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Geology at the Vanderbilt mansion Mar. 21, 2019

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The Fall of the House of Vanderbilt
Stories in Stone
Oct. 29, 2004
Robert and Johanna Titus

Do you remember the story of that neighborhood in Schenectady that suffered the slump late last winter (2018)? Two houses and the earth beneath them suddenly began a slow collapse. A dozen or so people had to be evacuated. It made quite the splash in local news, for a while, and then faded from our regional consciousness. Well, we have followed the story and the end was sad, but predictable. It was ordered that both houses be razed. The danger was deemed too great to allow people to return to their homes.
We wrote about this back then and warned that this was no isolated event. Slides of this sort are common where there is uniformly fine-grained sediment, and that is throughout much of the Hudson Valley, including many areas in Columbia County. Our valley once lay beneath the waters of Glacial Lake Albany. Thick sequences of soft clayey sediment accumulated and, periodically, masses of this stuff slide downhill. The formal term is earth flow. It has happened in a lot of places. It will happen again.
You can go and see for yourself one other place where this has been going on and get a good look at how it affects the landscape. At the same time, you can see how a fine piece of architecture is threatened by a future earth flow. Head south down Rte. 9 to Hyde Park and visit the grounds of the Vanderbilt mansion there. The place belongs in Newport, Rhode Island, a great edifice of Indiana limestone. Around it, and to the north and south, is a sprawling estate that lies on a great bluff towering above the Hudson River. The Vanderbilts had a fine view of the Hudson and that must be why they chose this location. In the long term it may have been a fatal choice.
If you look around the mansion you will quickly notice that the grounds are smooth and flat. It might seem unnatural and you might suspect that the landscape was bulldozed, but Nature did this herself. There is an ice age heritage here. About 14,000 years ago this was Glacial Lake Albany. And back then the local stream, “Crum Elbow Creek,” flowed into the lake. This little stream carried a lot of sediment and deposited it in the form of a large delta that expanded out into the lake. It is the nature of deltas to have flat tops and very steep fronts. That accounts for the flat landscape here and also the steep slopes that face the Hudson Valley. The Vanderbilt mansion was built on the edge of the ice age delta. While you are walking the grounds, imagine yourself in chest deep icy lake waters.

Walk south from the mansion, towards the formal garden, and notice that the forested slope has a scalloped appearance; it looks as if a large ice cream scoop took out masses of earth. This is typical earth flow landscape. Each “scoop” represents an old slide. These have had the time to “heal” with the return of the forest.

Return to the south end of the mansion and take the dirt path downhill. Beyond is a long grassy meadow. If you look along the edge of this meadow you will, once again, see that scalloped appearance.
Now head north from the visitor’s center on the estate driveway. Soon you will find a very nice vista of the Hudson Valley. It’s worth the trip by itself. But, once again, look over the edge of the steep slope here and see the scalloped appearance. Over the eons many earth flows have occurred all along the edge of the old Crum Elbow Delta.
There is no reason to think that any of this has stopped. We would expect that every century or so, more of these events will occur. Now look and see how close to the edge of the delta the great mansion is. We are predicting that someday, much as was the case in Schenectady, a sizable portion of the Vanderbilt mansion will begin a downhill slide. Earth movements are very egalitarian; they affect the rich as well as the poor.
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Contact the authors at randjtitus@prodigy.net. Join their facebook page “The Catskill Geologist.”

Kaaterskill Clove by air March 14, 2019

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Palenville by air
The Catskill Geologists
The Mountain Eagle – June 15, 2017
Robert and Johanna Titus

We would like to welcome what we hope are a large number of new readers from Palenville. The Mountain Eagle has expanded its coverage to your town. Palenville has an extensive historical heritage. It has been a place where visitors have long begun their ascent into scenic Kaaterskill Clove. Originally a tough trek, nowadays there is a modern highway so the journey is easy. In the 19th Century Palenville became an artist’s colony. Landscape painters of the famed Hudson Valley School of Art commonly spent their summers there and devoted themselves to sketching and painting the area’s scenic landscape. A lot of very good work was done in the vicinity of the clove. Palenville has always seen a great number of tourists passing through on their ways to the mountains.
Let’s visit the town of Palenville as geologists; and, let’s ask a deceptively simple question: why does it exist? The answer takes us back to the Ice Age. Geologists have long been drawn to Kaaterskill clove to view its landscape with a more scientific eye. That’s where we fit into the story. We love to hike the clove and the mountains north and south of it. There is an awful lot of very good geology to be seen there. So, when we got the chance to fly over it, we welcomed the opportunity. We had a pretty good idea of what we would see. Kaaterskill Clove is a great gash in the Catskill Front. Most of it was carved during the Ice Age, especially during the closing phases of that time. Melting glaciers provided enormous amounts of water that cascaded down the canyon, eroding it. Think of it as an oversized gulley!

