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Woodstock in the Ice Age; South by Southwest

On The Rocks; The Woodstock Times. 2008

Updated by Robert and Johanna Titus

We and many of our colleagues practice an art that doesn’t have a formal name. It should go by the name “rockcraft,” but to our knowledge that word is never used. Rockcraft must be related to woodcraft, both are outdoorsy pursuits. A person who practices woodcraft is familiar with camping out, especially in the wilderness. They know the plants and the animals and know how to read the signs and the seasons. They are well-versed in outdoors survival skills, mostly through experience.

People who know their rockcraft, are similarly experienced. After years of outdoors study, they know how to read the signs of the rocks. They are alert to what the rocks have to tell them. Rockcraft is a less known skill; there are no b\ Boy Scout merit badges in rockcraft. Also, rockcraft is not likely to help you survive if you are lost in the wilderness. But it is a very rewarding skill, simply for the understanding of what nature has to tell you about its distant past. In a way rockcraft is what this column is all about.

One of our personal favorite aspects of rockcraft is the pursuit of glaciers. Of course, there are no glaciers in this area and there have been none for about 14,000 years, but there once were and they can still be followed. The main thing to watch for in pursuing a glacier is the glacial striation. Advancing glaciers are likely to bulldoze away all or most of the soils that they overrun. having stripped the landscape down to bare rock, the ice scrapes across it. If, as is highly likely, the ice is carrying cobbles and boulders with it, then those rocks will gouge scratches into the bedrock as they are dragged along. This is the origin of glacial striations, among the most commonly seen ice age features.

If you know where to look, striations can be quite commonplace. Naturally any time you see bare bedrock, it is worth taking a look. We always watch for roadside outcrops. It is commonly the case that after the highway construction has cut into the bank, erosion will sweep the rocks clean and expose the striations. We also watch the tops of ledges; they are so common throughout the region and often reward us with striations. Then there are the tops of cliffs along the Catskill Front. We have found them at the top of Overlook Mountain and all along the escarpment trail.

Naturally, the striations will be aligned according to the direction of movement of the ice. So, when we find them, we can take a compass reading and when we have collected enough such readings in an area, we will be able to document the history of the flow of ice.

During the ice age, glaciers expanded out of northern Canada and drove their way into the northern United States, including the Hudson Valley. We can trace the path of that ice as it passed through this area. What you do is go out and watch for those glacial striations. We have been doing this for quite some time now and we think that we have collected enough data to form a firm opinion of which way the ice flowed.

And we found absolutely no surprises. The ice, here in the Hudson Valley, was funneled through the valley. The striations almost always line up close to a compass direction of south 30 degrees west. It’s sort of a chicken and egg issue here. The structure of the bedrock geology first dictated the alignment of the valley and steered the glaciers. But then, the glaciers scraped and eroded the valley as they passed through it. In so doing they enhanced the southwest lineation of the valley by straightening and steepening the great wall of the Catskill Front.

Even if there were no surprises in what we found, it was still nice to have good documentation of the flow of the ice and to further demonstrate the relationship between the Wall of Manitou and the glaciers that once flowed past it.

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

The Zena Ice Field

On the Rocks; The Woodstock Times, 2009

Updated by Robert and Johanna Titus

The very first time we ever visited Woodstock, we entered by way of Zena Road. We slowed down at the wonderful view of Overlook Mountain. We remember a cornfield there and that added to the view. Some time later this field was threatened with development. Thankfully, the Woodstock Land Conservancy managed to save it and now the land and its grand view are, forever, just as they were and “have always been.” The site with its view is a very emblem of Woodstock itself. We can all be very glad it has been preserved.

But we are geologists, and we see a lot more when we pull over there and gaze north. We did so recently, and it was quite the experience. We saw the Zena field as it was 23,000 years ago. It was heavily forested then, and we could only see the top of Overlook. The forest was just what you would expect; there were oaks, maples and birch. There were a lot of chestnuts back then too. Many of these were enormous trees, there had never been any cutting in this forest; trees grew to great age and size.

As geologists we were blessed with being able to watch this forest for centuries, a lot of them. We noticed that the summers were getting shorter and grayer. They seemed to stop getting really hot; in fact, it was downright cool and cloudy. There seemed to be fewer warm weather birds. We thought there were fewer summer insects as well; we rarely heard katydids.

The winters were not all that cold though, but they too were overcast. It always seemed to be about 31 degrees out and snowing. We got to be a little weary of the snowfall, but it would not stop. As more centuries elapsed, we noticed that the trees atop Overlook seemed to sicken. Even in late August they seemed pale, even yellow. With more centuries I saw that some of them were dead.

