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.

Someone once described the goldenrod that seems ubiquitous this autumn as “quill pens signing summer’s eviction notice.”  Whether it was the blooming of goldenrod or some other harbinger of summer’s end that inspired the autumnal imagery of his classic, melancholy “Elegy Written in a Country Churchyard,” English poet Thomas Gray wandered through a rural cemetery “Far from the madding crowd’s ignoble strife” and in the evocative silence brooded over the lives of the souls interred there.

From their names and fleeting scraps of information carved on their tombstones, Gray inferred details of their triumphs and tragedies, their loves and losses, and their aspirations and failures, now marveling at the longevity of some or mourning the brevity of the lives of others. He read more into the moss-encrusted stones than most observers would — or would care to.

But it is a little-known fact that, to generations of geology professors, country cemeteries have frequently served as outdoor laboratories for the demonstration of many aspects of the cycles of weathering and erosion.

These are points that can, of course, be easily made using a textbook with its graphs and photographs.  But geology — perhaps more so than any of the other natural sciences except for biology — is best taught as a field science.

This is a fact that I can personally attest to from memorable courses I have taken at Acadia National Park, the Grand Canyon, Mammoth Cave, and other venues in which the complexities of the effects of mineral content, climate, exposure, and age on the weather-erosion cycle are clearly displayed.

And in a number of those courses, the professors packed students into vans and shuttled us off to old country cemeteries in which whatever geologic principle being taught was clearly and sometimes dramatically displayed.

The idea for this article came to me on a hot day in late August during a visit to the Town of Rose Cemetery in western New York in which some of my mother’s ancestors are buried. The cemetery sits on the slope of a drumlin, a glacially-deposited hill that is one of hundreds scattered across much of western New York and the Northeast. 

Drumlins and related glacially-formed hills called kames have frequently served as the locations of cemeteries, partially because their elevation above the surrounding landscape has symbolic meanings, but also because their composition of an unconsolidated mixture of soils and rocks makes them well-drained — ideal for burials.

One thinks of the high and windy hill that is the site of the Grover’s Corners cemetery in the melancholy third act of Thornton Wilder’s classic play “Our Town.”

Perhaps it is partly the inevitable association of cemeteries with Halloween that evokes their solemn atmosphere, and in this one even on a bright late-summer day there was a particular monument that has always saddened our family.

It stands a little over five feet tall and is carved from white Vermont marble, a very ancient rock formed during the Ordovician Period, some 450 million years ago, during the event known as the Taconian Orogeny.

The ancient ocean known as the Iapetus that lay off what is now the east coast of the United States was beginning to close as the process known as plate tectonics brought small land masses into collision with it, pushing up mountains and forming marble through metamorphism of pre-existing limestone.

Next to the monument, a bronze receptacle holds a flag, indicating that two of the dead memorialized here — my mother’s great uncles — died in the Civil War. The young men were inspired by the powerful words of  “The Battle Hymn of the Republic” — “As [Jesus] died to make men holy/Let us die to make men free.”

Their tombstone records that one of them named James Otto starved to death and was buried in Andersonville, the infamous Confederate prison in Georgia; the other, his brother Guilford, is actually interred here.  He and a fellow soldier were murdered by a Pennsylvania farmer with pro-slavery sympathies when they were sent to him purchase horses for the troops.

The memorial must have been splendid when it was erected around 1865. Today, the graven inscriptions recording the young men’s sacrifices have become difficult to read. In a decade or two, the inscription will be obliterated and it will stand as do so many other old marble headstones and monuments, their honored dead anonymous.

Marble is a very hard, dense rock that resists the absorption of water from rain or melting snow and therefore does not easily break down due to freezing and subsequent thawing in the process known as physical weathering; however, marble is composed of calcium carbonate, and as any high school chemistry student knows, calcium carbonate dissolves in acid.

Falling rain and fog pick up minute amounts of carbon dioxide from the atmosphere, producing a mild solution of carbonic acid. Ordinarily, carbonic acid of this strength is harmless to plants and animals but over many years it will slowly but relentlessly dissolve any calcium carbonate surface in a process known as chemical weathering.

Consequently, given that the monument was erected in Rose Cemetery over 150 years ago, it is surprising that the inscriptions are legible at all. But their saving grace has been the fact that the monument is situated on an open slope facing south, which means they are exposed to sunlight virtually all day when the sun is not obscured by clouds.

