Cold snaps?
The Mountain Eagle, Nov. 22, 2019
The Catskill Geologists
Robert and Johanna Titus

We have seen some pretty cold weather lately. November 12th and 13th witnessed what was called “historically cold weather.” Forecasters warned that this may be repeated, perhaps many times this winter. Specifically, they predict that cycles of cold Jet Stream air masses will pass slowly across North America during this year’s winter. Each pass is expected to bring similar “cold snaps.” Each cold episode can be an alarming event. How many times have you heard people say, “What happened to climate warming?” That’ a fair question, so we would like to give answering it a try in today’s column. Our argument is that there is, indeed, an explanation for this weather, and it may actually be that has been caused because of, not despite global warming. Obviously, we have a lot of explaining to do.
Let’s begin with a short overview of what the jet stream is. In North America the jet stream is a massive, high-altitude eastward flow of air lying at the boundary the Arctic and the Mid Latitudes. The stream typically undulates up and down through broadly prominent ridges and troughs. See our first illustration. It’s the temperature difference between the cold Arctic and warmer Mid Latitudes that drives the jet stream; the greater the difference, the faster the jet stream. That difference drives the cold troughs and warmer ridges across America. That brings a lot of weather to us, especially as it did in what came to be called “Novembruary.”

Normal jet stream, Illustration courtesy of Wikimedia Commons.
In recent decades there has been a consistent and pronounced warming of Arctic realm climates. That’s something we remember that climate scientists predicted at least 30 years ago. At the same time the mid latitudes have only warmed a little, so the differences have been greatly reduced. That has, as would be expected, slowed down the movements of those ridges and troughs. What results is a lot like what happens to auto traffic when it is slowed down. The cars behind catch up with those in front. The ridges and troughs become slower and more closely spaced. But there is more; in order to keep all those air masses moving, both the ridges and troughs must become more expansive. See how, in our second illustration the ridges and troughs are so accentuated. We call this a higher amplitude.

High amplitude jet stream. Courtesy US Geologic Survey
Each trough is a mass of slow moving very cold weather. Just what we saw in middle November. Each trough becomes at least a few days of very cold weather. Each expands far to the south and spreads across a vast expanse of our continent. We all, especially in the south, find this most unsettling. But, as you can see, it’s all a very explainable phenomenon. We think it is something that you should understand.
In the end we are hoping that you will pay more attention to the jet stream part of your local weather forecasts and have a better understanding of what they have to tell.

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

The top of a nose, the bottom of a lake?
The Catskill Geologists, The Mountain Eagle 2018
Robert and Johanna Titus

We certainly hope to be writing large numbers of columns for the Mountain Eagle. And, over and over again, we plan to take you on journeys into the past. Our strategy is simple; in each column we will be looking at a modern landscape somewhere, and at the same time, gazing into that location as we think it was thousands, and even hundreds of millions of years ago.
Let’s start today. We would like to take you up the trail that ascends Vroman’s Nose in Middleburgh. It’s a moderate climb and most of you can do it. In fact, we are guessing that most of you have done it. We want you to be watching for exposures of bedrock along the way. If you find a good enough one, then you are likely to see flat lying strata. Each stratum was once a horizon of sediment that had been deposited at the bottom of an ocean called the Catskill Sea. It’s flat because sea floors are almost always perfectly flat. Those sediments are about 375 million years old; that’s how long ago the Catskill Sea existed. Reach out and touch one of those strata; you are literally touching the bottom of that ancient sea!

