— Photo by Mike Nardacci
A boulder freshly broken from the bedrock of Stark’s Knob shows tiny pits called vesicles where bubbles escaped from the lava when it was still molten.
The rocky promontory known as “Stark’s Knob” rises a short distance north of the village of Schuylerville and when the leaves are off the trees its summit affords a panoramic view of the Hudson River.
Though its human history is but the wink of an eye compared to its geologic past, it played a pivotal role in the American Revolution. From its summit, the rebelling colonists observed British ships moving up and down the river.
Under the command of New Hampshire General John Stark, they moved cannon and other armaments to a flat area between the Knob and the Hudson River to prevent British troops from escaping after the battle of Saratoga.
But the Knob is also widely known as “the Schuylerville volcano,” and though it is not now erupting, the name conjures up visions of fiery fountains of lava and plumes of sulphurous smoke spilling out over the landscape.
But it was never a volcano and it did not originate in its present location. However — it is made of lava that has solidified in the form of bulbous mounds called “pillows,” and an unweathered chunk of its bedrock shows holes called “vesicles,” which are the remains of bubbles of escaping gasses.
Such “pillows” are forming today from fissures in the waters off the Big Island of Hawai’i as lava is ejected from fractures in the ocean floor. Curiously, some of the rocks in Stark’s Knob have been found to contain tiny fossils of shallow-water dwelling snails that lived in the Ordovician period, some 450 million years ago.
Clues to the past
Exposures of bedrock that have not vanished under the thick foliage that covers much of the Knob show the rounded, humpy “pillows” and in them and in their fossils lie the keys to understanding the Knob’s formation.
Some 450 million years ago during the Ordovician Period, the landmass that would someday be North America lay bordering a vast body of water known as the Iapetus Ocean, the name of which derives from Greek mythology.
Iapetus was a member of the race of giants called Titans and was known as the father of Atlas. The Iapetus long ago vanished as the plates of the Earth were beginning to assemble themselves into the supercontinent Pangaea, which millions of years later broke apart giving birth to a new ocean: the Atlantic.
In the mid-Ordovician Period — roughly 450 million years ago — the east coast of the United States corresponded roughly to today’s Hudson Valley and off that coast lay an arc of islands similar to those that make up Japan.
As the landmass that would become Africa closed in on the coast in a sliding, scraping motion known as a “transform fault,” those islands got caught up in the crunch and were plastered onto the coast. This action resulted in massive earthquakes and submarine fissures extruding lava — hence the formation of the lava making up Stark’s Knob.
As a result of the chaos, huge slabs of terrain were pushed westward, and the solidified mass of igneous rock that would be known as Stark’s Knob was pushed into its present position from the region that would become Vermont.
To use an obscure term that might be the $2,000 answer on Jeopardy — the solidified lava mass making up Stark’s Knob is allochthonous (al-LOCH-thon-ous), which the Dictionary of Geologic Terms defines as “Said of rocks or materials formed elsewhere than in their present place.”
New York state contains within its borders geologic phenomena that make the teaching of geology here the envy of those in many other states. New York has:
— The vast eroded sedimentary rock layers that constitute the Allegheny Plateau, containing fossils that are the keys to understanding Paleozoic life;
— Billion-year-old-plus rocks in Southeastern New York, Manhattan, and the Adirondacks, providing evidence of great upheavals in the Earth’s crust;
— Hundreds of square miles of karst terrain, laced with caves, underground streams, and springs;
— Dinosaur fossils in the rocks that border New Jersey; and
— Perhaps — perhaps — beneath the lofty and mysterious Adirondacks lies a “hot spot”: a plume reaching down into Earth’s mantle that might in some far future break the surface and produce a series of real volcanoes like those in Iceland.
And overlooking the Hudson just north of the village of Schuylerville lies a mass of solidified lava called Stark’s Knob, providing evidence of the titanic forces that drive Earth’s plates and quite literally move mountains.
— Photo by Mike Nardacci
A stretch of the Onesquethaw Creek near the intersection of Routes 85 and 443. Much of the year, the streambed appears dry and its water flows underground but wet weather and snowmelt can overwhelm the subterranean conduit and cause water to flow over the surface bedrock.
Rainy weather is the bane of most geologic field trips; perhaps the only weather worse is wet falling snow. A geology field trip in our part of the country often involves tramping through rough and sometimes wet terrain in search of locales in which our ubiquitous forests and ground cover do not obscure the bedrock; hence it may reveal fossils or minerals or tectonic structures contained therein and precipitation in any form can make for a genuinely miserable learning experience.
But the exceptions are field trips illustrating karst features. In times of snowmelt or heavy rainfall, a karst landscape reverberates as its sinkholes, grikes, springs, and disappearing streams gurgle with the sudden flow of turbulent waters.
At such times, it is well worth the effort to put on a rain slick and waterproof boots and head off into one of the many karst preserves of the Helderberg area and appreciate the dynamic features of these landscapes and of the hidden mysteries that lie beneath them.
However romantic the notion of cave geology may seem, the understanding of karst begins with a singularly mundane fact: Caves are in essence natural storm drains.
The term karst itself is derived from “Kras,” which is a plateau bordering on Slovenia and Italy. In the 19th Century, geologists recognized that its limestone bedrock laced with caverns and featuring sinkholes, underground rivers and streams, and springs represented a whole relatively unexplored branch of geologic studies.
The storm drains found in city streets, which are often miscalled “sewers,” transport runoff beneath the streets to the nearest river or stream without filtering it.
Likewise, in a karst region, rainfall and surface waters that are naturally mildly acidic can dissolve carbonate bedrock such as limestone or marble and produce subterranean streams that can flow for miles before they reach a place where they return to the surface in springs that may be either gravity-fed or artesian defying gravity. And in doing so they often carry volumes of sediments — both organic and non — and spew them back into the world.
Much of the Helderberg Plateau contains limestone surface bedrock. In the area of Thacher Park, two limestone layers named the Coeymans and the Manlius form a cliff 100 feet high in places featuring numerous small caves. A couple of hundred feet higher is a broad terrace formed on top of the Onondaga limestone cliff and traversed by the Beaverdam Road.
There are on the surface great numbers of sinkholes and fractures called grikes that can take water in wet times, and the caves in these limestone strata will then produce springs that burst from the cliffs under the pull of gravity and flow down into the valley below.
A similar gravity spring emerges from Barton Hill in Schoharie above Route 146. These springs frequently produce micro-environments conducive to the growth of mosses, ferns, algae, and watercress. At times — often seasonal — the waters emerging from gravity springs may be saturated with calcium carbonate in solution and will coat the rocks and organic materials in their paths with the mineral producing a spongy-looking rock known as tufa.
In dry times, water may be flowing just beneath the surface of dry-looking stream beds but will overflow to the surface during periods of snowmelt or high precipitation. One such example can be found in the upper reaches of the Onesquethaw Creek where it flows beneath a bridge near the intersection of Routes 443 and 85.
What for much of the time is a flat, arid limestone pavement featuring numerous grikes and other fractures becomes a series of plunge pools and rapids when excess precipitation renders the conduit just beneath the surface inefficient to carry the excess water.
Similar weather conditions can also produce temporary artesian springs in which water under pressure flows upward against gravity. The volume of water in a sizable cave passage overwhelms the ability of the cave to carry it, just as storm drains blast water to the surface when the volume of water exceeds the ability of the conduit to transport it.
An impressive example occurs several times each year near what is called the Gregory Entrance to Clarksville Cave. A fracture at the base of the surrounding cliff exhibits an impressive artesian spring: a cloudy pool with a surging hump of water in the middle as turbulent waters flow upward out of the cave and down an otherwise dry streambed and under Route 443.
This spring not only flows during times of snowmelt but may form and be gone within 24 hours in warmer weather following sudden heavy rainfall.
Disappearing streams
But perhaps the most impressive feature of a karst landscape during periods of exceptionally wet weather or spring thaw is the presence of disappearing streams. Pockmarking the terrain will be dozens — sometimes hundreds — of sinkholes that form when surface bedrock collapses into a void below.
At such times, flowing liquids will head toward the lowest topographic point and will produce streams that may flow for hundreds or thousands of feet over bedrock that does not dissolve as limestone does or tightly-packed glacial debris, both of which are common in the Helderberg area.
Suddenly reaching a sinkhole, a raging stream may vanish abruptly into the darkness below, leaving the surrounding landscape quiet except for bird calls. A well-known example is the sinkhole entrance to the Onesquethaw Cave system south of the village of Clarksville.
Sport cavers have long had great respect for Onesquethaw, which is capable of sudden flooding with rapidly-moving water following short periods of intense precipitation. The sinkhole entrance is in a very low area surrounded on its west side by steep shale hills, the runoff of which can cause huge volumes of water to cascade into the entrance. The flow resurges in a gravity spring a mile or so away off Route 32.
Geologists are known for braving dangerous topography and unpleasant weather conditions in pursuit of knowledge and mild, dry weather will ordinarily be most welcome on expeditions. But to truly appreciate a karst landscape it must be seen in weather conditions that would keep the less adventurous indoors.
For when the heavy rains fall or the snows melt, the landscape comes alive, with otherwise dry fractures in cliffs and other bedrock exposures suddenly blasting great volumes of sediment-laden water. These waters form rushing, meandering streams that seem to have come from nowhere; fields and forests full of gaping sinkholes that swallow those temporary streams then conduct the waters through dark chambers to often unknown destinations.
It is a landscape filled with mysterious sounds and sights that are well worth the temporary discomfort in experiencing them.
— Photo by Mike Nardacci
A gaping sinkhole in the McFails Cave Preserve swallows a stream that flows through McFails Cave and resurges over two miles away.
Most New York State caves are closed to visitors from Oct. 1 to May 1. For information about McFails Cave and other area caves, visit www.northeatserncaveconservancy.org.
Karst lands such as those in Albany and Schoharie counties in New York State and elsewhere on our planet have long been described as “hollowed ground.” When the surface bedrock is limestone — and less commonly marble, dolomite, or gypsum — rainwater or surface water that has become mildly acidic due to the absorption of carbon dioxide will infiltrate the bedrock under the influence of gravity; it will then dissolve the rock away, creating underground streams and rivers along with extensive cave systems.
In many regions, thick layers of limestone may be underlain by a type of rock such as shale or sandstone called an aquiclude that will not readily dissolve in acidic water, producing what geologists call base level; the water can then no longer dissolve downward but must find a way out of the rock and emerge as a spring, perhaps in a cliff such as those at Thacher Park or an artesian spring in which water under pressure flows upward against gravity.
Cave passages frequently develop along tectonic faults or angular cracks in the bedrock called joints, and so it is possible for several caverns with a common base level to join and form one extensive cave system.
