Time in winter, part II

Windows Through Time

Robert Titus

Feb. 11, 2010

Last week we drove along Rt. 32, pulled over to the side of the road and gazed up at the Catskill Front. We found that, at this time of the year, we could look through the leafless forests and see the rocks so clearly. We became philosophers as we contemplated the millions of years of geological history rising before us.

Let’s look into all this again, and this time let’s understand some of the mechanics of this passage of time. Our key to understanding the rocks comes from understanding the City of New Orleans! Does that surprise you? Read on.

Many of us learned a lot of geology when Hurricane Katrina struck. One of the most remarkable things was that most of New Orleans currently lies below sea level. How could that be? Were people idiots when the city was first founded? Of course not! Three centuries ago, when New Orleans was settled, it lay above sea level. During those centuries it has slowly sunk until now most of it is below sea level. It would have been flooded decades ago except for the construction of manmade levees.

Ironically, the levees may have caused more damage than they were worth. Obviously they weren’t up to the job when the hurricane struck; the city flooded anyway. But there was something else equally important. Floods bring sand down the river and deposit it, spread out across the delta top. That can’t happen if levees get in the way. New Orleans, being surrounded by levees, did not frequently experience flooding, but the city never received the sand that floods would have brought. The city continued to subside, but the sand, which would have kept it above sea level, never got there. That’s an irony!

My point here is that great deltas slowly subside under the weight of their own sediments. As thousands and then millions of years pass by, enormous thicknesses of sand and mud accumulate on them: first hundreds of feet and then thousands. That’s what we are looking at when we gaze up at the Catskill Front. Had there been a city of “Old Orleans” on the Catskill Delta, back during the Devonian time period, then this fossil city would still be up there – somewhere along the Catskill Front.  And it would likely be buried beneath many feet of sedimentary rock. What a strange thought!

But, this is science, and that is where the evidence leads us. When I look up there and see all those ledges of sand, I realize that these are the deposits of great flooding rivers. I see countless cities of Old Orleans and I see countless Hurricane Katrina’s. I go back into time and watch as the old Catskill Delta slowly subsides, and I see all that sediment piling up. Eventually all of these strata sink into the depths. Thousands of feet of new sediments bury the old. The weight of all this is stupendous. And given still more time, and a lot of it, these sediments begin to harden into rock.

Eons of time are now flying by in my mind’s eye and I am nowhere near the end of it. I still have to contemplate the erosion of the Catskill Front to create the wall of rock we see here. Only Nature can do that through the weathering of rock, turning it back into sediment and then the erosion of that sediment. Nature must be very patient. But for a person to stand along the side of the road, to look at the strata above, and see all this is a marvel. These are awesome notions; no wonder a geologist becomes philosophical.

But where did all that sand and mud come from? Now I must stop looking west at that ancient delta and I turn around to look to the eastern horizon. There, in front of me, is the ghostly silhouette of a long lost mountain range. It rises above today’s Taconic Mountains and it dwarfs those puny peaks. The sediments and the sedimentary rocks of the Catskills came from the weathering and erosion of that towering range of mountains, called the Acadians. These may have risen to elevations of about 30,000 feet. I instinctively look up, but they are not there . . . anymore.

   Profile of Acadian Mountains against profile of modern Catskills, Hudson Valley and Taconics

   I look east to west, then west to east. I see 30,000 feet of old mountains (east) having been converted into about 9,000 feet of modern Catskills (west). Old mountains were turned into new mountains. And Nature presents us with a cycle here. That conversion of old mountains to younger mountains will all probably happen again – and then again. It was the English naturalist James Hutton who first understood things such as this. He marveled about time, saying “We see no vestige of a beginning, no prospect of an end.” With his thoughts geology became a philosophical science. Reach the author at titusr@hartwick.edu  Find more at the facebook page “The Catskill Geologist.”

Looking at Time in Winter: Part One

Windows Through Time

Robert Titus

Winter is not always the best season to be a geologist. We do greatly prefer the warm months when we are better able to get out and explore. But there are some compensations. This is the season when, with all the leaves down, we can see so much that will be hidden come next summer. I have in mind a good look at the great Wall of Manitou, the Catskill Front. From numerous sites down in the Hudson Valley you can gaze up at this massive wall of sandstone and shale and see details that are usually hidden.

I stopped along the road down in Palenville and did exactly that, and I was soon able to wax poetic about one of my favorite topics in geology. That would be the enormous lengths of time that we see recorded in the strata. We geologists routinely travel back hundreds of millions years into “deep time.” Much of my own work involves Devonian age rocks which are mostly a bit less than 400 million years old. Much of the rest of my work takes me to ice age deposits which are a mere 15 to 20 thousand years old. We geologists get to be a little jaded with all this. What’s a couple of hundred million years in a universe that is more than 14 billion years old? Still, sometimes it is nice just to go and “look” at all that time. That’s what I did in Palenville.