Then down below, we noticed the same affliction in the forest of Zena. Their August leaves were small and yellow. Summer was just not warm enough to allow healthy growth of these trees. What was going on? We were the only humans in all of North America; there was nobody to go and ask.

Now we noticed that the snowfall was lasting into May and then June. The new snows were returning in October and even late September. We are used to climatic cycles, but our droughts are always followed by rainy seasons, our heat waves are balanced by cold spells. We were watching a one-way process. Woodstock was changing into a land without summer. Now the forests up on Overlook were all dead and the trees of Zena were dying as well.

There was something else. we saw weeks of weather when the skies were blue, clear, and cloudless while cold, very dry winds blew steadily out of the northeast. We wondered if there was something cold and dry in that direction. It was a relentless wind that got on our nerves after a while, but it would not stop.

The snows lay on the ground longer into the “summer” season. We saw dirty old snowdrifts in mid July. One summer the ground never thawed out and that was the year all the trees finally died.

Trees don’t make noise, but once they are dead all the noise makers soon leave. We watched as all the birds, all the noise-making insects and all the grunting animals left. The dead forest became unnervingly silent.

But real silence was rare; those howling dry winds soon desiccated the dead trees. Soon, the brittle twigs were blown down, then the branches and finally even the dry limbs crashed to the ground. The forest was a very noisy place . . . until only the tree trunks were left.

Later we heard a distant crashing and falling sound of a different sort, and then another. Soon this became routine, and we wondered what was going on. It took months, but then we found out. A great glacier was moving south, through the Hudson Valley and it was plowing down all the dead trees. Now, at last, we comprehended. When the glacier got to us, we climbed up upon it and reached its top. Now we had a better view of it all. As far as we could see to the north and east there was a flat, endless expanse of ice. It was a frightening sight. To the west and south, dead forests somberly awaited their destruction.

Then we looked up and beheld a horizon of ice rising above the top of Overlook itself. Soon, this great sheet of ice, thousands of feet thick, stretched from the western to the eastern skyline. Down below, the local ice mostly advanced westward; Woodstock was next.

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

The Zena Ice Field

On the Rocks; The Woodstock Times, 2009

Updated by Robert and Johanna Titus

The very first time we ever visited Woodstock, we entered by way of Zena Road. We slowed down at the wonderful view of Overlook Mountain. We remember a cornfield there and that added to the view. Sometime later this field was threatened with development. Thankfully, the Woodstock Land Conservancy managed to save it and now the land and its grand view are, forever, just as they were and “have always been.” The site with its view is a very emblem of Woodstock itself. We can all be very glad it has been preserved.

But we are geologists, and we see a lot more when we pull over there and gaze north. We did so recently, and it was quite the experience. We saw the Zena field as it was 23,000 years ago. It was heavily forested then, and we could only see the top of Overlook. The forest was just what you would expect; there were oaks, maples and birch. There were a lot of chestnuts back then too. Many of these were enormous trees, there had never been any cutting in this forest; trees grew to great age and size.

As geologists we were blessed with being able to watch this forest for centuries, a lot of them. We noticed that the summers were getting shorter and grayer. They seemed to stop getting really hot; in fact, it was downright cool and cloudy. There seemed to be fewer warm weather birds. We thought there were fewer summer insects as well; we rarely heard katydids.

The winters were not all that cold though, but they too were overcast. It always seemed to be about 31 degrees out and snowing. We got to be a little weary of the snowfall, but it would not stop. As more centuries elapsed, we noticed that the trees atop Overlook seemed to sicken. Even in late August they seemed pale, even yellow. With more centuries I saw that some of them were dead.

Then down below, we noticed the same affliction in the forest of Zena. Their August leaves were small and yellow. Summer was just not warm enough to allow healthy growth of these trees. What was going on? We were the only humans in all of North America; there was nobody to go and ask.

Now we noticed that the snowfall was lasting into May and then June. The new snows were returning in October and even late September. We are used to climatic cycles, but our droughts are always followed by rainy seasons, our heat waves are balanced by cold spells. We were watching a one-way process. Woodstock was changing into a land without summer. Now the forests up on Overlook were all dead and the trees of Zena were dying as well.

There was something else. we saw weeks of weather when the skies were blue, clear, and cloudless while cold, very dry winds blew steadily out of the northeast. We wondered if there was something cold and dry in that direction. It was a relentless wind that got on our nerves after a while, but it would not stop.