This results in the constant warming and drying of the surface, preventing its rapid dissolution and largely preventing growth of lichens and moss — the same factor that causes them to grow mainly on the north side of trees. They secrete small amounts of natural acids that in a damper, more sheltered environment can wreak havoc on organic or mineral surfaces — such as marble headstones.

Farther up the slope is another monument marking the graves of some other ancestors — in this case, my mother’s great-grandparents, whose surname was Briggs.

It was carved from gray granite, an igneous rock brought perhaps from New Hampshire or Maine and formed during the Devonian Period, in an event known as the Acadian Orogeny, some 380 million years ago; at that time, an ancient landmass known as Avalon — which would eventually become Europe — was subducting under North America and creating massive amounts of igneous rock through explosive volcanic action.

The monument stands over five feet tall and its rectangular base holds a massive sphere, an unusual design in this relatively modest graveyard. But although it, too, is over 100 years old, from its appearance one might think it had been placed there last week.

The sphere and the sides of the monument were highly polished and on a sunny day the reflection from the sphere can be blinding. Granite’s two major constituents are visible crystals of feldspar and quartz, both of which are capable of appearing in a spectrum of colors, though varying shades of pink and gray are most common.

The important fact is that neither of these minerals is easily susceptible to chemical weathering and given the extreme hardness and density of the stone and its openness to sunlight, even after a century the monument looks as fresh as if it had been erected very recently.

Almost all of the older headstones and monuments in the Rose Cemetery are carved from either marble or granite and their presence tells another story. Neither of these stones is found locally near the Rose Cemetery; they must have been imported from out of state and their inscriptions carved painstakingly by hand — which bespeaks the affluence of many of the cemetery’s silent residents and their families.

Contrast this one with many of the mossy pioneer cemeteries scattered throughout the Helderbergs in which many of the headstones of the hard-working people buried there were carved either from the native limestone or the local somewhat porous sandstone — both dating from the Devonian Period — and observe how the names of the deceased and their memorial inscriptions have largely vanished.

However, the High Point Cemetery above Altamont on Old West Road with its elegant entrance gate and meticulously-constructed stone wall is another example of a southerly-facing country graveyard in which both marble and limestone monuments a century or more old are still well-preserved.

Many of these stones are carved from marble but they face the southwest, and the view across Old West Road to a wide field is unobstructed by trees; consequently, the stones are dried and warmed from sunrise to sunset on days when the sky is not mostly overcast.

Many of the headstones are on a gentle slope and apparently were never set into concrete bases, and as a result they show the tilting common among monuments in older cemeteries caused by the slow, steady downward movement of the ground known as soil creep.

Frequently, in older cemeteries, this can cause the stones to topple, but High Point Cemetery is obviously lovingly maintained, its grass trimmed and even its very old headstones mostly upright. 

However, a collection of toppled, heavily-weathered markers in the shaded rear of the cemetery has been set aside against the old stone wall, their inscriptions mostly vanished along with record of the deceased they were intended to memorialize.

And, in a few cases, small, closely-spaced, rough-cut markers without inscriptions — harvested, perhaps, from tilled fields or pulled from stone walls — tell sad stories of deceased infants.

Shade can help to speed the forces of weathering and erosion in a humid, changeable climate such as ours — and a prime example is the venerable old cemetery near Reidsville.

With its ancient, very tall balsams and spruces, the cemetery is situated behind an evocative, slightly rusted cast-iron fence — the stereotypical locale for a Gothic ghost story. In the late 1800s and early 1900s, Reidsville was a village with a population of over a thousand.

Largely due to the quarrying activities that supplied the attractive sandstone known as Helderberg bluestone to many localities in the Albany area, the village grew, at one time boasting a hotel, a popular tavern, two churches, two retail stores, and a blacksmith shop — traces of which have largely disappeared.

The quality of the granite and marble stone monuments in the cemetery is once again evidence of the relative affluence of its occupants. Yet, although the majority of the headstones face east and could therefore be expected to get drying sunlight at least in the morning, the immense trees cast much of the cemetery into shadow and their thick boughs steadily drip moisture from rain and melting snow.

Some of the trees show the growth of the lichen commonly known as “Old Man’s Beard,” which resembles Spanish moss and flourishes in very humid boreal forests, especially those near great bodies of water such as the Acadian Coast of Maine and Canada. The damp, pitted ground surrounding many of the old headstones is deep with mosses, which do not flourish in sunlight.