If you get the chance, please do the same. Follow Rt. 32 and pull over someplace where you can get a good view of the Catskill Front. I picked just south of the intersection with Rt. 32B. Gaze up at wall of rock and really appreciate what is before you. There are about 2,000 feet of stratified rock up there and all of it was, originally, sediment. The strata that you can see clearly are layers of sandstone; they make up those many horizontal strata. That’s sturdy stuff and it has held up well in the face of eons of weathering and erosion.

What you can’t see is what lies in between the sandstone ledges. That would be mostly red shale. Shale was mud to begin with and that makes it pretty soft stuff. Nature has little trouble with shale; she likes to erode it away and she is good at that, turning it into soil. So you rarely get to see shale in steep slopes like this. They are there, but they are buried in their own soils.

So, we have a pattern here. There appear to be countless horizons of sandstone, interbedded with equally countless horizons of shale. All were once soft sediments. Layers of sand alternated with layers of mud. And there before us are about 2,000 feet of all this, all deposited one stratum at a time. How long did it take? Well, that’s my main point today: it took a very long length of time!

Geologists estimate that the Devonian time period stretched from 419 to 359 million years ago. What we are looking at here is perhaps about a fifth of the whole. That suggests that what we are looking at are about 11 million years. My estimate is very rough so I will ask you pay it little heed. But we are certainly dealing with millions of years of time, and in Palenville you are looking at all of them.

For all of those millions of years our region witnessed the steady accumulation of layers of sand and layers of mud. Many of these sediments are red and that indicates that they were terrestrial in origin. The red is the mineral hematite and that forms only on land. The sands accumulated in stream channels; the mud of the shale formed on floodplains. This was a great delta, called the Catskill Delta.

You stand along the road, you gaze up, and you are looking at the cross section of something akin to the Mississippi Delta. Imagine if some enormous creature could slice 2,000 feet into the southern reaches of the Mississippi delta. If that giant then peeled away the earth, it would expose a cross section of the sediments of that delta. Those sediments are probably all still soft; they have not yet hardened into rock. But, in every other respect, our slice of Louisiana would look exactly like what we see here.

I spoke of waxing poetic before, and I guess that a person can actually get that way when he contemplates such thoughts. I could have spoken of waxing philosophical and that might be appropriate. We geologists do find all of this very spiritual and maybe that is the best word of all. Reach the author at titusr@hartwick.edu  or at https://thecatskillgeologist.com

Colonel Pratt’s Pyramid

Windows Through Time

Robert Titus

Columbia/Greene Media

July 23, 2009

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 history, and at the same time, it represents many of the mistakes people made as our region developed.

Zadock Pratt was the towering 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 on the bark of the hemlock tree, and when all of those trees were cut down, the industry closed.

We frown upon the wanton destruction of the Catskill hemlocks that characterized the 19^th Century, but our collective wisdom is based up 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 effort in the field. He laid out the streets, built the Greek Revival style 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 I suspect history would have mostly forgotten him except for the one singular act of vanity he was responsible for. Pratt, the Rameses II of the Schoharie Creek Valley, is remembered for Pratt Rock, his would-be tomb.

Pratt Rock consists of a series of stone carvings on a glacially cut cliff along State Route 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 up stone seats thoughtfully carved into the rocks of the mountain.

The main level of carvings displays images and symbols of Pratt’s life; there are carvings of the hemlock tree, a horse which hauled the bark to the tanneries, a strong arm to do the work, along with other emblems of the great man’s life. There is a poignant carving of his only son, who died in the Civil War. Then there is the Pratt burial chamber, the point of it all.

                                                         Pratt Rock

   Unlike the pharaohs, Pratt was never buried in the grotto carved out for him. One story is that the chamber was rendered unsuitable for burial by the fact that its roof leaked when it rained. The chamber is still there, and when I looked it over, I found 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, back and forth, across this location and emptied their waters into the old ocean.

There is thus a lot of geological history here. I had little trouble finding bits and pieces of the old Gilboa Forest, and I could picture its foliage along the old stream banks. But the most interesting horizons I found were those at the burial chamber.

The ceiling of the chamber is made up of inclined strata. These horizons of rock formed on the sloping floor of an old stream channel. The beds slant down to the right, away from which was once one side of a river, and farther along the outcrop, they rise up again onto the river’s other shore. When I looked at the chamber ceiling I found a horizon rich in a hash of broken plant remains. This stratum is likely porous and it’s quite possible that accounts for the leakage that caused the burial project to be abandoned. The pharaohs of arid Egypt faced no such problem.

                                           The burial grotto, at bottom

   And so it is that this in one of the many ironies of geology. The great Zadock Pratt is buried in a nearby graveyard with all the common folk of old Prattsville. That indignity may be because about 380 million years ago some inconspicuous river made a wrong turn. It’s not Pratt buried in Pratt’s tomb, but the sands of an ancient river! Contact the author at titusr@hartwick.edu Join his facebook page The Catskill Geologist.