The snows lay on the ground longer into the “summer” season. We saw dirty old snowdrifts in mid July. One summer the ground never thawed out and that was the year all the trees finally died.

Trees don’t make noise, but once they are dead all the noise makers soon leave. We watched as all the birds, all the noise-making insects and all the grunting animals left. The dead forest became unnervingly silent.

But real silence was rare; those howling dry winds soon desiccated the dead trees. Soon, the brittle twigs were blown down, then the branches and finally even the dry limbs crashed to the ground. The forest was a very noisy place . . . until only the tree trunks were left.

Later we heard a distant crashing and falling sound of a different sort, and then another. Soon this became routine, and we wondered what was going on. It took months, but then we found out. A great glacier was moving south, through the Hudson Valley and it was plowing down all the dead trees. Now, at last, we comprehended. When the glacier got to us, we climbed up upon it and reached its top. Now we had a better view of it all. As far as we could see to the north and east there was a flat, endless expanse of ice. It was a frightening sight. To the west and south, dead forests somberly awaited their destruction.

Then we looked up and beheld a horizon of ice rising above the top of Overlook itself. Soon, this great sheet of ice, thousands of feet thick, stretched from the western to the eastern skyline. Down below, the local ice mostly advanced westward; Woodstock was next.

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

A Woodstock Ice Age, Part 7 – The Comeau Hill

On The Rocks; The Woodstock Times, July 2, 2009

Updated by Robert and Johanna Titus

The Comeau is one of Woodstock’s most valuable and beloved properties. Its land use has, of course, been the subject of great controversy, and of many Woodstock Times articles, but no one has ever disputed that it should be there for the benefit of the residents. We have long believed that an appreciation of the geological history of a location adds greatly to its enjoyment, and we would like to continue on that theme today.

In an earlier article we described how this stretch of the Saw Kill Valley was once at the bottom of an ice age lake. Now we would like to focus on second ice age chapter in this area’s history. Most of the Comeau lies atop a sizable and broadly rolling hill. The soccer field is located precisely at the top of this hill. We had, for quite some time, struggled to understand the origins of this hill. Geologists are condemned to do such things.

Top of Comeau drumlin.

We really couldn’t fathom how this hill came to exist where it is. It is composed of Devonian bedrock at its eastern end, but the perfectly rounded shape to the west did not conform to what bedrock should look like. Sometimes this sort of problem makes your head hurt and that was the case until we hit upon a very possible solution to the problem.

If you read our last column then you learned about two hills lying southeast of Woodstock. These hills are known to geologists as drumlins. They were sculpted by the passing ice at the very end of the Ice Age. They are shaped like upside down spoon bowls. That makes them perfectly rounded at their tops.

We had not considered the possibility that the Comeau Hill had been a drumlin. But then, one day, we took another look at the satellite photo of the Saw Kill region, and it hit us. The Comeau hill was indeed a drumlin. It’s not a big drumlin but that is, we believe, what the hill amounts to.

  Comeau drumlin just right of center.

The two (or maybe three) drumlins lying southeast of Woodstock are full-sized, well sculpted drumlins. They display everything that you want to see in a drumlin. They record what may have been the third advance of the ice into the Saw Kill Valley. And that, it seems to be, is exactly what formed the Comeau hill. That final advance of the ice split into two lobes. One passed to the southeast while the other advanced further up the Saw Kill. It probably ran out of steam just a little to the west. That lobe made the hill.

Most geologists argue that drumlins form when a glacier advances across an older pile of ice age sediment and reshapes it into that spoon shape. Other geologists, however, argue that there is a second mechanism for making a drumlin. They make the case that a drumlin forms when a glacier rides over a knob of bedrock. The ice of the glacier can easily pass over the obstruction, but not without being altered in the process.

You see, there is usually a lot of water within a glacier of this sort; they are just very wet. That water cannot climb up over an obstruction and pass on to the other side. So, when the ice does reach the other side, it is a lot drier than it had been. Apparently, this robs the glacier of much of its ability to transport sediment. That sediment is smeared out on the downstream side of the obstruction and sculpted into a drumlin.

That seems to be the case here. Take a look at our satellite image. The Comeau drumlin, unlike the others in the region, appears to be an obstruction drumlin. The glacier encountered that eastern bedrock, I spoke of earlier and created the drumlin. Late at night in geology bars, we debate this sort of thing and not everybody ends up in agreement. But the Comeau hill strikes me as a very good argument for the obstruction hypothesis.