As a result, even some once-stately granite monuments show evidence of heavy chemical weathering and are stained by dark lichens.  The contrast between them and some equally old, much-less-weathered stones in the more open rear sections of the cemetery is sharp.

And especially on a gloomy autumn day, the scene epitomizes Thomas Gray’s lines:

“Beneath those rugged elms, 

   that yew-tree’s shade

Where heaves the turf

   in many a mould’ring heap’

Each in his narrow cell

   forever laid,

The rude forefathers

   of the hamlet sleep.”

(In Gray’s time, the word “rude” had nothing to do with manners but rather denoted “unsophisticated.”)

In recent decades, upright stone grave markers have largely gone out of fashion due to the great expense of preparing them and in many newer areas of cemeteries they are prohibited, replaced by bronze markers which lie flat upon the ground.

An alloy of copper and other metals, bronze tends to resist chemical dissolution although after decades of exposure to moisture it may weather to a dull shade of green like a copper penny. But being at ground level, if not carefully maintained, these markers can soon be covered by grasses and weeds, hiding their inscriptions as surely as if they had been dissolved away.

A walk through a cemetery, especially one with familiar names on the memorials, may bespeak many aspects of the history of a town and its inhabitants along with many other profound thoughts that cemeteries are supposed to bring.

But a close examination of its location, the composition of its monuments and their condition reveals much about its geologic history as well: accounts of continental collisions, ancient rock changing through metamorphism, new rock forming from violent volcanic eruptions, and the much more recent passage of the great ice sheets. In all — a veritable textbook of geology.

The stream called “Onesquethaw” undergoes extensive changes as it flows from its placid source in our portion of the Appalachian Plateau known locally as “the Helderbergs.” It incises its way through several rock layers — or “strata” — from the Devonian Period, which are between 360 and 400 million years old.

It has formed canyons, flows lazily over stretches of level terrain, and gurgles over gentle rapids and through potholes. Eventually it joins with Coeymans Creek before discharging into the Hudson River where its waters mix with those of thousands of other tributaries on the river’s course toward the Atlantic Ocean.

Some of the Onesquethaw’s most rugged and picturesque segments are off limits to most hikers as it flows through private lands; however, a stretch that parallels Lower Flat Rock Road off the section of Route 443 known as the Delaware Turnpike is easily accessible by car or bike and provides a quiet place to reflect on our area’s almost unimaginably long geologic history and the thoughts that changing seasons bring.

Privately-owned Helderberg Lake lies just north of Route 443 where it briefly runs congruent with Route 85. The lake was enlarged by an artificial dam in the 1930s and at its southern end its overflow becomes the Onesquethaw Creek as it cascades down a series of terraces and has carved out a steep gorge that descends for a mile or so as it plunges out of the steep hills of the town of Berne.

Almost entirely on parcels of private property, the gorge is formed from the thin-bedded Hamilton rock layers, strata composed of dark sandstones and shales. About 220 million years ago, a vast landmass that was to become Europe was beginning collision with proto-North America in one of the great movements known as plate tectonics.

The collision was closing the body of water that had divided the two landmasses and was pushing up a towering range of mountains in what is today eastern New England. Rain and snowmelt washed millions of tons of sediments from the slopes of these ancient mountains, filling in the waterway between the land masses and forming a series of interlocking deposits termed by geologists “the Catskill Delta.”

The deposits eventually turned to rock and are visible in western Albany County and throughout the extensive eroded plateau known as the Catskill Mountains.

This material alternates between being moderately resistant to stream erosion and poorly resistant, and thus the gorge below Helderberg Lake frequently exhibits a profile similar to that seen in many canyons in the West such as the Grand Canyon: a series of alternating steep and gradual slopes covered with piles of enormous quantities of eroded fragments called “talus.”

Near the area where Wolf Hill Road, Route 85, and Route 443 intersect, the Onesquethaw has cut down through the sandstone and shale layers to the Onondaga Limestone, the highest stratum of limestone in Albany County. The Onondaga is a hard, clean gray stone, indicative of its formation during the Devonian Period in clear, shallow, warm waters.

It is rich with fossils of many kinds of corals and in places features nodules and beds of chert, a dense rock commonly known as flint composed of silica. A number of extensive Albany County caves have formed in this layer.