That’s some pretty interesting geology all by itself, but it’s not the main focus of our story today. Keep going up the trail. When you get to the very top, you find yourself on a great flat ledge of bedrock; it’s called the “dancefloor.” This cliff overlooks the valley of Schoharie Creek. We want you to look south, down to the bottom of the valley; that’s where our story is. It is awfully flat down there. It’s even flat as set by the standards of river floodplains. But it is not a floodplain. It is, in fact, the bottom of an ice age lake.
Now, our journey into the past has begun in earnest. We still stand atop Vroman’s Nose, but we have traveled about 15,000 years into the past. We are witnesses to the final phases of the Ice Age. There had recently been a substantial glacier filling the whole valley. Look down there and, in your mind’s eye, fill the valley with ice. But now the climate has been warming and that ice has been melting away; the valley glacier has been melting back to just about where Middleburgh is today.
All that ice fills the valley and acts as a dam, plugging the Schoharie Creek Valley. That dam has blocked the flow of Schoharie Creek and the valley below us has filled with water – creating a lake. The lake has a name; geologists call it Glacial Lake Schoharie. It stretches out before us, extending as far as we can see to the south.
That makes it a very large lake and it is a deep one too. The bottom of the lake is at 600 feet in elevation and the top of Vroman’s Nose is at 1,200. We are looking down 600 feet into the deep, dark bottom of a very substantial lake. We promised you, right at the start, that we would be looking into the past. We think we have kept our promise.
When you get a chance, why not climb Vroman’s Nose and see it as we do.

Contact the authors at randjtitus@prodigy.net. Join their facebook page “The Catskill Geologist.” Read their blog postings at “thecatskillgeologist.com.”

Glacial Lake Albany
The Greenville Press; Mar. 20, 2003
Updated by Robert and Johanna Titus

The upper Hudson Valley is a very picturesque region. Most of us take at least a little time to wander around and just plain enjoy the scenery. That includes us but, as geologists, we have the privilege of seeing the world around us in more than just one way. Just like you we see the scenery all around as it is today and, as we said, that is very nice around here. But there are two other landscapes that we are very fond of enjoying. One of those is the landscape preserved in the rocks. Whenever we see an exposure of the local bedrock, it takes us back to a Greene County of long ago. And we mean very long ago; we are witness to the landscapes and seascapes of hundreds of millions of years ago. These rocks are time machines that really can transport us, in our mind’s eye, to those distant eons. Then there is still another vision of the past, that’s the one preserved in today’s landscapes. We geologists call the science of landscape geomorphology and when we study our landscapes, we see the scars of the past. When you learn to read landscape, you learn to read history. It’s a history just a little less ancient than that preserved in the rocks, but just as fascinating.
Here in Greene County, if you know what to look for, there is a fine record of a wondrous geological event of the recent past. That event is one of the most remarkable discoveries in the history of geology: The Ice Age. A mere 20,000 years ago the whole Hudson Valley, including Greene County, was in the grips of a great glaciation. Thousands of feet of glacial ice lay upon our landscape, and that certainly includes right where you are today. The best evidence for that event is in the lay of the land, and you might be surprised to learn that it is in the most inconspicuous part of the landscape. A great deal of eastern Greene County is made up of very flat land. That’s the swath of land lying within five miles of the Hudson River. That’s pretty much everything east of the New York Thruway, much of it is traversed by Rte. 9. we are not talking about a flatness to rival Iowa, but we are talking about a reasonably widespread flat landscape. Pay attention as you drive around just east of the Hudson and see if you notice this yourself.
A level landscape may seem monotonous, but we have to be careful here. What does all that monotony represent? The answer is that this is the floor of an old lake. It was a very big lake and it dates back to the end of the Ice Age. Wherever you are, we would like you to go outside and look north. In your mind’s eye we would like you to see a great glacier in that direction. It towers hundreds of feet above the horizon and stretches off to the east and west. It dominates the landscape, but this is the end of the Ice Age and it is melting. Great volumes of meltwater are cascading off of it.

