Robert Titus - page 21

Late Lakes

The WoodstockTimes

ON THE ROCKS Updated by Robert and Johanna Titus

It’s always so important to use just the right words. For example, there are all sorts of terms for small bodies of fresh water. One is a puddle. Puddles aren’t very big nor are they very deep. A pool is both bigger and deeper. But pools are smaller than ponds, and ponds are smaller than lakes and so on. Nobody knows exactly where to draw the lines, but there are differences, and you must always use the right words.

In the end, however, it is a somber fact that all these bodies of fresh water, big and small, are doomed. None of them will survive. Lakes become ponds, ponds become pools and pools become puddles. Eventually puddles disappear altogether. Again, nobody can draw sharp lines and you can never watch as a pond becomes a pool. The process is geologic and, thus always, too slow to see.

But there is one time of the year when the process speeds up enough so that we can go out and watch the destruction of a pond and this is that time. Late August is a time of dramatic growth of pond plants. Find a small pond in your area and give it a look. Quite likely, all around the edge, you will see a thick scum of algae. There’s quite a lot of biology going on in there right now especially among the algae. All summer long, algae population curves have been steadily and slowly rising. But in late August the population growth curve steepens – dramatically. Algae populations skyrocket, frighteningly. Not surprisingly, populations exceed what’s called the “carrying capacity” of the environment. Probably such materials as nitrogen, potassium and phosphorous run out. Then populations crash catastrophically. A population crash should be an awful event, but algae don’t care. Come next year their populations will resume the cycle and start rising again. All will be repeated next season.

It’s not just algae, there are plenty of pond plants rooted in the shallow waters. They are growing rapidly as well. All in all, the edge of a small pond is right now a fine place for plants and plant debris to accumulate. And a little later in the season, tree leaves will fall into the ponds and wind will blow them into the shore zone as well. Over the winter, the remains of dead vegetation sink to the bottom and become part of the sediment down there. That makes the sediment around the edge of a pond all the more fertile, more nitrogen, potassium and phosphorous. Next year more and more plants will participate in this seemingly endless cycle.

It is the nature of things for a floating mat of plant debris to develop around the edge of the pond and, with time, this mat expands outward toward the middle of the pond. Meanwhile the remaining clear waters, out there in the middle of the pond are becoming more fertile themselves, still more nitrogen, potassium and phosphorous. A feedback process may well occur. The fertility of the water encourages plant growth and plant growth contributes to the fertility of the water.

The foliage around the edge of a lake serves as a trap for wind-blown sediment, mostly silt and clay. Grains blow into the water and settle, as sediment, into the space between the plant roots. With time, an impressive accumulation of organic-rich sediment develops around the edge of the pond. As the sediment fills in the pond shrinks.

As time passes, advancing mats of plant debris will form a material called peat and it is peat, along with the sediment, that will eventually fill in the entire basin. In the end the pond is doomed. It will fill in with peat and a mixture of silt and clay. As things continue to change you have to keep finding the right words. The pond will evolve into swamp, the swamp will become a marsh, and the marsh will transform into a bog. These are often called “wetlands,” and people protect wetlands. But even protected wetlands are doomed. Wind will bring more silt and clay and fill in the space where water once was. The wetlands thus dry out and disappear altogether. That’s the nature of things geological; nothing lasts forever.

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

A winter’s snow

Windows Through Time

Updated by Robert and Johanna Titus

As you might have already guessed, we spend a lot of time writing. We do these columns and many more for other newspapers and magazines. Sometimes, it would seem deserved, that we might get a little time off. Today is one of them. Today we are watching one of those occasional grand snowstorms developing. There is, coming from the far west, a lines of storms, called a “clipper.” That’s a typical event this time of the year. Most of our weather comes west to east across the continent. What makes today special is that there is a coastal storm front coming up from the south. This is air that got its start in the Gulf of Mexico. It was warm and humid when it began its journey towards us. Now it is cooling off rapidly. Air can hold a lot of humidity when it is warm, but not when it is cooling down. That humidity is turning into snow, right now and right in front of we.