 

Kaaterskill Clove had been there before our most recent ice age. It probably began eroding at the end of the Ice Age’s previous chapter. But about 13,000 or 14,000 thousand years ago there was another time of melting . . . and another time of erosion. You have to visit the clove and imagine it with deafening masses of raging, foaming, pounding whitewater thundering down its canyon. Erosion would have been going on at an alarming rate. Where there is erosion, the destruction of rock, then there must also be the production of large masses of sediment. Rock is converted into sediment, and it must be deposited somewhere. That is exactly what we were going to see.
Palenville has long been recognized by geologists as something that is called an “alluvial fan.” That is a large, fan-shaped heap of earth. Such fans spread out across a dry valley floor at the bottom of the sediment’s source. In this case, large amounts of sediment traveled down an eroding Kaaterskill Clove, and then spread out into a fan shaped heap at the bottom of that clove
A trained geologist can recognize such a feature on any good topographical map, and we did this a long time ago. But now, we were up in a plane, and there it was. As we flew by, we gazed into the great wide yawning clove. And spread out before it was the alluvial fan. We could recognize three roads that we knew. These were Bogart Road, Rt. 23A, and Rt. 32A. The three of them radiated out from the bottom of the canyon and spread out across the top of the fan. Nobody knew it at the time but, as laid out, those roads all descend the gentle slopes of the alluvial fan. The fan made an ideal location to build homes and, one by one, they appeared. And that is the geological story behind the origins of Palenville.
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Reach the authors at randjtitus@prodigy.net and see more at their facebook page “The Catskill Geologist.

The Cohoes Waterfalls March 7, 2019

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Family Day Trip: Cohoes Falls
Windows Through Time
The Register Star
Robert and Johanna Titus
Nov. 27, 2015

There’s probably some good weather ahead of us so let’s go for another “family day trip.” That’s when we tell you how to get to some wonderful geological location that just happens to be far enough away so that you have to spend the day getting there, seeing it, and coming back. That’s something that the two of us enjoy doing, especially when the children and grandchildren are visiting. This time let’s go to the town of Cohoes.
You have probably heard of Cohoes, but perhaps you have not visited it. The town is famed for three things: 1) the Cohoes mastodon, whose skeleton is now housed at the New York State Museum; 2) the old Harmony Mills factory, which was one of our state’s premier industrial centers back during the 19th Century; and 3) the Cohoes Falls which the Mohawk River tumbles over. As it happens those all three are very closely associated with each other. An elephant, a factory, and a waterfall? How could they have anything in common, never mind a lot? Obviously, we have a great deal of explaining to do. Today let’s hold off on the mastodon and focus on the other two.
Harmony Mills is typical of New York State industrial might, not so much today, but back in the 19th Century when the “Empire State” was almost truly imperial. You have to go there and see them to believe them. To properly describe Harmony Mills we have to use two words that we usually hate to use: the Mills are an awesome icon of 19th Century industry. Those words have come to be used far too often in modern vernacular. They should only be employed when they are truly needed; here they are. The mills were based on water power and all that water power came from just a little upstream; that’s where the falls are. In the 19th Century waterfalls were an important component of our energy needs. Where there were awesome waterfalls then there would soon be large iconic factories. Harmony Mills was an enormous textile mill complex. It was constructed in 1872; it fell into hard times and closed in 1988. Today, it has been converted into upscale lofts.