In central Kentucky, for example, a number of lengthy individual caves on a plateau above the Green River have been found to connect to Mammoth Cave, producing a system now known to be over 400 miles in length. And similar geologic conditions in the plateau for thousands of surrounding acres hint that the cave’s passages may someday be found to extend for additional hundreds of miles.
The plateau stretching for miles above the city of Cobleskill can be seen as a somewhat smaller-scale version of the Mammoth Cave karst area: smaller-scale because its fossil-bearing Devonian-age Manlius and Coeymans limestone layers are much thinner than the 400-foot-thick limestone strata of central Kentucky and this fact limits the depth and number of the levels on which local caves can develop.
The forests and fields of the Cobleskill Plateau abound in known cave systems of various lengths, and yawning sinkholes — some 70 or more feet in depth — swallow rushing streams in warm months and belch clouds of icy condensation during times of severe cold, creating landscapes out of “The Lord of the Rings.”
Some of the plateau’s cave systems are known or suspected to connect with one another but dozens of sinkholes that are occluded by glacial boulders and soil allow only water to infiltrate and travel underground to previously known cave systems or still unknown destinations, effectively excluding human explorers.
Discovering McFails
One cave in particular, called McFails, the extent of which was unknown until the 1960s, has long excited both sport cavers and geologists. Its historic 110-foot vertical entrance lies in a stretch of mossy, shadowy acres of hardwoods and hemlocks filled with fissures, gaping sinkholes, and disappearing streams, all of which are known to feed into McFails.
Its name derives from the report that in the 1870s on a particularly hot and humid July day, a professor from a local academy by the name of T.C. McFail had descended on a rope ladder to the interior of the cave, a tight, wet, muddy fissure.
Whether he went any farther is unknown, but on his way back up the ladder — which he was climbing without a safety line — he passed suddenly from the 46-degree temperature of the cave into the sultry July heat and fainted, falling from the ladder and striking his head on a boulder. Despite his companions’ rescue efforts, he died, leaving his name as an ironic memory of his ill-fated exploration.
For nearly a 100 years, explorers entering the cave with proper technical equipment found only a few hundred feet of gloomy stream passageway, becoming too tight for human passage upstream and vanishing into a floor-to-ceiling pool downstream.
But in 1961 during a time of low precipitation, explorers from Cornell University found several inches of air above the pool and, though they had to get thoroughly soaked, they managed to push through the pool to find themselves in a high canyon with a rushing stream sometimes waist-deep that stretched for two miles and was filled with pristine formations.
And, as the canyon expanded into a series of chambers that rivalled in size those in nearby commercial Howe Caverns, another large passage — this one with a tubular cross-section and bearing another stream — entered from the northwest.
It was initially thought to extend for over a mile and terminate in a pile of huge breakdown boulders and slabs but explorers have pushed through it to find more of the main passage and side chambers that are still not fully explored.
Downstream the rushing creek passes through several “sumps” in which the water rises to the ceiling. These have been penetrated by divers to a point at which the passage becomes blocked to further human exploration.
And more recently, intrepid explorers have found an upper level to the canyon passage filled with stalactites, stalagmites, and exceedingly delicate, glittering formations called helictites, all of which form through the evaporation of mineral-saturated water. Most visitors are encouraged to avoid the area to avoid damaging them.
Owned today by the National Speleological Society, the cave and its surrounding karst features are managed by the Northeastern Cave Conservancy, and draw scientists and adventurers from all over the world.
Connections
Years ago, the historic entrance to McFails became unstable and collapsed. Today, entrance to the cave is made through either of two vertical drops requiring ropework.
One has the Tolkien-ish name of “Ackshack” and also requires an exhausting 100-foot crawl leading to the main cave. The other is a dizzying descent of a silo-like pit that frequently takes explorers through a gushing waterfall.
In any case, the preserve rules require visitors to wear wetsuits to avoid hypothermia on trips, which frequently last upward of 12 hours.
Hydrogeologists use a technique called “dye tracing” when water is flowing through a cave system with fissures that are too tight for human passage. A harmless dye is injected into the water and watch is kept on springs and streams in nearby caves to see where it emerges.
Years ago, it was determined that in times of normal flow the stream flowing through McFails Cave eventually finds its way to Doc Shauls Spring — an enormous artesian spring located in a crater-like depression more than two miles from the main entrance to McFails. From there it becomes tributary to the Cobleskill Creek.
However — in times of heavy snowmelt or excessive precipitation such as a tropical storm, the main passage of McFails becomes inefficient to carry all of the water rushing through the cave and the excess overflows into Howe Caverns, also more than two miles away from its insurgence points.
What makes the geologic situation even more interesting is the fact that a number of caves in the hills around Howe Caverns are connected to it — or were in the past. The remnant downstream section of Howe Caverns that was largely destroyed by quarrying operations is joined to Barytes Cave, which still exists.
Barytes in turn receives water from another undeveloped (or “wild”) cave called Benson’s, which is connected hydrologically to commercial Secret Caverns. These caves are all formed in the Manlius and Coeymans limestone layers and have a common base level.
Hence, estimates are that, if all of the known or suspected fragments could be joined, Schoharie County could boast of a cave system around 26 miles long. But then the Cobleskill Plateau is pockmarked with many karst features that could eventually be found to lead to new, separate cave systems or to be part of the vast complex.
In the shadow of looming Barrack Zourie Hill, one other such independent cave is known; it has been explored for a distance of two miles and has a stream that is also a tributary to the Cobleskill Creek.
The Cobleskill Plateau has long been known for its lush hardwood forests — enticing in all seasons, spectacular in the fall — its rocky cliffs and stony streams, its diverse animal and plant life, its fertile fields and orchards, and its long and colorful history from the days of its indigenous inhabitants through its Colonial period, down to the present.
But its fame as a geologic wonder has for a long time been much less appreciated. Under the plateau’s ancient, rolling hills, chemistry and gravity have been at work for millions of years, creating a vast and still not completely known network of long, meandering channels through the darkness that beckon the curious to explore.
Photo by Michael Nardacci
The farmhouse from which D.C. and Ada Robinson ran their commercial operation of Knox Cave stood on the Knox Cave Road until it was destroyed by fire around 1968
Most New York State caves are closed to visitors from Oct. 1 to May 1. For information about Knox Cave and other area caves, visit www.northeatserncaveconservancy.org.
Filled with darkness and featuring passages that twist and meander, caves by their very nature evoke legends and lore. Under one of the fields outside of the village of Knox, an eponymous cave has incited geologic interest and lore, and drawn explorers and scientists — and, from time to time, tourists — since the 19th Century.
Old histories of the Helderbergs make mention of its steep-sided entrance sinkhole though they do not record any exploration. Formed from the Devonian-age Manlius and Coeymans limestones, the cave consists of a series of parallel passageways on multiple levels formed along great vertical fractures in the rock called joints.
Knox is not among the longest or more challenging of the caves of the Northeast — it has around 4,000 feet of passage and only two sections require technical climbing (involving ropework). However, its notorious Gunbarrel passage (of which more later) and an arduous climb and crawlway that lead to the remote and once-beautiful Alabaster Room as well as the cave’s many legends have attracted sport cavers and scientists for many years.
Newspaper accounts dating to the 1920s report sometimes fanciful— or wishful — excursions into the cave, believed then to be miles in length. There were also apparently limited commercial excursions offered by members of the Truax family that owned the cave prior to the 1930s.
One can imagine hardy explorers venturing into the cave in the long-ago style made famous by Lester Howe in his own cave in the 1800s, scrambling over fallen boulders and through chilly pools, clad in canvas cloaks and bearing kerosene lanterns.
At some point in the 1930s, the Truax property was purchased by a retired couple from Long Island, Delevan C. Robinson — known as “D.C.” — and his wife, Ada. D.C. held a Ph.D. from Carnegie Tech and his wife had a master’s degree and had taught English on the secondary level.
He built an elaborate series of stairs that descended to the floor of the cave (over 110 feet underground) and he installed electric lighting in a section that was to be a tourist route. Wishing to keep his cave in a natural state, D.C. made walkways out of flat slabs of Manlius limestone from which lower levels of the cave were formed. As an additional draw, he built a large roller-skating rink that at times also functioned as a dance hall.
The problem that D.C. and others who attempted to commercialize Knox Cave encountered was the fact that, although the section of the cave easily accessible by the staircase featured several large, impressive chambers, tours lasted only about 45 minutes. This was far shorter than tours at nearby Howe Caverns, and those areas lacked an atmospheric gurgling stream such as Howe’s “River Styx” or any flowing water for that matter — a most curious fact for a New York State cave.
Some of the most interesting sections lay beyond the famous (infamous?) Gunbarrel. This is a 47-foot-long tubular passage, and its average diameter is only about 14 inches (that is not a typo!) through which paying customers could hardly be expected to squeeze.
In any event, in the early 1950s, D.C. also set out on an ambitious program of exploration in an attempt to find new and more accessible passages and to prove that Knox — known then to be only about 3,000 feet in length — was the longest cave in New York State.
Negley’s exploration
To that end, he enlisted a shadowy figure known as “Buck” Negley who was apparently a postal worker, spending his free time exploring Knox. Very short in stature and wiry, Negley could slither through cracks and crevices that many people would regard as impossible and he evidently did much of his exploring alone. (Serious violation of caving rules!)
Prior to his explorations, the cave was known to continue beyond the intimidating Gunbarrel to a roomy chamber that terminated in a pile of loose rocky debris. Pushing aside boulders and slabs (and probably placing his life in jeopardy), Negley was able to squeeze through and discovered a maze of lofty canyons and domes and a yawning pit.
He also navigated his way through a tight, tortuous passage known as the Crystal Crawlway for its pockets of calcite crystals and was able to climb down into what became known as the Alabaster Room. Once admired for its displays of milky, translucent stalactites and flowstone, the chamber today is a sad sight.
Incredible as it might seem, some of the visitors to this remote, hard-to-reach grotto have damaged or carried away many of its delicate formations. Oddly — though the room appeared to be the northern termination of Knox Cave, Negley claimed to have found a passage continuing beyond it, for which explorers searched for years.
But in the 1990s determined cavers dug out a clay-clogged passage in a secluded spot below the Alabaster Room and broke into a low, thousand-foot-long canyon carrying a stream, far below Knox’s once-commercial passages, solving a mystery of Knox Cave’s hydrology and perhaps vindicating the legendary Negley.
But another of Negley’s claims has yet to be confirmed. He insisted that he had wormed his way through a tight crawl east of the old commercial sections and found a room he described as “larger than a football field.”