There are thus two storms out there and, as we write, they are headed for a collision. In the parlance of our times, that is called a “perfect storm” after the title of a book that came out about years ago.  Perfect or imperfect, we are about to get clobbered. Scientists have studied such storms for generations; they seek to understand the physics of them, with the goal of being able to make sense of their seemingly erratic behavior.  Nature writers have written about them too; seeking to express their feelings as such storms pass. They are artists, seeking to paint with words the passage of a winter storm.

As it turns out, we possess both scientific and nature writer personalities, so we suppose we bear an extra burden if we choose to write about what it being called a “winter storm Nemo” We decided to take both the nature writer and the scientist out today and into the forest that makes up most of our property in Freehold. The four of us walked down the trail we have put together and took in the early hours of the storm.

The scientists got the better of it, we think, at least at first. They looked at the flakes coming down and marveled about how snowflakes are composed of a mineral called ice. Ice, indeed, is just as much a mineral as is quartz. But quartz never falls out of the sky; ice does. The scientists went on to note that ice is the only mineral that falls out of the sky. That threatened to take all the beauty and wonder out of what was happening all around us.

The nature writers motioned us to pause and listen. The woods all around us had become still, absolutely silent. All of the birds were hunkering down somewhere, hidden from view. There were, of course, no insects either. The snowfall was a quiet one, so no winds or even breezes could create any rustling sounds. But this was not an absolute silence that we experienced. In the far distance we could hear the flowing of Catskill Creek. The sounds of its rushing waters were normally muffled by a nearby din, but not on this type of day.

All four of us took note of the colors in the woods. There were only two of them. One was easy for me to describe; it was “snow white” and there was a lot of that all about us. But the other color was tough to put into words. Even the nature writers struggled. “It is an off gray” they said. “What on earth is an off gray“the other two of us laughed. “Well, okay, it is a gray with just a little of brown and a little less green in it” was the best the nature writers could do. The scientists struggled equally. “On a cloudy day only limited spectra of visible light reach the ground and only two colors are reflected back off a landscape. There is the white here and that peculiar gray.” It all sounded so erudite, but it smelled fishy, very fishy.

We continued our trek and soon encountered footprints in the snow. Deer were common, but there was something else that might have been a coyote. We debated that but had found something equally appealing to the four of us. It was fast getting dark and we hurried our pace heading back to home. We each had seen the snowstorm in a different way; it was a decidedly different experience for each of us. But all four of us had the good sense to appreciate it for what it was; a wondrous and beautiful natural event.

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

Journey to the Center of the Earth, Pt 2

On the Rocks, the Woodstock Times

Nov 12, 1998

Updated by Robert and Johanna Titus

Last week we began a rather remarkable journey into the Earth’s interior. We traveled to the town of Catskill and visited a site that was once possibly miles beneath the surface. We saw beds of stratified rocks there that had been extensively folded by the intense pressures that occur at such depths. But, if a few miles may seem a lot to us, it’s not terribly deep by the standards of the planet. You would have to travel 4,000 miles to get to its center, a mere two or three is hardly anything. So, let’s try to do better this week.

From Woodstock travel across the Kingston-Rhinecliff Bridge. Head east to Rte. 9 and follow it north to Upper Red Hook. County Rte. 56 takes you east to County. Rte. 55 and that runs along the western shore of Spring Lake. We did some exploring at the north end of the lake and we found some fine outcroppings of a rock type we had not seen before in the Catskill-Hudson Valley region.

The roadside outcrops are excellent with very good exposures. As you approach these rocks you will observe that they really are unlike anything else in the area. If you have been visiting the sites we have described in our columns, you will have seen nothing like them. Virtually all of the bedrock in the region is stratified sedimentary rock; the beds are bedded sandstones, shales and limestones for the most part. They were once sediment, deposited in sheets that hardened into strata. But at Spring Lake the rocks are not bedded at all. Instead they are composed of shiny, crenulated masses of very dark rock.

The rock is called phyllite. It belongs to a broader category, commonly called metamorphic rock, and it has had a very long and hard history, even by the tough standards set by rocks. The phyllite here didn’t always look like this. A metamorphic rock, as the name implies, has been metamorphosed, changed in its appearance. It was formed originally as something quite different. It may well have been a sandstone or a shale in the very distant past, but it came to be altered. It was buried under very thick sequences of other sedimentary rock, many thousands of feet or even miles of other rock. Then it was caught up in a great mountain building event.

