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History of the Mohawk Valley: Gateway to the West 1614-1925
Chapter 1: The Geology of the Mohawk Valley.

[This information is from Vol. I, Vol. I, pp. 45-82 of History of the Mohawk Valley: Gateway to the West 1614-1925, edited by Nelson Greene (Chicago: The S. J. Clarke Publishing Company, 1925). It is in the Reference collection of the Schenectady County Public Library at R 974.7 G81h. This online edition includes lists of portraits, maps and illustrations. Some images have been relocated to the area in the text where they are discussed. As noted by Paul Keesler in his article, "The Much Maligned Mr. Greene," some information in this book has been superseded by later research or was provided incorrectly by local sources.]

Contents | Biographies | Illustrations | Maps | Portraits

Go back to: Foreword | ahead to: Chapter 2

The Mohawk Valley physiographic province and its geographical importance — The Adirondack and Catskill regions of the Mohawk Valley — Little Falls Gorge, "the Gateway to the West" — Its mighty potholes — Little Falls "diamonds" — The Devonic fossil trees of Schoharie County, the world's oldest forest — The eastward and the westward flowing preglacial Mohawks — Glacial and postglacial periods — The mighty "Iromohawk", which made the Mohawk Valley of today.

To perpetrate an Irish bull, "Where would we be without the ground we stand on"?

If the reader considers that the story of the rocks of the Mohawk Valley has no bearing upon its history and his own life, and if it is without interest to him, then he had best skip this chapter. However, anyone who remains ignorant of the making of our river, its hills and vales, misses one of the most interesting parts of the story of the Valley in which we live.

In truth, the briefest description of the making of the topography and geology of the Mohawk Valley, requires considerable space, for this story goes back to the very beginnings of things — through the long ages of geological time. We should be proud of this fact, however, because it shows that the Mohawk Valley is an "old timer", and that its rocks have existed through a great part of the geological history which is known to us today.

The geology of the Mohawk Valley is most important in its relation to that of the State of New York, and its history, and also to the making of this national transportation route, which would be impossible without our "Gateway to the West".

Little Falls Gorge — Gateway to the West

We know that this important Gateway exists today, and this Valley geology is merely the answer to the question, "How was this great Gateway to the West created"?

Let us take our stand on the summit ledge of the "burnt rocks" in the famous Gorge below Little Falls, and look about us at the rugged scenery. At the lowest level is the dark river flowing in a channel cut in the igneous rock on which the world is built.

The most characteristic and impressive part of the Gorge is this eastern section below the lower dam and falls of the River, the recess in the rock on the north shore, known as the Gulf, and eastward for a mile. This section embraces the site of the ancient cataract and its deep pothole, rugged Moss Island, with its wonderful potholes, which also are easily seen on the north shore near the Turnpike.

The cliffs of syenite are locally known as the "Burnt Rocks," and the bottom of the Gorge, as the "bed rock", although both are of the same syenite, which is a massive plutonic rock resembling granite, except that it contains little or no quartz. Plutonic rocks are those cooled and solidified from molten materials at considerable depths below the surface of the earth and subsequently uncovered by erosion.

Above the syenite rocks of the Gorge, rise steep ascending cliffs of Little Falls dolomite, but, except in the Rollaway cliff to the north, this dolomitic limestone is generally covered with soil, trees and other vegetation. Above this the extreme summits are of limestone and shales of the Trenton period, and of the Lorraine formation.

Down below us in the Gorge, the great barges of commerce are coming back and forth from the Big Lock, while, on a shelf near the base of the Burnt Rocks, the New York Central trains thunder by continuously. Close to the river, a constant stream of automobiles rushes east and west over the Mohawk Turnpike. To the west, are the chimneys of the teeming industrial town of Little Falls. To the east we visualize as fair a stretch of farmland and river-shore as the eye can see anywhere in this country. It, indeed, is a picturesque panorama on all sides.

But where we stand there are nothing but rocks, rocks below us, rocks to the right and rocks to the left — not broken masses but a solid mountain of stone, cut through by a great Gorge, with sides and floor consisting of rock materials many millions of years old.

How came this Gorge of the Mohawk, this Gateway of the West? What mighty forces carved so great a channel through this mountain of stone? Surely its making forms a story of absorbing interest, because it truly embodies the creation of the Valley of the Mohawk as we know it today.

[Map: The Little Falls Gorge.]

Topographic map showing the deep, narrow gorge of the Mohawk River at Little Falls. The walls of the gorge rise fully 50 feet above the river which is less than 400 feet above sea level. The gorge is postglacial in origin and before the great ice age it was replaced by an important divide with one stream (Mohawk River) flowing eastward and another stream flowing westward. Part of Little Falls (U. S. G. S.) quadrangle. Scale, about 1 mile to the inch.]