Many scoffed at his claim — but the fact remains that the thick Coeymans and Manlius limestone strata that cover many square miles of woods and fields around the village of Knox are filled with sinkholes and fractures carrying surface water to unknown destinations and in which large caverns could develop.
It is not inconceivable that the black vastness of Negley’s Lost Room may yet await discovery for some intrepid — or very thin — explorers.
Frustration Crawl and New Skull Cave
Another more tangible mystery involves a tight tunnel known as “Frustration Crawl,” which has tantalized explorers for decades. Cavers can enter it on hands and knees but it soon turns into a flat-out belly crawl, its walls worn smooth from the abrasion of thousands of passing bodies.
But, after a hundred feet or so, human intrusion is halted by two thick curtains of flowstone that have descended from either side. Looking through a narrow space between them, cavers can see that the tunnel continues but they cannot.
However, the crawl is headed straight for another large cave system less than 1,000 feet away known as “New Skull Cave,” a tortuous, wet, muddy cave system known to have over five miles of challenging passageway. Off limits to sport cavers for years, New Skull has not been fully explored and may well continue for additional miles.
Were “Frustration Crawl” to connect Knox Cave to New Skull there would be the potential for one of the largest cave systems in the Northeast.
And why the designation as “New Skull?” A few hundred yards away from both the Knox and New Skull entrances there once was a wide, vertical sinkhole around which legends abound. A local tale says that in the mid-1800s, a farmer climbed down some 60 feet into it and entered a dripping, gloomy chamber, the floor of which was littered with human skeletons and the bones of large animals.
Some versions of the tale say the animals were long-horned steers, others that they were the remains of a giant Ice-Age ground sloth. In any case, horrified by his discovery, the farmer dumped huge boulders into the sinkhole and then filled it to the surface with dirt.
The upper 10 feet or so of the sinkhole was still visible in the 1960s and geologic features in its walls called fluting indicated that in the distant past it had been the insurgence point for large volumes of water. Today, the sinkhole reputed to lead to what has come to known as “Old Skull Cave” is no longer visible, having been completely filled with soil making it level with the surrounding fields, but its memory adds to the legends of the area, a lure as tantalizing as “Frustration Crawl.”
Access to Lemuria?
Doubtless the weirdest legend associated with Knox Cave derives from the book “I Remember Lemuria” by Richard Shaver published in 1948. In it, Shaver claims that far beneath the earth and accessible through certain caves is a whole separate and highly advanced civilization called Lemuria.
Its super-intelligent inhabitants do not want intruders from the surface and so they have bred a race of huge ape-like creatures armed with clubs to guard the access points and bash in the heads of any surface people who happen to wander in.
Shaver asserted that one of the caves offering access to Lemuria was Knox. Surely no comment on this story is needed; however — when I have taken groups of schoolkids into the cave in one of my Heldeberg Workshop summer caving classes, I have found that recounting the legend to them is a very effective way to keep any of them from wandering off.
The last attempt to commercialize Knox Cave occurred in the late 1950s, and tourist brochures as well as other ephemera of the cave from that period survive. When I was a boy, my parents took me on what turned out to be among the last commercial tours of Knox.
Even as a youth, I knew that the descent from the surface on that stairway was going to be intimidating to many tourists, especially the elderly — a far cry from the elevator that carried visitors effortlessly into Howe Caverns.
Brief though the tour was, the guide’s recounting of the cave’s history and lore was captivating. He spoke of the high narrow fracture called “Skeleton Passage” in which six human skeletons had allegedly been found along with a number of ancient torches — their whereabouts even then unknown.
He also fascinated visitors with tales of a mysterious tablet in an off-limits section of the cave which had inscribed upon it the hieroglyphic writings of the Nephites, who Mormons believe inhabited North America in the years before the Christian Era. (These subsequently proved to be natural solution channels carved into the Manlius limestone by dribbling acidic water.)
And the guide hinted at new discoveries which might stretch the cave’s length to 13 miles — an elusive goal, to say the least.
By the time the cave closed for commercial tours for the final time, D.C. Robinson had passed away, but the cave remained open for sport cavers and scientists. His wife, Ada, was known to all as a delightful woman who enthusiastically welcomed visitors, telling them perhaps wistfully that the cave had been “entered but not explored” for 13 miles.
Readers acquainted with “Aunt Arie” from the Foxfire books would have recognized her double in Mrs. Robinson with her print dress and apron, hair in a bun, and effervescent personality. Upon her death in 1964, the cave went through a period of confused ownership during which people came and went freely onto the property and into the cave.
Fires determined to have been arson destroyed first the abandoned skating rink and then the Robinson house.
Then, in 1976, a group of college students attempted to enter the cave in winter, crawling through an opening in a mass of ice that blocked the entrance. A huge chunk broke off, killing one student and seriously injuring another.
Another period of confusion followed but eventually Knox Cave was acquired by the Northeastern Cave Conservancy that now controls access. The nearby Knox Museum features a Knox Cave room, filled with photographs, memorabilia, and newspaper articles from the cave’s glory days, as well as plaster impressions of the “Nephite hieroglyphs.”
And so, from May 1 to Oc. 1, both sport cavers and scientists from all over the world hike the surrounding fields past the disintegrating ruins of the Knox Skating Rink and descend the gaping sinkhole to explore and study the cave’s geologic mysteries.
The vast entrance rooms still astound, the claustrophobic Gunbarrel still calls explorers to the chambers beyond, and reaching the long-unknown river passage still challenges cavers’ strength and endurance. And perhaps from some dark recess, the ghost of the mysterious Buck Negley urges the intrepid to push beyond one last tight squeeze that opens into an echoing chamber the size of a football field.
Among the many 19th-Century graffiti on the walls of the Clarksville Cave is the elegantly-carved “D.C. Gould August 12, 1864.”
Most New York State caves are closed to visitors from Oct. 1 to May 1. For information about Clarksville Cave and other area caves, visit www.northeatserncaveconservancy.org. I thank David Wallingford and his son Owen Tobias-Wallingford for their assistance in photographing the Clarksville Cave.
For generations, the Clarksville Cave system has drawn sport cavers and scientists alike.
Lying under a preserve owned and managed by the Northeastern Cave Conservancy, the cavern is half-an-hour drive from downtown Albany, just off Route 443. Histories of the village record visits to the cave in the mid-1800s, and graffiti from the Civil War Era and before are carved in sometimes elegant characters on its walls. (The precise moment at which graffiti go from being vandalism to history has never been determined, but carving on cave walls today is — to put it mildly — strongly discouraged!)
There are forms of vandalism other than carving, of course — spray-painting and littering of the passages with trash are sadly not unknown; some forms such as muddying formations by climbing on them may be unintentional but are no less damaging.
Regrettably, most of the Clarksville Cave’s delicate formations such as stalagmites, “soda-straw” stalactites, and the translucent “draperies” were broken off long ago, though in hard-to-reach areas of the cave some flowstone deposits and the unusual natural dams called “rimstone pools” have managed to escape vandalism.
In years’ past, visitors were invited to scratch their names into the walls; two of the most prominent were left by one “D.C. Gould” whose name was carved in neat letters on Aug. 12, 1864, and one “E. Brinley” whose name was incised in 1839 on a wall above a pool.
Yet, in spite of visits by untold thousands of people over the decades, the Clarksville Cave and its preserve remain iconic examples of geologic processes, and specifically of cave geology — known as speleology. Teachers of Earth science and geology in both secondary schools and colleges have used it as a resource for many years and, in the summertime, camps and environmental groups from all over the Northeast run field trips to the cave.
The preserve covers some 19.4 wooded acres, and within the forest are trails that lead not only to the cave’s multiple entrances but past classic examples of karst geology features: exposures of the bedrock called the Onondaga Limestone in which the cave has formed; mossy sinkholes and vertical shafts; and long solutionally-widened fractures in the bedrock called grikes.
In very wet weather, one of the cave entrances becomes an artesian spring and hourly thousands of gallons of turbulent water under pressure bubble upward against gravity and flow into the nearby Onesquethaw Creek.
The Onondaga limestone formed in a warm, shallow sea during what geologists call the Devonian Period, some 400 million years ago, when the landmass that would become North America lay much farther south than it is today and the Equator ran through the section that would become New York State.
It is a very clean limestone — almost pure calcium carbonate — with little or no clay or sand within it. This indicates that there were no high mountains near where it was forming that would have shed sediments into the water. It is densely packed with fossils such as crinoids (sea lilies), trilobites, clam-like brachiopods, and several species of coral.
The corals in particular are indicative of an environment of clear, relatively shallow, water. In some sections, the limestone is studded with nodules and shelves of the silicate rock called chert — or flint — which has precipitated there through processes still not completely understood.
The ages of caves are often difficult to determine. Except for lava caves such as those in Hawaii that form in real time as lava flows cool, the age of a cave has nothing to do with the age of the bedrock from which it has formed.
But one of the obvious features of the Clarksville Cave system is that it contains enormous deposits of rounded pebbles and cobbles in a clay matrix: remnants of debris left when glaciers retreated at the end of the last ice age some 12,000 years ago and their meltwaters roared through the cave carrying massive quantities of sediments.
These deposits can be found in even the loftiest parts of the cave. They indicate that the cave passages were there before deglaciation and for a time were choked with tightly-packed sediment; subsequently post-glacial streams found routes into the cave through the limestone bedrock layers that border Stovepipe Road west of the hamlet and elsewhere and began to flush out the sediments.
However, clues to a cave’s age are the features known as speleothems: stalactites, stalagmites, and flowstone that form from mineral-saturated water seeping into the cave. The old rule-of-thumb that every cubic inch of such features requires 100 years to grow has been shown to vary tremendously from one cave to another, but a massive flowstone feature such as that in the accompanying photo (Figure 3) undoubtedly required tens of thousands if not hundreds of thousands of years to form.
To put it simply — Clarksville Cave is old!
It has formed along a tectonic fault that shows itself in many places in the cave passages and at the surface where scratches called slickensides and folds in the bedrock appear. One particularly prominent display is in the bed of the Onesquethaw Creek just a few yards east of the stone bridge on Plank Road.
Within the cave, the ceilings of many passages show a slight tilt from west to east as a result of the fault movement. This tilt has allowed great quantities of mineral-saturated water to enter the cave over millennia, with the result that masses of flowstone accumulated on the western sides of the cave passages — much of it now damaged — and in some places the waters have acted as a natural cement, turning large piles of glacial debris into the sedimentary rock called conglomerate.
The cave was frequently visited in the 1800s — at least for a time its owner offered guided tours by lantern light and the cave was written up in Harper’s Weekly.