     
Glaciers are heavy, so heavy that they actually press down on the land and cause the crust to sag beneath them. Back then our Greene County had been glacially depressed by about several hundred feet. That created a basin and that basin was kept filled with the very cold waters flowing out of the melting ice. That’s our lake. It’s called Glacial Lake Albany and back its waters stretched south most of the way down the Hudson Valley.
Lakes accumulate sediments, mostly clay, silt and sand, and our lake was no exception. In fact, our lake accumulated very thick sequences of sediment at a very rapid rate. The sediments here are at least scores of feet thick and probably even more than that. Lake sediments are spread out by lake currents and that makes for flat lake bottoms. When the waters drain away, those old lake bottoms are left, high and dry, as flat landscapes and that is what you will see throughout eastern Greene County.
How deep was the lake? Geologists can’t help but ask that question. We found that the bottom of the lake in Leeds was at an elevation that is today 150 feet. The shoreline of the lake can be determined where the flat lake bottoms disappear. The shorelines appear to be at about 220 feet and therefore the lake must have been about 70 feet deep. That’s a preliminary figure; we have a lot more research to do here, but that’s a lot of lake.
There were islands in this lake as well. They are hills now, rising above the flat old lake bottoms. The western side of the city of Catskill is an old island. So too is Flint Hill, a site famous as the site of an Indian flint making industry. You should try to get used to this as you travel around eastern Greene County. You will soon become comfortable with the flat old lake bottoms and, after that, you should soon find it easy to “see” the old islands. It makes a difference in how you see this region.
Lake Albany did not last all that long, perhaps only for centuries; we are not sure. With time the glaciers melted away to the north. With their weight removed the landscape rebounded; it physically rose upwards a couple of hundred feet. With that, the waters of Lake Albany were unceremoniously dumped down the Hudson and into the sea. Eastern Greene County returned to its normal condition as a dry landscape. But it had been changed, as the old lake bottoms were left, mostly undisturbed. In the thousands of years that have passed by since then, local rivers have carved their valleys into the old lake bottom and a lot of that flatness has been lost, but much or most of the lake bottom is still here to be seen.
Again, we would like you to notice this. Please do watch for those long flat stretches of landscape as you drive around. We like the stretch of Rte. 9 for the five miles south of Coxsackie. You will notice a lot of flat land here. Pick a good place and then stop, get out of your car, look up, and return to the past. High above, you can see the Sun’s rays shining through the surface waters of the lake. As waves pass by above you, the sunlight sparkles in the choppy waters. Here and there, you can observe the undersides of small drifting cakes of ice, tiny icebergs, searching vainly for tiny Titanic’s. Now look around you and see the ancient lake bottom as it was. The muds lie silently at the bottom of the lake. There are few currents this far down. It is mostly very cold and very dark down here. Our journey to the bottom this glacial lake is merely a fleeting journey of the imagination, but it should give you a very different impression of eastern Greene County, and take you, perhaps for the first time, into the geological past.

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

JIMMY DOLAN NOTCH
On the Rocks, The Woodstock Times
Nov. 9, 1996
Updated by Robert and Johanna Titus

The fair-weather hiking season begins slowly. In April the first clear, dry, warm days lure us out into the mountains. We take a professional interest in that time of the year; there are no leaves yet and we can see all the bedrock exposures very well. As the weeks advance the foliage appears and the green, even if it does hide the rocks, adds much to the views. The richness of the color increases until late August which is gorgeous with its dense botany of spinach green. Nature seems to celebrate its own bounty at that time of the year. But it gets even better as autumn approaches. Now nature deems appropriate a grand and glorious climax to the season. There is a brief but intense explosion of color like the end of a long fireworks display. What hiker can resist this seasonal finale?
And, so it was, in the middle of October, as the foliage hit that climax, that we had the opportunity to accompany a small group from the Adirondacks down for their first hike into the Catskills. Our goal was Twin Mountain. This peak, being right in the heart of the Catskills was a natural choice for newcomers.

