the rock from which Earth is made.
Location:
— Photo from Mike Nardacci
A field of glacial erratic boulders lies on a mountain west of the Great Sacandaga Lake.
— Photo from Mike Nardacci
Hadley Rock: Adirondack resident Steven Rider stands in the weathered-out fissure of an immense glacial erratic boulder
Acadia National Park on Maine’s “Down East Coast” is a place of mystical wonders: sheer granite cliffs rising from the sea, washed in the salt spray of enormous waves crashing against them; barren mountain peaks that seem much loftier than they really are, climbing upward from sea level and splashed with the colors of flowers normally found hundreds of miles farther north; spectacular stone bridges in the most unlikely places in the Acadian forests, gifted by John D. Rockefeller and looking like leftover sets from The Lord of the Rings films; and miles of fir and hemlock coastal forests, the dark green boughs hanging with the lichen called Old Man’s Beard, wreathed in fog and dripping in a silence broken only by the haunting cries of gulls and the clanging of buoys.
But Acadia is also an enormous outdoor natural history classroom, and educational institutions such as the College of the Atlantic in Bar Harbor frequently use its features for courses in geology, marine biology, botany, and environmental chemistry, among others.
The mountains of Acadia and other even higher summits in interior Maine must have been among the last places in the northeastern United States to have had glacial ice when the vast Wisconsinan glacier — the most recent continental glacier — retreated as Earth warmed over the last 15,000 years. U-shaped valleys, the odd asymmetrical mountains called “roches moutonnees” (which translates as something like “sleeping sheep”), bedrock showing the striations (scratches) caused by the advance of the glacier, and immense deposits of glacier-borne rock material all testify to the recent — in geologic time — Ice Age.
Glaciers are immensely powerful agents of erosion, and much of the upper part of the continental United States is covered in the debris they left behind.
The poet Robert Frost wrote frequently of the hardship of being a New England farmer — not the least of whose problems was the immense quantity of rock left behind in the landscape presenting an appalling challenge to the horse-drawn plough. His poem “Mending Wall” deals with the boulders — “some like loaves and some…nearly balls” that are ubiquitous in fields and which farmers for generations have used for stone walls and house foundations and churches.
The beaches of the Acadian Coast are famous for the almost infinite variety of types and colors of rocks found on them, many of which may have been transported for hundreds of miles from their point of origin: For it is a rule of glacial geology that an advancing glacier acts as a bulldozer, scraping away loose sediment and vegetation right down to the bedrock and then proceeding to abrade it, too, away; but a melting or evaporating glacier acts as a dump truck, leaving behind all sizes of rock particles from tiny clay and silt to huge cobbles and boulders in one heterogeneous mess called glacial drift.
The larger particles — the cobbles and boulders — are known by the quaint name glacial erratics. The high summits and slopes of Acadia are dotted with thousands of erratics, and on many of the peaks such as Cadillac Mountain, the highest mountain on the East Coast of the country, they sit in rugged isolation, often looking like the remnants of the mysterious rocky circles found in Ireland and England.
One of them is a famous landmark for visitors to Acadia: It is called Bubble Rock and it perches picturesquely on the steep slope of the summit of a small mountain known as South Bubble. It is an enormous chunk of the Lucerne Granite, a beautiful black-and-white speckled stone with large crystals that forms the bedrock some 40 miles north of Mount Desert Island
The sight of it challenges credibility: The slope appears to exceed the physicist’s “angle of repose” and it looks as if the slightest touch would send it careening noisily into the valley below it, smashing rocks and trees as it went.
Many visitors to Acadia National Park have appeared in the apparently obligatory photograph in which they attempt to dislodge it. Legend has it that, on a Halloween night some years ago, the entire football team of a local high school hiked up and attempted to push it off South Bubble. But there it stands.
A charming children’s book (now, alas, out of print) attributed the precarious position of the rock to Acadian trolls. But it must be remembered that on what is now the coast of Maine, the continental ice sheet was greater than a mile in thickness and thus had immense power to transport rocky materials: Retreating, it left this erratic and many others behind, sometimes in the most unlikely of locations.
Our own Helderberg hills and the Adirondacks also feature vast numbers of erratic cobbles and boulders, but, given the thickness of the forests that grow on them, erratics are often hard to spot, except when they are exceptionally large.
A relatively low mountain to the west of the Great Sacandaga Lake has a ridge running from its summit that features dozens of fairly large boulders of gneiss and anorthosite, transported from the High Peaks of the Adirondacks. Just below the mountain’s summit is a gigantic erratic, split down one side by frost wedging and the action of tree roots.
Far larger than Bubble Rock, it sits on a much gentler slope, and, located as it is in some fairly remote wilderness, it has likely had few visitors. Doubtless, hundreds more like it are scattered throughout the Adirondack fastness.
But we in the Albany area do not have to look far to find glacial erratics. Anyone who lives outside of the city of Albany — especially in the Altamont and Voorheesville area on the west side of the Hudson and in the Wynantskill and East Greenbush area on the east side — has found the same problem as the New England farmer in attempting to dig on one’s property: the enormous quantities of rocks in the soil.
They may have many different points of origin, of course, but one that is very common is a purplish rock often found as a smooth cobble or boulder, deposited directly by the ice or perhaps rounded and polished in a vigorous stream pouring off the melting glacier. These are samples of what is called the Potsdam sandstone and they originate far to our north near the border with Canada.
The fact that erratics’ points of origin can be determined with precision is useful to glacial geologists, who sometimes refer to deposits of such rocks as boulder trains. Appearing in more or less straight lines that strike roughly north-to-south, they allow the directional motion of the glacial ice to be determined very accurately.
When I am conducting geologic field trips, I usually toss out this question to participants: Just how long ago was the Ice Age?
Unless respondents are exceptionally knowledgeable, answers are usually accompanied by a shrug of the shoulders: “A million years ago?”
That is not a bad answer as a million years ago the ice was, indeed, in control of much of this part of the world.
But people are often unaware that even 10,000 years ago there was glacial ice on some of the highest peaks in the Northeast, and that we are living in what geologists call a glacial interlude.
But aren’t we in a time of global warming? Yes, there is evidence of that assertion. But all evidence is that the warmest Earth has been in the last 20,000 years occurred 7,000 years ago in a time geologists call the “hypsithermal,” and the glacial ice is poised for its return in a few thousand years.
In a few weeks, we will be entering the first stages of fall, and the average day-to-day temperatures will begin to drop. From time to time, we may see exceptionally warm days — we can all remember days in October and even November when the thermometer incongruously hit 80. But no one is foolish enough on such days to think that summer is coming back.
We are living in a geologic period of continental glaciers and the little purple stones in your backyard not only tell us that the last glacial advance was not so long ago; they may be harbingers of cold, cold days to come!