Until the early 1960s, the system was regarded as two separate caves, with one entrance in the village close to Route 443 called “Gregory’s Cave” after its then-owner. It consists of a series of lofty chambers connected by a wide tunnel carrying a meandering stream and terminating after around 450 feet in a pool rising nearly to the ceiling — a feature which cave explorers call a “sump.”
A longer section entered through a sinkhole in the woods bordering the hamlet trends north and was known as “Ward’s Cave.” Around 1,200 feet long, this section resembles a subway tunnel through which flows the upper stretch of the same gurgling stream, rising in a deep artesian pool near the north end, known rather grandly as The Lake.
But for years after the 1948 publication of “Underground Empire” by Clay Perry, which dealt with the caves of New York State, explorers were intrigued by Perry’s statement that the two caves were connected by what he described as a half-mile long tunnel lined with calcite crystals.
Then, during the summer of 1962, an extended drought hit New York State and the water level in the sump in the Gregory section dropped almost three feet. Following the cave explorer’s directive — “Follow the water!” — within a couple of days of each other, one group of explorers from Albany and another from the Boston area waded through the sump and found that the cave continued in the direction of the Ward section.
To this day, no one is certain which group was first; cavers are notoriously — some would say obsessively — reluctant to give details about their discoveries. But within weeks the word was out that a major breakthrough had been made in Clarksville and that the two caves were now connected.
To everyone’s amazement, in lamplight the then-pristine formations in the connection section did indeed sparkle in the form of calcite crystals that seemed to cover every surface. This discovery obviously raised the intriguing possibility that some intrepid explorers in the distant past had also made the connection yet somehow left no trace of their passage.
Alas, most of the crystalline surfaces are today obscured under a coating of mud left by the boots and clothing of more recent visitors.
Yet even so, the connection is not without its wonders: mysterious side passages that sometimes loop back upon themselves; the artificial-looking rimstone pools; bedrock twisted and distorted under pressure of the fault movements; great slabs of rock coated with slickensides; a high, funereal chamber where lengthy roots from trees in the forest above hang like black veils in the gloom; a 40-foot wide waterfall whose currents of crystal-clear water send echoes throughout this section of the cave, sounding eerily like energetic conversation; and on almost every exposed surface the marvelous, mysterious Devonian fossils.
One can easily understand why the Clarksville Cave is considered a veritable textbook of geologic phenomena.
Today, being under the protection of the Northeastern Cave Conservancy and its appointed cave managers and lying so close to so many colleges and primary and secondary schools, the Clarksville Cave will continue to attract sport cavers, adventurers, and students for generations to come.
And, while walking or crawling through its inky-black recesses, one can only wonder what secrets the cave yet holds in the unknown passages from which its waters come, and the mysterious conduits into which they flow.
Petrified ripple marks on a boulder eroded from the Manlius limestone tell of the rock's formation in shallow tidal waters. (Photo by Mike Nardacci)
A recent issue of the “Friends of Thacher Park” newsletter featured an essay by state geologist Dr. Chuck Ver Straeten describing some of the rock layers that form the Helderberg Plateau. Reading it got me thinking about my many trips to Thacher Park over the years and my slowly dawning awareness of the geologic history locked within it.
The Irish novelist James Joyce defined the word “epiphany” as a moment of sudden insight into oneself or some situation — a moment when disparate facts or events come together to bring about a revelation, and since I was a kid I have had more than one such revelation there.
My memory of my first trip to Thacher Park is lost in the mists of my early years on this planet, but by the time I was old enough to understand the word “fossil” I had come to marvel at the fact that the craggy, forest-draped plateau to the west of Albany contained many traces of past life on Earth.
I can remember even as a small child being excited that it seemed that every rock I picked up in the park contained curious shapes — tubes, rings, and frequently whole or fragmented seashells. My father told me that they were there because “a long time ago” — I doubt I could have comprehended the phrase “hundreds of millions of years ago” — the whole Helderberg area was at the bottom of the sea.
By the time I entered high school, on my trips there I would sometimes search the rock outcrops for dinosaur tracks or bones — unaware that the rocks of Thacher Park were laid down around 180 million years before the first dinosaurs walked the Earth.
Early in my college years, I had become involved in the sport and science of caving (adherents consider the term “spelunking” to be rather politically incorrect!). As my friends and I crawled and climbed our way through Knox Cave, the Clarksville Caves, gloomy Onesquethaw Cave, and others beneath the hills, we had all learned enough to comprehend the term “Devonian Period” to classify the time in which the rock layers had formed.
The fact that this made them something like 400 million years old was — and remains — exceedingly difficult to comprehend for humans accustomed to think in terms of years, decades, and centuries. I also had become aware that caves tended to form in certain types of rock — most commonly limestone — but do not recall when I first heard the term “strata” to describe the rock layers that make up the Helderberg Plateau or to wonder why they looked different from one another and weathered differently.
But when I began my first teaching assignment — English and American literature and language — I was fortunate to make the acquaintance of the high school’s Earth Science teacher who coincidentally had done some caving. I assisted him on some field trips into the Helderbergs and began to learn as did his students about the fact that every rock layer is of an age different from those above or below it and formed under sometimes wildly different conditions.
I became aware that the rocks making up the plateau vary in age from the Ordovician Period — prior to 420 million years ago — to the Devonian Period — roughly 400 million years in the past — and contain within them stories of rising and falling sea levels, the building and erosion of mighty mountain ranges, and the emergence of strange forms of life, many long gone extinct.
A “geo-epiphany” to coin a term!
Layers of history
The strata of the Helderberg Plateau consist mainly of sandstone, shale, and limestone. Each of these rocks types forms under different physical and climatological conditions and it must be understood that, during the times in which they formed, the landmass that would become North America lay far to the south, with the Equator running through the middle of what would become New York State.
Through much of this time — the late Ordovician Period through the later Devonian — roughly 500 million to 360 million years ago — this area was under warm, shallow waters much like the sea surrounding today’s Bahamas.
A view of the Helderberg escarpment at Minelot Falls offers a cross-section of many of the major “strata” — or “formations” — that make up the plateau and which form the cliffs that tower above the Indian Ladder Trail. Rising up from the valley below in the talus slopes are the Ordovician Period Indian Ladder beds atop the Schenectady Beds.
The latter are difficult to see because in the valley the sandstone and shale strata of the Schenectady Beds are covered with glacially-deposited soils and rocks; the shaly Indian ladder beds rising up to the base of the escarpment are in many places obscured by gigantic boulders and sediment deposits that have crashed down from the cliffs.
Both of these strata contain marine fossils, but the sand and clay content indicate that they formed in muddy waters containing large quantities of sediment, likely shed from ancient nearby mountains.
Atop them are two relatively thin layers often regarded as having formed in the Silurian period, some 440 million years ago. The lower of the two is the Brayman shale/sandstone, which has not been found to exhibit fossils though the shale layers contain tiny, gleaming crystals of iron pyrite — “fool’s gold.”
Like the two strata below it, the Brayman seems to have formed from the petrification of sediments eroded from nearby highlands, perhaps in an environment that was hostile to life.
Immediately above it is a layer of limy shale called the Rondout. Like the Brayman, it does not display fossils in the Helderberg area but some of its thin layers show mud cracks, indicating that from time to time the sediments that formed it were exposed to the drying effects of the sun.
These layers are poorly resistant to the effects of weathering and erosion and have formed a shallow shelter at the base of the cliffs known for years as “Paint Mine Cave.” The name apparently derives from the presence of rusty iron deposits found in the strata that supposedly in the 19th Century were mined and mixed with sour milk to produce a reddish paint.
These layers also feature streams issuing from a number of small caves and one larger one, known traditionally as “Fool’s Crawl.”
Forming at the boundary between these lower layers and the towering limestone cliff above them, they represent the resurgence points of underground streams that have worked their way down through the limestone — composed of the mineral calcium carbonate — and encountered layers that their mildly acidic waters cannot dissolve.
This boundary has also been regarded by some paleontologists as representing the transition between the Silurian and Devonian periods of geologic time — an interpretation that has been sometimes energetically disputed.
The great escarpment is formed mainly of two limestone layers, the Manlius and Coeymans, named for the localities in which they were first studied. Each of these is a nearly pure limestone containing little or no sand or clay, indicating they formed hundreds of millions of years ago in clear water with no mountains around to shed muddy sediments into them.
Resembling nothing so much as stacks of manuscripts, the thin layers of the Manlius show evidence of having formed in a coastal environment during a time of rising sea levels. Some fragments that spill from the cliff show mud cracks or ripple marks. These tell us that the limy sediments that formed the rock were from time to time exposed to the drying sun, characteristic of a tidal environment.
The Manlius is sometimes known as the limestone of the “tentaculites” — tiny, needle-like fossil shells that coat the surface of slabs that weather from the bedrock. The exact nature of these marine creatures is still being debated but they are found throughout the layers of the Manlius in outcrops that stretch from the escarpment at Thacher Park west to Gallupville and beyond.
They frequently line up on rock samples in parallel displays consisting of thousands of individuals, much as boats in ocean bays form parallel patterns from receding tidal waters.
Due to its being almost pure calcium carbonate, the Manlius dissolves readily in acidic water and many caves in the Helderberg area have formed in it. There are disputes as to whether the Manlius represents a late stage of the Silurian Period or as having formed in the early Devonian period — known to paleontologists as “the age of fishes.”
However, fish fossils have not been found in local exposures of the Manlius. The upper layers of the formation, visible in exposures on the Indian Ladder Trail, are marked by the presence of thick masses of stromatopora — extinct coral-like fossils.
Above the Manlius is the massively-formed Coeymans formation, described as a semi-crystalline limestone that contains great numbers of a rich variety of fossils: trilobites, crinoids (sea lilies), corals, and clam-like brachiopods, among others.
Interestingly, some years ago, two geologists from Brown University rappelled down the cliff face and noted that there seemed to be a cycle in the fossils as they descended: deeper-water fauna alternating with shallower-water creatures — a pattern perhaps indicating the rise and fall of sea levels during a Devonian ice age.
Like the Manlius, the Coeymans is a clean, pure limestone with little mud content — indicating, once again, that it formed in waters that were far from any mountains that were shedding sediments. Many area caves such as Howe Caverns are formed through both of these formations, and their thickness has allowed high passageways and chambers to have developed within them.
Higher and later
Moving higher in the geologic cross-section and into the later Devonian period are the strata called the Kalkberg and New Scotland limestones. Their fossil fauna are similar to those in the Coeymans, showing the continuing marine environment in outcrops visible in the valleys descending from higher areas in the Thacher Park area carrying streams in wet weather that produce impressive waterfalls as they cascade from the cliffs.