As luck would have it, this long-planned hike fell on a perfect autumn day. We began our ascent at the Prediger Road trailhead and soon entered into the forest preserve. The trail takes you up along an unnamed creek to a fine gap in the mountains called Jimmy Dolan Notch. From there we turned west and continued up the slope of Twin Mountain itself. A final 500-foot climb took us to the top of the easternmost of the two summits that collectively make up Twin Mountain. There before us were the southern Catskills in full autumnal regalia. To the east was Plattekill Clove, to the southeast was Overlook Mountain, and to the south was Cooper Lake. On the distant horizon was the Burroughs Range, with Slide Mountain reaching the highest. But it was to the southwest where the slopes of Olderbark Mountain could be seen that we found most picturesque scene. The whole autumn season could be seen there. The lower slopes of Olderbark were mostly green; it was still September down there. Above, the slopes steepened and graded into a yellow gold, and there it was October. From there to the top, the mountain was brown and then gray. There it was already November and the leaves were gone.
The top of Twin Mountain made for a wonderful stop before pushing on and we enjoyed the view as much as any landscape artist might. But geologists never go off duty and we had seen something on the way up which gave our mind’s eye a very different view of this landscape. Jimmy Dolan Notch was peculiar; it was asymmetric. The northern slope to the notch was steep but unremarkable. The southern slope was different. Looking south through the notch, there is a lovely view of the mountains beyond, but the view is through a surprisingly vee-shaped notch. This vee had caught our eyes, and on the way down, we explored it. It was the kind of notch usually carved by a powerful whitewater stream. We could easily imagine loud, raging, foaming currents passing down the mountain here. But there was no stream and no evidence of one. And where could the creek have come from anyway? Whitewater streams are common on the lower slopes of mountains, but not at the tops; there is no source of water up there. Then we found a theory to explain what we were looking at.
About 17,000 years ago a massive ice sheet abutted the central Catskill Mountains along a line that extended from Plattekill Mountain to Twin Mountain to Stony Clove and then westward. It’s been called the Wagon Wheel ice margin. Some of the ice probably poked its way through Jimmy Dolan Notch, but then, as the climate warmed, it began melting. As we turned north and looked back through the notch, we could now “see” that great ice sheet rising just a little higher than the notch itself. It glistened wet in the sun that was melting it. Between the ice and Twin Mountain was a small meltwater lake. From it, water was cascading through the gap. There was the whitewater stream that we had needed to explain our landscape problem.
Such beautiful but different scenes at the same site and at the same moment: we looked south through Jimmy Dolan Notch and there was a perfect golden autumn afternoon. Then we turned north and looked through the notch to see an ice age vista during one of the high points of glaciation. Twin images at Twin Mountain.

Learn more about Catskill glaciers in the Titus’ new book The Catskills in the Ice Age, the expanded and revised 3rd edition from Purple Mountain Books and Black Dome Press.
Contact the authors at randjtitus@prodigy.net. Join their facebook page “The Catskill Geologist.”

WHAT’S REALLY BURIED IN THE COLONEL’S TOMB?
On the Rocks
The Woodstock Times, Oct. 24,1996
Updated by Robert and Johanna Titus

Prattsville, along the banks of the Schoharie River, is steeped in Catskills history. It’s emblematic of the most progressive aspects of the area’s story, and at the same time, it represents many of the mistakes people made as our region developed. Zadock Pratt was the towering, overwhelming personality in the town’s development. Even today his influences permeate the village.
Pratt was a founder of the Catskill tanning industry. From 1833 to 1846 his Prattsville tanneries turned out shoe leather for the New York City market. His tanneries, however, were dependent upon the bark of the hemlock tree, and when they were all cut down, the industry closed. We frown upon the wanton destruction of the Catskill hemlocks that characterized the 19th century, but our collective wisdom is based upon a history of trial and error. It was men such as Pratt who provided the errors.
But Pratt is also remembered for progressive attitudes toward urban planning. His Prattsville was a pioneering model in that field. Pratt laid out the streets, built the Greek Revival homes and planted the 1,000 trees that lined the village streets. Pratt founded churches and the town’s academy as well. Prattsville today is still truly Pratt’s town.
Zadock Pratt was a great man, but we suspect that history would have mostly forgotten him except for the one singular act of vanity that he was responsible for. Pratt, the Rameses II of the Schoharie, is remembered for Pratt Rock, his would-be tomb.