  Phyllite

Metamorphism occurs under such circumstances. The rocks are first subjected to the great pressures that are associated with deep burial. Then too, having sunk to great depths within the Earth’s crust, the rocks enter very hot realms and become, quite literally, baked. Combine the effects of high temperature with high pressure and you get metamorphism. The rocks become contorted and crenulated with the pressure. They become shiny as mica minerals begin to grow within them. That new rock is phyllite.

Surprisingly, phyllite is what is called a very low-grade metamorphic rock. That means things could have been much worse. In the deep interior of this enormous planet, even higher temperatures and pressures are encountered and higher grades of metamorphism are found.

If you look at these outcroppings, you will find a number of seams of course, white crystalline minerals. This is quartz and it probably formed here late in the metamorphic history of the rock. The quartz is interesting but not central to our story.

When did all this happen? The answer is probably during the Devonian time period, during what is called the Acadian Mountain building event. That was one of the three big uplifts that led to the creation of what we call the Appalachian Mountain chain. In effect, then, as we travel to Spring Lake, we enter into the deepest interior of the old Appalachians. No, we have not traveled to the center of the Earth, but we have made quite a very good try at it.

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

A real geological mystery, and at Pratt’s Rock

The Catskill Geologists

Robert and Johanna Titus

We were invited to speak at the Pratt Museum recently. Our topic was the glacial geology of the Schoharie Creek Valley. After that, a group of us went to Pratt Rock and climbed up the trail there. We took a look at Colonel Pratt’s carvings and continued on to see some nice ice age features. But, along the way, we ran across one of those mysteries we have long struggled with.

We were first alerted to this particular mystery by Paul Misko, a veteran Catskills hiker. Paul told us of some “very strange structures he had found in Phoenicia. Paul has a real eye for unusual geology, so we paid attention to his “very strange” claim. We saw his Phoenician structures and now we have found more of them at Pratt’s Rock. Take a look at our photo and then climb up the steep incline at Pratts Rock and keep an eye out. Towards the top you will find sizable ledges of sandstone. This is rather commonplace stuff: very typical Catskills bluestone ledges. These ledges are, in essence, the cross sections of a very old streams. It’s, like all rocks in the Catskills, Devonian in age, something a bit less than 400 million years old.

None of this surprised us in the least but that’s where we encountered that mystery. Take another look at our photo and see what you think. See the cluster of closely spaced and very strange cavities just above the hand. Their shapes vary considerably, but they all show a sort of boxy nature and they seem to form an interlocking network. We would like to use the term honeycomb here, but honeycombs show a consistent hexagonal shape; we don’t see that with these. The rock remaining in between these cavities is narrow. The cavities do not penetrate too far into the rock, just a few inches. And there is no reason to think that there is another horizon of these cavities under the ones that are visible. Thus, they appear to be surficial features. Many of these cavities are spaced so close together that they comprise a bigger compound cavity. Whatever it was that formed them was focused.

All in all, this is one of the most puzzling phenomena that we have seen in the Catskills. There is no trouble putting a name on what is here; these structures are called “tafoni.” Each individual cavity is a tafone; lots of them are tafoni. And the terminology keeps getting better; when tafoni occur on cliff faces, as here, then it is called lateral or sidewall tafoni. But, putting a name on something is not the same as understanding it.

What are these features? They seem to be chemical weathering phenomena. Somehow, they appeared on the rock surface and grew slowly into their observed shapes, but exactly how? And, also, how is it that they grow in size until they abut each other but do not grow into each other? How do they grow in size without intersecting? Those are very puzzling questions and just naming these things does not provide answers.

Tafoni have been weakly associated with poorly defined stratification on the sides of cliffs and that is the case here: sort of. But that still leaves a lot unsaid. Why does this “association” occur? What are the specifics? Salt is commonly cited as an agent in tafoni development. They are sometimes found on coastal outcroppings, splashed by ocean waves. But there is certainly no source of salt here on a sandstone cliff in Prattsville, and certainly no waves. And, why do only a few Catskill Cliffs display these? That begs the question: what exactly is different about his cliff? Why don’t all cliffs have tafoni? Why isn’t it that none of them do? There must be something here, right in front of our eyes, which we have missed. This is the sort of thing that makes science so much fun.