But the debate may be lost on most residents of Woodstock. What you can appreciate is the ice age origin of this lovely hill. When you are up there watching a soccer game or just walking around, please notice the gently rolling shape of the hill. Gaze west and appreciate the sculpting that went on here. Over the decades there have been a lot of sculptors living in Woodstock, but Nature was the first and that was about 14,000 years ago.

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

The Glasco Pike #5: How long is time?

On the Rocks; The Woodstock Times

Updated by Robert and Johanna Titus

The one thing that geologists can truly claim is that we have a very well-developed understanding of the vastness of time. We deal in enormous amounts of time all the, well, time! Today we continue our own journey through the eons, one that has taken us along the Glasco Turnpike. We are looking at the history of Woodstock and all of Ulster County as it was during Devonian time, a little less than 400 million years ago.

Last time, we had reached a point one mile west of the Plattekill Bridge. There we saw a petrified river channel. We had entered into the realm of the Catskill Delta. That’s a great delta complex of the Devonian age; it is comparable to the Ganges Delta of today’s Bangladesh. Now we continue westward along the Glasco Turnpike on a journey which will carry us toward Overlook Mountain.

This trip of several miles will carry us uphill about 500 feet, but it will also carry us “uphill” through time. As you head this way as you pass the occasional outcrop of bedrock. For the most part these rock exposures are of sandstone. It’s the type of sandstone that we, around here, call “bluestone.” Each of these ledges is similar to the outcrop we saw in our last installment; they are all Devonian river channel deposits.

But there are so many of these deposits; it leads to a simple question: how can there have been so many rivers in the Woodstock area way back during the Devonian? And, as we learn more, the mystery gets even better. All of these ledges have a gentle incline to them; they dip to the west. That means that if we drive down the highway and pass one ledge and soon pass another, then we have, in fact, passed two successive ledges in a stratigraphic sequence. There is a sequence of inclined ledges arrayed down the highway. Each ledge represents an ancient river.

What this means is that, through time, many successive rivers flowed across the Catskill Delta. The delta, like today’s modern Mississippi Delta, was constantly sinking. As the old delta surface subsided, new rivers would flow across new surfaces, carrying with them new deposits of sand to make new bluestone. Try to appreciate this as you pass the many ledges along the Glasco Turnpike. You are passing through a stratigraphy, and you are passing through time, a lot of time.

That has been the point of our whole series of visits along the Glasco Turnpike. We have used this highway to make a journey, a Darwinian journey, through time. Let’s make a few stops or at least slow down a little.

Just 7/10’s of a mile west of the Rt. 212 intersection is an outcrop that displays a nice example of a river sandstone, which lies immediately above a fossil soil horizon. This is what happened there. There had been a delta plain surface which, over a period of time, developed a good thick soil. Then, probably very gradually, the delta plain subsided. A nearby river jumped its old channel, moved here and eroded its way into the soil that we see here. For a long period of time that river flowed this way and then, at a much later date, it jumped its banks and moved somewhere else. While at this location all the sands of the ledge you see accumulated.

Keep going west and just 1/10^th of a mile west of Plochman Lane is another fine outcrop. The lower 2/3rds are made of strata of red silty sandstone. These might be considered as more fossil soils; they would remind you of Georgia red clays. That is pretty much what you would expect, considering that this was a tropical climate way back then. The rest of the outcrop is another river channel.

At Meads Mountain Road you can turn and drive uphill. If you wish, you can stop at the trailhead for Overlook Mountain. From there you can hike up to the top of the mountain. All the way, you will continue to pass more ledges of river channel bluestone. Commonly you will see more horizons of red fossil soils. You are traveling upwards through the sediments of the Catskill Delta, once one of the world’s great delta systems. You are watching as it gradually subsided and gradually accumulated more sediment. That took a lot of time.

And, once again, that is the whole point of our journey. We have traveled, these past five chapters, from Glenerie to the top of Overlook Mountain. We have watched as a shallow tropical sea came to deepen into an abyss. Then we watched the waters shallow again and soon a huge delta complex overwhelmed the whole Catskill region. From the top of Overlook Mountain, we can gaze back towards Glenerie and now have a real understanding of what the rocks between here and there represent. We have an inkling of the enormous amount of history that has unfolded before us. Now we also have an inkling of how long is time.

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

The Glasco Pike #4: A Fossil River

On the Rocks; The Woodstock Times

Updated by Robert and Johanna Titus

We have been exploring time itself over the course of the past several columns. Physically, we have been moving westward along the Glasco Pike. But, in terms of time, we have gone back to the early Devonian time period and have been moving forward. Our goal is to look at our local geological history in the way that geologists see it. We are looking at several million years of time and history. This is history that took place during the Devonian time period. Young world creationists do not believe in the Devonian. They commonly attempt to fit their view of geological history into the catastrophe of the Noah’s Flood. Our job is not to criticize that but to explain the point of view of geologists. Let’s continue our journey.