Pratt Rock consists of a series of stone carvings on a glacially plucked cliff along Rte. 23, just east of town and overlooking the old Pratt farm. The site is now a town park and open to visitors. You can hike the winding path up the steep slope toward the main carvings. If you tire along the way you can sit upon stone seats thoughtfully carved into the mountain. The main level of carvings displays images and symbols of his life. There are carvings of the hemlock tree, a horse which hauled the bark to the tanneries, a strong arm to do the work and other emblems of the great man’s life. There is a bust of Pratt himself and a poignant carving of his only son who died in the Civil War. Then there is the Pratt burial chamber itself.
Unlike the pharaohs, Pratt was never buried in the grotto carved out for him. One story is that the chamber was unsuitable for burial as it leaked water when it rained. The chamber is still there, and when we looked it over, we found that there may be some truth to that tale, along with a good geological story about Pratt Rock.
Pratt Rock is carved into sedimentary strata from the old Catskill delta. Deposited nearly 400 million years ago, the sediments here record the coastal regions of a delta similar to that of the Mississippi River today. This was once the coastline of the old Catskill Sea. Rivers flowed across this location and poured their waters into the old ocean.
There is a lot of history here. We had little trouble finding bits and pieces of the old Gilboa forest, and we could picture its foliage along the old stream banks. But the most interesting horizons we found were those at the burial chamber itself. The ceiling of the chamber is made up of inclined strata. This horizon of rock formed on the floor of an old stream channel. The beds slope down to the right, which was once one side of a river, and farther along the outcrop they rise up again on the other shore. When we looked at the chamber ceiling, we found a horizon rich in a hash of broken plant remains. This stratum is likely very porous and it’s quite possible that this accounts for the leakage that caused the burial project to be abandoned. The pharaohs of arid Egypt faced no such problem.
And so, this is one of the many ironies of geology. The great Zadock Pratt is buried in a nearby graveyard with all the other common folk of old Prattsville. That may be because about 375 million years ago some small river made a wrong turn. It’s not Pratt buried in Pratt’s tomb, but the sands of an ancient river!

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

A River of Rock
The Greenville Press
Updated by Robert and Johanna Titus

One of the most scenic descents out of the Catskills is along Rte. 23, downhill from East Windham. To your left is the vast expanse of the upper Hudson Valley stretching, it would seem, forever. We enjoy a good view as much as anybody, but when we travel along this road, today’s scenery has to compete with an ancient one. There are a many excellent, large exposures of bedrock along the way. They are all of an eye-catching red and thus are typical Catskill lithologies.
Brick red is the emblematic rock color of the Catskills bedrock. It is the color of the red soils and sediments that accumulated on the great Catskill delta complex of the Devonian time period. In your imagination, take yourself back almost 400 million years to the Devonian time. All around you are the low swampy bayous of a great delta. It’s an ancient version of Louisiana. To the east a great mountain range rises above the horizon. This is an ancient version of the Himalaya. There is a lot of imagery in these old Catskill Delta deposits and this stretch of Rte. 23 may be one of the best locations to learn how to interpret them. And, of course, we don’t just mean learning to make cold scientific judgments about the rock, but to really travel through time to this place as it once was.

Heading up the road from the south, watch for the Cornwallville Road. Just past it is a parking area with a fine panoramic view to the northeast. The view certainly deserves some attention, but we are here to see the rocks. Across the road and between 0.1 and 0.2 miles farther uphill is a fine and very typical outcropping of the Catskill Delta. As you approach it, watch for two striking channel-form structures (A&B on picture). These are actually the cross sections of two Devonian rivers, stacked one upon the other. The upper channel is composed of massive beds of sandstone, the very sands that filled the old channel. This channel eroded its way into an even older channel (A); the lower one is composed of thinner-bedded sandstones. At the bottom of this river of rock can be seen a deposit of gravel (C), it was carried here by strong currents and left at the bottom of the channel. To the right is a steep bank margin (D), this was probably the erosive side of the river. Beyond that is a sequence of red sandy shales (F). These sediments accumulated upon the floodplain, probably during floods. Floodplain deposits, of our Devonian time, were turned red by oxidation. That’s common throughout the Catskills and the origin of that brick red color that I extolled earlier.
To the left of the channels you might notice some dark, sometimes rusty-looking horizons (E). These strata are thinly bedded, just laminations. Dark sediments, like these, were never oxidized, they were waterlogged instead. Floodplain organic matter was preserved and darkened the beds. This appears to be a floodplain swamp. Below it you can see a peculiar horizon. It has an olive color with many blotches of yellow and green. This has been interpreted as a fossil floodplain soil.