The falls were harnessed to provide the awesome amounts of energy needed, so let’s talk about them. You can visit a site that has been developed to provide the most awesome possible view of this natural icon. Find your way to North Mohawk St. and head north through town until you can turn right onto Cataract Road. There you can park, get out and walk to the viewing stand. It provides an iconic vista of the falls, which lie maybe a mile to the northwest. Why are they there?
The falls are mapped as belonging to one of the most important rock units in all of the Hudson Valley – that is the Normanskill Formation. It is a mass of dark gray sandstone and black shale. The sediments that formed these first accumulated in an awesomely deep marine basin. The Normanskill Basin was likely tens of thousands of feet deep. Sediments, mostly awesome amounts of sand, tumbled down its steep slopes as submarine landslides, and piled up at the bottom. Those sediments eventually hardened into dark gray sandstones. During the awesome stretches of time that passed in between the landslides, muds accumulated and those hardened into the black shales.
When, and just after they were deposited, these materials formed flat sheets of sediment. But, if you look at our photo, you will see that the once horizontal strata are now steeply inclined. They were deformed during one of several mountain building events that shaped the Appalachian Mountains as they are today. A geologist looks at such deformation and interprets it as evidence for ancient mountain building. Our guess is that this event was the one called the Taconic Orogeny and that it occurred during a time called the Late Ordovician, about 450 million years ago.
If we could we would climb down to the falls and take a good look at the rock types that make them up, our guess is that a lot of those strata are composed of those dark sandstones. Sandstone is mostly composed of quartz and that’s a very resistant mineral. It makes very good cliffs and even better waterfalls.
We are guessing that, a long time ago, those strata came to be tilted during that mountain building event. Many hundreds of millions of years later, the Mohawk River started cutting across the Normanskill rocks. When the river encountered those tough sandstones, it had a very difficult time cutting through them. The result was the waterfalls.

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Contact the authors at randjtitus@prodigy.net. Join their facebook page “The Catskill Geologist”

Name your Poison Feb 28, 2019

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Name Your Poison
On the Rocks/
Updated by Robert and Johanna Titus
June 18, 1998

Black sedimentary rocks are occasionally seen in the Hudson Valley. Recently, we described some along Rt. 209, south of Sawkill. The dark appearance of these strata makes them remarkably eye-catching and, when they make up tall cliffs, they loom, dark and menacing, over the landscapes.
It’s the shiny, jet-black shales that we are talking about. They are often rich in undecayed organic matter; it’s the carbon that makes these rocks black. This generally suggests to the geologist that there were low-oxygen conditions in the sea waters at the time of deposition. Without oxygen, most decay bacteria cannot function; they die before they can completely destroy the organic matter. But why low oxygen? That takes us back in time.
Back in the early Devonian Period, these shales were accumulating in a deep sea, immediately adjacent to the rising Acadian Mountains of western New England. Thick soils formed on the rapidly weathering mountainsides. The soils were easily and rapidly eroded and provided sediments that were eventually transported into the nearby Catskill Sea. This material was rich in dissolved nutrients, such as nitrates and phosphates. They fertilized the water and that led to the next step in what was to be a complex chain of events.

The fertilized waters were ideal for algae; they experienced algal blooms, great population explosions in the surface waters of the Catskill Sea. A whole ecology became established as dense mats of floating, or planktonic, plants and animals grew, somewhat similar to that of today’s Sargasso Sea. While all this was great for the plankton it was deadly for just about every other category of marine organisms. As the plankton died, they were attacked by decay bacteria; the algae bloom led to a bacteria bloom. But the decay process consumed so much oxygen that the seas soon became oxygen-depleted. The hapless bacteria had, in effect, poisoned their own habitat, because they needed oxygen too. Their numbers quickly plummeted and very soon, all types of animals, as well, suffocated in the oxygen depleted sea. But the algae just kept on proliferating in the surface waters where there was plenty of oxygen, diffusing in from the air above. Soon, large masses of undecayed biological material were sinking to the floor of the ocean. The climate was tropical, and the nearby coastal lowlands provided lots of vegetation, much of which drifted into the basin, adding more organic matter to the black shales. Almost all of these organics accumulated as thinly laminated, shiny black shales.

 

Back then, the Catskill Sea was largely isolated from other deep bodies of water; it was nearly surrounded by land or very shallow water. To its east, land blocked weather patterns and shielded the basin from most storm activity. All of these conditions promoted what are called stagnant, thermally-stratified waters. The sunbaked surface layer was hot, while deeper water remained cool. Depth stratification and a dense planktonic mat combined to prevent agitation and mixing of the waters, causing stagnant sea floor conditions to develop. Virtually nothing could live in this sea, except at the surface where there was always plenty of oxygen. This was truly the poison sea.
Many of the earliest Catskill shales are jet black, and they form the Bakoven Shale at the base of what is called the lower Marcellus Group. As we have seen, they are the record of the Catskill poison seas. The upper beds of the Marcellus Group are similar looking but very different deposits. These are fossiliferous black shales and dark gray sandstones. They sometimes have rich assemblages of brachiopods, clams and even corals. These were still mud-bottomed seas, but they were deposited at times when there was a fairly large amount of oxygen in the water, at least enough to allow marine shellfish to survive and even flourish. These can be fun rocks to poke through as they are occasionally richly fossiliferous, and the preservation of those fossils can be very good.
See the Bakoven Shale on Rt. 23A where it crosses Kaaterskill Creek east of Kiskatom. Go visit that large outcrop along Rt. 209, between Kingston and Sawkill. The far south end is the real poison sea; as you travel upwards and north from those beds you are looking at shallower waters which had more oxygen.