   Do you have any ideas or questions? Have you seen tafoni somewhere? Contact the authors at randjtitus@prodigy.net. Join their Facebook page “The Catskill Geologist.” Read their blogs at “thecatskillgeologist.com.”

The Austin Glen Formation.

On the Rocks – The Woodstock Times 1998

Updated by Robert and Johanna Titus

The east side of the Hudson River has some very different rocks from those we see around Woodstock. They’re older too and so, of course, they must have different stories to tell. Cross over the Kingston-Rhinecliff Bridge and you won’t have to go far before you see some of these strata. On the north side of the highway (Rt. 199) We found a nice road cut. It was a sequence of dark, thin-bedded shales interbedded with many thick strata of brown and gray sandstone. You are likely to have passed this outcrop many times without taking note of it and we don’t blame you. The unit of rock here is called the Austin Glen Formation and it is certainly not much to look at, gray sandstone alternating with dark shale is hardly picturesque. But to appreciate a unit of rock you have to really understand it and, dull as it looks, the Austin Glen is a most remarkable sequence of strata.

Austin Glen to the right.

There are problems with the unit which, when solved, lead to a fine story. Let’s see. The black shales of the Austin Glen pose little trouble in understanding, or so it would seem. Black shales were once black mud. Such mud accumulated on the quiet floor of a deep ocean and I mean really deep, maybe tens of thousands of feet, a real abyss. So that’s that; the Austin Glen must have formed in the depths of one of the earth’s deepest oceans, or so the shales say. But the sandstones tell a different tale. The sandstones were deposited by fast-flowing currents. we looked and found laminations that are typical of such conditions. And there were also ripple marks preserved in the sands, these are the sculptures of powerful currents. Such currents are most often found in shallow waters. So, the Austin Glen must have formed in a shallow sea, or so the sands say.

So, which is it? Are the shales correct in their tale of deep, quiet waters or are the sandstones closer to the mark? Who’s telling the truth and who is trying to fool us? This is the sort of problem geologists frequently face. Fortunately, this problem had already been solved. Our interpretation of the shales was probably okay, but we must confess that we did get the sands all wrong, at least at first telling.

The sandstone beds of the Austin Glen weren’t deposited by shallow water currents; they were gravity deposits, essentially submarine avalanches. The Austin Glen did indeed, as the shales said, accumulate in very deep, quiet seas. At least they were usually quiet and most of the time the soft muds settled to the bottom of this oceanic basin. But this sea floor was at the bottom of a steep and very deep marine slope. From time to time earthquakes occurred and these triggered the sudden downslope displacement of large amounts of sand, submarine avalanches. We call these “turbidity currents,” and their sandy deposits are called turbidites. Their rapid downward rush slowed near the bottom of the slope and then deposited the laminated and

sometimes rippled sands that we see today.

After each avalanche the sea returned to the slow piling up of more mud. Hence thicknesses of black shale were commonly punctuated by layers of sandstone. In the end the typical Austin Glen strata formed. All this took a very long time and a total of more than 500 feet of Austin Glen strata piled up.

That outcrop, east of the Rhinecliff Bridge, is thus a history, written in rock, of the hit and miss crustal activities of long ago. As we walked along the outcrop we sometimes saw thick sequences of shales; those were the long quiet periods between earthquakes and turbidity currents, when only muds accumulated. There were also a number of thin sandstones, they were turbidites of lessor magnitudes. But then there were also sequences of very thick turbidites laid down in quick succession. We thought about those times; they must have been difficult chapters in our local history, times when powerful earthquakes may have rocked the area, sending great turbidity currents plummeting into the abyss. These were remarkable times, but they would have been forgotten except that they were preserved in the roadside rocks.

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

What’s the Point?

On the Rocks

The Woodstock Times Oct. 14, 2998

Updated by Robert and Johanna Titus

To most people the Shawangunk Mountains are best known for the Mohonk Mountain House or for the hang gliders and rock climbers you will see in abundance on sunny summer Sundays. While the Shawangunks may be a lessor mountain range by world standards, they are still very substantial landscape features in the Hudson Valley. They are geologically distinct from the neighboring Catskills and they have their own story to tell. If you are interested, then a good place to begin to learn the story of the “gunk’s” is at Sam’s Point.