* * *

The geological importance of the Mohawk Valley is shown by the fact that it forms one of the ten physiographic provinces or districts into which the State is now divided, as follows: Mohawk Valley, Adirondack Mountains, Tug Hill Plateau, Erie-Ontario Plain, Southwestern Plateau, Catskill Mountains, Hudson Valley, Champlain Valley, St. Lawrence Valley and Long Island.

The Mohawk Valley is bounded on the north by the Adirondack Mountains, which form nearly one-quarter of the Valley's surface; on the northwest, by the Tug Hill Plateau, in which the Mohawk River has its source; on the west by the Erie-Ontario Plain, which reaches to the eastern end of Oneida Lake; on the south by the Southwestern Plateau and the Catskill Mountains, which form the greater part of Schoharie County; and on the east by the Hudson Valley.

The later periods of geologic time, particularly the Tertiary and the Quaternary, are necessarily the most interesting to dwellers in the Mohawk Valley, because, in the Tertiary, the land of our State was elevated and eroded to its present form; while, in the Quaternary, came the Great Glacier, which rounded our mountains and hills; gave us our beautiful lakes; and created, here in the Mohawk Valley, a great river which cut out the channel of the Little Falls Gorge, and the pass between the Noses. New York State and the Mohawk Valley can thank this great glacier for the rock sculpturing it did to give us the famous water level route through our Valley from Lakes to Sea.

The geological history of the Mohawk Valley is a long look into the past — into the aeons of time which the human mind is utterly unable to grasp. This is particularly so because so much of the northern half of our Valley lies within the Adirondack region which comprises rocks which are to be classed among the oldest in the world and one of the most ancient of land elevations. It is only when the reader knows the story of the Mohawk Valley in its relation to the later geological periods, the Tertiary and the Quaternary, that he feels a true realization of time and space. The 25,000 to 50,000 years which have elapsed since the melting of the great glacier, are comprehensible to us; though the millions of years of some of the main geological periods are almost meaningless, so great is the time involved.

There is much interest to Mohawk Valley people in the story of these mighty forces of nature and the sedimentation of the ages, which made the Valley of today. Here are some of the most unusual geological remains in the whole world. The greatest potholes in existence are those cut by the postglacial Mohawk River and cataract in the bed rock at Little Falls. The fossil remains of the oldest forest in the World were discovered at Gilboa, Schoharie County, in 1869. They were "fern trees" of the Devonic period; some of which were taken up and removed to the State Museum, at Albany. The foregoing constitute but two of a number of features which give our Valley unusual geological interest.

* * *

The Geological History of the State of New York, by William J. Miller, Ph. D. of Hamilton College, was issued in 1913 as a bulletin of the New York Museum of the University of the State of New York. Dr. Miller's classifications are used in this geological chapter, and much use is made of certain of his material. This chapter is intended exclusively as a geological history of the Mohawk Valley, with some references to its adjoining provinces, where they affect that of our Valley. Dr. Miller's work is a condensed and clear book on the State's geology and can be heartily recommended to the layman. Several of the maps illustrative of this book are included in this chapter, by the kind permission of Dr. Miller. This geological work is a great credit to Dr. Miller, to the Mohawk Valley, of which he was a former resident, and to the western Valley college of Hamilton, which makes much of geological study, with particular attention to that of the Mohawk Valley.

It is only with reference to the geological and physiographic systems of New York State in their relation to the Mohawk Valley, that the following geological description of our Valley is here given.

Of all the great systems of geology, only the Permic and the Jurassic are absent from the surface rocks of New York State. The ten others are all represented: Precambric, Cambric, Ordovicic, Siluric, Devonic, Carbonic, Triassic, Cretacic, Tertiary, and Quaternary.

New York presents a most unusual revelation of the geology of America, and the surface rocks of our State form a virtual sermon in stone, as well as a textbook of geology. The names of our Valley localities have been given to a number of different rock systems, because of their typical presentations in the outcrops near the Valley towns mentioned. Eleven of the forty-two rock formations, given in Dr. Miller's geology, bear Mohawk Valley names. The Mohawk Valley has an area of 3,485 square miles out of the State's area of 50,326 square miles. Our Valley's territory is about one-fifteenth of that of the State, while the Valley furnishes over one-quarter of New York's geological strata designations. This should bring home to the reader the geological importance of the Mohawk Valley in its relation to that of our State and our Nation.

The great central river belt of the Mohawk Valley is occupied by rocks of the Ordovicic period of the Paleozoic era. Precambric rocks occupy the Adirondack districts of northern Fulton, Herkimer, and Oneida counties, with outcroppings of Cambric rocks in Herkimer, Montgomery, and Fulton counties. Siluric rocks run along the southern rim of the eastern and central Mohawk watershed in a narrow belt, widening to fill the western half of Oneida County. Devonic rocks cover the extreme lower ends of Oneida and Herkimer counties, and the lower half of Schoharie County. Note the map published herewith concerning the geological rock systems of New York State. In all this description of Mohawk Valley geology, the accompanying maps should be frequently consulted to get a clear idea of our Valley's story in stone.