Along the lower section of the Beaverdam Road that ascends from Route 157, the Becraft Limestone forms a flat stretch featuring numerous grikes — cracks in the bedrock that have been enlarged and deepened through solution by mildly acidic surface water.
The Becraft appears to be made almost entirely of fragments of shells and crinoids, similar to coquina — the rock formed from naturally cemented such fragments found in the waters off Florida and elsewhere in the Caribbean. The stone can be cut and polished to a high sheen, producing an attractive surface for counters and tabletops.
The presence of the fragmented fossils indicates that the Becraft formed in a near-shore environment in an ancient sea in which powerful waves transported and smashed fragments of sea creatures.
Atop the Becraft lies the Oriskany Sandstone, which in most areas of the Helderbergs has a thickness of little more than three feet. The Oriskany is what geologists call a “calcareous sandstone,” meaning that, although its matrix is common silicate sand, it is packed with shell fragments made of calcium carbonate.
It apparently formed in the environment of an ancient locality termed a carbonate beach. A famous modern example is Sand Beach in Acadia National Park in Maine. The presence of so many fossils makes the Oriskany highly sought after as a decorative stone, appearing in many places in the Capital District in exterior walls and fireplaces.
Above the Oriskany is a gritty shale layer known as the Esopus, named for its type locality, a small settlement near Kingston. It spreads over a large section of New York State, having its greatest thickness — nearly 300 feet — in the southeast part of the state. In the Helderbergs, it is around 100 feet thick and appears as a gray or tan rock that weathers to fragments easily.
Exposures of the Esopus such as those along the Beaver Dam Road usually feature piles of dusty, crumbly gravel at their bases. Rock such as this forms in extremely muddy marine environments, indicating the presence of nearby highlands from which torrents of sediments are being shed and deposited in the ocean.
Such an environment is not conducive to the sustaining of much life, and the only fossils common in the Esopus are those of a humble marine worm known by biologists as zoophycos. Existing side by side in the thousands on exposed surfaces of the Esopus, such as in the Onesqethaw stream bed in the village of Clarksville, the worms’ fossils confused some early paleontologists who mistook them for patterns in the ancient mud caused by spinning currents in the water and termed them “rooster tails.”
Each worm anchored itself on the seafloor and formed a series of curving tubes radiating out from the anchor point in search of food. The great thickness of the Esopus indicates that this muddy, low-oxygen environment persisted for many millions of years.
Above the Esopus is another massive layer known as the Onondaga, indicating an abrupt change to conditions once more conducive to the formation of limestone. A pure, heavily fossiliferous stone again indicating the presence of clear, warm, sunlit waters, with no high mountains nearby to shed muddy sediments into the sea, the Onondaga is rich in the fossils of corals, sea lilies, and brachiopods whose pearly remains stand out clearly against the clean, gray limestone.
Towering outcrops of the Onondaga are visible near Clarksville in the gorge of the Onesquethaw Creek on the south side of the village and in the arc-shaped fold of the bedrock known as an anticline that borders Route 443 just west of Clarksville. The popular Clarksville Cave system that stretches nearly a mile through a preserve in the village and is well-known for its fossils, underground stream, and classic geologic features is dissolved from the Onondaga.
Major change as plates shift
Following the formation of the Onondaga, a major change was occurring involving the tectonic plates that would eventually become North America and Europe. The plates were moving together, resulting in the great mountain-building episode known as the Acadian Orogeny, and in the area that is today northeast of the Helderberg region an extensive range of lofty mountains of Himalayan grandeur was rising.
But, as a land mass rises, the forces of weathering and erosion immediately begin to attack it and its ultimate elevation depends on whether the processes of elevation or of leveling predominate. For millions of years, as the mountains rose, they shed immense masses of sand, silt, and clay that spilled down through the valleys that separated the summits and into the shallow sea in which the Onondaga had formed.
These sediments buried the limestone and eventually filled up the sea, forming the series of interlocking deposits known as the Catskill Delta from which our present-day Catskills and much of the Appalachian Plateau evolved after the delta was elevated far above sea level in the continuing plate collision.
A dramatic illustration of these great geologic events is visible in one of the many sinkholes that border the south side of the Beaver Dam Road above Thacher Park. The surface bedrock of the broad, flat terrain on which the road lies is the top of the Onondaga limestone layer and directly above it are slopes composed of the shales and sandstones of the non-carbonate rocks known as the Hamilton strata.
These layers do not dissolve in the mildly acidic waters that fall from the skies or collect in pools on the surface; therefore, those waters flow down from the heights in small permanent or seasonal streams. But, as they meet the soluble limestone, they are able to infiltrate it through sinkholes and produce underground streams in caves.
The sinkhole called “TV Tower Cave” with its mossy natural bridge lies precisely at the boundary between the two rock units, illustrating the beginning of the formation of the Catskill Delta as the Acadian Mountains rose those hundreds of millions of years ago.
In higher elevations of the delta’s layers near Rensselaerville, the rocks begin to show ripple marks indicating the shallowing of the ancient seas and near Gilboa are the petrified trunks of giant ancient fern trees, some of Earth’s oldest large land plants.
The section of the Appalachian Plateau known locally as the Helderbergs once stretched to the base of the Adirondacks and, over millennia, erosion has caused it to retreat far to the south. Viewed from any distance, its strata resemble a series of stacked books.
And metaphorically — that is what they are: the record of stretches of Earth’s history so far back in time that the mind boggles trying to comprehend their age and contents.
But they tell of great movements in the planet’s surface, climatic changes, and the rise and erosion of great mountain ranges, and they preserve traces of the emergence and sometimes extinction of strange creatures from the past — all of which constitute a mind-expanding epiphany in the Helderbergs.
— Photo by Mike Nardacci
The famous Knife Edge on Maine’s Mount Katahdin was formed when glaciers on opposite sides of the mountain slope carved it into a narrow, perilous ridge.
The goal of every serious mountain climber in the Northeast is to bag the three Big Ones: New York State’s Mount Marcy at 5,344 feet; Maine’s Mount Katahdin with its famous — or infamous —“Knife Edge” at 5,267 feet, and New Hampshire’s magisterial Mount Washington at 6,288 feet with its notoriously changeable weather that has killed more climbers than the other two peaks combined.
Since not one of these is much more than one mile above sea level, in-shape climbers are not likely to be much affected by the drop in air pressure on any of them. However — especially on the summit of Mount Washington — many climbers who carry sealed bags of chips or trail mix will notice that the bags have puffed up and appear ready to explode as air pressure drops noticeably even over that relatively small elevation change.
Mountains generally form through one of two processes: volcanic eruptions and tectonic plate collisions. Many great mountains in the contiguous United States such as mounts Rainier and Hood and Mount St. Helens are active volcanoes formed largely of the light-colored igneous rocks rhyolite and andesite and dark rocks called basalt and gabbro, and are high enough to have glaciers spilling down them.
When they erupt ,as in the devastating Mount St. Helens event in 1980, the glaciers instantly melt and produce catastrophic blasts of boulders, pulverized rock, and searing poison gasses known as pyroclastic flows, which devastate the landscape and bury everything around them in a slurry of hot mud and ash.
On the other hand, many of the high peaks in the Northeast such as Katahdin, Washington, and the other White Mountains, rose millions of years ago when the tectonic plate that would become Africa and Western Europe collided with the plate that would become North America in the event known as the Acadian Orogeny (“orogeny” means a mountain-building episode). The plates were like two 18-wheelers crashing into each other nose-to-nose, crushing and distorting the cabs, trailers, and their freight.
Mountains such as these — once of lofty Himalayan grandeur but torn down by erosion — tend to be composed of igneous rock such as granite and metamorphic rocks such as gneiss and schist. The origin of the Adirondacks — which continue to rise — and the West’s Rocky Mountains, all of them far from tectonic plate boundaries, are geologic mysteries over which geologists contend in sometimes heated debates.
One recent theory holds that far beneath the Adirondacks lies a crustal “hot spot” similar to the one beneath Iceland that millions of years hence may erupt in a series of volcanoes.
In any case, Mount St. Helens tops out at over 10,000 feet along with others in the Cascades and the Rockies, many of which rise to over 14,000 feet. They are not only high enough to have year-round snowfields and glaciers but extend into the upper reaches of the layer of the atmosphere in which we live called the troposphere.
Half of our atmosphere’s weight is packed into the lowest 3 ½ miles; even at 10,000 feet — less than two miles, far higher than any of our eastern peaks — most people will begin to find breathing labored and even the most fit climbers will note the increased effort in ascending, especially with packs.
Attempting Rainier
Some years back, having climbed Washington, Katahdin, and Marcy along with 38 other of New York’s fabled “Forty-Six” peaks over 4,000 feet, I proposed to a friend that we fly to Seattle and join an expedition with a company called “Rainier Mountaineering” to the top of Mount Rainier.
The company offered two-day treks to the mountain’s glacier-encased summit led by highly experienced guides, some of whom had climbed in the Himalayas. We prepared for it as we would for any Eastern peak — running a few miles on alternate days and doing limbering exercises.
But, when we met our companions the day before the start of the expedition, we got a rude awakening. Many of them had spent the previous two weeks in Colorado or California climbing mountains of equal height to Rainier but without the glaciers — and they had carried 40-pound packs.
It turned out that our lead guide was going to be celebrity climber Ed Viesturs, who had just returned from his fifth ascent of Mount Everest — and he had done it without oxygen tanks.
My friend and I gave each other looks that said, “We are seriously in over our heads.” We learned later from his autobiographical book, “No Shortcuts to the Top,” that Viesturs has a lung capacity almost 50 percent greater than that of the average male.
Day One of the trek began at 10 in the morning at the venerable Paradise Lodge at an elevation of 6,000 feet on Rainier. Though the date was July 6, there was close to five feet of tightly-packed snow on the ground, melting rapidly into rushing rivulets and rills beneath the high summer sun.
With 10 companions and the energetic Mr. Viesturs in the lead, we began our ascent of the steep snowfields up a series of switchbacks following red flags on stakes that led to Rainer’s summit.
It was a stunningly beautiful climb. The trail at first wove its way through groves of pines, gradually decreasing in size with altitude but it soon led us above timber line with spectacular views of the gleaming blue and silver glaciers plunging down from Rainier’s summit.
To the south loomed some of the great volcanic peaks of the Cascades — mounts Jefferson and St. Helens — the whole scene under a radiant azure sky that occurs only at high altitudes. And indeed we felt the altitude, especially later in the afternoon as we arrived at Camp Muir, Rainier’s base camp.
Muir is situated at over 10,000 feet on a wind-blasted rocky ridge, perched picturesquely above one of Rainier’s glaciers with a series of dangerous-looking crevasses dropping into shadowy depths. Every step we took had been labored and the desert-dry air induced the need for constant gulping of water from the four canteens we carried.