Contact he authors at randjtitus@prodigy.net

A petrified delta Feb. 21, 2019

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A Petrified Delta?
The Catskill Geologists
Updated by Robert and Johanna Titus

We’re back! Did you read us back when The Mountain Eagle was part of Columbia-Greene Media? Well, here we are again. We will be making frequent contributions to the “new” Mountain Eagle and hope you will be watching for us. We are Robert and Johanna Titus, and we have a long history of writing geology columns here in the Catskills. Run a search on us and you can learn a lot more.
When you begin writing for a newspaper the first thing you ask is about where does it circulate. The Mountain Eagle can be found throughout all of Schoharie County and a good part of Greene and Delaware Counties. That is the heart of the Catskills and that gives us a lot of geology to write about. So, a good place for us to start today is to describe the geology of our mountains in the broadest terms. Let’s ask a deceptively simple question: What are the Catskills?
And (without a drumroll) the answer is – the Catskills are a petrified delta. A what?? Does that surprise you? Well then, maybe you need to start learning some geology. Let’s begin by looking at a typical outcropping here in the Catskills. See our photo; the upper half of this outcrop is typical Catskill sandstone. It’s often called bluestone, but it is actually brown to gray. There is a lot of similar sandstones found throughout the Catskills. We would like you to be watching for these stratified rocks as you travel around.
That sandstone was once sand and that means there must have, long ago, been an environment of deposition that accumulated this sediment. What was it? Geologists have been studying these sandstones for more than a century and they have concluded that these sands were deposited in the channels of ancient rivers. When you find a thick sandstone of this type, we would like you to pause in front of it, and imagine the currents that once passed through right where you are standing. Hold your hand up and feel those long-ago currents; you are now using your mind’s eye, and you have traveled into the distant past; what geologists call the deep past.
How old are these sandstones? Geologists have been collecting fossils in the Catskills for almost two centuries. The ages of these fossils goes back to a time called the middle Devonian. That makes these stratified rocks roughly 380 million years old! Can you imagine anything being that old?

The strata at the bottom of our photo are red shales. The key is the color. This sort of red is an iron oxide, typical of an ancient terrestrial setting. These shales were originally muds and they were deposited in what geologists call overbank settings. That means these red shales were the soils on the floodplain that our river flowed across. All around the world today we see similar red soils. They are almost always found in tropical settings; you will see a lot of such soils in the Amazon and Congo Basins. So, now our typical Catskills outcrop has brought our mind’s eyes onto a Devonian age, tropical floodplain, watching a river flow by. But, why is this a delta?
Geologist have found that these Catskills sediments lapped up against the western Appalachian sequence. These, the rocks of New England, are the roots of an ancient mountain range. These were not the Appalachians; instead geologists call them the Acadians. It is estimated that these Acadians were, back during the Devonian, between 15,000 and 30,000 feet tall. Only the Berkshire and Taconic Mountains remain; what happened to the rest?
They eroded away.
These lofty mountains were destroyed by weathering and erosion, and their bedrock crumbled into enormous quantities of sediment. That sediment was transported by sizable rivers and it came to be deposited on something called the Catskill Delta. The delta was spread out west of the Acadians. And it is that delta, now petrified, that makes up the Catskills where the Mountain Eagle can be read.
Contact the authors at randjtitus@prodigy.net Join their facebook page “The Catskill Geologist.”

The Hoogeberg Range Feb. 14, 2019

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The Hoogeberg Range
On the Rocks – The Woodstock Times
Updated by Robert and Johanna Titus

We often use lots of words without having a precise notion of what they mean. English is designed for that as sometimes its words need to have just a touch of (appropriate) vagueness. For example, just what does the word “mountain” mean? There are many good answers to that and each one is different from all of the others, and each one may still be correct. Similarly, what exactly does the word “hill” mean? It gets worse. What does “foothill” mean? Hills don’t have feet, so let’s pursue the issue and do it with a good local example.
The Catskills are often called mountains although many debate that heatedly. Our Catskill Mountains have foothills and some of those are very close to Woodstock. The foothills that we are speaking of are the hills of the Hoogeberg Range. If you have never heard the term that’s quite excusable, the Hoogebergs are not great or famous peaks.