Mohawk Valley Province

Dr. Miller says:

"The Mohawk Valley province, though comparatively small, is of great importance because it so clearly separates the Adirondack highlands on the north from the highlands of the Catskills, and the southwestern plateau province on the south. In fact, it should be noted that the Mohawk Valley is by far the lowest passageway across the mountains between the St. Lawrence River and the southern end of the Appalachian range. The low pass is one of the great eastern 'gateways' which, with the St. Lawrence, have afforded the easiest means of communication between the Atlantic seaboard and the Great Lakes."

The comparatively narrow inner valley through which the river now flows, is often erroneously called the Mohawk Valley, but in reality the wide depression, from 15 to 50 miles wide and from 1,000 to 2,000 feet deep, between the northern and southern highlands of the State, should be called the Mohawk Valley. "At Little Falls, the inner valley narrows to a gorge several hundred feet deep, where the river has cut its way through a preglacial divide. Had it not been for the recent cutting of this gorge through the barrier at Little Falls, the Mohawk Valley would never have been so important as a great gateway between the Atlantic coast and the West. Today the four tracks of the New York Central Railroad, two tracks of the West Shore Railroad, Barge Canal, an important highway, many telegraph and telephone wires, and the Mohawk River all pass through this narrow gorge within a few hundred feet of the sea level.

[Map: New York State Geological Provinces.]

[Map: Grabau's Interpretation of Late Tertiary Drainage in the Eastern Great Lakes Region.]

"Eastward and westward from Little Falls, the inner Valley is generally fairly wide and open. At Little Falls, the Mohawk River is less than 400 feet above sea level, and even at Rome, in the western part of the province, the river shows an altitude of only 420 feet.

"The principal rocks of the province are shales, sandstones and limestones of Cambric and Ordovicic ages; of these the soft, black shales of Trenton, Utica and Frankfort ages are in greatest abundance. The Valley owes its existence largely to the presence of this belt of shales lying between the hard crystalline rocks of the Adirondacks on the north and the comparatively hard limestones immediately southward. The work of erosion has made rapid progress in the belt of weak rock, and at two places, Little Falls and 'The Noses' (Yosts), the river has cut down to the Precambric (Adirondack) rock. In general, the rock formations of the province tilt slightly southwestward and show folding only on a very small scale. From Little Falls eastward, however, the strata are greatly disturbed by numerous nearly north-south faults which are often of considerable magnitude."

The northern part of the Mohawk Valley is included in the Adirondack physiographic province, and this region forms so much of the Valley's area that it demands a description along with that of the Valley itself. Outside of Schoharie County, the Mohawk Valley is generally comprised in a geological and physiographic district which might justly be called the Mohawk Valley — Adirondack Region. Schoharie County lies mainly in the Catskill Mountain area, to the south. So it is plainly to be seen that the Mohawk Valley is a break between the Catskill and Adirondack Mountain systems, and comprises both of these mountain sections within its area.

Dr. Miller describes the Adirondack Mountain physiographic province as follows:

Adirondack Mountain Province

"The Adirondack Mountain Province comprises fully one-fourth of the area of the State, and it consists of a great, nearly circular mass of metamorphic and igneous rocks of very great age, that is Prepaleozoic. This large mass of crystalline rocks is completely surrounded by the practically unaltered Cambric and Ordovicic rocks. The whole province is typically mountainous and heavily wooded, often being truly wilderness in character, with very few roads or settlements other than summer resorts. Except along the immediate borders, the elevations range from 1,000 to over 5,000 feet. The greatest axis of elevation extends from southern Hamilton County (2,000 feet) northeasterly into Essex County, where the highest mountains are grouped around Mount Marcy, and where the mountains commonly attain altitudes of from 3,000 to 5,000 feet. In the eastern and southeastern portions there is a well defined tendency in the mountain masses to be arranged in long, nearly parallel ridges or ranges, whose general trend is north-northeast to south-southwest. This structural feature is due to numerous faults or fractures in the earth's crust. In the northern and western portions, the mountains are very irregularly arranged. Viewed as a whole, there are no high, sharp-topped peaks, which stand out prominently above the general mountain level, and the flowing or rounded outline of topography is by far the most common. The very ancient Grenville rocks occur throughout the region, and the great masses of igneous rocks have been forced through these. All these rocks have been subjected to tremendous earth pressure which has folded and completely metamorphosed them."

The Tug Hill Plateau — Source of the Mohawk

The Mohawk River has its source in the southern part of the Tug Hill province which bounds the Mohawk Valley throughout the northwestern part of Oneida County. Tug Hill is unique in that it is an erosion remnant of the great upraised Cretacic plateau, which formerly covered all of New York State.