Take Rte. 209 south to Ellenville, then take Rte. 52 east up the west slopes of the Gunks. From there take Cragsmoor Road to Sam’s Point Road and watch for the signs. There is a parking fee. It’s a bit of a trip so allow a whole day. Sam’s Point is the property of the Nature Conservancy. The ice caves are only open seasonally but there are still many open hiking trails with fine views of the Hudson Valley region. The trail to Sam’s Point is a short, easy walk. It takes you along and under a cliff and then up to Sam’s Point itself. If it’s clear you can see all the way to the tower at High Point in New Jersey. To the north you can see most of the rest of the Gunks.

We wondered what the Shawangunks were and why are they were here? The answer began to appear as soon as we saw the rocks of Sam’s Point. They are of a striking lithology, almost all thick-bedded strata of bright white quartz sandstone. The name implies its composition; it’s a nearly pure quartz sand. Even the grains are tightly cemented together by a quartz cement.

Quartz sand grains glued together by quartz cement; that’s a recipe for a very sturdy rock. Quartz sandstone is about as resistant to all of the processes of weathering as any type of rock in the world. No wonder there is a mountain here. There are actually two massive layers of quartz sandstone here, each running about 250 feet thick. They are separated by a horizon of softer, more easily weathered rock. The two have slowly eroded into separate ridges. It adds some variety to the landscape.

As we climbed around and looked at those strata, we found that there was more than just sand here. Much of the volume of the original sediment was a quartz gravel. Technically this is not a sandstone; when gravel is this abundant, the rock is better called a different name: conglomerate. This one is officially named the Shawangunk Conglomerate.

Where did all this sand and gravel come from and how did it get here? The answers to those questions take us back to the Silurian time period, a little more than 400 million years ago. Back then there was a mountain range, known as the Taconic Mountains, located in western New England. Even back then these were old mountains, and they were then in the final stages of dissolution. Weathering and erosion had slowly been wearing them down and grinding them into sediment. With such very old mountains there has been plenty of time for the weathering processes to destroy the softer and weaker minerals. For the most part their grains are entirely dissolved or converted into clay and washed away. What’s left is quartz, that most resistant of minerals.

So that, in a nutshell, is the history of the Gunks. In the past they started out as a deposit of quartz sand and gravel, accumulating on the floor of a shallow sea, adjacent to the crumbling remnants of a once mighty range of mountains. Slowly these sediments came to be cemented into masses of white sandstone and conglomerate. Then they were gradually uplifted into hills and then even more slowly eroded into the morphology we see today, a scenic but lessor range of mountains. But these mountains, like the ones before them, are doomed. Weathering and erosion will cause them to crumble. Someday these grains will be part of a newer quartz sand sediment, located in the Atlantic Ocean. Those sands will start to harden into a new quartz sandstone and the cycle will start all over again.

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

Down the Pike

On the Rocks, The Woodstock Times

Sept. 17, 1998

Updated by Robert and Johanna Titus

Sometimes it’s well to pause and take stock of things. If you have been reading these columns the past two years, then you have been introduced to a rather eclectic view of the Woodstock area landscape, our landscape as a geologist sees it. The column is meant to be as much for fun as for education, so we have not tried to be too serious, or too focused. The column is not a formal course in geology, and you won’t get college credits for it. Still, this week, why don’t we try to draw together some of the many strings we have been following. There’s a nice afternoon trip that can do just that too.

The road we have in mind is a venerable one, it’s County Rt. 32, but it’s better known as the Glasco Turnpike, and it cuts through a lot of geology. Pick up the pike at its intersection with Rte. 9W, at Glenerie. All along the east side of 9W you will see the Helderberg Limestone. This represents Woodstock in the early Devonian Period, about 400 million years ago. The limestone formed on the floor of a shallow tropical sea. There’s good fossil hunting here, shellfish that lived upon the soft sands and inhabited the clear waters of an aqua colored “Bahamas

Woodstock, however, has not always been such a nice a place as it was during Helderberg times. Cross the bridge at Glenerie and head west on the pike. You will pass a great outcrop of black shales. We have traveled in space, but more importantly, we have traveled in time. This is Woodstock at a younger and very non-Bahamian time. Off to the east the Acadian Mountains were rising. Curiously, as mountains rose in New England, here crustal subsidence created a deep basin. When we visit those shales, we enter that basin: A deep, dark, mud-bottomed sea that replaced the Helderberg. There was nothing very pretty about this moment in Woodstock’s past. In fact, this ocean could be downright ugly. It was definitely inhospitable, a deep and dark, and sometimes even poisonous sea where few creatures could endure.