 

The Hoogebergs are a series of small hills lying parallel to the Catskill Front, the great eastern escarpment of the Catskills. They are found just a few miles east of the Catskills and rise to only 600 or 700 feet in elevation. That’s merely a third of the elevation of the Catskills themselves. Thus, they are adjacent and parallel to Catskills, but short. They are like a practice run before the big mountains, hence the term foothills. You can see the Hoogeberg Range if you drive north on the Kings Highway (Rt. 31), south of Saugerties and Rt. 32, north of Saugerties. The ridge looms to your left (west). It forms a fairly impressive horizon.
You can easily go and see the rock that makes up the Hoogeberg Range. There are several locations where there are gaps in these hills, and they let you drive right through the bedrock. Rte. 212 cuts through at the village of Veteran, Rte. 32 cuts through at Quarryville and the Glasco Pike cuts through at the village of Mt. Marion. In each of these locations there are fine exposures of the bedrock right along the road.
What is the Hoogeberg and why is it here? Visit the Rte. 212 exposures and you will observe some very fine, thick, rugged sandstones. These are tough rocks and they have resisted the efforts of weathering and erosion. To the east and west, softer rocks have eroded away, and as they did the Hoogeberg came to be sculpted into a series of hills. These sandstones belong to a geological unit called the Mt. Marion Formation. It is mostly this sandstone and it makes up the Hoogeberg Range. Park along Rte. 212 here and poke around for a bit and look the sandstones over. You may find the fossils of some marine shellfish. That tells us a lot. The Mt. Marion sands accumulated at the bottom of an ocean, sometimes called the Hamilton Sea. The sands once made up the floor of that sea.

At the Glasco Pike exposure you will learn more about the Mt. Marion and the Hoogeberg. This outcropping is at the bridge which crosses Plattekill Creek. The lower levels of the exposure are mostly black shale. Up above, however, those sandstones make their appearance. We talked about this in an earlier column. This sequence of strata records a transition from an offshore, deep water setting to a nearshore, shallow ecology. The offshore accumulated muds that hardened into the shales while coastal sands would eventually harden into the Mt. Marion sandstones.
If you look carefully you may notice that the strata at these locations are not perfectly horizontal; they dip gently to the west. These rocks were all here during the late Devonian time period and they were involved in crustal tilting that was part of a mountain building process, then going on in New England. The tilting of these resistant strata raised those sandstones and exposed them to erosion. They responded by eroding into the hills we see today. The tilting accounts for much of the form of the Hoogeberg. Its west-facing side is generally a gentle slope, reflecting the original tilting, while the east-facing front was eroded into a steep slope, often a cliff.
Crustal tilting, shallowing seas, ancient shellfish, there’s a lot of history in these pretty little foothills and they do make up a significant feature in our local landscape, even if they are just foothills.

Contact the authors at randjtitus@prodigy.net. Join their facebook page “The Catskill Geologist.”

Honk if you love reefers Feb. 7, 2019

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Honk of You love Reefers
ON THE ROCKS – The Woodstock Times
May 21, 1998
Updated by Robert and Johanna Titus

We geologists owe a great deal to the highway departments. It is necessary for them to cut great slashes into the hills and mountains so as to allow the passage of roads. And thus it has been that they have, especially since the 1950’s, been providing us with thousands of beautiful exposures of bedrock. Many of these are quite impressive – great, towering cliffs of rock, rising above the passing traffic. They are like magnets to geologists, they lure us to stop and explore.
Rte. 209, south of the Saw Kill, displays one of the area’s better exposures. It’s a very impressive cliff of black stratified rock. The beds of rock here are called the Mt. Marion Formation. That’s one of the area’s more important units of rock. It’s a big, thick sequence of sandstone and shales; the beds piled up to a thickness of about 500 feet. Not surprisingly, these are the layers of rock that make up Mt. Marion itself.
The sedimentary rocks of the Mt. Marion Formation record a distant moment in the history of this region. They were deposited as black muds and dark sands at the bottom of the relatively deep ocean that once existed throughout all of eastern New York State. But that was about 380 million years ago.
As we said, these exposures are irresistible magnets for all geologists, and we are no exceptions. We drove down Rte. 32 and turned onto the Rte. 209 ramp and took a nice slow drive along the great exposure. It was well worth the effort; our luck was very good.
Practically the very first thing that we noticed was a fine specimen of a fossil coral. That was a big surprise, as we had never imagined that this would be a place to search for corals. We usually find fossil corals in limestones. Limestones record ancient shallow, tropical seas, places ideal for corals to grow and flourish. In such locations, corals grow into the great colonies that we know as coral reefs. Each reef is composed of thousands of individuals living together in a single colonial skeleton. But as we looked up at the strata of the Mt. Marion Formation, we could not imagine such an image for this unit of rock.