Erie-Ontario Plain

The extreme western end of the Mohawk Valley is bounded by the Erie-Ontario plains province, which extends a short distance into Oneida County. The most marked relief features of this region are the hundreds of low glacial knobs or drumlins.

Southwestern Plateau

The Southwestern Plateau is a great physiographic province which borders the Mohawk along two-thirds of the southern rim of the Mohawk Valley, on its western and central portions, while the Catskill Mountains bound the southern Valley at its eastern end in the Schoharie region.

Dr. Miller says:

"The Southwestern Plateau is the largest clearly defined physiographic province, occupying nearly one-third of the area of the State. The rocks are unaltered sediments of the Devonic age which consist of shales, sandstones and conglomerates. There are a few patches of Carbonic rocks in the southwest. In marked contrast to the Adirondack province, the rock masses of this Southwestern Plateau are practically devoid of displacements, the only disturbance being a slight tilt (30 to 50 feet to a mile) of all the strata to the south or the southwest associated with a low northeast-southwest undulation… Physiographically, the Plateau province is the northernmost extension of the great plateau which lies along the western base of the Appalachian Mountains. On the east, the province is bounded by the Catskill Mountains, which are in no sense sharply separated from the plateau itself. On the west and north, the province is bounded by the Erie-Ontario Plain and Mohawk Valley provinces."

Helderberg Escarpment

"The northern limit of the Southwestern Plateau is pretty clearly marked by what is called the 'Helderberg Escarpment' of Devonic limestone. This limestone, being of considerable thickness, and of more resistance than the neighboring formations, has generally stood out boldly against erosion, thus causing an abrupt change in relief. The Escarpment is particularly prominent along the boundary of the plateau and Mohawk Valley provinces where the hard limestone lies at an altitude of more than 1,000 feet, and directly overlies the soft shales of the Mohawk Valley whose altitude is generally only a few hundred." This Helderberg Escarpment, as it runs westward, takes on the names of Schoharie Hills, Cherry Valley Mountains, Susquehanna Hills, Unadilla Hills, etc. It sharply divides the Mohawk Valley from the Southwestern Plateau and Susquehanna Valley on the south.

A belt of soft Ordovicic shales, running east and west, lies between the hard granites of the Adirondacks and the hard limestones of the Helderberg Escarpment. The Mohawk and its tributaries eroded the Valley basin in the soft shales, between these hard rock sections to the north and south, thus creating the trough of the Mohawk Valley, which is a broad basin from ten to fifty miles wide at different points, and which averages from 1,000 to 2,000 feet in depth between its watershed heights.

The Helderberg Escarpment is peculiar in that it forms a narrow band comprising the paralleling outcrop of several rock formations. It averages but a few miles in width but extends from the eastern face of the Catskills northward to the Helderbergs, in Albany and Schoharie Counties, and thence almost due west to the Niagara River, a distance of over three hundred miles. As it lies along and on the southern rim of the Mohawk Valley watershed, the rocks composing the Helderberg Escarpment lie in the following north to south order; Salina, Helderberg, Oriskany and Onondaga strata, with the Helderberg greatly predominating. The Oneida formation is also associated with the Helderberg Escarpment.

The summit of this Helderberg Escarpment generally forms the watershed rim of the southern Mohawk-Susquehanna divide, and, from these heights, the traveler frequently gets magnificent views into both valleys. This is particularly true on the road from Sharon Springs over the Escarpment (Cherry Valley mountains) into Cherry Valley village.

[Map: New York State during the last Ice Age, depicting the Ontarian Lobe of the Labradorian Ice Sheet.]

Catskill Mountain Province in the Mohawk Valley

The Catskill Mountain province forms part of our Valley area, and comprises the greater part of Schoharie County, in its southern section. The Schoharie, through a large part of its course, is a typical Catskill stream. This province also bounds the southern side of Schenectady County. "It is the most rugged of all the physiographic provinces of the State, and, next to the Adirondacks, contains the highest mountains. Slide Mountain (4,205 feet) is the highest, but a number of peaks rise to altitudes of from 3,500 to over 4,000 feet. The face of these mountains looking eastward toward the Hudson have frequent steep elevations (of 3,000 feet or more) which afford some of the finest views in the State. The rocks are all of Devonic age, and consist largely of sandstones and conglomerates." Most mountains are the result of the folding or faulting of the strata, but the Catskills are the direct result of erosion, a rare cause of mountain-making. The oldest fossil trees in the world were uncovered at Gilboa in this Catskill region of the Mohawk watershed.