The lengths of time

Windows Through Time

Robert Titus

Columbia/Greene Media

July 9, 2009

One of the most scenic wonders of our region is Kaaterskill Clove. It is a breathtakingly beautiful canyon cut right into the Catskill Front. It is the sort of landscape feature that one normally associates with the great American West, but it is right here.

Kaaterskill Clove from the air

The clove from Poet’s ledge

There are trails which navigate hikers around the rim of this canyon, but for most, the easy way to enjoy the views is to drive Route 23A, up or down the canyon. It is a grand experience, any time of the year.

You have probably driven the highway, but I don’t imagine that you put much thought into the bedrock cliffs that line the road. They are pretty; they contribute so much to the scenery, but think about them? Not many do that. Too bad, there is much to ponder here.

Let’s take a ride up the clove.

Our trip starts out at the western edge of Palenville. The highway crosses a bridge there and we get our first glimpse of the rocks. I would like it if you paid attention to your driving, so just give those rocks a few glimpses. You will quickly note large ledges of sandstone and that is about all you need to see here for now. You will very soon pass another huge cliff and then cross More’s Bridge. A quick look at the cliff will reveal, again, a sequence of red shale and brown sandstone. Now is the time to begin pondering what we are actually seeing.

Keep heading up the canyon. Not too much farther up the road there are a couple of places where you can pull over, get out, climb down and take a more leisurely look at the rocks. Just across the canyon from the highway is something called the “Red Chasm.” Its name is well chosen because it is a very handsome shade of red. Take a good look and you will see thick layers of red shale. These were, long ago, formed as floodplain deposits. Then too, there are a large number of thick ledges of gray and brown sandstone. These were once the deposits of river channels. What you are looking at is an ancient delta. It’s called the Catskill Delta and back during the Devonian time period it boasted numerous rivers flowing across its surface.

                                                                                                         The Red Chasm

Floodplains and river channels; you have just learned about 90% of what there is to know about Catskills geology. As you travel throughout mountains, it is red shale and brown sandstone that make up most of the bedrock that you will encounter. And that will prove true for the rest of our drive up the clove.

Each stratum of this sedimentary sequence represents a short chapter of time. Each had its turn being the surface of the Catskill Delta. The top of each red shale stratum was once the surface of the ground. If you could travel back through time then you could walk on that surface and leave footprints there. You could return to the present and go searching for your own fossil footprints. Too bad we can’t time travel, but we can’t. Not literally.

Let’s continue our drive uphill. We will pass more outcrops of sandstone and shale. We gradually begin to appreciate how much time is involved here. Each horizon of rock really was the surface of the Catskill Delta for a brief moment, so long ago. Each of those landscape surfaces would have, back then, had the look of permanence about it.

But that look of permanence would have been deceptive. It is by driving up the canyon that we begin to “see” the passage of time. The strata, as we pass them by, record the history of the deposition on the Catskill Delta. They record time itself, a lot of it, and we are traveling through that time.

Our journey up the canyon will eventually take us into Haines Falls, passing many more strata of sandstone and shale – and a lot more time. We will have passed by a thickness of about 1,200 feet of strata. Try to imagine, for a moment, how long it took for all that sediment to be deposited on the Catskill Delta. It must have been many hundreds of thousands of years and, quite possibly, millions – I do not know.

But just how thick is the whole Catskill Sequence? I asked Dr. Charles Ver Straeten, research geologist of the New York State Museum, and he told me that he had just made that calculation. From the bottom of the Devonian sequence, in the Hudson Valley, to the top of Slide Mountain, there are about 9,000 feet of stratified Devonian sandstones and shales. I asked him how much time was involved in this same sequence and he gave me a chart that showed that, if we read it right, a bit more than 60 million years had passed while those strata were being deposited. Our journey through Kaaterskill Clove seemed to have taken us through an enormous length of both rock and time, but it is perhaps only approximately one seventh of the Catskill sequence! Time, it would seem, is very long.

Contact the author at titusr@hartwick.edu  Join his facebook page The Catskill Geologist. Or visit his blog site thecatskillgeologist.com

                               The Hyde Park Deltas – Part two

thecatskillgeologist.com

Robert and Johanna Titus

Nov. 2016

_____

This is the second of two new articles about the Hyde Park deltas.

Last time, we began investigating the Hyde Park Deltas. These ice age features have been recognized by glacial geologists for decades and they are seen on the New York State Museum’s map of New York State glacial geology. That map recognizes two deltas.  But we have found something remarkable and, we feel, revealing. Those two deltas represent two chapters of delta formation. That needs to be explained. So – we are going to, herein, record the sequence of events that we have deduced to, we hope, explain all this. We are, in short, going to record a sequential history of the formation of the Hyde Park Deltas – and thus Hyde Park itself.

1) It all began sometime close to the end of the Ice Age. The Hudson Valley glacier had been melting and vacating the valley, and it left behind a sizable lake. That has long been recognized as Glacial Lake Albany. The lake stretched across the Hudson Valley and, at Hyde Park, it was nearly two miles wide.