We are going to drive about a mile west of our last stop where the Saw Kill crossed the Glasco Turnpike. We will climb a hill and then, to the right, is a fine ledge of rock. Parking is tricky here and we don’t want anyone to be hurt so use good judgment. You might just glimpse and run. It’s best to view the ledge from across the highway. When you do so then you can begin to see what these sandstones represent. They make up a fine cross section of an ancient river channel. Take a good look; you will see the channel is deepest in the middle and it shallows both left and right.

This is a petrified river. That is likely to be a novel idea for most of you. There are petrified trees and petrified dinosaurs, but a river? Who has ever heard of such a thing? Well, Catskill area geologists have, and they have heard of a lot of them. When we left off last time, we were watching the Woodstock area as it was rising out of the sea. Our view of the outcropping along the Saw Kill showed a shallowing sea. The strata at the top of that outcrop formed near the ancient shoreline. If that interpretation is correct then it cannot be much of a surprise that younger, overlying rocks should display evidence of having formed in a terrestrial landscape. What is more “terrestrial” than a river?

We have entered into the realm of the great Catskill Delta. It is a petrified delta and there we encounter another one of those surprising phenomena. Yep, there are petrified trees and maybe petrified rivers but a delta!? Look out the window and up into the Catskills. Try to imagine that the whole thing is a petrified delta. Kind of changes your perspective on things, doesn’t it?

The best way to come to understand the Catskill Delta is to get out a good map of Bangladesh. That Asian nation has been developed upon the Ganges River Delta. A good map will show a landscape dominated by scores of rivers, big and small, all emptying into the Bay of Bengal. Our little petrified river was very similar; it was one among scores of rivers crossing the Catskill Delta and emptying into a body of water called the Catskill Sea. Our river’s waters had descended down the slopes of the Acadian Mountains: a great range of mountains in what is today New England. Mountain streams had eroded into the Acadians and turned a great deal of mountain into sand. Our river had carried a lot of that sand as a channel deposit. See top of our first photo.

When you look at a river, it appears to be something that will last forever. Who can possibly imagine the Saw Kill or the Esopus Creek not being where they are? But rivers don’t last forever; someday even the Hudson will disappear. It’s easier to lose a river on a delta. There rivers have a habit of jumping from one site to another. During great floods, a river can be diverted of to a new direction, leaving its old channel abandoned. This is, no doubt, what happened to our little petrified river. Its flow of water jumped to a new site and went in a new direction and the old channel sands were left to slowly petrify. All memory of that river was lost until geologists came along and recognized what is there, along the Glasco Turnpike.

Charles Darwin is remembered mostly as a biologist, but he was a very good geologist as well. He would have understood the story of the Catskill Delta and this view of rocks would have fit very nicely into his mindset.

Young Earth creationists will likely have a problem here. If the Catskills are a great petrified delta, then that is something that must have taken an enormous amount of time to have been deposited. A mere 6,000 years is not going to be enough time, geologists think that it took many millions of years. And that is the point of this whole series of columns; We am laying out the evidence. We report and you decide!

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

Retreat of the sea

On the rocks, The Woodstock Times.

Robert Titus

Charles Darwin’s great theory is based upon two of the fundamental concepts of geology: first, the Earth is a very, very old, very slowly changing place and, second the fossil record has been gradually changing throughout all that vast length of time, with primitive creatures coming first and more advanced forms coming later.

We have been journeying down the Glasco Turnpike with the intent of testing these notions to see if Darwin was right. If he was right, then our explorations into the distant past should bring us to very different images of the Woodstock region from that which we know today. We should find a fossil record which reveals very different plants and animals from those of today’s Ulster County.

So far, so good: these rocks are a little less than 400 million years old, and they speak to us of a slowly changing Ulster County. Our first stop brought us to the shallow tropical seas of the Helderberg Limestone. We saw bedrock composed of lithified sedimentary limestone that had accumulated on the floor of something very much like today’s Bahamas. Our second stop, at the Bridge that crosses the Esopus Creek, at the eastern end of the Glasco Turnpike, showed us the same ocean after it had become much deeper and very stagnant.