Hudson Valley Province

The Hudson Valley province bounds the Mohawk Valley province on the east front of Schenectady and Saratoga counties (the southwestern third of Saratoga County being contained in the Mohawk Valley). The Hudson Valley province is a depression lying between the western highlands of New England (remnants of the ancient Taconic range) and the eastern highlands of New York, including the Catskills. The Hudson is a large and varied province which could easily be divided into four or five provinces and which deserves a whole chapter to itself because it is the seat of the world's greatest city, and therefore the most important river valley in the world today. The Hudson and the Mohawk Valley provinces also deserve great consideration from the student as they contain the world's greatest highways and waterways.

* * *

Mohawk Valley Geological Names

The eleven rock formations which have Mohawk Valley place names are fully described in the next chapter. They are as follows (from the earliest to the latest formations): Little Falls (Cambric) dolomitic limestone; Trenton (Ordovicic) limestone and shale; Canajoharie (Ordovicic) black shale; Utica (Ordovicic) shale; Frankfort (Ordovicic) shale and sandstone; Oneida (Siluric) conglomerate; Clinton (Siluric) shale, sandstone, limestone and iron ore; Cobleskill (Siluric) limestone; Helderberg (Devonic) limestone; Oriskany (Devonic) sandstone; Catskill (Devonic) sandstone.

The Catskill and Helderberg rocks are included in the Mohawk Valley geological names because they cover a large part of the Schoharie Valley, which comprises over one-fourth of the area of the Valley of the Mohawk. We are therefore as much entitled to use these names as local to the Mohawk watershed as is any other section of New York State.

In our consideration of the geology of the Mohawk Valley, the rocks which precede the Cambric period are classified as Precambric, the latter probably being one of the most extensive of all the divisions of geological time. The oldest known rocks, in this period, are the Grenville metamorphosed sediments which cover many portions of the Adirondacks (including the northern Mohawk Valley) and the Highlands of the Hudson. Metamorphosed rocks are those which have been changed from their original sedimentary form by great heat, at considerable depths below the surface. They have been uncovered subsequently by uplifts, folding, erosion, etc.

The Precambric Period

The Grenville rocks take the form of crystalline limestone or marble; quartz forms, including rocks rich in garnet and graphite, which latter is mined from the Grenville rocks in Essex and Saratoga counties and used in the manufacture of pencil leads, crucibles, etc.

The lead in the pencil you use may contain fossil remains of the world's oldest known life forms, provided it came from the graphite mined from the world's oldest known rocks which occur in the Adirondacks and the northern part of the Mohawk Valley. Near Little Falls, the Grenville rocks are exposed northward from a point in the East Creek Valley about six miles northeast of the city. The Grenville rocks appear in the earliest Precambric period, which is an arbitrary term implying precedence over the Paleozoic period. All sedimentary rocks are formed from sediment eroded from near by land masses, but it is a matter of conjecture as to where the land masses were located which formed the Grenville strata.

The Adirondacks form one of the few ancient existing land masses which have survived the geological changes since their birth from the sea. Following and with the Adirondack upheaval, the upper area of our present Mohawk Valley gradually arose above the ocean, and so our Valley's northern region is one of the Earth's oldest land surfaces. Igneous activity and intrusion of molten rock materials characterize later Precambric period and it was probably, in this morning of the world, that the Adirondacks were upraised together with the Highlands of the Hudson.

These ancient Adirondacks were then probably much higher than at present, as they have endured great erosion and many geological changes since those early days, but the fact that their peaks have always been above water since their birth seems positively assured. In their earliest days, the Adirondacks probably constituted a mountain mass equal to the Alps in height, and the Highlands of the Hudson also formed a lofty range.

Cambric Period

In the Cambric period the Adirondacks were lowered and later raised so that much of northern New York became dry land. The New York State rocks of the Cambric period (from the bottom upward) are Georgian slate and quartzite, Acadian limestone, Potsdam sandstone and limestone and Little Falls dolomite. While the Potsdam rocks appear in the Mohawk Valley, its most interesting Cambric rock feature is the Little Falls dolomitic limestone which probably forms a belt entirely around the great Adirondack region. This dolomite also forms the upper heights of north and south Fall Hill in the Little Falls Gorge and the great rock cliff there known as the Rollaway, where it has its most evident and typical exposure and from which it takes its locality name.

[Photo: Trenton Falls, West Canada Creek.]

Ordovicic Period

The great Ordovicic period which followed is interesting to Mohawk Valley people, as many of its rocks bear the names of Valley localities where they typically outcrop, as will be seen by the following list of the Ordovicic rocks arranged in their strata order from the bottom upward: Beekmantown limestone, Chazy limestone, Black River limestone, Trenton limestone and shale, Canajoharie shale, Utica shale, Frankfort shale and limestone.

The Ordovicic sea covered more of the present United States than any other ocean since the Precambric period. In New York the Adirondacks stood out as an island above this ocean.

A high continental land area, known to geologists as Appalachia, extended from the coast of the present United States to an unknown distance into the Atlantic ocean. Appalachia, doubtless, was responsible for much of the sedimentary rocks of our coastal states and of New York. This mysterious continent persisted from Cambric times up to almost the beginning of the Cenozoic period, or the "modern times" of geology, when it disappeared beneath the Atlantic at a time coeval with the subsidence of the coast line.