 
Think about what is here. This is an ancient river and floodplain. The channels, river banks, floodplain soils and swamps are just as real now as they were about 375 million years ago. Back then, however, this was a living environment, composed of soft sediments and inhabited by green plants and breathing animals. Today that’s all still here; it’s just been converted into a stone sculpture. What we see is just the surface exposure, a fragment of what is truly here. The rest must be imagined. Beyond our seeing and buried in the mountains, an ancient river of rock flows through a stone landscape. The river, a meandering ribbon or rock, reaches westward, today as it did in the Devonian, and flows into a buried ocean of rock.
All this is routine for geologists. We approach outcrops expecting to be transported to some ancient habitat. We grow accustomed to this, but we never forget what a miracle it really is.

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

A Shallow Sea
The Cooperstown Geologist
Updated by Robert and Johanna Titus

Geologists are deductive scientists. We go out and study outcroppings of sedimentary rock with the purpose of gathering evidence of how they came to be formed. The evidence is mostly descriptive; we look at the rocks and see things in them that speak to us of ancient environments. Each small observation leads to a deduction and a series of observations and deductions leads us to broad conclusions. Let’s go out and see how this works.
An especially fine outcrop can be found in Mohican Canyon just west of Lake Otsego’s Five Mile Point. Five Mile Point is a mass of sediment that projects out into the lake. You guessed it; it’s five miles north of Cooperstown. Take Route 80 north until you get there and then turn left onto the road that ascends the hill. On each side of the road you will encounter very fine exposures of rock. The rock is made up of layers; it is stratified. That leads us to our first deduction; layered rock forms at the bottom of the sea. We learned earlier about the Catskill Sea which once covered our region. We have gone back about 375 million years and found that sea once again.
The strata are a mixture of sandstones and shales. We can make more deductions. Shale forms as mud on the bottom of quiet, probably deeper, seafloor. Sandstone accumulates in more active, perhaps more shallow seas. When shale dominates, then we deduce deeper water; when sandstone predominates we can deduce shallower settings. When sandstone and shale are evenly mixed we are in between.
The thickness of the strata helps too. When the beds are thin we can deduce the likelihood of quieter, and probably deeper, conditions. When the beds are thick we can deduce rapid current activity which is associated with shallow seafloors.

The lower stretch of our outcrop is mostly of thin bedded shale. We can deduce that this sequence represents fairly deep water sea bottom. But as we ascend the road, things change. More and more sandstone starts to appear in the outcrop and more and more often the sandstone is thicker bedded. Some sandstone strata are a foot thick.
If you have a chance to take the trip, then start at the bottom and stroll slowly towards the top of the outcrop. See if you can agree with our observations. But what all does this mean?
We need to do a little stratigraphy. That’s the science of stratified rocks and it’s practiced a lot in the Leatherstocking Country. All of our rocks up here are stratified. The rocks at Mohican Canyon are classified as belonging to something called the Otsego Sandstone. That’s a unit of rock which is commonly seen at outcrops in our area. The lower stretch of the Otsego is called the “Otsego A” and the upper part is the “Otsego B.” That’s fairly informal but quite functional stratigraphy and it leads us to our most important deductions.
The sequence here speaks to us of a shallowing sea. During Otsego A times, the Catskill Sea was quiet and accumulated lots of mud. Still water runs deep and that’s the case with the Otsego A; it was a relatively deep body of water. Today, you would have to go quite a distance offshore to get to a modern Otsego A. But time never stops and as our region passed from the time of A to the time of B, the waters of the Catskill Sea were shallowing.
We geologists find shallowing sequences quite often. Our observations and deductions lead us to recognize times when seas were shrinking away. We call such events “regressions” and the one at Five Mile Point is a gem. We are looking at real history here; this actually happened. Once there was a deep beautiful saltwater Catskill Sea here in Otsego County. It spread across upstate New York for an enormous length of time and then it began to disappear. Where did is come from and where did it go? We have just begun our story; we need many more observations and many more deductions.