For the next couple of miles, the stream runs parallel to Route 443 over nearly flat terrain with a surface bedrock of the Onondaga which in this stretch is highly fractured. In dry times of the year, the stream may flow entirely under the exposed streambed leaving it bleached and dry. In periods of heavy storms and snowmelt, the Onesquethaw boils to the surface and, gathering temporary energy from the flood pulse, may create whirlpools and rapids as it flows south toward Clarksville.

But approaching the hamlet, the stream’s path is temporarily diverted east by imposing Bennett Hill, a glacially-sculpted “rock drumlin” composed of the Hamilton strata. Eroded by the mile-high glacier that passed over it thousands of years ago, the step-like terraces of Bennett Hill are visible for many miles.

The Onesquethaw again becomes somewhat energized as it cuts through the limestone at the base of Bennett Hill and flows down through another impressive canyon. Here the stream encounters an extensive series of faults whose “slickensides” — tell-tale parallel grooves carved into the bedrock during an earthquake — are visible in sections of the canyon walls and the streambed, and in places the strata are bent and contorted by the movement of the ancient fault.

Within the canyon are small caves and springs, plunge pools, enormous potholes, giant boulders and slabs detached from the bedrock, and thick deposits of sediments composed of many rock types, some carried down from the Helderbergs, others left behind long ago by the retreating glaciers.

But in this stretch, the Onesquethaw is described as an “underfit” stream, meaning that with its average velocity — which for most of the year in these modern times is not much more than a trickle — it is incapable of eroding great chunks of the canyon’s hard bedrock or transporting and polishing large boulders. Much of this erosion occurred at the end of the glacial period when the Onesquethaw may have carried hundreds of times its present-day volume due to the melting of the glaciers.

As the Onesquethaw approaches the eastern boundary of the village, it cuts down into the crumbly Esopus Shale and for a stretch of several hundred feet it has exposed the marvelous fossils characteristic of the Esopus known commonly as “rooster tails.” These fossils represent a vast colony of tube worms whose feeding tunnels radiate out from a single point.

They indicate an ancient environment of relatively deep, calm water in which the delicate worms could have remained anchored to a single point on the sea bottom for a lifetime and burrowed through the murky organics-laden mud absorbing nutrients.

Just beyond the rustic stone bridge over the Onesquethaw on Tarrytown Road there is a pull-off on the left side of the road where a short path leads to the stream’s edge and offers a dramatic view of strata contorted by the movement of an ancient fault.

Beyond this point, the Onesquethaw is not visible from any public road and flows through private land. It continues to cut downward through the Esopus Shale and cascades over an impressive waterfall into a plunge pool.

It finally incises its way through the entire exposure of the Esopus and comes into contact with an even older Devonian layer known as the Becraft Limestone. But it is not until the stream bends and enters the wide, shallow valley through which passes Lower Flat Rock that it again becomes easily accessible and enters one of its most evocative sections.

Here for a thousand feet or so paralleling the road the Onesquethaw flows due south and is bordered on both sides by a forest of hemlocks and pines, floored by ferns, mosses, and other vegetation that flourishes in humid, shady environments. The stream itself broadens out and descends a series of low terraces producing miniature rapids as it continues through a bewildering maze of gurgling and babbling channels, potholes, and plunge pools.

The Becraft limestone layer has a thickness of only about 20 feet in this part of the county, but along Lower Flat Rock Road the rock has been smoothed off by the passage of the ancient glaciers in a broad plain known to geologists as a “bench.” Although much of the bedrock is covered here by a thin layer of soil and the forest it supports, the Onesquethaw’s path reveals the Becraft with its fascinating collection of fossils and erosional features.

The Becraft is a very hard rock and, because its surface was subjected first to abrasion by the glaciers and subsequently polished naturally over centuries by tiny water-borne sediments acting like fine sandpaper, exposures show the clean, gray limestone is flecked with thousands of closely-packed fossils. Mainly these are the shells of sea creatures known as brachiopods and they stand out as shiny white circles or crescents.

The Becraft resembles a rock type called “coquina,” which consists of great masses of fragments of sea shells naturally cemented together by calcium carbonate and often found near reefs and on the coast of Florida and islands in the Caribbean Sea. That most of the shells have been shattered indicates that the rock formed millions of years ago in relatively shallow-water environments in which the shells were subjected to violent agitation and deposition by waves in Devonian seas.