Black shales and sandstones are different from limestones. They accumulated on murky, dark sea floors, places not usually well-suited for corals. But the corals we found here were not the regular run of the mill forms; these ones are known as horn corals. Horn corals are, as the name implies, uncanny duplicates of the horns of cattle. They are widest at the top and taper downwards to a point. The specimens we had collected are probably called by the Latin name Cyathophyllum. They would have been pretty well-adapted to life on the dark, muddy sea floor. We suspect that they grew upwards so that their sharp pointed bottoms stuck into the mud like golf tees. Their wide openings would have projected above the sea floor and they would have avoided being clogged with mud.
Corals are predators of sorts; obviously they do not stalk their prey. Instead they are known as “awaiters;” they lay upon the sea floor and wait for some unwary prey to come by. They have tentacles that capture their prey and pull these victims into their gullets for digestion. That’s not a very exciting life, but it works well; corals have been around for about half a billion years and they are likely to be around for another similar length of time.
And, so it was, as we drove along the black shales of Rte. 209, that we imagined ourselves at the bottom of an ancient sea. All around us, on a dark muddy bottom, lay numbers of horn corals with their light colored, fleshy tentacles waving back and forth at the surrounding waters, each one grasping greedily in hopes of food. There is certainly a great difference between the world as it is, and the world recorded in the strata.
Contact the authors at randjtitus@prodigy.com. Join their facebook page ‘The Catskill Geologist.”

Juxtaposition Jan 31, 2019

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On The Rocks
Dec. 6, 2007
Updated by Robert and Johanna Titus

Geologists are generally very good at spatial relations. There must be some lobe in the brain that functions to give us a special edge in that facility. We need it; we are always envisioning the many complex geological structures that we come across. But there is more; there is, after all, a fourth dimension and that’s where geologists are very, very good. Come along and see.
Let’s take Rt. 9W down to the malls, just north of Kingston. You might not think this would be an attractive field trip site for a geologist, but you just might be wrong. At the south end of the malls, just across from the Red Lobster, the road forks. We were down there on Black Friday and soon we found ourselves, armed with a camera, risking our lives for you the readers of the Woodstock Times.
Black Friday is certainly quite a moment in time. Hoards of avaricious shoppers descend upon all those retail outlets, determined to begin their annual rites of Christmas shopping. The highways are crammed with traffic and that is where we found ourselves. We stood, precariously perched on a supposedly safe set of double orange lines, with traffic streaming by on both sides. Oblivious to our near certain doom we looked south: and into the deep geological past.
Just where the highway forks, between the two lanes, is a very fine outcropping. Beyond, and off to the left, was another equally impressive ledge of rock. These were exposures of the Helderberg Limestone, one of the most important units of rock in the area. We said we were looking into the past, and what we saw there was the Helderberg Sea.