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

Flocks of geologists
Windows Through Time, The Register Star
June 4, 2009
Updated by Robert and Johanna Titus

Dear Robert and Johanna – I have been enjoying your columns in the Hudson-Catskill newspapers. I have a question. I wonder what so many college groups have been studying at the Leeds exit along Rte. 23? – WJM – Athens

WJM: Thanks for the good question. Over the years we have heard this one from a lot of people. Anybody who frequently drives this stretch of the road in the autumn or the spring will have seen sometimes large groups of college students climbing over the rocks at this site. You will be interested to know that this is one of the great “geological tourist traps” of the American northeast. Any eastern geologist who is anybody in geology has been to this location. I wonder if we even know any geologist who has not been here. So, what is the big draw?
The answer is that this outcropping displays something called an “angular unconformity,” and this one is a very historic structure. Read on and learn about this peculiar feature. If you are going by it sometime soon, you might want to stop and see for yourself that which captivates so many young geologists. If you do, you will see some interesting geology.

The right (east) side of the outcrop displays what are called stratified sedimentary rocks. These are thick horizons of alternating gray sandstone and black shale. Each layer of rock was once deposited as sediment at the bottom of the sea. Back then, these were horizons of sand and mud. That’s a most surprising observation. Look around. Do you see and saltwater here? This does not look like the bottom of an ocean, but it once was. That’s incredible but true.
We see these rocks; we look into their distant past and see the ocean that was once here. It has been a very long time since the earliest geologists figured this out. So long that we have forgotten who first made this amazing deduction. The first person to write these thoughts down was Scottish geologist James Hutton in the 1790’s. This was not only one of the most important discoveries in the history of geology but of science itself. Look around and think about it. You are standing at what really was the bottom of a sea. These strata of sand and mud formed on that long-ago seafloor. Turn a full 360 degrees; hold up your hands and feel the saltwater that was once here. Times have changed!
But there is something else here and it is also important. Notice that the sandstone and shale strata are tilted, they are nearly vertical. When sediments are deposited on the floor of an ocean they are laid down in horizontal sheets. These strata should have stayed that way, but that is not the case here. Again, they are nearly vertical. They must have come to be tilted and that’s where the story gets even more interesting. Think about how heavy these rocks are and how much energy it would take to tilt them. The only processes that can lift and tilt such rocks are those of mountain building events.
These rocks are from something called the Ordovician time period; they are about 450 million years old. That’s when North American was enduring a great collision with an eastern landmass much the size of today’s Japan. You would call it Europe or – better – “proto-Europe.” Collisions, of this sort, initiate chapters of downwarping. The crust folds downward and the seas flood the region. Those seas accumulated the sand and mud that hardened into today’s rocks. Then continued collision came to reverse the whole process and caused a massive mountain building uplift. All this is how those rocks formed, and how they were tilted and raised to above sea level. But, of course, there is still more.
The rocks on the left (west) side of the outcrop are limestones. They formed during a time that is called the Devonian Period and they are only about 420 million years old. They formed in a shallow tropical sea and the rocks are sometimes rich in marine fossils. If you stop here, perhaps you can find a few. This was the bottom of a second ocean!
These too are stratified, but these strata dip to the left. Once again, North America was enduring a collision with another Japan-sized land mass. It was “déjà vu all over again!” Once again, the crust was folded downwards and that is when the limestone formed – in a shallow tropical sea. That downwarping would eventually be followed by another uplift. That’s when the second tilting occurred.
The boundary between these two units of rock is what we call an angular unconformity. The word angular refers to the angle between the strata of the two rock units. The word unconformity refers to the period of period of erosion that followed the first mountain building event and preceded the second.
And that is the centerpiece of what we, and all those college students, are looking at. This is a petrified record of two mountain building events. There is a lot of history here and young geologists come from all over to see it. You can too.