There was life in the Cambric, Ordovicic and Siluric seas. The Precambric had the earliest known life forms, as evidenced by the graphite in its rocks. The Cambric and Ordovicic formed the Age of Invertebrates. Simple fish forms begin in the Siluric, while the Devonic is known as the Age of Fishes.

There were simple plant forms in the Cambric and seaweeds and algae in the Ordovicic seas. In these seas lived coral, graptolites, starfish, brachipods, and trilobites, but so great has been the change in life forms since then that not a single species of that distant day has survived.

The Taconic Revolution

The great Taconic revolution marked the close of the Ordovicic period, when a high range of mountains was upheaved along the present line of eastern New York. These great mountains are now represented by the Piedmont Plateau in Virginia, the Highlands of the Hudson, the Berkshire Hills, and the Green Mountains. At the end of this upheaval all of New York State was above the sea with the exception of the western part.

The surface rocks of the central belt of the Mohawk Valley were laid down during the great Ordovicic period. These are the rocks that in the main underlie the towns of the Mohawk and the central belt of our beautiful farming country. As they belong to the daily life of the people of the Mohawk Valley they are therefore the rock formations of the greatest interest to us. Upon the Ordovicic shales, sandstones, and limestones, our Mohawk River towns and our great railways and highways are built. Many of our Valley's oldest houses were built of these ancient limestones. The average thickness of the Ordovicic strata in New York State is between 2,000 and 3,000 feet.

Siluric Period

Depressions of the land followed in the early Siluric period so that about half of present New York State was under water. The eastern half was dry land, the western half was submerged. The Mohawk Valley, the Adirondacks, northern New York and the Hudson Valley were above the sea. Siluric rocks form a narrow band along the southern half of the Mohawk Valley.

The principal Siluric rocks are (as deposited stratum upon stratum): Medina sandstone; Oneida conglomerate; Clinton shale, sandstone, limestone and iron ore; Rochester shale; Lockport and Guelph dolomites; Salina shale (the strata from which the Syracuse salt wells produce their salt water), salt, water lime; Shawangunk conglomerate; Cobleskill limestone; Roundout limestone, water lime; Manlius limestone. The thickness of the Siluric rocks in Central New York is between 1,000 and 1,500 feet.

The three Siluric strata named after Mohawk Valley localities are the Oneida conglomerate, the Clinton series and the Cobleskill limestone.

Devonic Period

The Devonic Sea which followed the Siluric covered the Catskills and the Southwestern Plateau region. It deposited strata from the Catskills to Western New York. The Devonic rocks consist of a thin bottom layer of limestone overlaid by a thick body of shales and sandstones, piled layer upon layer. These rocks are land-derived sediments, which were washed into the Devonic Sea by sediments from the Taconics on the east and the Adirondacks and Canadian land masses which are known to have existed to the northward.

The Devonic rocks (from lowest to uppermost stratum) lie as follows: Helderberg limestone, Oriskany sandstone, Onondaga limestone, Marcellus shale, Hamilton shale, Tully limestone, Genesee shale, Portage shale and sandstone, Catskill and Chemung sandstone.

The rocks immediately concerned with the Mohawk Valley are, first, the Helderberg limestone, which is the watershed summit rock of the Helderberg Escarpment which forms the southern Valley divide (excepting the basin of the Schoharie Valley). The second series of Devonic rocks of the Valley are the Oriskany sandstone and the Catskill sandstone (in the Schoharie basin).

Bold, outcropping edges of thick Devonic strata face toward the Mohawk Valley and form the abrupt northern face of the Helderberg Escarpment (particularly in Albany County). The Helderberg Escarpment, in varying elevations, extends westward clear across the State to the Niagara River, being called in that section the Niagara Escarpment. It is accompanied by outcrops of the Oriskany sandstone.

At the end of the Devonic period, all of the northern and eastern parts of the State (including the Adirondacks and the Mohawk Valley) were above the sea, while the western and southern parts were generally below it.

Dr. W. J. Miller says, in his Geological History of New York State:

"The Devonic strata, from oldest to youngest, abounds in the fossils of marine organisms, and some fossil land plants have also been found. * * * The Devonic furnishes the first really authentic existence of land plants. Such plants as ferns, lycopods (club mosses) and equisitae (horse tails) grew to be large treelike forms and in considerable profusion. Remains have been found of these in the Devonic strata of New York. All of them belong to the very simple non-flowering plants and were closely related to the plants of the next succeeding Carbonic (coal) period.

"Among the fossil animals especially abundant in the Devonic rocks of the State are: sponges, corals,star fishes (echinoderms), brachiopods, mollusks (including the bivalves, gastropods, and cephalopods), and anthropods [arthropods?] (including trilobites and eurypterids). The graptolites became almost extinct during the Devonic."