Our journey, today, has taken us west to just across the Plattekill Creek. Towering above the highway is an almost magnificent outcrop. It rises a hundred feet or more above the Plattekill. The lower half of the outcrop is composed of very dark shale. Above that are a number of lighter colored, thick strata. All these strata belong to something called the Mount Marion Formation, which makes a lot of sense as that mountain rises above us at this site. This thick sequence speaks to us of a very important chapter in the history of the Woodstock region.

Those black shale beds, at the bottom of the outcrop, tell us about the moderately deep water, very quiet sea that was once here. Try to imagine a very dark, very still sea bottom. Current activity is rare, so silt and clay particles have no trouble settling to the bottom. That’s the stuff that has hardened into the dark shale. There was nearly no oxygen in the sediment and that is why it is so dark. Black is the color of carbon-rich biologic material which is all that is left of most of the few animals that once lived here. Oxygen, in the sediment, would have destroyed that dark stuff and bleached the rock, but there just wasn’t very much of it.

That absence of oxygen was important. It was too deep and dark for any plants, so they didn’t make any. It was too quiet for currents to sweep oxygen downwards from the air above so, all in all, this was nearly an oxygen-free habitat. That’s likely why fossil shellfish are so uncommon here; I remember finding a few ten years ago when I last searched this location, but I found none this time.

How deep is deep would be a fair question. But we geologists get really evasive when asked that one. It is not easy to come up with a good estimate. We would guess a few hundred feet, but another geologist might come up with a very different “guestimate.” We don’t know!

It’s the upper half of the outcrop where things get a lot more interesting. If you look up there carefully you will see a number of much thicker strata. We weren’t ready to scale these heights, but we strongly suspect that these beds are thick sandstones. Usually this is the product of moments of depositional excitement. Something, probably a major storm, stirred up the old seafloor and transported large quantities of sand far enough offshore to get here. After this curious event, things settled down and more dark shale was deposited.

The fact that these sand beds are found only in the upper half of the exposure suggests strongly that this was a shallowing sea and that the shallowing was associated with an advancing shoreline. As the shoreline approached and the waters shallowed, it became easier for storms to stir things up here and to form those strata of sand. We call such a shallowing sequence a “regression.” The sea was literally draining away.

We are not used to seeing regressions in modern times. The glaciers have been melting and, worldwide, the pattern has been one of rising seas over the past 10,000 years or so. We live in a time of transgression and that just, to us, seems to be normal. But, in the distant past, things were often different. Earth history presents us with as many regressions as transgressions. In the Glasco Turnpike is showing us one of them.

But there must be a bigger picture here. There must be a lot more to the story. There is. Next time we will rise out of the sea.

Reach the authors at randjtjtitus@prodigy.com. Join their facebook page “thecatskillgeologist.”

The Poison Sea

On the Rocks; The Woodstock Times; Feb. 3, 2011

Updated by Robert and Johanna Titus

We have been, in this column, spending several months driving west on the Glasco Turnpike. We are actually exploring time. Our goal is to come to truly understand something about the passage of enormous lengths of time and to see how a region changes through those lengths. This is the vicinity of 74 degrees west longitude and 42 degrees north latitude. We want to see how this dot on the globe changed as millions of years of the Devonian time period passed by.

We are also interested in testing the theory of evolution. Darwin’s great theory predicts that the world is very old. Creationists, who challenge the theory, often argue that the planet is only 6,000 years old. Who is right? We shall continue to see some of the evidence.

Last time, we visited the Helderberg Limestone, along Rte. 9W. This time let’s turn west onto the Glasco Turnpike itself and cross the bridge. There on the other side is a very fine outcrop. It is definitely not the Helderberg Limestone; it is a towering cliff of fine grained, black rock. The unit has a name; it is the Esopus Shale. That’s a bit of a misnomer as the rock is not actually shale. Geologists have struggled to find just the right name for it, without much success. Some call it the Esopus Grit and that might be as good a name as any. Whatever its name, it does have a story to tell.

If you visit the site, you will see what appears to be stratification in the rock; these “strata” are nearly vertical. That is an illusion. We will come back to this in a later column, but for now, take a closer look. About two thirds of the way up the outcrop, you can see the real strata, they are very faintly seen as bands of dark and very dark gray. These strata, like other rock units in the area, are tilted to the west.

To us, what this rock is today is less important than what it was in the distant past. It is Devonian in age, and a little less than 400 million years old. This dark, fine-grained rock used to be dark, fine-grained sediment. Anybody would have looked at it and called it mud. Back in the Devonian the mud would have been very wet and squishy. It quite likely would have reeked with a foul, maybe sulfurous stink.