   2) Crum Elbow Creek was flowing south by southwest, east of, and parallel to, the lake. This took it across a newly deglaciated landscape. We suspect that, at least at first, it was a far more powerful stream than it is today. It does not amount to much today, but back then, it may have been swollen with very dirty meltwater. It, we think, it (must) have been a very erosive stream.

Crum Elbow Creek today, upstream.

3)  If so, then Crum Elbow Creek had to have carried a very substantial load of sediment which came to be deposited in Lake Albany. Most of that sediment formed what we are calling the Roosevelt Delta (see yellow on our map). The waters of Lake Albany, at that time, reached a level of 180 feet in modern elevation. The delta’s topset was, likewise, at today’s 180 feet.

The Hyde Park deltas; Roosevelt Delta in yellow; Vanderbilt Delta in brown.

4) We conclude that, back then, Crum Elbow Creek did not turn sharply to the west as it does today. Instead, it continued its southwest path which took it past today’s Wallace Center and onward, just a little north of the Roosevelt mansion, Springwood. Its old channel can still be seen adjacent to the parking lot at the Wallace Center (see map and see photo). This is the time when the stream deposited the Roosevelt Delta (again, see our map).

“Old” Crum Elbow Creek, highlighted in red. “New” Crum Elbow Creek (blue) extends off to the west.

Now dry channel of “Old” Crum Elbow Creek, just north of Wallace Center. “Old” Crum Elbow Creek once flowed at the bottom of this small valley.

   5) Next, there came a time when Lake Albany (suddenly?) drained down to a level of 170 feet. We do not know why, but with that lowering, a remarkable event ensued. A small stream, one that had just begun flowing along the northern edge of the Roosevelt Delta, became quite erosive and, by headward erosion, it worked its way up along that northern flank of the Roosevelt Delta. Stream piracy was now occurring. The path of this stream, “New” Crum Elbow Creek, can be followed along East Market Street (aka County Route 41). It can be seen that this stream had been erosive enough to cut down into the bedrock there (see our photo) and create something of a canyon.

East Market Road follows canyon of “New” Crum Elbow Creek. The creek is just out of sight on the far right; it presumably cut the steep slopes of this canyon.

6) With time, this growing creek would intersect “Old” Crum Elbow Creek and divert its waters into the present-day path of “New” Crum Elbow Creek.  Also, a new delta, our “Vanderbilt” Delta, began to form. This younger episode of delta building apparently did not last as long as the previous one, and the new delta never got to be as large as its predecessor. The old Roosevelt Delta leveled off at 180 feet; the new Vanderbilt one at 170.

7) During the period of stream piracy, “Old” Crum Elbow Creek continued flowing in its old path. But that path was about ten feet higher above the new level of Lake Albany. This higher level promoted active erosion of the “Old” Crum Elbow channel. This old channel is the one visible just north of the Wallace Center parking lot. More of the old channel can be traced through Hyde Park.

More channel of “Old” Crum Elbow Creek (left center) on the Yellow Trail at the Winnakee Nature Preserve, just north of Rte. 9.

8) After stream Piracy was complete, the “Old” Crum Elbow channel was left high and dry as is seen at the Wallace Center today (our photo, above). Another dry channel can be seen immediately north of the old Roosevelt family stables. (See our photo below). That had been a tributary of Old Crum Elbow Creek.

Dry canyon of a tributary of Old Crum Elbow Creek, just north of Roosevelt family stables on the Cove Trail.

Sometime later, Lake Albany dropped the remaining 170 feet, down to its present level. Today’s “New” Crum Elbow Creek came into its modern form by eroding those 170 feet. This is best seen where the bridge crosses the creek at the south end of the Vanderbilt Estate.

Crum Elbow Creek at the Vanderbilt Estate.

We believe that this history accounts for pretty much all the landscapes we see, today, at Hyde Park. It is an account that describes the very origins of Hyde Park itself and is thus a fascinating history. We invite you to tour the town and see the geologic sites that we describe here. Then, take Rte. 9, north and south of Hyde Park, and see what the vicinity would have looked like if the deltas had never formed.

We have long been impressed with how ice age events explain so much of what we see in our scenic Hudson Valley. This is a fine example.

            The Hyde Park Deltas – Part one              

   Thecatskillgeologist.com

Robert and Johanna Titus

   Nov. 2016

Most of the time we are re-running old newspaper columns on this site. But we expect to do some original work as well. That is the case here today. We are publishing the first half of a study we recently did on the geology of the Hyde Park ice age deltas. We hope that you will be able to go to Hyde Park and see what we have seen. We are publishing this again because we have new photos for Part Two

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The town of Hyde Park is built upon a broad flat platform. It’s a natural landscape feature and it needs to be understood. When you drive into the town, we want you to take note of it. From the north, you pass the Vanderbilt Estate with its endless front lawn. Then the highway passes through the urbanized part of the town. That area is just as flat. Farther south is the Roosevelt Library and Museum. See its expansive and, again, very flat grounds. All this flatness begs to be understood. There is a pattern here, and we always say “when Nature presents scientists with a pattern, she demands an explanation.”