Back, just a little more than 400 million years ago, during the Devonian time period, this was a very different place. There were no malls and no highways back then. What there was here was ocean. This Helderberg Sea was a very shallow, very tropical sea. Today you would have to visit the Bahamas or west Florida to find something akin to this.
But we were not in the Bahamas and we were not even of this time. For us, it was the Devonian and we were gazing across the shining, aqua-colored waters of the Helderberg Sea. Its shallow seafloor was visible from above. We looked down and saw just a few strange shellfish and fronds of algae waving in the active marine currents. The sediment was composed of calcium carbonate, a mineral those plants and animals secreted.
That sediment long ago hardened into limestone and that is the rock exposed across from today’s Red Lobster. We were back in the present, and noisy Black Friday traffic streamed by us. We had the presence of mind to shoot a couple of photos. Then we noticed something about the stratification; it was tilted, with the beds of rock inclined to our right. The same was the case with that second outcrop, just a little farther down the road. Then we were swallowed up into the past once again, this time it was to a different past.
All around us was total darkness, but we could see, we just don’t know how. We were still in exactly the same place where we started our journey, but there was no highway and, of course, no orange stripes. In the spooky darkness before us we could make out the very same inclined bedding we had just been looking at. But now, each of those strata continued upwards, rising far above us. We had traveled forward through time about a hundred million years. The Helderberg Sea was long gone. It had been buried in a mile-thick accumulation of sediment, mostly sand. Then all those sediments had hardened into rock and the whole sequence had been uplifted and tilted.
Above us, for a mile or so, was the bedrock mass of a great mountain range, called the Acadian Mountains. Most of its highest peaks were off to the east in what is now New England. That’s where most of the uplift and folding had occurred, but the deformation in front of us was nothing to sneer at. We were now deep inside a still rising mountain range. It was very much as if we were a mile beneath the surface of today’s Nepal with the high peaks of the Himalayas nearby.
Now we noticed the heat and the intense pressure that comes with burial at such depths. There were some occasional groaning sounds; deformation of the rocks was ongoing. All this could do us no harm for, on this journey, we were the mind’s eyes, and little harm can befall the human imagination.
But living bodies can be run over by cars. We found ourselves back on the orange stripes of Rt. 9W on that busy Black Friday. We took one more photo and scrambled off the highway, still in one piece. Our journey was a fine exercise in spatial and temporal relations; we had seen the Kingston malls of today and we visited the same sites in moments of their distant past. It’s all the same, kind of. We geologists are good at this sort of thing.
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Contact the authors at randjtitus@prodigy.net. Join their facebook page “The Catskill Geologist.com.

Can you fold a rock? Jan. 24, 2019

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Can you fold a rock?
Windows Through Time
Updated by Robert and Johanna Titus
Register Star papers
March 22, 2012

Sometimes we geologists are just as dangerous as bird watchers. Bird watchers are notoriously bad drivers. They will be sailing down the highway when, all of a sudden, some marvelous bird goes flying by. Cross your fingers if you happen to be driving nearby. And, if you are a birder, don’t write us to deny it; we know better!
Well, as we said, we geologists can be just as bad. We too, can be sailing down the highway when, all of a sudden, there is some marvelous outcropping of rock: something we never expected to see. Watch out, we are liable to hit the brakes and come to a screeching halt, with you screeching too.
Well, you can probably see where we are going on this. Recently, we were on driving on Tarrytown Road, off Rt. 32, on our way to a lecture up at the Thacher Nature Center. Just after the road makes a sharp right turn, there was an absolutely beautiful folded mass of rock. This was stratified rock and, specifically, limestone.
Did we say “folded rocks?” We think we did. If you are not a practicing geologist, that may seem like an unlikely notion. How on earth do you fold rocks? Take a look at our photo and see for yourself. It shows the outcropping that we saw. The strata are from the Helderberg Limestone and there they are, folded into a broad curve, an upside down U. Geologists see such folds a lot; we call them “anticlines.”


It must stretch a good 50 feet from end to end. And it must rise up ten feet or so. But how can such a thing happen? Go find the strongest man you know and give him a rock and ask him to fold it. There is not a chance that he can do that, not even with a small thin rock. But there it is, a great mass of folded stratified rock.
We wonder what professional geologists thought of all this, centuries ago when the science was young. They could not have had any ideas, none at all. It must have been such a mystery. That happens a lot in science, right up to this day. We see a phenomenon and we just can’t explain it.
But geology is not a young science; it is a venerable old one. We have been solving our problems for a very long time now and we can explain a lot of them. So, how did these folds occur? The best answer involves the science of plate tectonics. That was the great revolution in geological thought that occurred in the middle 20th Century. We now know that continents and subcontinents can move across the surface of the Earth. North America is sliding west, right now and beneath your feet. It’s very slow so you can never feel the motion, but it is happening.
Starting during the Devonian time period, about 400 million years ago, a landmass named Avalonia was moving westward across an early version of the Atlantic Ocean, sometimes called the Proto-Atlantic. Avalonia eventually collided with North America and that generated a lot of pressure. The stratified rocks of North America came to be squeezed. You can simulate this with a large paperback book. Hold it in your two hands and press. The book will fold, quite likely into an anticline. One hand is North America while the other is Avalonia. It’s a nice easy lab experiment; you are doing science. Well, that is was happened to the strata along the highway.
But our problems are not all solved. We didn’t hit the brakes because we had seen a fold. We hit the brakes because of which rocks were folded. You see, the problem is that there are no other folded rocks in this vicinity. There are lots of outcrops of the Helderberg Limestone all around, but none of them are folded. These strata lie just a little too far to the west to have been folded by the effects of a colliding Avalonia. You can go see this for yourself. Just wander the highways around there and see what you can find. The answer is nothing but flat lying rocks.
We must say that we are flummoxed by all this. How could it be? A lovely anticlinal fold just seems to rise up out of the ground without a proper explanation. We may be flummoxed, but not bothered all that much. In truth, it is nice to still have mysteries. We don’t envy geologists or other scientists of the future. They will have so many fewer problems and mysteries to go out and solve. Or will they? That’s debatable. But we do have problems. We are blessed with lots of them.