From the great abundance and variety of fishes the Devonic is frequently referred to as the Age of Fishes. Remains of Devonic fishes have been found in considerable numbers in New York State. These are of simple type without the true bony skeletons of modern fishes. From its land plants and fish life, the Devonic might well be called "the Age of Fishes and Land Plants."

The most remarkable examples of Devonic fossil plant life were uncovered in our Mohawk Valley at Gilboa, in Schoharie County, on the upper Schoharie River in 1869.

The World's Oldest Trees in Schoharie County

This most ancient of fossil forests is described as follows in the New York State Museum Bulletin of December, 1919, under the report of John M. Clarke, director of the New York State Museum.

"A great autumn freshet in the upper valley of the Schoharie Creek in 1869 tore out bridges, culverts and roadbeds around the little village of Gilboa and exposed, in the bedrock of the hills, a series of standing stumps of trees. These stumps stood all on the same level in the rock and their rootlets ran down into the original mud in which they had grown, now turned into a dark or greenish shale. All had been cut off by some ancient flood at about three feet above the base; some were large and some were smaller, the largest having a diameter in the shaft of two feet or more with broad expanding rootbase like a flaring turnip. This has brought to light the standing remains of the most ancient growth known in the geological records in any part of the world. Ten of these tree stumps were taken out from their ancient forest, all at the same level in the rocks, and most of them were brought to the State Museum, where they have long constituted one of the remarkable exhibits of the vanished flora of the State.

"The effort made this year (1919) to relocate this primeval forest of the Devonian Period or to find some additional evidence of its extent has proved successful. The old locality is deeply covered and the rocks of that level, which carried these trees, do not come to the surface again in this vicinity. But the work has been attended with unexpected results in finding the stumps of other trees of the same sort at a level 60 feet higher in the rock beds, giving evidence that the forest growth had reappeared in the same region at a later stage in the Devonian history. * * *

"The story of the earth's primitive forest when fully written promises to be an interesting one, and it is hoped to reproduce, in part at least, in the State Museum, this picture out of the dim past."

This work is now, 1924, in progress in the State Museum.

The location of the new series of stumps has been due to Herbert S. Woodward, who has had the assistance of Messrs. Ruedemann and Hartnagel in the careful extraction of the remains and in the important discovery of the fruit cases.

* * *

[Photo: Little Falls Gorge East of Railroad Curve.]

[Photo: One of the Gilboa Fossil Tree Trunks in Place.]

Miss Winifred Goldring of the New York State Museum is the author of a paper, "The Upper Devonian Forest of Seed Ferns in Eastern New York," published in Museum Bulletin 251, issued in 1924. Following is an extract from its Summary, which shows the botanical character of these first trees:

"In 1869 was made a remarkable discovery of fossil tree stumps in the upper Devonian (Ithaca) beds of Schoharie County, in the vicinity of the village of Gilboa. In 1897, a few loose trees were reported from a higher horizon at the Manorkill falls a mile above the old locality. Special efforts in 1920 led to the discovery of these stumps in place at the Manorkill locality at the 1,120-foot level 100 feet above the old locality. Since 1920 the City of New York has been doing construction work at Gilboa preparatory to impounding the waters of the Schoharie Creek to meet future demands. In the course of operations, the old locality, at the spot where the dam is being built, was uncovered and several specimens obtained; a new quarry at the 960-foot level was opened up 2,300 feet north (downstream) of the old location and has yielded the greatest number and the largest stumps hitherto found, one of the largest of this group having a circumference at the base of 11 feet. With the recent additions to our collections the Museum now has a total of forty stumps, partial or complete. At all three horizons the stumps were found with their bases resting in and upon black shale representing the trunk extending into the coarser sandstone above. At least, then, three successive forests of these trees reared themselves to great heights along the marshy borders of the unstable coast line of the shallow Devonian sea, were submerged, destroyed and buried.

"At the same time that the new tree horizons were discovered, a shale bed, in the vicinity of the Manorkill at the 1,020-foot level, yielded specimens of roots, foliage, and most important of all, seeds and sporangia-bearing organs; all of which taken together with the character of the stumps and trunks have shown these trees, originally described by Dawson as tree ferns, under the names Psaronius, to be seed ferns (Pteridospermophytes) intermediate between the ferns and higher seed plants. The name Eospermatopteris is proposed for this Devonian seed fern which bears a resemblance to the Carboniferous seed fern, Lyginopteris.

"The bases of the stumps are bulbous as might be expected of trees growing under swampy conditions, and show a circumference at the base from 3 feet 10 inches up to 11 feet. * * * The outer cortex as in Lyginopteris consists of interlacing strands of sclerenchyma tissue, forming a network, or more or less parallel; the inner structure is not preserved. Consideration of the size of the stumps and study of the parts of the trunk found indicate that the largest of these trees must have reached heights of at least 30 to 40 feet.