We like to bring a barbeque skewer along with us wherever we go. When we want to investigate this sort of flatland we try to drive it into the ground. If there are rocks, which there usually are, we have little luck. But – if the skewer slides in easily – then we have likely found a glacial lake bottom. That is the case at Hyde Park. Take a look at our map. All the yellow is flatland where there are few, if any, rocks in the ground.

Yellow on map is delta flatland. Base map courtesy of US Geological Survey

But, is this a simple lake bottom or is there more to the story? Notice that, on our map, the yellow flatlands lie at the downstream end of a stream with the unlikely name of Crum Elbow Creek. Long ago, glacial geologists recognized that that all these flatlands comprised an ice age delta, sometimes called the Hyde Park Delta, the delta of Crum Elbow Creek. The New York State Museum map of ice age features actually portrays two deltas here, one north of Crum Elbow Creek, with a second and larger one, just to the south. This is important, and we should name the two deltas. Let’s call the northern one the Vanderbilt Delta (brown) and call the other the Roosevelt Delta (yellow).

Roosevelt Delta in yellow; Vanderbilt Delta in brown.

Back during the Ice Age, there was a sizable lake flooding all of this part of the Hudson Valley. It has been called Glacial Lake Albany. Crum Elbow Creek is a long flow of water and, back then it was likely carrying a lot of sediment. Most of that sediment was deposited as the delta where the creek flowed into Lake Albany. The top of a delta is always flat and it roughly corresponds with the old lake level. That’s called the topset of the delta. That would have been at about 180 feet in today’s elevation.

The front of a delta is typically a steep slope called a foreset. That explains another landscape feature that we see throughout Hyde Park. Take a look at our photo from the Vanderbilt mansion. The mansion was located at the top of the steep foreset slope. That offered the Vanderbilt’s a nice view of the Hudson River. Walk north and south from the mansion and enjoy this view.

The Vanderbilt Mansion from the south. Below it is the foreset slope.

Foreset slope, north of the Vanderbilt mansion, with its view of Hudson.

Now we have learned a lot about Hyde Park. You are not likely to be able to pass through town without envisioning yourself in a very different landscape, an ice age one. With your mind’s eye look west and see Glacial Lake Albany spread out before you. It extends all across the Hudson Valley. The lake was almost two miles wide here. That’s about four times as wide as today’s river is.

But, the more we worked the area, the more we saw problems that needed to be explained. For starters, we thought the flow of Crum Elbow Creek was a bit odd. The stream has its head about ten miles north of Hyde Park. It flows in a remarkably straight line, just a little west of south, all the way to Hyde Park. Much of the way, it follows Rte. 9G. But then, at the village of East Park, it turns sharply to the west and flows directly into Hyde Park and, from there, into the river (see our maps).  Back during the Ice Age, that took it right into Glacial Lake Albany. We wondered if there was a story to that sharp westward turn. We are scientists; again, we are supposed to wonder such things.

Then it began to bother us that Crum Elbow Creek did not match the delta all that well. It certainly did a good job of explaining the northern part of the delta, the Vanderbilt Delta. But how was it that the delta spread out so far to the south? How could delta sediments extend a full two miles, south of Crum Elbow Creek? In short we just did not think that Crum Elbow Creek was accounting for the Roosevelt part of the delta complex. Again, we are scientists.

That’s when another problem appeared. We were now looking more carefully at the map and we suddenly noticed that, while there were two deltas at Hyde Park, they were also of two different elevations. The Roosevelt Delta, south of Crum Elbow Creek, had a topset at about 180 feet in elevation, but the Vanderbilt Delta, north of the creek, lay at just about 170 feet. We were, clearly, looking at two separate events.

This is when it started getting exciting. We soon had a flash; all of a sudden we saw what had happened, and that was a genuine epiphany. We will be back next Thursday with the solutions to these problems, but in the meantime we want you to have a chance to ponder them, and see if you can come up with the solution yourself. We leave you with a blown-up version of our map, focusing on the southern part of the Roosevelt Delta. Take a good look and see if you can solve these problems without our help.

Do you have some ideas? Write to our facebook page “the Catskill Geologist.”

Close-up of the southern delta.

THE BLUES ON A RAINY NIGHT

On the Rocks

Robert Titus

The Woodstock Times

Nov. 21, 1996

This is an old one, from my first year at the Woodstock Times. This column has been adapted for several editions of “The Catskills: a geological Guide.”

“Carved in stone” is a common enough cliché. Its meaning is plain enough: any concept etched in stone is permanent, it will never go away or be altered. There is an important implication in the term; something carved in stone must be of some real importance. Otherwise – who would bother?

To a geologist things carved in stone are much more commonplace. Lots of things are carved in stone. Some of the most mundane events have, by happenstance, been recorded not by a skilled engraver, but by the everyday events of nature. If you know what to look for, sometimes the rocks light up with unexpected etchings.