This sort of stuff accumulates at the bottom of a very deep and very stagnant ocean. Stagnant seas never have enough agitation to bring oxygen in from the air above and, in the absence of oxygen, there is no decay. Without decay, all the black organic matter remains well preserved and hence the dark, malodorous nature. Today, the Black Sea of Asia is a modern analogue; scientists, such as Bob Ballard of Titanic fame, have to technology to actually go down and see such a deep seafloors. But we are the mind’s eye and we don’t need technology.

We would like you to stand along the edge of the highway here and wave your hand through the space around you. This space was once at the bottom of a very deep sea. We are the mind’s eye and we can go back to that seafloor. It’s inky black, too deep for any light to penetrate. These are the tropics and the water is quite surprisingly warm. There are no currents down here and, of course, there is no oxygen. All this helps to make it stagnant. Because of that, there are no animals to be seen. No fish have swum in these depths and not even shellfish can be found. It is a spooky place.

It is quite a contrast to our last visit into the past. Recently we stopped along Rte. 9-W and saw the Helderberg Sea. That had been a very shallow tropical sea, something of a paradise in that it had a very rich assemblage of animals living in it. Now, everything is different; the waters are deep, dark and lifeless. What happened?

Between the times of the Helderberg and Esopus Seas, the crust has experienced a dramatic subsidence; it has just plain sunk. The waters have grown progressively deeper. Off to the east there is a rising land mass and off to the west the waters are still very shallow. So the Esopus Sea is an isolated deep basin. That’s how it came to stagnate.

We have just witnessed the sort of dramatic change that can affect a region over a very long period of time, a few million years, no doubt. This is the length of time needed for evolution to occur and this is the sort of environmental change that helped to drive evolution. In this, our second stop down the Glasco Turnpike, we have continued to explore a changing geology that is very much in accord with the Darwinian view. But we still have a long way to go. (Next time: retreat of the sea)

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

The Glasco Turnpike 1: its Ancient Tropical Sea

On the Rocks; The Woodstock Times, 2008

Updated by Robert and Johanna Titus

Wherever you might happen to find yourself while reading this, please wave your arm through the air around you and begin to wax philosophical about it. This spot has been here for as long as the Earth has been here and that is about 4.6 billion years. Contemplate the history that has unfolded right here. Think of the plants and animals that occupied the very space where you are now. Geologists are accustomed to being awed by the things they discover and encounter and this is one of those marvels.

This location has a longitude and latitude. Woodstock is at 42 degrees latitude by 74 degrees longitude. If we could go back in time and bring a GPS device, we could find this spot and see what it was like way back when. That notion is mostly beyond the reach of science but just not entirely. We would like to take you back in time to this location and see what it was like at several important moments in time. It is all part of our effort to bring to meaning of the theory of evolution to you, the local readers.

Evolution only works if the world is very old, billions of years, in fact. Our aim over the next five columns is to take a journey through time, curiously our trek will be mostly along the Glasco Turnpike. Let’s head east on the Glasco Turnpike until we arrive at its intersection with Rte. 9. Turn right, which is south, and go a short distance, just a half mile or so. Notice the gray ledges along the east side of the highway. That is our first time-travel destination.

This is the Glenerie Limestone. It is very, very fossiliferous so we geologists are very fond of these rocks; they are always a lot of fun to visit; their time is fun to visit too. As you approach the roadside outcrop, notice the horizontal layering to the rocks. This is, of course, called stratification. The marvelous thing about these horizons is that each was once the bottom of the Glenerie Sea. When you get to the outcrop, put your finger on one of those beds of rock. You are actually touching a seafloor. That’s not exaggeration, it’s not literary license, it’s a fact. The water is gone, and the old sediments have hardened into limestone, but each horizon was once the bottom of a sea.

That was a long time ago; in fact, that’s the whole point of this article. We have now visited the Devonian time period; it is just a little more than 400 million years ago.

Now, take a good look at the various strata. Some are not very exciting, just dull gray rock. But other horizons are enormously fossiliferous. You will quickly find beds of limestone which, upon careful viewing, appear to be all broken shells. Some of these beds are just a complete hash of shells. They have lost their original bright colors, but they are still shells.

These are invertebrates, mostly forms called brachiopods. Like modern clams, they had two shells, but that’s all the similarity that the two groups share. Brachiopods are not mollusks; they belong to a wholly different category of invertebrate. They were very abundant back in the Devonian and made up the dominant form of sea life here.