In addition, the Becraft in the streambed shows many fractures and joints — cracks caused by repeated freezing and thawing over centuries as well as expansion of the bedrock as upper layers are removed by erosion.

Because the limestone and its fossils are made of calcium carbonate, the rock is subject to chemical weathering by mild natural solvents such as carbonic acid, formed when water absorbs carbon dioxide as it falls through the atmosphere or flows over rotting duff on the forest floor.

As a result, the mildly acidic Onesquethaw waters have worked their way through every crack and crevice in the streambed, dissolving the maze of channels and potholes visible along Lower Flat Rock Road. Small channels encounter larger ones, fractures lead into potholes and plunge pools, and the tiny distributaries enter a confusing pattern of flow, sometimes briefly backwards or sideways or in miniature whirlpools, but eventually forward toward the Hudson under the pull of gravity.

Tiny dams formed by the presence of water-loving plants or water-borne debris create miniature pools of slow-moving or still water in which minnows and pollywogs and water bugs find refuge, feeding on tiny prey or bits of organic matter carried by the stream.

And of course, the patterns of flow and the sounds they produce change with the seasons and the weather.   Snowmelt and seasonal rainstorms raise the volume of the stream, causing the channels to overflow and create earnest-sounding if temporary rapids.

In dry times — especially late summer and fall — low flow in the Onesquethaw reduces the sounds of the stream to whispers. In winter, thick layers of ice form on the bedrock beneath the overhanging boughs of hemlock, creating weirdly-sculpted shapes in the streambed as well as yet more channels and dams, and water may burst from them like the icy rivers that emerge from the base of glaciers.

At such times, the stream appears black and lifeless and the sounds of fracturing and shifting ice may shatter the quiet of the valley. But with spring will come again the agreeable babbling of the brook and the cries of peepers.

A professor of mine once told our class that to be an effective geologist, one must have a good imagination — and this portion of Lower Flat Rock Road is an excellent stimulant to the mind.

Standing on its banks, one can imagine the crash of ancient seas transporting and depositing sediments and sea shells, the growth and grinding of glaciers during the Great Ice Age, and the relentless shaping and reshaping of the landscape and the labyrinths of the streambed as the Onesquethaw continues its unrelenting search for the sea.

The precise locations of the caves referred to in this column have been left deliberately vague to protect both the caves and inexperienced persons who might wish to enter them. Those interested in local cave exploration are urged to check out the website of the Northeast Cave Conservancy — www.necaveconservancy.org — and to consider a cave trip tailored to their abilities during the period between May 1 and Sept. 30 when the caves are open for visitors.

One might — in a whimsical moment — regard it as “The Spelean Archipelago.”

Though sport- and scientific-cavers have long frowned upon the term “spelunker,” the noun “speleology” — the scientific name for the study of caves, derived from “spelaion,” the Greek word for a cave — and the adjective “speleological” have long become standard usage.

Across the northeastern United States, preserves in karst areas dot the map, ranging in size from a single acre to hundreds — “karst” being the term for a region of limestone or marble bedrock containing caves.  They are owned and/or managed by two organizations known as the Northeast Cave Conservancy, which recently celebrated its 40th anniversary, and the National Speleological Society — commonly referred to respectively as “the NCC” and “the NSS.”

The preserves protect numerous caves, the watersheds they involve, the unique life within them, and the classic karst surface features such as sinkholes, disappearing streams, and springs. Many local cavers are members of both organizations, the websites of which detail the history and geology of the various preserves.

From May through September, the NCC also offers instructions on access to the caves for the qualified public. From Oct. 1 to the end of April, many Northeastern caves — and all of those under the ownership or management of the NCC and NSS — are closed to protect the caves’ bat populations, which in recent years have been ravaged by the insidious disease known as “White Nose Syndrome,” or “WNS.”

Commercial caves such as Howe Caverns and a number of privately-owned caves that do not harbor bats remain open; however, winter has never been a very popular time for sport caving except for the most dedicated cavers, given the fact that Northeast caves are almost by definition very wet, and slogging through snow in sub-freezing temperatures to and from the caves can be extraordinarily miserable.

The National Speleological Society was founded in 1941 by a small but dedicated group of cave explorers and since has grown to become an international organization with thousands of members. In the Northeast, the NSS owns three Schoharie County cave preserves: Schoharie Caverns, the Gage Preserve, and McFails Cave, the most extensive in the Northeast. All three properties were donated to the NSS by generous patrons and have been maintained over the years by dedicated volunteers.