You have, no doubt, commonly walked the sidewalks on a rainy night. To the young and in love it can be a great pleasure; to most of the rest of us it’s just cold and wet. But, in the Catskills, a dark, rainy night can bring a journey into the past. You see, most of our Catskill villages still have a lot of old bluestone sidewalks, and each old slab can be a time machine.

Bluestone has long been quarried in the Catskills. This durable and attractive stone holds up very well to the traffic of feet. It was deposited nearly 400 million years ago mostly near the coastline of the ancient Catskill Sea. Its sands once traveled down the rivers of the Catskill Delta and came to be deposited as flat sheets on the shallow sea floors or within the river channels themselves. With time came hardening and then lithification. With a lot more time came quarrymen to chisel out these stones and cut them into sidewalk slabs. Now they line our streets, but they often still retain vestiges of their venerable past.

Go out, find some bluestone walks, and really take a look at them. Most Woodstock sidewalks are now of concrete, but there still are some old bluestone slabs. Look at the sidewalk along the cemetery on Rock City Road, and on Tinker Street near Maple Ave. Look also at the stones leading to people’s front doors. Many are featureless, but many others display sedimentary structures which take us back to moments of time in the Devonian.

Look for two of these structures. The first is the most obvious; these are the ripple marks. Devonian age currents passed across these Devonian sands and sculpted them into the delicate ripples. Often the ripples are steeper on one side. That steep side is inclined toward the direction the current was flowing. It is a most remarkable experience to visualize these briefest and most ephemeral events of so long ago. They should not exist. How could such delicate structures survive long enough to turn into stone? And yet, there they are. Were these currents of any importance? Not at all; they were just the most everyday of events and yet they are “carved in stone.”

Bluestone slab with ripple marks

The other structure is the flow lineation. Again as currents sweep across sea floors or stream bottoms they sculpt the sand. This time the resulting feature is virtually invisible. The grains are lined up into a subtle lineation which only appears millions of years later when the stone cutter splits the rock. The resulting fracture has a faint lineation to it.

Bluestone slab with flow lineations, oriented lower right to upper left

Both of these features are quite clear in broad daylight and not much harder to see at night, under street lights. But on a rainy night, when the street lights are reflected off the wet sidewalks, these features light up. They are almost electric. It’s something to look for anywhere there are bluestones, which is all of eastern North America. I found a lot of flow lineations on the bluestones of Woodstock, but only one good ripple marked slab. That was on the first place I looked: the doorstep of Woodstock Wine and Liquors.

So you don’t have to be young and in love to enjoy a walk on a dark rainy night. Ripple marks and flow lineations are nice too, although they do come in a distant second place.

March 14th, the year 387,469,184 BC, late afternoon

All day long, very moist air has been rising up the slopes of the Acadian Mountains, and this has triggered a series of severe thunderstorms. Dark banks of towering storm clouds rise above the 32,000-foot-tall mountain peaks. A great col lies between two adjacent summits, and this forms a huge geographic bowl. Three closely spaced lines of thunderstorms have unloaded, in quick succession, upon this vicinity, and the rains have flooded the bowl. The rain of the first line of storms quickly waterlogged the soils and the subsequent torrents have raced off downhill in deep, fast-flowing erosive streams. Deep gullies have been rapidly cut into the soft, blue-black upper slopes of the bowl. Vast amounts of sediment have been mobilized and a thick ooze of dirty water (in fact, almost watery dirt) has funneled into gullies too numerous to count. Downslope, the gullies combine into several powerful cascading streams. The flows are now too great to be accommodated by the temporary channels they have cut, and so the deep channels are being widened rapidly. More dark earth is engulfed by the erosive powers of the expanding flows, and whole earthen slopes crash down into the torrent. The rush of the confined water is being pushed and hurried along by the great amounts of water backed up behind.

From various compass points, similar flows combine to a point well down on the face of the Acadian massif. Here, today’s cascade, and many earlier ones like it, have combined to carve a great vee-shaped cleft in the mountain range. This gap dwarfs the canyons above it. Through this cleft, on this day, flow several large Niagara’s; this is a catastrophic event, a thousand year flood.

Below these narrows, the Acadian slopes level out. Vast piles of coarse sand and gravel have formed an enormous, rounded apron of sediment, draped against the slopes of the Acadians. As it flows across this slope, the water breaks up into a number of smaller streams, which continue several miles down the gentle slope until a level nearly that of the sea is reached. At sea level, the streams enter a broad, flat delta top landscape, which is a morass of flooded bayous, marshes and ponds.

The drainage of the Acadian slopes thus forms a great hourglass, and this whole drainage system functions as a giant mountain-destroying machine. The upper basin makes up the wide top of the glass where the rain water is gathered. As it cascades down the slope, it erodes into the mountainous landscape. Below, the narrows make up the constricted middle of the hourglass; here the flow is most effective, and water with its burden of sediment is efficiently transported away from the mountain. The gentle slopes reach down to the flat morass that makes up the bottom of the hourglass. This is where all the material eroded from above ends up.