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Contact the authors at randjtitus@prodigy.net. Join their facebook page “The Catskill Geologist.”

Closely shaved rocks Jan. 17, 2019

in Uncategorized by

Getting a Close Shave
On the Rocks
Updated by Robert and Johanna Titus

Rockcraft 101 – the Shaved Rock – We occasionally write about a mythical field we call “rockcraft.” There’s really no such thing or the Boy Scouts would have a merit badge and a handbook about it. But if there were a field of rockcraft it could keep an outdoorsman quite busy. Rockcraft would be the use of signs found in rocks to guide you in the woods. Believe us, glaciers would be responsible for a great deal of rockcraft.
Think about what a major glaciation amounts to. In this vicinity, for example, at about 20,000 years ago, there was a sheet of ice about a half mile thick. Imagine the weight of all the ice. Not only is the pressure of that weight bearing down upon the underlying countryside, but there is the frictional drag which comes with the southward movement of the ice sheet. That’s a lot of stress.
It gets worse. The bottom of a glacier is, to say the least, dirty. There is a great deal of silt and sand down there. Also, there are likely to be many cobbles and boulders being dragged along. And all of this material is pressed onto the underlying countryside. It’s no surprise to find out that a passing glacier leaves a lot of evidence behind.

  shaved off rock

There are a lot of glacial phenomena that we like to watch for. One of them doesn’t even have an official scientific name that we have even seen. So, we just call it “shaved off rocks.” This is what happened. Here in the Catskills there are a large number of sedimentary rocks that are rich in small and large cobbles. The rest of the rock is usually a sandstone, so imagine cobbles floating in a matrix of sandstone. When a glaciation occurs, it is normal for a bedrock to become ground down by the sand and silt in the passing ice. The behavior is exactly like what you get with sandpaper, only this process is much more effective; it can grind away inches of solid rock.
When a glacier is grinding away at a sandstone it is eventually liable to encounter some of those cobbles we mentioned. These may become popped out by the moving ice, but they are more likely to be held in place as they are well cemented into the rock. That means that the grinding process will begin to bevel right through the cobbles and shave off their tops. What’s left behind is half a cobble with the top planed off to a flat surface.
That leaves a very distinctive rock outcropping, a sandstone surface with the beveled off cross sections of cobbles upon it. A good place to go and look at such rocks is along the escarpment trail, right at the edge of the Catskill Front. Your best chances of seeing these are at North Lake State Park, just north and south of the lake itself. We have seen some very nice beveled off rocks immediately south of Boulder Rock and also up on Newman’s Ledge (Park maps will guide you to these sites). If you find either of these locations try to imagine the thick sheet of ice that was once here. Then remember that the ice filled up the entire Hudson Valley below.
If there is anything bad about these shaved rocks, it’s that usually you cannot tell which way the ice was moving. That’s not always the case. When the ice was relatively thin, it did not press down as much. Under those circumstances a solid quartz cobble might put up enough fight to resist the beveling at least to a certain extend. That’s when you get something called a “rat’s tail.” A vee-shaped cone of sandstone lays on the protected downstream side behind the cobble and is sculpted by the passing ice. The protected cone points in the direction of flow. We found one of those on the point of rock between North and South Lakes.
Our field of rockcraft is rarely about very important phenomena. It’s, instead, a field devoted to recognizing interesting things in the rocks. Shaved rocks are not terrible important, except as testimonies to the erosive power of a glacier. That’s good enough.
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Contact the authors at randjtitus@prodigy.net. Join their facebook page at “The Catskill Geologist.” Read their blogs at “thecatskillgeologist.”

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