We are the mind’s eye; we have waved our arms through the air, and traveled back into time, all the way to the early Devonian. We find ourselves adrift on the surface of the Helderberg Sea. All around us, in every direction, an empty and endless sea stretches out to the horizon. There is no land to be seen anywhere. The waters are aqua in color, that’s typical of a tropical sea. And that is exactly what the Glenerie Sea is. We feel the water temperature and it is a balmy 82 degrees.

Below us, the sea is so shallow that we can see the bottom. There are active currents and that has swept much of the seafloor clean. We see a lot of pink, very coarse sand drifting and shifting back and forth as waves sweep across the bottom. There are a lot of broken shells down there, most all of them are from brachiopods; they have suffered during common storm events and have come to be broken up into a colorful hash. We look around but do not see and living brachiopods. That’s just bad luck; we picked the wrong moment to visit the Glenerie.

It is an exhilarating experience to travel through time like this. It is such a privilege to see the distant past. But the main point is that this bas been a Darwinian journey to a very ancient world populated by very different creatures from those of today. Such visits are always all too brief. In a blink of the eye, we are back on Rte. 9G. It is winter in Ulster County. The highway is dirty with grit and salt; the outcrop is dirty and drips with icicles.

Next time: the stagnant sea.

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

A High Impact Event

Stories in Stone; The Columbia County Independent

Updated by Robert and Johanna Titus

Is there anything more emblematic of domestic bliss than a husband and wife trading sections of the morning newspaper over the breakfast table? Well, it’s just a little different when both are scientists. So, it came as no surprise when Johanna, the molecular biologist, handed Robert a copy of the Proceedings of the National Academy of Sciences and asked him if he had read an article in it. He was glad she did as he might well have missed it and the story was a very good one. It led the two of us to envision another of those very rough days that occasionally affect Columbia County, and, at the same time, it may have solved several longstanding geological mysteries.

Geologists have long known of a series of enigmatic crater-like structures, scattered across the eastern coastal plain of North America. They are called the “Carolina Bays.” Elliptical and oriented from the northwest to the southeast, they have long suggested an ancient impact event, but we have never been quite sure. We have also long known of a puzzling thousand-year long cold spell called the Younger Dryas. Then there was the mystery of the extinction of the North American megafauna and the sudden disappearance of the Clovis Indian Culture. Many large mammals, and the Indians that may have hunted them, disappeared, or at least declined abruptly about 13,000 years ago. All these puzzling events may have recently been tied together with a thin seam of dark earth. Read on.

It seems a large team of high-powered scientists had recently described an inch-thick, carbon rich seam of earth that is found at sites across much of the continent. The seam is rich in iridium, magnetic micro-spherules, soot and glass-like, carbon-rich nano-diamonds. The seam, in the many places it has been found, is always dated at just about 12,900 years in age. It has been found at exactly the top of strata containing Clovis points, which is also the same horizon where mammoths and other large fossil mammals disappear. The age of this corresponds to the start of the Younger Dryas cold spell. The seam has been found to pass through a large number of the Carolina Bay craters. It is an incredible find; it ties together all the above-described scientific problems. But what exactly does it tell us?

The word iridium may remind you of the ash deposited by the asteroid which is thought to have wiped out the dinosaurs. If that catches your attention, it should. It sounds like we, all across North America, had our own mini dinosaur extinction event. From the composition and abundance of the impact materials it is estimated that the object was actually a comet, and it was four kilometers across.

If you know much about the turn of the century event in Tunguska, Siberia, then you can envision the story. Here in the Hudson Valley, we would have seen the comet coming in from the northwest at an oblique angle. At some point it exploded and the enormous impact of all this caused the great continental glacier below it (remember, this was still the Ice Age) to largely melt. Vast quantities of meltwater resulted. But the impact was so very hot that, not only did the ice melt, but farther south, vast stretches of forest caught fire. Huge widespread wildfires raged across North America. That’s where all the soot came from. An impact of this sort tosses huge amounts of rock and earth up into the sky. When it comes down, friction sets it ablaze and so even more fires are set. You get the picture.

The result is something that is often called a “nuclear winter” and that gets us to the Younger Dryas cold spell. The dark sooty clouds, generated by the impact initiated a cooling that would last for a full millennium. The extinction of about 30 types of large mammals suddenly has a natural explanation. The Paleo-Indians, it would seem, are off the hook for this crime. But human populations plummeted as well. It must have been a very difficult time for Indians and the Clovis Culture disappeared altogether. All this reminds us, once again, how fragile our existences are.

We wrote this years ago. Sadly, this hypothesis currently seems to be falling out of favor.

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