Continue west on the pike, cross the Kings Highway, and then the Thruway. About a half mile down the road you will reach Plattekill Creek. To the left, a very impressive cliff towers above the road and the creek. That’s the Mt. Marion Formation. It represents the last stages of that deep, mud-bottomed sea. The shales can be good fossil hunting, if you are patient. Horn corals and other fossils have been found here. Near the top of the exposure you will notice that there are thick ledges of gray sandstone. That’s important; the seas were at last shallowing and strong coastal currents were carrying masses of sand to the Woodstock area.

As the Acadian Mountains continued to rise in New England, the seas here once again shallowed and the coastline advanced westward. We call that a marine regression. Let’s see the results. Drive uphill from Plattekill Creek. Soon you will start passing very thick ledges of gray sandstone. There is a pattern to the road from here on to the west as far as you care to go. The pike will commonly rise up over a ledge of sandstone and then dip down into a swale beyond. Soon another ledge appears and the road rises again, only to drop down still one more time. And so on it goes down the road. Each sandstone ledge is the cross section of a Devonian river. Each swale is composed of dark, soft shales; they were deposited in coastal lagoons or on marshy coastal flood plains. Our regression has brought us out of that deep ocean basin and into the coast of a great delta complex.

The delta has a name, the Catskill Delta, and you pass into the heart of it as you cross Rt. 212 and continue west on the pike. Along the side of the road you will see more thick river sandstone ledges, much like those behind us, but now there are also many red shales. Red is a common color among terrestrial sediments, and these are the deposits of the flood plains across which the rivers flowed. There were once forests on these flood plains. And also, the Acadian Mountains towered above, perhaps as high as today’s Himalayas.

Our trip it over, but it has taken us mountains of nearly 400 million years ago through a lot of geologic history and it has given me a chance to organize a number of themes that I have written about these last two years. I hope you can get a chance to follow the Glasco Turnpike, see its history, and maybe begin to really understand the Acadian Mountain building event. After all, the Acadian Mountain building event pretty much made Woodstock.

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

An Overlook that’s Overlook’s Overlooked Twin

On the Rocks

Nov. 5, 1998

Updated by Robert and Johanna Titus

As you drive up Rte. 23A and approach Kaaterskill Clove you can look upwards and see two great sandstone cliffs, way up toward the top of South Mountain. The higher of the two is known as the Palenville Overlook. It’s an out of the way site with a lot of geological history.

The Overlook is not hard to get to, but you do have to know the way. Start at the parking lot at North Lake and head due east toward the escarpment. You will find a marked snowmobile/horse trail there. It used to be the historic mountain road that brought carriages to the old Catskill Mountain House Hotel. Follow it downhill which takes you north, then watch for a right branch and take it. There’s a sign pointing toward the overlook. You will then be heading back to the south and you will soon cross the gash in the forest where the Otis Elevated Railroad once passed. Keep going south on the trail for a half hour or so until you reach a left fork. That fork continues to take you south and, in another ten minutes or so, you have arrived at the Palenville Overlook. It’s best to bring a map.

You won’t have any trouble knowing that you have gotten there. It’s a grand location; below yawns Kaaterskill Clove at its widest and deepest. Immediately to the west is another ledge called “Point of Rocks.” We haven’t been there yet but it appears to be a Palenville Overlook twin. Beyond the twin is all of Kaaterskill Clove itself. The Overlook is a place worth visiting at different times of the day and different seasons of the year. On many mornings there is fog in the valley below. As the day progresses the fog lifts and the great view emerges. Golden, in this autumn season, it will soon turn gray and then, as the cycle of the seasons continues, light and dark greens follow.

  The Palenville overlook

To the east is the expanse of the Hudson Valley. A geologist can’t help but to imagine the past when he looks into the valley. The great flat width of the valley floor below was the site of glacial Lake Albany at the end of the ice age, maybe 14 or 15 thousand years ago. It’s also easy to imagine the large valley glacier that was once down there as well.