Knox Cave tragedy leads to stewardship

Yet the NCC was born as the final result of a tragic winter caving accident in 1975.

In March of that year, several students from the State University of New York Outing Club were attempting to enter Knox Cave through its ice-encrusted sinkhole.

The cave near the hamlet of Knox had sporadically been run as a commercial operation like Howe and Secret Caverns in Cobleskill, most famously under the ownership of Delevan C. Robinson and his wife, Ada. In the mid-20th Century, the couple were responsible for the building of an elaborate staircase offering access to the cave, which lies over 100 feet underground, and for constructing walkways and installing lighting for tourists.

D.C. seems to have had what the Irish call “the gift of blarney,” and some of his descriptions of the cave and its extent were — to put it gently — fanciful. But the cave features both large, easily-accessed passageways and more challenging sections that require stamina and sometimes ropework of explorers, and it has attracted serious cavers for many generations as well as tourists during the relatively brief periods when it was commercialized.

The Robinsons also built a large roller rink adjacent to the cave’s entrance sinkhole, which for a while in the 1940s and 1950s was the scene of skating parties and country dances. It seems to have formed a center of social life for the Hilltowns in the days when not many hardworking Helderberg folks could afford the time or the money to travel to nearby cities for entertainment.

But following D.C.’s death in 1961, commercial operation of the cave ended for the last time though sport cavers and scientists continued to gain access to Knox Cave with the kind permission of D.C.’s widow until she died in 1964.

Some time in the mid-1960s, the largely abandoned property was purchased by a Long Island corporation called “Organa Industries,” which announced its intention to restore the cave and dig out a boulder-choked sinkhole adjacent to its classic entrance to allow a through trip.  But Organa Industries went belly-up and the restorations never took place.

Old-timers in the Knox area may remember the huge steam shovel that stood for years in the field next to the commercial entrance but it seems never to have been employed in digging the clogged sinkhole and it eventually collapsed into a rusty pile of warped metal and cables.

The result was that access to Knox Cave was without any sort of control; in the years that followed, the staircase and the walkways deteriorated and the lighting system and many of the cave’s natural decorations were vandalized and the skating rink and the Robinsons’ 200-year-old farmhouse were torched.

Even the massive frozen waterfalls that formed in winter from drainage in the fields around the Knox sinkhole did not deter visitors from entering the cave. Sometimes the warmer (48-degree) air within the cave would melt a tight hole allowing access to the adventurous — or risk-takers — while at other times the even more foolhardy were rumored to be using sledge hammers to smash their way through the ice to gain entrance.

In any case, one day in March, 1975, although snow still covered the ground, the temperature rose to 50 degrees as a group of students from SUNY Albany tried to enter the cave. Runoff from the melting snow poured in a cascade behind the ice deposits and the result was that a massive block of ice broke away and came crashing down, killing one student and leaving another paralyzed from the neck down.

By that time, the cave and surrounding land had been sold for non-payment of taxes to a doctor from Schenectady. Fearing additional injuries and lawsuits, the doctor attempted to donate the cave to the National Speleological Society.

But the same fears caused the NSS to reject the offer and a group of cavers became concerned that the cave might be acquired by someone who would ban all exploration or even bulldoze its entrance sinkhole, effectively closing it permanently.

Thus, in 1978, three area men — Dr. Art Palmer, Robert Addis, and Jim Harbison — formed the Northeast Cave Conservancy as a not-for-profit corporation and Knox Cave has continued to be made available to qualified cavers. Over the years, subsequent exploration has added close to 1,000 feet of previously unknown passage to the map of Knox Cave and revealed another segment of passage yet to be connected to Knox known as Crossbones Cave.

And over the years, through purchase or donation, the Northeast Cave Conservancy has acquired a number of other parcels of land containing caves that are also well-known to explorers.

Caves galore

A western portion of the Helderberg Plateau known as Barton Hill in Schoharie County rises steeply above the Fox and Schoharie creeks. A standing joke among cavers is that the hill is hollow because of the numerous caves that underlie it.

One large parcel of land owned by the NSS was donated by long-time caver and local attorney Jim Gage and contains Schoharie Caverns, which resembles a slot canyon; its entrance lies at the base of a limestone cliff on the edge of the plateau.