The morass I speak of makes up the great Catskill Delta. Now, its various glutted and disorganized channels of water make their ways toward the sea. These channels are not nearly large enough to hold the water, and they are in full flood. The blue-black floodwater streams have fanned out across the delta plain. Much of the foliage that had grown along the streams has been swept away. Beyond the now-submerged stream channels, the flood currents slow down and the sediments begin to be deposited as dark horizons of muddy sand. Many plants are being buried within these sands; those that had hung on against the currents are being buried in an upright, standing position.

Meanwhile the main flow continues down the channels of the delta. Downstream, the flow is still rapid, but it is beginning to ebb. Colonies of river-dwelling clams are overwhelmed and are quickly buried by masses of sand. These clams have little to fear; muscular and active burrowers, they will not remain buried for long. At the mouths of the Catskill Delta rivers, the waters, dark with sand and silt, are being disgorged into the western Catskill Sea. From above, large plumes of dirty water can be seen slowly expanding out into the sea. Many tree trunks and a flotsam of broken foliage drift seaward, half hidden in the dark plumes.

By midnight the storms have long been over. The skies are clear and the stars shine, competing with a wine-colored moon. The upper slopes of the Acadian Mountains are now dark and silent. Further downstream, the churning flows of the day are still rapid and gurgling with noise, but the normal languid flow of the delta will soon return. The rivers are still dirty, but they are clearing. Offshore the plumes of sediment are settling into thick strata of sticky sand. A large number of shellfish are dying in that burial; they are the ones which cannot burrow to safety. Their shells will lie, buried as fossils, for at least 400 million years.

It has been a very hard day for the biota of the Catskill Delta. But nobody cares. The world of the Devonian is a soul-less one; there is no mourning, no grief, no pity or even self-pity. Indeed, there is no real understanding of exactly what happened today, and by midnight, there are few living creatures who can even remember these terrible events.

Overnight, the currents will slow down enough so that horizontal horizons of sand will accumulate across large expanses of river bottom and seafloor. These deposits will become bluestone.

Up river, the first of many freshwater clams is emerging from the sands, having escaped its entombment. Life goes on.

Those bluestone sidewalks

Windows Through Time

Robert Titus

July 2^nd, 2009

We rarely pay sufficient attention to the very greatest emblems of our history, in time to save them from destruction. The old covered bridges were replaced by modern spans and, not until only a few were left, did anyone bother to care. By then it was nearly too late, but a few were saved and are still to be seen. All across the land, beautiful old barns have been left to decay and fall down. Today you can actually see signs along the highways, posted by people who wish to buy old barns and tear them down to salvage and sell their wood. It’s such a shame. I fear that nobody will do anything until just a handful of barns are left.

There’s another emblem of the past that I seem to find myself alone in worrying about. That is the bluestone sidewalk. We see them all over the place, but they are being replaced by cement and that has been the case for a long time. Many are still there, but for how long?

Old bluestone sidewalk

If you care to take notice, they can be seen. There are several of them in my town of Freehold. I still see some in Oneonta where I teach. The city of Hudson has some and so on. They are old; they were installed a long time ago, and they are showing their age.

But just what is bluestone? That, of course, is something any local geologist will know about, and I am no exception. Bluestone is a type of sandstone and thus (guess what?) it is composed of sand. It is quartz sand as a matter of fact. So, where did all that sand come from?

Much of Catskill sandstone was originally formed as sediment in the channels of ancient rivers. There were a lot of rivers around here during the Devonian time period and so there is a lot of sandstone. When it has just the right amount of the mineral called feldspar in it, then the sandstone takes on a vaguely blue appearance and, presto, it is bluestone.

Those Devonian age rivers sometimes had powerful flows of water within them. These currents swept along large masses of sand. We are probably talking about Devonian age flood events. At the peak of a flood, the currents were powerful and dirty with sand and silt. But floods don’t last forever; they do abate. As the currents, once again, slowed down, they could no longer continue to transport their load of sand. Most of it had to be deposited. At exactly the right current speed, sand is deposited in thin, very flat sheets. These strata are the ancestors of sidewalks.

The horizontally laminated rock that results is well-suited for splitting. Long ago quarrymen learned how to do this, and they became very skilled at splitting and cutting the rock into slabs just the right size to make sidewalks. It was backbreaking work; I hate to think how hard it must have been. But, the pay was pretty good by the standards of the 19^th Century, and so many were attracted to the work. Good bluestone quarries sprang up in the Hudson Valley, west of the river. Then more were opened up in the eastern Catskills. You can still see the old, now abandoned quarries; they are common

View of an old bluestone quarry

The earliest quarries eventually played out and were abandoned. The industry has slowly migrated westward across the Catskills, and now it’s centered in the vicinity of the Delaware River. People still produce very good bluestone out there.