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

Name Your Poison
On the Rocks; The Woodstock Times
Updated by Robert and Johanna Titus
June 18, 1998

Black sedimentary rocks are occasionally seen in the Hudson Valley. Recently [1998], 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 suffered 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 Rte. 23A where it crosses Kaaterskill Creek east of Kiskatom. Go visit that large outcrop along Rte. 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 the authors at randjtitus@prodigy.net. Join their facebook page “The Catskill Geologist.”

Gaps in our Knowledge
On the Rocks/ The Woodstock Times
Jan. 22, 1998
Updated by Robert and Johanna Titus

Take Rte. 28 west from Woodstock, turn right at Dancing Rock Road (it’s two miles east of Boiceville) and go up one mile to the end of the paved road. Look south and, there below, is the Ashokan Reservoir. Above it, on the horizon, is High Point Mountain. The mountain profile is nothing particularly unusual except for one feature. There is a notch cut into the top of the mountain. It is the sort of landscape feature that you pay little heed to; it doesn’t seem all that strange until you look at it carefully and ask a simple question. How did it get there?
The notch has a name: it’s Wagon Wheel Gap. we suspect that the name came from the deep ruts that old fashioned wagon wheels carved into roads before the auto age. The gap is at least 200 feet deep and steep on both sides. It seems to be something cut into the mountain. It was. Not surprisingly this odd landscape feature does have a story to tell and it is a surprising one.
Wagon Wheel Gap is a glacial feature, but different from most. Glaciers are very good at eroding landscapes and they can carve notches into the landscape. But that kind of glacial erosion produces a nice, smooth, U-shaped gap. West Kill Valley is a good example. It’s relatively wide and rounded at the bottom. Stony Clove is narrow like Wagon Wheel Notch but it has been cut right down to the level of the valley. Wagon Wheel Gap is altogether different. There’s nothing broad and round about it. It’s a sharp slash, like something cut by a knife. The bottom of the gap lays well above the level of the nearest valley, in fact 700 feet above. Wagon Wheel Gap seems something quickly and violently cut into the High Point mountain.

The story of Wagon Wheel Gap takes us back about 17,000 years. At that time a large glacier was pushing up the Esopus Creek valley. It passed the present site of the Ashokan Reservoir and pushed on; we are not sure how much farther. This ice did reach a still-stand and then, with warming climate, it began a slow retreat. The warming halted briefly, and the glacier reached another still-stand, just exactly abutting against the present-day gap.
The ice acted as a dam and so it blocked the whole upper Esopus Creek which then filled with a reservoir of cold water. The water had to drain off somewhere and it made its way across the slopes of High Point and drained off to the south. In what had to be a very short period of time, that flow of water cut into the mountain and carved the gap we see today. It’s quite something to imagine. There would have been an enormous amount of water pouring through the gap back then. There would have been all of the normal flow of the Esopus Creek plus all the water provided by the region’s melting glaciers. That’s a lot.
The flow must have positively raged through the Wagon Wheel, perhaps the mother of all whitewater flows. And loud too, a thunderous, pounding cacophony. It must have torn into the mountain with an effect something akin to a buzz saw. At any rate, the flow must have continued while the Esopus glacier retreated down the valley. Eventually the flow of water must have found other ways out of the valley and Wagon Wheel Gap would have been very abruptly abandoned. The whitewater flow would have dried up overnight.
And there it lies today, an abandoned notch, lying there silently in the mountain. It’s a landscape oddity with a colorful past. But how many people know even to notice such a thing. It’s, to most, just a notch in the mountain, nothing of note. What a marvel it is that glacial geologists can come along and understand these things.

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