Schoharie Caverns consists of nearly half-a-mile of streamway featuring beautiful stalactites and stalagmites, which decades of visits by college outing clubs and other groups have left marvelously intact.  A spartan cabin on the parcel is maintained by local cavers and is available for groups visiting Schoharie Caverns and other nearby cave preserves.

And there are many. The NSS also owns another large parcel of land on Barton Hill donated by Jim Gage and named in his honor; it contains Ball’s Cave, named after its 19th-Century landowner. Its vertical entrance lies in a heavily-wooded section of the hill and has drawn visitors for over 150 years.

The cave features immense rooms as well as low crawl ways, and a diminutive flooded segment of the cave known as the “Lost Passage” requires cavers to experience an “ear dip” to pass through it. (Do you really want to ask?)

Although there are a number of other known or suspected caves on Barton Hill not under the control of the NSS or NCC, Spider Cave was recently donated to the NCC by a local landowner.  ts alluring entrance has been described as “Storybook,” but explorers have found that it is a very short story except for those intrepid enough to challenge its agonizingly tight, wet main passage that extends for over 1,000 miserable feet into the plateau. And those who enter its easily accessible first hundred-or-so feet will encounter hundreds of its eponymous creepy occupants scampering across the cave’s water-smoothed walls.

McFails is the jewel

Generally considered the “jewel in the crown” of northeast caves is McFails Cave on the Cobleskill Plateau. Its entrance is in a beautiful hemlock and hardwood forest pockmarked with gaping vertical sinkholes, some of which take voluminous quantities of water from time to time.

Only a short and very unpleasant segment of McFails was known until 1961 when some students from Cornell University plunged through a pool with just a few inches of airspace and discovered that the cave did not end at the uninviting pool.

Today the cave is known to be over seven miles in length, much of which consists of high canyons and large chambers beautifully decorated with calcite formations. But the cave can be treacherous: Entrance requires rappelling down seventy feet — in wet weather through a waterfall — and much of a cave trip involves constant immersion in a cold stream, making the wearing of a wetsuit a necessity.

The cave has been hydrologically connected to other caves on the plateau, meaning that water in them them has been traced to McFails. Thus the potential exists for a cave system some 26 miles in length — a fact likely to draw intrepid explorers for years to come.

Clarksville Cave is the best known

Undoubtedly the NCC-owned cave that is best known to the general public is Clarksville Cave, which has drawn visitors for well over 150 years. Groups from camps, schools, churches, and colleges regularly visit the cave between May 1 and Sept. 30.

Clarksville has three known entrances and lies beneath a hardwood forest laced with nature trails. While much of the cave consists of subway-tunnel size passages, more adventurous visitors are drawn to its tight — and wet — challenging sections that lead to pools and a picturesque waterfall.

Despite its easy accessibility and heavy traffic in summer months, much of the cave is relatively pristine and its numerous classic features both above and below ground make it a veritable textbook example of cave and karst geology.

Ominous Onesquethaw

Not far from the village of Clarksville is the lesser-known Onesquethaw Cave also owned by the NCC.  Named for the stream that flows through the valley in which its entrance lies, its low, twisting passages are studded with fossils and its sometimes maze-like layout gives the cave a certain allure.

But Onesquethaw is not for the novice cave explorer and has long had a somewhat ominous reputation.   It lies in a low area that is prone to flooding and in times of sudden heavy precipitation a roaring stream enters the cave and can fill its passages to the ceiling.

In 1991, a group of students from Syracuse University became briefly trapped in Onesquethaw when a torrential surge of water flooded the cave, setting off a massive rescue effort that drew news organizations and cave-rescue teams from all over the Northeast. The students had fortunately found a room with a high ceiling and were able to cling to the walls until the water levels finally dropped and allowed them to leave the cave.

As the students’ experience in Onesquethaw Cave demonstrates, the subterranean world demands respect of those who enter it. The Northeast Cave Conservancy and the National Speleological Society have not only managed to acquire and keep open many classic Northeastern caves for qualified visitors, they have educational and scientific components as well.

Through work with the general public as well as scientists and qualified students, ranging from grade school right up through university-level students, the organizations have helped to maintain and protect the resources of the world beneath our feet.

And the NCC and NSS are not alone. All across the 48 contiguous states and in Hawaii many hundreds of acres of karst lands and areas underlain by lava caves have been acquired and protected by organizations of dedicated cavers: a “spelean archipelago” indeed.

Could statehood be far behind?