The plan was for climbers to sleep until midnight and then begin the final ascent to the summit. In summertime, the dark hours are the safer times in which to ascend through the snowfields and over the glaciers, before the high sun can melt masses of snow and set off avalanches.
Most of the party members were too pumped up with adrenaline to sleep and the couple who did snored loudly enough to be heard in Seattle. In any case — word came late in the evening that a storm was brewing just east of the mountain and was expected to hit around 1 a.m. — just when the climbing teams would be heading for the summit and so the climb had to be “turned” as the climbers’ expression has it.
We were offered a second chance to try for the summit later in the summer — but all dates for the next few weeks were fully booked and so with a mixture of disappointment and relief we started down at sunrise.
We felt disappointment because, as we descended, the shimmering snowfields and glaciers against the cobalt-blue sky above Camp Muir were like the Sirens’ call — alluring almost beyond resistance; relief, because we knew we were not up to this challenge.
We were neither acclimated nor in physical shape for climbing above this altitude. Drained and dehydrated, we were sobered by the thought that we would have had nearly 4,000 more feet to ascend — roped together in teams and making our ways with ice axes — in the company of people who were far more fit than we were.
And yet — though our trek on Rainier was terminated, it remains one of the greatest of all my life’s adventures and the memory of those two days on that magnificent mountain is its own success.
Pikes Peak
My next attempt at climbing at high altitudes came a year or so later when, at the invitation of some friends in Colorado, I began taking on the challenge of climbing some of Colorado’s “Fourteeners” — Rocky Mountains higher than 14,000 feet.
The first mountain was going to be Pikes Peak with a massive profile that looms over the city of Colorado Springs. This time, I was determined to be more prepared and spent several days in the city itself getting acclimated to the elevation.
“The Springs” as the locals call it has an elevation of 6,300 feet — a thousand feet higher than the “Mile-high city” of Denver. And the setting is deceptive: Since “the Springs” lies at the base of 14,109-foot Pikes Peak and other high summits of the Rockies that rise like a gigantic wall above the city, the impression is created that its elevation is far lower than it actually is.
Travelers newly-arrived are unnerved to find that simple acts such as carrying a suitcase up a flight of stairs can leave them gasping for breath and their hearts pounding. As it happens, Colorado Springs has a paved running trail that meanders through the city’s outer neighborhoods, bordered by yucca and cactuses and other desert plants; it traverses moderately steep hills, making it an ideal course on which to get acclimated to the elevation.
I did a series of runs in the days before we set out for the mountain and was somewhat intimidated by the effort resulting from the lower oxygen levels.
The most popular trail to Pikes Peak’s summit departs from the neighboring town of Manitou Springs, a 27-mile-round-trip that most people do over two days. With backpacks and walking sticks, we set out early one morning following a series of switchbacks on a well-defined trail that led into the Pikes Peak wilderness.
Pikes Peak and many surrounding mountains are part of what geologists term a batholith — a gigantic mass of igneous rock, in this case a beautiful deep-red granite — that has been pushed forcefully from deep within the Earth.
As it rose, it broke through horizontal layers of russet iron-bearing sandstone, creating the spectacular tilted and sometimes vertical slabs of Denver’s Red Rocks Park and the Garden of the Gods in Colorado Springs. Wind, water, and glacial ice have subsequently sculpted the granite mountains into rugged summits, several of them —Pikes Peak included — high enough to retain snowfields even in the summer.
Our first day’s trek took us up through some wild forests in which mountain lions are known to roam, attacking solitary climbers. But on a summer’s day, “solitude” is not a state to be found anywhere on Pikes Peak and scores if not hundreds of people may be making the ascent — the most intrepid and fit completing the entire round trip in a single day.
We were seldom out of sight of other climbers and their echoing voices frequently distracted from the natural sounds of wind and birdsong in the stunted pines. We camped for the night at a very primitive but crowded campsite just above timberline at around 11,000 feet.
After nightfall, far below us, the lights of Manitou Springs and Colorado Springs were spread out toward the horizon in vast, vertiginous, glittering geometric patterns. High altitudes can inhibit both appetite and sleep, but with over 3,000 feet to ascend the next morning, before sliding into our bedrolls for a night of fitful slumber, we managed to chow down on high-protein food reconstituted with our mini-camp stoves.
To our disappointment, the bright glow of the sprawling cities below tended to dim the light from the stars, which should have been brilliant at that elevation.
We were awakened from a restless sleep at dawn by the voices of literally dozens of other climbers for whom today was “summit day.” Fortunately, the changeable weather of the Front Range Rocky Mountains had given us a clear, dry morning.
We set out for the summit up a seemingly endless series of switchbacks; this meant slow upward progress but it also reduced the effect of the increasingly thinning atmosphere. In less than three hours, we arrived at the top — and were overwhelmed by the crowds.
Like Mount Washington and New York’s Whiteface, Pikes Peak has an auto road to its summit; also like Mount Washington, it has a cog railway to bring up tourists in great numbers.
Some of them looked shaky, seriously affected by the rapid increase in altitude, and were looking for a place to sit down or were quickly returning to the cog railway car in which they had come up. The railroad allowed only 40 minutes on the summit for its passengers and even that was too much time for the unacclimated.
Heart palpitations, headaches, and nausea are common among people who venture into regions of thin air — even sometimes for those who are acclimated.
The sweeping view from the top inspired Katherine Lee Bates to compose “America the Beautiful”: To the east, the Great Plains stretched into the dusty distance; north and south, steep peaks and passes of the Front Range of the Rockies lumbered toward both Wyoming and New Mexico; to the west, rugged summits of the Sawatch Range and the Presidential Peaks receded into a blue haze.
But the noise from crowds and cars overwhelmed the scene, making it more a tourist attraction than a conquered summit, seemingly diminishing our effort to achieve it.
Mounting Massive
But the following summer, at the invitation of one of my former students, I accepted the challenge to climb Mount Massive, an enormous “Fourteener” that rises above the village of Leadville and the Animas River Valley west of Denver.
Massive is an isolated peak with a jagged summit and, like Mount Washington, it is known for its violently changeable weather even in summertime. At 14,421 feet, it is also the second highest mountain in the Rockies, rising a few miles north of Mount Elbert which is the highest.
Pikes Peak and the other soaring Rocky Mountains rose during the Laramide Orogeny, some 80 million years ago. But the rocks of which these mountains are made are far older — metamorphic rocks such as schist and igneous granite from Proterozoic time, some 2.5 billion years in the past.
As the Rockies are far from any tectonic plate boundary, the forces that caused the Laramide Orogeny are — as the saying goes — “not well understood,” but the result was a chain of peaks many of which are over three miles high, and Massive — as its name suggests — is one of the most impressive and challenging.
Our climb began at dawn at the end of a gravel road near the Colorado Trail, which heads south along the base of the Sawatch Range of the Rockies, passing through some very high, remote wilderness. Though it was July and the sky was a clear Colorado azure, the ground and the stunted tree trunks and foliage were covered in frost — common at this elevation even in summer.
We encountered no one else on the trail, but talked loudly and made every attempt to make noise as we walked, wary that these high forests are home to mountain lions and bears known at times to be aggressive. The path to the summit departed west from the Colorado Trail, and soon we were above timberline.
This trail was far different from the gentle switchbacks of Pikes Peak and every step became an effort as the air thinned; steep and sometimes poorly defined, the path reached upward past frost-blasted cliffs and outcrops of gneiss and granite and our footing became treacherous as we made our way over boulders and jagged piles of glacial debris.
Toward noon, what had been a mild morning breeze became a low, menacing wail and gradually the sky was dimming to a featureless gray haze. A rule of climbing in the Rockies is to make summit by 2 p.m. because that is when the high sun can begin to breed storms from rising air currents and experienced climbers will begin their descents.
The top of Mount Massive is not a single point but an undulating plateau of nearly a half square mile with three ragged elevated points, the highest in the middle. We could see the actual summit only a few hundred feet away but in the thin air, even on a now much-gentler gradient it became an effort just to breathe and walk and we settled into a rhythm — 25 steps and a rest; 25 steps and a rest — until we reached the summit cairn lording over a rocky wilderness.
Though the cold wind had risen to an increasingly menacing howl, with our ascent over, it became pleasurable to be able to breathe without feeling we were gasping for oxygen. That climbers — some of them without oxygen canisters — ascend to twice this elevation in the Himalayas into what is called “the Death Zone” in temperatures well below zero was almost unthinkable.
We did not linger after snapping a few photos and headed back down through the stony wastes. The saying goes that a mountain is not climbed until you are down, and the view to the west where Massive’s notorious storms breed had become a deep, dirty gray that was slowly resolving itself into voluminous clouds.
Even at these altitudes, descending is much less taxing than ascending and it was a relief when we dropped below timberline into the Colorado forest. Though we heard a couple of rumbles of thunder as we made our way down from the trailhead and along the Colorado Trail, the full fury of the storm was not unleashed until we had returned to Leadville.
By then, all of Massive had vanished into ominous dark obscurity and when dawn broke the next morning the mountain gleamed under a fresh coating of snow that streamed from the summit in lacy filaments. The prospect of having been caught in that storm was sobering indeed.
Legendary peaks
Over the years I have climbed six more of Colorado’s “Fourteeners,” none of them as daunting as Mount Massive, but each with its own alluring scenery and challenges.
I have also summited a number of peaks in the Canadian Rockies, lower than those in the United States but often still in the grip of extensive glaciers from the last ice age: Rising above meltwater lakes of stunning shades of turquoise, they are icy peaks covered in lichen-besplotched boulders from which tough little rodents called pikas and marmots whistle warnings to their companions; crystalline streams meander down through the rocky debris and vanish mysteriously into great fractures in the glaciers.
But there, too, the weather is shockingly changeable and sometimes on warm sunny afternoons the sudden odor of ozone in the air may accompany approaching lightning and a violent snowfall.
Yet I realize I have hiked only among the lower, more accommodating of the peaks that rise into Earth’s thin air. But I often read about expeditions into the legendary peaks that soar into the regions of the world above 25,000 feet with awe for those who venture there.
And sometimes I dream of snowy, wind-ravaged summits bedecked in Buddhist prayer flags where — arm-in-arm with Sherpas — only the bravest venture.
Location:
— Photo from National Park Service
Boxwork, at Wind Cave in South Dakota, is called cratework when it is this large.
A recurrent problem in geology is the sudden appearance of what researchers term a “leave-it.”
Surrounded by his grad students, a professor has examined a site; rock outcrops and sediments, and erosional or tectonic phenomena have been observed, and, following appropriate consideration of all of the facts, the professor proposes a theory to explain the site.