The rock is found all over the world, but the best bluestone comes from the Catskills. Our stone is enormously resistant to weathering, and that is why it made such good sidewalks. The rock doesn’t become very slippery when wet and that helps too. Blocks of it, cut a century ago, have had people walking across them for all that time and they often show little wear from all the abuse. But, they are getting old. It’s the corners that go first. Weathering works in from both sides of a corner and gradually decomposes it. Then, commonly, stresses build up within the stone, resulting in its cracking. That hurries things along quite a bit.

So, sadly, town fathers look at their old sidewalks, and decide they have to go. They come to be replaced, usually by cheaper cement. There is probably little that can be done to stop or even slow this, but it is sad. Still, we should appreciate this fine old stone, and we owe it to ourselves to be a little more aware of these sidewalks when we see them. They are part of our heritage and a very important part of it. You can tell your grandchildren about them. And tell me too, if there are good bluestone sidewalks near you. Contact the author at titusr@hartwick.edu

Joints on the Wall of Manitou

Windows Through Time

Robert and Johanna Titus

Three weeks ago this blog was about the Wall of Manitou. We wrote about its origins but, ever so coyly; we were not very specific in this. The wall is ten miles long, straight as an arrow and that arrow has a compass direction of south-30 degrees west.

                                                                                Satellite image of the Wall of Manitou.

And two week ago our blog described long straight fracture patterns called joints. They are very frequent throughout the Catskills and, remarkably, most of the time, they also have compass directions of south–30 degrees west. This was a hint, a big one. Did you pick up on that? There is a story here. Those joint fractures and the Wall of Manitou have too much in common for it to be an accident. There must be some sort of a relationship. Well, there is.

We hope you remember that joints form when great masses of rock are compressed, usually during great mountain building events. The compression does not actually fracture the rock, that happens later in time, when the stress ends and the rocks “relax.” Our Catskills joints compressed sometime after 400 million years ago. Something you would likely call Europe had collided with North America and that collision resulted in the rising of mountain ranges throughout all of New England. Geologists call them the Acadian Mountains. If you keep reading this blog you will hear a lot more about these mountains. Anyway, that massive collision compressed rocks throughout New York State, especially the Catskills

The collision of “Europe” with North America and the resulting Acadian Mountains. See NE/SW orientation.

A long time after the uplift of these mountains, Europe broke free from North America and drifted back off to the east, leaving a growing Atlantic Ocean behind. That split was about 200 million years ago. And that was when all the relaxation occurred and that is also when all those joint fractures came into existence. Joints always form perpendicular to the maximum relaxation stresses. These maximum stresses, as it happened, were northwest to southeast. So the joints formed northeast to southwest, just what we see (We are ignoring secondary joints at a 90 degree angle to the primary ones).

Did you follow all that? Europe collided with North America, compressed North American rocks and, when Europe drifted away to the southeast, all those joints formed. Well, what does any of this have to do with the Wall of Manitou?

It has, in fact, everything to do with it. Perhaps you might like to hike the Blue Trail, north from North Lake. Along the way, here and there, you will find northeast/southwest trending joints. There are a lot of them.

Hikers stand upon Blue Trail joints.

   It must have been just like that during the Ice Age. During parts of the Ice Age the Hudson Valley was filled with ice, right to the top. And that ice was moving. It formed a great stream of ice, ever so slowly flowing down the valley, and of course, rubbing up against the Catskill Front.

Here’s where it gets interesting. Ice, when in tight contact with bedrock, forms a bond with the rock. In simple terms, the ice sticks to the rock. Did you ever stick your tongue to the bottom of an ice tray when you were a kid? Well, then you know exactly how sticky ice can be. That happened to bedrock along the Wall of Manitou, during much of the Ice Age.

Well, when enough of a tug was generated, the moving ice would, from time to time, yank huge masses of rock loose. And – you guessed it – those joint fractures proved to be weak points where the breaks could most easily occur. Had you been to North Lake way back then, you would have heard, sporadically, great echoing cracking sounds. Each would mark the breaking of a mass of rock off of the growing Wall of Manitou. Almost always, those fractures had a northeast to southwest orientation.

Over long periods of time – and this is geology; we always have long periods of time – the Wall of Manitou came to be shaped and steepened into what it is today. All the action was occurring out of sight, beneath the surface of the Hudson Valley glacier. Today, the great Wall rises about 2000 feet above the floor of the valley.  And it does something that most slopes don’t do. It steepens toward the top. That’s one good reason why it is such a scenic feature.

When we stand at the edge of the Catskill Mountain House ledge, we always look out at the valley before us and we always see it filled to the top by a glacier. The ice slowly moves by us, headed south. And every so often, we do hear those ear splitting cracks, generated by masses of rock breaking free and being dragged off by the advancing glacier. Then our mind’s eyes watch as the ice begins to melt away. The ice shrinks away from the ledge and reveals nature’s ice age handiwork. That Wall of Manitou rises out of the melting glacier. It is a marvelous revelation.

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