Like any good geologists, we wondered how the ledge got there. The first hint that we found was along the horse trail. Not surprisingly, there are some stretches of the path that cut across bare bedrock. Some of that bedrock had been scraped, ground down and polished by the passage of a glacier, maybe 20,000 years ago. The grinding passage of the ice carved striations into the bedrock and these have a north-to-south orientation; the glacier had headed this way long before we got there.

That’s pretty much all we had to know to figure out what had made the Palenville Overlook. That glacier was probably part of what is known as the Wisconsin ice sheet. As early as 22,000 years ago the ice had completely submerged South Mountain and was advancing southward across it. When a glacier reaches a cliff, it very often breaks loose large blocks of rock. We call that process “plucking.” Not that anyone has ever seen plucking; it’s something that only happens at the bottom of the ice, but we can imagine what went on down there. There may have been a couple of thousand feet of ice here back then, and the weight of all that ice pressed down heavily upon the bedrock. That’s how the grinding, polishing and striations came about, and it probably also has a lot to do with the plucking. It seems that the thick ice presses onto and adheres to the bedrock. Then, as the ice moves on to the south, it literally yanks loose large blocks and drags them off. What is left behind is a jagged scar, the plucked cliff.

Plucked cliffs are very common throughout glaciated mountainous areas. There are a large number of them in the Catskills. Here in Woodstock, you can climb Overlook Mountain and see a good plucked cliff at the top of Lewis Hollow. That’s the cliff right in front of the old hotel ruins. The very same glacier that overrode Palenville also passed across Overlook and left the same features behind.

It’s autumn in the Catskills. You should never let this season go by without getting out. Palenville Overlook is just the sort of hiking goal that makes the season the grandest of the year.

Contact the authors at randjtitus@prodigy.net. Join their facebook page “thecatskillgeologist.com.

Crack Me Up

On the Rocks – The Woodstock Times

1998

Updated by Robert and Johanna Titus

Middle and late summer often brings the dry season of the year to the Catskills. The streams run dry or nearly so. The cobbles and boulders become light with a coating of dry and bleached algae. Nervous fish circle in the remaining pools of unhealthy, stagnant water. Along the stream banks, dry weeds have a lifeless look to them. If the plants are thirsty, then it’s at least partly their own fault: They have drawn so much water out of the ground.

It’s not a pleasant time of the year for those plants and animals that depend on lots of water and it never has been. Our August cycle is just this year’s edition of something that always has been, and probably always will be. It’s hot in August and when it’s hot things dry out. If we said that it was like this back in the Devonian time period when the Catskills were a great delta complex, we think that you might believe us. But if we said that you can go and still see some of the damage done during Devonian droughts, we would expect at least some skepticism. And yet it is so.

Sedimentary rocks, take sandstones for instance, are records of conditions as they were when the sediments were being deposited. Our Catskill sandstones were deposited in a multitude of delta environments, but one thing was certain. When there were droughts, pretty nearly the whole delta dried out. And that is reflected in the sedimentary rocks.

Sediment is generally deposited in some sort of watery environments. Catskill sediments were deposited in streams, ponds, pools, marshes and all sorts of watery settings. So, they were very nearly always wet upon deposition. But that didn’t mean that they would stay wet. Back in the Devonian there were dry seasons and dry years. Ponds and pools evaporated, shrank and dried up. Even rivers could run dry in the worst cases. Similarly soils and sediments dried up as well, although we geologists like to say they “desiccated.” At any rate, the last thing to happen was that the still wet muds at the bottom of any body of water were exposed to the sun and began to dry out. The clays within them would begin to shrink and so too would the whole mass of sediment.

Mud does not just dry out; it begins to divide into many small individual masses. Each of these continues to dry out and shrink towards it’s own center. The result is a maze of interlocking polygonal blocks. We call these “mud cracks.”

All this kind of explanation works better if you can go outside and see some of these features. Drive up to Kaaterskill Clove and find a place to park near the clove’s first legal parking. Then hike up to a fine waterfall, Fawn’s Leap. There is a bridge below the falls and below that bridge you will find a prominent ledge of very red sandstone. Climb down and look carefully. It shouldn’t be long before you see some green mud crack polygons, standing in sharp contrast to the red sandstones. That’s them.