Then someone — one of his grad students, or worse, someone with no geologic training whatsoever who just happens to be accompanying the researchers on their field excursion — picks up a rock, shows it to the professor, and says, “What’s this?”
It happens that “this” is the proverbial monkey-wrench in the works, the very presence of which undercuts the entire carefully-constructed theory of the site’s origin and history. After careful examination, the professor may toss the sample in hand once or twice and then give it a mighty heave, while mouthing the words — “Leave it!”
While there are undoubtedly more “leave-its” in New York State than many scientists would want to admit — and they are by no means confined to the geologic sciences — there are two in particular, one in Albany County and the other in the Adirondacks, worthy of consideration.
Interesting mysteries in themselves, they are also reminders of the fact that nature has many secrets, and human abilities to decipher them in the end are not without limits and should inspire humility in all science researchers.
The “Boxwork” rocks of the Clarksville Gorge
On the edge of the village of Clarksville is a gorge through which flows the Onesquethaw Creek. Cut millennia ago when the great glaciers were melting and the Onesquethaw was vastly more voluminous and powerful than it is today, the gorge features small caves and springs in rugged limestone cliffs towering over terraces pockmarked with potholes along with mounds of sediment carried down by the Onesquethaw from bedrock layers higher in elevation in the Helderbergs.
There are also pebbles and cobbles scraped from the bedrock and transported from the Adirondacks and regions above the Canadian border and then left in great deposits of sediments as the glaciers retreated. Such rocks are called “glacial erratics” and identifying their sources allows geologists to map the paths of advancing glaciers. The gorge is a veritable textbook of geologic processes.
Yet, among the chaos of sediments, a patient observer can find some curious rocks that are wildly out of place in this part of New York State and whose ultimate bedrock source is a mystery. The rusty-red sandstone rocks are found as jagged samples, their color revealing the presence of quantities of iron — the same element responsible for the color of the landscapes of Utah and the planet Mars.
But what makes the samples unusual is the fact that they are highly fractured, and the intersecting fractures are filled sheets of white quartz, formed from the silica that makes up much of the sandstone matrix and forced into the fractures under immense pressure. Known to geologists as “boxwork,” structures such as this are sometimes found in caves such as Jewel Cave and Wind Cave in South Dakota.
But these caves are dissolved out of limestone — made largely from calcium carbonate — and the sheets that make up the boxwork are pure calcite, which is more resistant to weathering and erosion than the limestone and the “boxes” therefore tend to project from surfaces.
And the question arises: Where did these rocks come from? There are no rock layers in Albany County or the lands to the north in New York State whose bedrock is known to contain structures such as the boxwork in these samples.
Glacially-transported rocks are usually somewhat rounded off, their sharp corners abraded by slow grinding against other hard sediments within the ice. Some of these rocks are partially rounded but many are jagged — though the presence of the angular “boxes” would likely result in fracturing rather than rounding.
And then there is the question of why these rocks are found in the Clarksville gorge of the Onesquethaw but are not reported from other sites in the Helderberg area or elsewhere in the state. “Leave-its” indeed!
The “Tafoni” of Snowy Mountain
Above Indian Lake in the Adirondacks looms Snowy Mountain. Rising to 3 898 feet above sea level, Snowy falls 102 feet short of being a true New York State “high peak.”
But it offers sweeping views of the surrounding mountains and lakes and its location west of many of the other soaring summits crowned by Mount Marcy make it less likely to be the goal of “peak baggers,” especially on weekdays. Snowy’s bedrock is a mélange of the rock types shared by most of the mountains of the Adirondack region: igneous and metamorphic rocks such as granite, gneiss, schist, gabbro, and anorthosite.
On a slope of Snowy Mountain and not far from a meandering highway is a collection of enormous boulders known as “tafoni.” The term is obscure; my dictionary of geologic terms published by the American Geological Institute does not even list it. According to Wikipedia, the word may be of Sicilian or Corsican origin and simply means “rocks with holes.”
On the other hand, the similar phenomenon known as “honeycomb weathering” is well known to geologists and found fairly commonly in the states of the “Four Corners” area in the Southwest. I recently photographed a textbook example along the highway known as the “Turquoise Trail” that runs southeast from Santa Fe, New Mexico.
Honeycomb weathering generally occurs in rock that contains or consists mainly of calcium carbonate — limestone and calcareous sandstone — and forms when the slight acidity of rainwater chemically dissolves the mineral randomly over centuries, producing the pockmarks.
Some igneous or metamorphic rocks also contain calcium carbonate or other minerals that may dissolve very slowly in natural acids but it is believed that sandblasting can also create honeycomb weathering. A combination of chemical weathering and sandblasting may well explain the tafoni of the Turquoise Trail outcrop and that of other sites in the Four Corners states.
New York’s tafoni lie in a heavily-wooded area on a fairly steep section of Snowy Mountain’s western slope: enormous boulders covered in mosses and fern gardens, pocked with pits of varying depth, some only a couple of inches in diameter, others big enough to walk into.
The larger hollows frequently have smaller pocks within them. Chalk markings and abrasions show that some of the largest have been climbed by boulderers and one has a rickety old ladder, allowing a precarious ascent to its top.
But the enormous tafoni of Snowy Mountain present a puzzling case. For one thing, the boulders do not contain calcium carbonate or any other mineral that dissolves readily, even when doused in hydrochloric acid.
They also are clearly not “in situ” — in other words, they are not weathered remnants of the slope on which they are located. They are somewhat rounded and they are not attached to the ground, clearly having been transported there either by tumbling from a higher location on the mountain or dumped there by glacial action.
But none of the cliffs and other exposures of the bedrock of Snowy Mountain show honeycomb weathering and there are no expanses of bedrock north of the mountain in the Adirondacks that are known to yield boulders that have weathered into tafoni.
Moreover, they are surrounded by thick forest, which would seem to preclude sandblasting as the cause of the pits, although in millennia past, in the wake of the glaciers, the slope would have been barren of protecting forest cover. In any case, the question arises — as with the boxwork rocks of the Clarksville gorge — where did the tafoni come from and how did the pits form?
Perhaps the solutions lie in the future in the research of graduate students completing theses for degrees.
In the film “Jurassic Park,” a biologist, contemplating the ingenuity of the dinosaurs, utters the famous line, “Life will find a way.”
And Earth’s restless crust and the great forces that churn beneath it also frequently confound science. Two-hundred years ago, most scientists and scholars believed that our planet was 6,000 years old and that all the great changes that had shaped its surface were divinely directed.
A hundred years ago, before the theory of plate tectonics was backed with irrefutable evidence and accepted as the cornerstone of modern geology, Alfred Wegener was almost universally derided for the notion that the Earth’s continents and seafloors moved around its surface like giant rafts.
And, among many other mysteries in modern science, geologists and biologists alike are intrigued by the source of the methane being detected emanating from the surfaces of Mars and Saturn’s moon Enceladus.
Mother Nature clearly does not play by our established “rules” and has many more mysteries — and surprises — in store for us yet.
The Enterprise — Mike Nardacci
A weathered section of tufa bedrock shows some of the many arches and overhangs.
Situated in the picturesque village of Vanhornesville west of Albany is a display of unique geologic features called “tufa caves” that — along with the village itself — are likely unknown to most people in the upstate area.
Located to the north of Route 20, Vanhornesville is accessible by State Highway 80, about a relaxed 90-minute drive from Albany, passing through farmland and woods as the roads traverse gentle hills. There are no signs along the way to announce the caves and only a couple of small ones within the village itself to point the way to the Outdoor Learning Center of the Owen D. Young Central School District, the preserve in which the caves have formed.
When most people think of caves, they are undoubtedly thinking of what geologists call “solutional caves,” such as the nearby commercialized Howe Caverns and Secret Caverns and the many wild caves that underlie the Helderberg and Cobleskill plateaus west of Albany.
Solutional caves are the product of the dissolving of carbonate bedrock such as limestone or marble by mild natural acids, most commonly carbonic acid. This acid forms when falling rain picks up carbon dioxide in the atmosphere or when pooled surface water absorbs the gas from decaying plant material.
It is an extraordinarily slow process and great solutional caves such as Mammoth Cave in Kentucky can take millions of years to form.
Other common cave types are fracture caves, caused by the gradual enlargement through erosion and weathering of natural joints in cliff faces; lava caves such as those in Hawaii formed by erupting volcanoes; and what are called “talus caves,” which are essentially enterable spaces between massive boulders that accumulate at the base of a cliff as a result of landslides. These caves are often scorned by sport cavers as “just a pile of rocks,” though geologists find they often contain complex and unique geologic features.
But tufa caves are relatively uncommon and are rarely very extensive, measured in feet rather than miles, unlike solutional caves that can extend for hundreds of miles. Nonetheless, like the tufa caves of Vanhornesville, they have their own attractions, one of which is that many of them require no special equipment to explore beyond a flashlight, and some are shallow enough that even that is unnecessary, though a helmet is recommended if an explorer wants to avoid bumping one’s head.
And the very process by which tufa caves are made is of interest, for, unlike solutional and fracture caves that form in pre-existing bedrock, tufa caves develop from the chemical deposition of rock from flowing mineral-saturated water.
Anyone who has visited a commercial cave has learned the mnemonic regarding the calcite formations that appear there: stalactites — there is a “c” for “ceiling,” and stalagmites — there is a “g” for “ground,” indicating the places where they form.
It is an oversimplification to say that they form from “dripping water,” though that is certainly more accurate than the explanations of the ancient Greeks and Romans who believed that they were some bizarre form of life and were literally “growing” in the cave environment.
But in fact what appears to be pure water dripping from the cave ceiling is a solution of calcium bicarbonate containing dissolved carbon dioxide that stays in solution as long as that liquid is within the confines of narrow fissures through which it is being pulled downward through the bedrock by gravity.
When the droplets emerge into the cave environment, the decrease in pressure causes the solution to “de-gas” — similar to what happens when the top is removed from a carbonated beverage — releasing the carbon dioxide and depositing a minute amount of calcium carbonate on the ceiling or on the floor.
The agitation of that liquid as it flows down the cave wall or splashes onto the floor can also cause it to de-gas, much as shaking a carbonated beverage may cause the carbon dioxide to de-gas forcefully. Over long periods of time, the result will be the growth of stalactites, stalagmites, flowstone cascades, and other cave formations.
But under certain conditions, the stream in a karst aquifer — a technical name for a solutional cave with flowing water — may itself contain large amounts of dissolved calcium carbonate and is either super-saturated or under sufficient pressure that the “degassing” process does not occur until the stream emerges from the bedrock and flows over the surface.
