Virtual Tour of Clarksville Cave

Virtual Tour of Clarksville Cave
By Mike Nardacci
Ably assisted by cavers David Wallingford and Owen Tobias-Wallingford

Owen Tobias-Wallingford at the “Gregory Entrance” to Clarksville Cave

(So named because in the 1960s the property was owned by Clarksville resident Frank Gregory).  Clarksville Cave is one of the best-known “wild” (i.e., non-commercial) caves in the Northeast and is a very popular destination for novice as well as experienced cavers, earn extra money if you are in need of a good work.  The entrance shown here lies at the base of a cliff formed from layers of the Onondaga Limestone which dates from the Devonian period of geologic time and is well-known for its wealth of marine fossils and its nodules of chert, a hard, dark rock formed of silica.  Known since the early 1800s, Clarksville Cave consists of about one mile of a variety of passages.  Some are walk-able, some are tight crawlways, some are dry stretches, and some are filled waist-deep or deeper with 46-degree water:  something for every level of caving competency!  The cave is owned and managed by the Northeastern Cave Conservancy and is open for caving from May 1 to September 30.  It is closed the rest of the year to protect its hibernating bats from the disease known as White Nose Syndrome which has killed millions of bats in the U.S.  The entranceway has a short narrow stretch but soon opens up into a chamber that permits walking and leads to deeper sections of the cave.

Owen Tobias-Wallingford descending the entrance

Shorter folks can walk down the sloping entrance–others prefer to slide down part of the way.  The passage is floored with layers of fallen leaves making it a bit slippery.  Much of the small room at the bottom is in an area known as the “twilight zone” of caves.  It gets some light from the outside but never full sun.  Bats seldom roost here because they tend to like total darkness but spiders and crickets may find the area much to their comfort.  In wintertime, temperatures in the twilight zone may drop below freezing, causing water dripping from the ceiling to form large displays of icicles and ice stalagmites.  Deeper in the cave temperatures fluctuate very little from summer to winter, and in our area they tend to hover around 48 degrees which is the average of our year-around temperatures.  The relative humidity remains constantly close to 100% which coupled with the cool temperatures necessitates the wearing of warm clothing.

A fossil coral in a wall of the first large chamber in the cave

(Hand of David Wallingford for scale) The Onondaga Limestone formed around 400 million years ago at a time when this area of the landmass that would become North America lay near the Equator under a warm, shallow sea.  This limestone is composed of the shells of billions of tiny sea creatures as well as some larger ancestors of modern-day shellfish, sea-lilies (an animal, not a plant), and corals.  In this photo the branches of a coral have weathered out of the cave wall as have other fossils throughout the cave.  In addition, as the glaciers retreated thousands of years ago, melt-water poured off them and flowed through the cave carrying sediments and organic remains from outside.  In the 1960s the bones of an elk—long since extinct in New York State—were found in a mudbank in the cave.  Fossils should never be removed from the cave, nor should formations or rock samples.

David Wallingford traversing a small pool in the passageway

Caves are natural storm drains and in New York State most of them carry streams throughout the year, even in times of drought.  A change in the shape of the passage or deposition of sediment may cause water to pond up, forming pools which may be neck-deep or deeper.  This stoopway collects water which is usually no more than a couple of inches deep and most people can cross through it getting only their feet wet.  However, in times of spring snowmelt or very heavy precipitation, this passage and the rest of the cave may carry huge volumes of rapidly moving water.  Clarksville Cave floods more slowly than some caves in the Helderbergs but it is always important to check the weather forecast before entering a cave.

Nineteenth-century graffiti

Visitors should always strive to leave no trace of their passing through a cave.  The rules are– “Take nothing but pictures, kill nothing but time, leave only footprints”—and even the last of these should be avoided where possible.  But in centuries past, it was considered the thing to do to leave one’s name and date of visitation scrawled on cliffs and cave walls.  Mammoth Cave in Kentucky has literally tens of thousands of such graffiti which are considered a part of that great cave’s history; today, marking cave walls is considered vandalism and certainly degrades the natural appearance of the cave.  This rather elegant carving records the visit of one “D.C. Gould” on August 12, 1864 and there are other even older carved graffiti in the cave along with more recent ones in spray paint.  Fortunately, due to the high humidity, sprayed graffiti do not fully dry, making the job of clean-up crews somewhat easier.

Owen Tobias-Wallingford in one of the high passages in the cave

Cave passages cut by fast-flowing streams tend to form what are known as “canyon” passages which are usually higher than they are wide.  If the streams are still active, they continue to cut into the bedrock, deepening the passageway.   Much of Clarksville Cave has formed following an ancient fault line.  The gentle tilt of the bedrock is seen here and a massive slab of limestone long known as “the shark’s mouth” has separated due to the movement of the fault and gravity will someday cause it to crash to the floor

Owen Tobias-Wallingford emerging from a tight crawlway

Cavers often encounter tight passageways which are not for the claustrophobic.  They may be floored with soft mud or sand but far more often require cavers to crawl over solid or fragmented bedrock, making knee pads a necessity.  Occasionally they may lead to dead-ends, but caves are unpredictable and tight squeezes such as this one often open up into spacious chambers.

David Wallingford and Owen Tobias-Wallingford on a massive flowstone formation

Surface water often picks up carbon dioxide (CO2) from rotting plant material on the ground above a cave and becomes slightly acidic, allowing it to dissolve the calcium carbonate in the limestone as gravity pulls it downward into a cave passage.  When it enters the cave it “de-gasses”—the (CO2) is driven off and the liquid deposits minute amounts of calcium carbonate making “speleothems” on the ceiling or floor such as stalactites and stalagmites, and flowstone on the cave walls.  In this section of the passage there must at one time been an active spring transporting mineral-saturated water into the cave, forming the huge deposit seen here.  This is a very slow process and this formation could easily be tens of thousands of years old.  At some point, the spring deposited so much mineral that it sealed itself up and this structure is no longer actively forming.  In commercialized caves, formations such as this one are often called “frozen waterfalls” or “pipe organs.”

Owen Tobias-Wallingford at the “E. Brinley” inscription

The oldest known of the graffiti in Clarksville Cave is this one which indicates an “E. Brinley” visited the cave in 1839.  Because the carving is near the entrance to a very wet passage called a “sump” leading deeper into the cave, it has given its name to the passage: “Brinley’s Sump.”

Owen Tobias-Wallingford on the bank of the underground stream at Brinley’s Sump

The water here is about three feet deep and it disappears under an arched passage about 3 ½ feet high.  Until 1962, this was considered to be the end of the cave.  But there was a drought in the Albany area that summer and a group of cavers found nearly two feet of air space.  Wading under the archway they discovered a whole new section of the cave which connected with what was then known as “Ward’s Cave” farther north in the woods. This section contains very unusual “speleothems” and interesting geology and is frequently visited by college geology classes and groups from summer camps. Today the whole system is called Clarksville Cave with multiple entrances.  Slogging through Brinley’s Sump has become a major attraction of visiting the cave because although passage through the sump usually requires briefly an almost complete immersion in the 46-degree water, visitors get a good idea of the conditions that prevail throughout most New York State caves.  And most visitors find it to be fun!

Clarksville Cave is open for visitation from May 1 through September 30.  It is off-limits the rest of the year because of the hibernating bats.  More information is available on the Northeastern Cave Conservancy’s website:


The Heldeberg Workshop is registered with the IRS as a charitable organization under section 501(c)(3) and therefore can receive tax-deductible donations.

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