It’s very kind of nature to give us those color contrasts, but there is nothing magical about it. Mud cracks tend to fill with quartz sand while the surrounding muds were rich in certain clay minerals. These clays tend to oxidize in the presence of air and that turns them red. The mud cracks, being of a different mineralogy and maybe being a little more waterlogged, don’t turn red, they turn green. Presto! Sharp contrast.

A mud cracked surface can be a lot of fun to crawl around on and study carefully. You can sometimes find insect tracks or bits of plant fossils. Raindrops prints are found where the rocks record a brief shower that interrupted the drought. Once I found a complete fish skeleton. The poor animal had died as its pond slowly dried up. As I said these are bad times for plants and animals. That’s the wonder of it; the rocks are records of the past. They speak to us of awful, killing droughts of long ago. Animals suffered in the heat and died painful deaths alone in the dust or dried out pools. But that was back in the Devonian and nobody cared, nobody mourned, nobody pitied. And, in the end, only the rocks remember.

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

Feeling out of place at North Lake

Windows Through time, The Register Star – May 20, 2010

Updated by Robert and Johanna Titus

We are all very fortunate to have a place such as the North-South State Campground in our region. It has been a very popular draw for visitors since the early 19^th Century and for good reason. It must be one of the most picturesque landscapes east of the Mississippi. The park sits atop the Catskill Front, overlooking a 70 mile stretch of the Hudson Valley with many breathtaking views.

There is a lot of geology to be seen in the park, so you have to make up your minds on what to do. You will want to walk around North Lake at, we hope, a leisurely pace. The walk will start at the Mountain House site parking lot and head north until you circle around most of North Lake and then return.

So, what is the geological “bait?” Well, mostly it is the Ice Age history of North Lake that you will want to explore. Both North and South Lake basins were scoured out by the glaciers, probably at the very peak of the Ice Age. Glaciers filled the Hudson Valley and then rose up and streamed into the area. You will want to walk along the eastern shore of North Lake and take a good look at the bedrock evidence of this. This rock records the passage of the ice. It’s actually been ground down and polished by the advancing glaciers. But the most striking features along the lakeshore are the striations carved into the rock. The glaciers dragged rocks along with them, and these gouged the rock. It’s a lot of fun to spot these and take note of them.  Each striation has the very same compass direction as the movement of the ice. Each is thus a history of Ice Age activity at North Lake.

But what we like even better than the striations are the Ice Age features that are called “erratics.” These are boulders, often very large, which were carried here by the moving ice. Glaciers are quite capable of lifting very large rocks and sweeping them along. We have been finding erratics here in abundance. Some of them are famous; maybe you have seen the one called Alligator Rock.  It, in fact, does look like the head of an alligator. It even has a large open “mouth.” People have been putting stone teeth in that mouth for as long as they have been coming here.

Dinosaur Rock

This great rock, and probably scores of others, dot the landscapes at North Lake. We think the largest number of them are found on the point that separates North and South Lakes. But there are many more, all around the lakes. What are they and where did they come from?  Well, the history of any erratic begins when ice was passing across its home bedrock. The ice tended to stick to that rock and, as the glacier advanced, it plucked the boulders loose and dragged them off. That’s what’s erratic about these rocks; they don’t match the local bedrock. The glaciers eventually melted and when they did, they left those erratics behind, right where we see them

today.

There’s more to the story.  Erratics are clustered in the North Lake vicinity,

suggesting they all came from the same glacier. When you get to North Lake, you

should look up to North Point and see where that glacier came from. Near the top of

North Point there is great basin, just below the peak. Geologists will recognize this as

what is called a cirque. Cirques are the basins in which Alpine glaciers had formed and

from which they began their downhill journeys. We will look up at that cirque and in our

mind’s eyes we will see an Alpine glacier. We will watch as it slowly descended the

slopes of Mary’s Glen, heading toward North Lake. We won’t be able to see them, but

that glacier was ripping up our erratic boulders and carrying them along for the ride. We

will watch long enough to see the climate warm and the ice melt. It is then that those

boulders will be left behind

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

Geologist.”

Dinosaur Rock