At that point, the deposition of calcium carbonate — calcite — will occur as the pressure is released or the saturated water mixes with plain H20 and anything in the stream’s path may become thickly coated with these deposits which are known as “tufa.” The resultant rock tends to be relatively soft and crumbly and porous and often has the appearance of petrified shaving cream, sometimes containing mineral-coated sticks and twigs and leaf impressions.
Along the section of Route 146 that runs parallel to the base of Barton Hill near Gallupville there are a number of streams resurging from small caves at the base of the cliff and in times of low flow those streams will deposit tufa, which may appear as a white coating on rocks in the streambed or form pebbles and cobbles containing sticks and twigs and leaf impressions.
A more dramatic example of this deposition can be seen on the north side of Route 443 between Gallupville and Shutters Corners. An extensive section of the hillside is covered with conglomerate — a naturally-cemented mass of rock fragments.
Here, long ago, tufa springs emerging from the cliff above cemented extensive deposits of glacial debris — or “drift” — and formed the conglomerate. These mineral springs eventually sealed themselves up and no longer flow. Today the conglomerate is fracturing and weathering away and may eventually cause a landslide onto Route 443.
The caves at Vanhornesville have formed a series of tufa deposits in a narrow valley that contains the Otsquago Creek. Saturated with calcium carbonate, the stream’s headwaters emerge from a series of springs and deposit the mineral.
At some point in the past, undoubtedly due to the melting of the glaciers at the end of the ice age, the stream carried a far greater volume of mineral-saturated water than it does today, resulting in the massive outcrops of tufa with their irregular, intricate openings: overhangs and tunnels and arches.
But unlike solutional caves, which can take millions of years to develop, these tufa caves are relatively young in geologic terms and are certainly post-glacial. Given the relative softness of tufa, the grinding effect of the continental glacier advancing over the landscape would have ground them away — although there might well have been an earlier series of caves that the glacier destroyed.
The porosity of the tufa allows it to hold water and makes it a perfect environment for moisture-loving plants. The walls and nooks and crannies of the Vanhornesville caves thus are covered with mosses, lichens, various types of ferns, and rare wildflowers in spring.
Though the entrances to the numerous little caves appear mysteriously alluring, upon entering one, the visitor quickly understands the adage, “What you see is what you get,” and there is no danger of getting lost in an underground labyrinth.
But to hike in and around the caves with their quirky, mossy, storybook ambience is to experience a unique example of what nature can create with time and some simple chemistry.
— Photo by Mike Nardacci
The view south from the trail to The Snow Hole shows Berlin Mountain rising in the center, the highest point in Rensselaer County.
— Photo by Mike Nardacci
The shady, moss-lined Snow Hole resembles a limestone sink hole. Except during mid-summer, its floor never receives sunlight and traps winter's cold air.
— Photo by Mike Nardacci
Research assistant Devin Delevan holds an ice ball made from snow compressed at the bottom of the fissure.
This archival photo of "Fat Man's Misery" in Thacher Park shows how weathering agents have separated a huge section of the cliff from the bedrock; the force of gravity will someday cause it to crash down to the talus slope beneath it.
To cross the Hudson River and head east on routes 43 or 2 or 7 onto the Rensselaer Plateau is to enter a landscape vastly different both geologically and topographically from that west of the river.
The Mohawk-Hudson lowlands stretching from Albany north to the shores of Lake George are composed of sand deposited on the shore of glacial Lake Albany, which formed over 10,000 years ago at the end of the last ice age and feature low, rolling hills and scattered lakes formed from glacial meltwater.
To the west and south of Albany rises the northernmost section of the Appalachian Plateau — called “the Helderberg Plateau” or simply “the Helderbergs” locally — consisting of mostly flat layers of sedimentary rock: sandstone, shale, and limestone deposited in the late Silurian and Devonian Periods of geologic history. Famous throughout the world to geologists, the layers — or “strata” — contain a vast collection of fossils of ancient species and have been called “the key to the geology of North America.”
The strata that once lay under the sea were elevated by plate tectonic movements during the “Appalachian Orogeny” some 290 million years ago when the land masses that would eventually be known as Europe and North America crashed together in the formation of the super-continent we call Pangaea. East of the river, Ordovician-age rocks took the full force of the collision, and were compressed, folded, and elevated much as the hoods of two colliding cars would be; to the west the Appalachian Plateau was elevated but little deformed — much, say, as the rear parts of the crashing cars might be pushed up above the chassis.
There was a time far earlier — some 475 million years ago — when the east coast of what would eventually become North America was located somewhere near what is today the Hudson Valley. It collided with another land mass consisting of volcanic islands in the great event called the Taconian Orogeny, pushing up mountains that may once have been as high as the Himalaya. Imagine today looking east from Troy and Albany and seeing a range of jagged, snow-capped peaks over 20,000 feet high!
Deep within these mountains, pressures were unimaginable and the rocks there were twisted and distorted and the resultant heat cooked the rocks in the process known as “metamorphism,” forming new minerals and rock types: slate, phyllite, gneiss, and schist, often laced with thick veins of milky quartz. Excellent displays are visible in Petersburg Pass on Route 2 not far from Williamstown.
But the inexorable forces of weathering and erosion — rain, wind, and sculpting glaciers — tore away at the peaks over millions of years. Their remnants in our part of the world — a series of much lower, often steep-sided knobs and ridges — are often called “the Berkshire Hills,” though Berlin Mountain above Petersburg Pass is a very respectable 2,818 feet in elevation, the highest point in Rensselaer County.
Examine the bedrock that is exposed in the pass — or bordering the ski trails on the summit of its neighbor to the south, Jiminy Peak — and you will find twisted and distorted cliffs and ravine walls of heavily fractured phyllite, a metamorphosed form of shale.
Both Jiminy Peak and Berlin Mountain are features of the Taconic Crest Trail, a 37-mile-long hiking path stretching from south to north, weaving in and out of New York, Massachusetts, and Vermont. Extending 60 miles or more on clear days, views from it are often stunning, especially in the fall when the hardwood trees that cover the surrounding slopes put on their spectacular colors.
The hike
From a parking lot on the high point of Route 2 at Petersburg Pass near where the borders of New York, Massachusetts, and Vermont come together, one segment of the Taconic Crest Trail leads south to Berlin Mountain. Another moderately challenging portion of the trail begins on the north side of the highway, leading to the curious feature known as “The Snow Hole”; it can be done as part of a much longer day hike starting farther south or as a 5-mile round trip from the parking lot.
Its ups and downs are for the most part not particularly steep — but as a friend of mine remarked, “It’s just that there are an awful lot of them!” In other words, good hiking shoes and perhaps a walking stick along with water and trail snacks are necessities and, given the often changeable weather, a rain slick is a good idea in warmer months. In winter, the trail is a superb and challenging snowshoe hike, but winds on the Taconic Crest Trail can be fierce and mandate a warm parka.
A steep but short pitch at the start of the trail soon begins to level out and offers an impressive view of the summit of Berlin Mountain and of the eastern and western slopes of Petersburg Pass. Though today the slopes are thickly overgrown with hardwoods, sporadically from 1962 until around 1980 there were trails here for downhill skiing at what was called Petersburg Pass Ski Center.
On clear days, the ski trails of Jiminy Peak and Bousquet may be visible, as well as the rhythmically rising and falling Berkshires to the east and the Helderberg Plateau to the west. A glance at a topographic map of the area shows that the trail runs first along the side of and then on top of a narrow, steep-sided ridge geologists call an arete.
Aretes form in areas previously glaciated when glaciers descend from opposite sides of a mountain, creating the feature that is also sometimes called a “knife edge.” The knife edge on Maine’s Mount Katahdin is undoubtedly the best-known in the east and has long been a heart-pounding challenge for climbers.
But the arete en route to The Snow Hole is far more user-friendly; it is broader and that fact and the thick forests of maple, oak, and paper-birch that cover the slopes bordering this trail prevent any dangerous exposure. There are occasional herd paths that wander from the trail, but the main route is wide and well-marked.
A hard-to-find side path departs from the trail at one point, leading upwards to a feature called “Jim Smith Hill.” This is supposedly named for the “James Smith Club” the main requirement for joining this national social organization is to be named “James Smith” (variant spellings of the names are allowed). Why this bump on the ridge was so named is as obscure as the feature itself.
The trail subsequently passes through a constantly changing variety of meadows and forests with occasional long views to the southern stretch of the Berkshires and west to Albany before reaching a loop trail marked by a sign directing hikers to “The Snow Hole.” After a few hundred feet, the trail begins to descend the north side of the ridge leading to a feature that looks for all the world like one of the sinkholes in the limestone karst areas of Albany or Schoharie counties.
The Snow Hole
The Snow Hole is a vertical fissure in the bedrock lined with mosses and other moisture-loving plants. One end offers a fairly easy descent to the bottom while the other end is a precipitous 60-foot drop. But the fissure is narrow enough and deep enough that its bottom never gets direct sunlight — and that leads to the conditions from which it gets its name.
Well into summer and occasionally into early fall, the bottom of The Snow Hole has a thick deposit of ice formed from pressure exerted by the deep snows that accumulate on the higher summits of the Berkshires during their long winters.
Sinkholes form commonly in carbonate bedrock such as limestone and marble when mildly acidic water from rainfall or runoff percolates through fissures and dissolves the rock, often feeding cave systems below. But The Snow Hole is what is known as a tectonic feature, formed by physical forces.
The steep slope of the ridge contains extensive cracks in its bedrock known as joints that run parallel to the ridge line. Over millennia, water and ice have eroded this fissure and, because it is located on the very steep north slope of the ridge, it has widened and deepened under the pull of gravity. Several much narrower fissures are found between The Snow Hole and the main ridge trail.
Another result of these same processes can be found in Thacher Park at the narrow cleft in the rock known for a century as “Fat Man’s Misery,” which offers access to the trail leading to Hailes Cave though it does not collect lingering snow. A massive section of the limestone has separated from the cliff and gravity has pulled it away sufficiently to allow slender hikers to traverse it. Someday it will tumble from the cliff and crash onto the talus slope below as have many such masses before it.
And this is the fate that ultimately awaits The Snow Hole of Petersburg Pass. Over time, the accumulating snows within it will continue to be compressed into ice, which will further deepen and enlarge the fissure; as the steep hillside is carved away by the agents of erosion the outer wall will collapse and become part of the talus slope that falls away into Vermont.
But there is another fissure between The Snow Hole and the top of the ridge that will also continue to deepen and widen — and some millennia from now it may become the next Snow Hole as the forces of weathering and erosion continue their relentless assault on the ancient bedrock of the Berkshires.