"The only specimen, in which are preserved the petioles of the fronds attached to the trunks, shows that these have a spiral arrangement in about five ranks. The fronds must have been at least six feet long and were tripinnate with the pinnules bilobed and of the Sphenopteridium type, bearing a resemblance to the sterile pinnules referred to Cephalopteris mirabilis Nathorst from the Devonian of Bear Island. The seeds were borne in pairs, at the ends of forked branchlets and were probably borne near the tip of the frond.

"Two species of these trees were distinguished by Dawson: E. textilis, in which the slerenchyma strands form a network, and E. erianus, in which the strands are more or less parallel. No further distinguishing characters have been found."

Miss Goldring has the following interesting addition to her paper:

"While this paper was in the press, new and valuable specimens of stumps, throwing light upon the nature of the root systems of these trees, was uncovered in 'Riverside quarry'. These specimens show the underside of the base of the stumps with the impression, in the sandstone, of roots radiating in all directions to considerable length. One specimen was removed and is in the possession of the Museum. This specimen, with the base of the stump having a diameter of about twelve inches, has root impressions measuring up to an inch or more across. Specimens were uncovered in which the roots were traced for a distance of six feet and the tips were not reached then. Unfortunately, it was not possible to take the large specimens from the quarry. However, they show that the root systems were considerably larger and more adequate than previously supposed; sufficient, at any rate, to support trees of the height to which these trees must have attained. The finding of the new specimens, with extensive root systems, also answers the criticism that the stumps as found were not in situ, because those so far taken out did not have the roots attached."

Carbonic Period

The Carbonic period, which followed the Devonic, was the great Coal Age, with non-flowering plants similar to those described in the Devonic fossil forest uncovered in the Schoharie River region of the Mohawk Valley. These made the coal, which is such a problem in the life of today. There are only small exposures of the Carbonic period in Alleghany and Cattaraugus counties in New York State.

Probably the oldest almost unaltered animal of today is the horseshoe crab which dates from the Carbonic period and which has experienced almost no structural changes during the interminable length of time which has since elapsed. It belongs to the spider family.

Permic Period

The Permic period is the last of the Paleozoic era, but its rocks are not represented in New York which was then probably all above sea-level.

Appalachian Mountain Upheaval

The great Appalachian revolution upraised a vast mountain system, from the mouth of the St. Lawrence to Alabama, at the end of the Paleozoic era. Then practically all the land of New York State (except the Hudson's mouth) was raised above the ocean and has so remained ever since.

Faults of the Mohawk Valley

The faults of the region of the eastern Adirondacks and the Mohawk Valley were probably created during this titanic upheaval of the Appalachians. These faults were formed by a gigantic slipping of the earth's crust and they had much to do with the present form and later geological history of the Mohawk region.

The main faults of the Mohawk Valley are at Little Falls, St. Johnsville, The Noses and Hoffmans Ferry. All of these faults have northward extensions. There are lesser faults at Dolgeville, near Schencks Hollow, at Fonda and at Tribes Hill. These crust cracks with uplifts and slippings of the rocks formed Fall Hill at Little Falls, the high ridge running from St. Johnsville northeast to the Garoga, the Noses and Touereuna Mountain at Hoffmans Ferry. In point of displacement the Hoffmans Ferry and Noses faults are the greatest in the Mohawk Valley.

Triassic Period

The Triassic period found New York State and eastern North America a mountainous continental land body. It was the age of amphibian animals and cycad plants. At this period, the lava flow occurred which caused the Palisades of the Hudson.

Jurassic Period

The rocks of the Jurassic period are absent from New York State because its surface was elevated above the sea and there was consequently no sedimentation. Birds first appeared in Jurassic times.

Cretacic Period

Because New York was then well above the sea, the Cretacic period which followed is marked only by the clay and sand deposits on Long Island and Staten Island. The Jurassic and Cretacic form the Age of Reptiles. Trees and flowers of modern aspect first appeared in the Cretacic. New York had largely been reduced to the conditions of a plain with only moderate elevations in the Adirondacks and the Catskills at the end of the Cretacic, by the erosion of countless centuries. The Tug Hill Plateau is a remnant of this plain.

Rocky Mountains Elevated

The elevation of the Rocky Mountains, the greatest upheaval in the geological history of North America, occurred toward the close of the Cretacic period. At the same time the plain of northeastern United States was raised from 2,000 to 3,000 feet with its maximum rise along the Appalachian backbone running along the Fall Hill ridge across the present Mohawk Valley into the Adirondacks.

Disappearance of the Ancient Continent of Appalachia

The close of the Cretacic, which ushered in the "modern times" of geological history, was marked by the subsidence of the coast line and the disappearance of the land of ancient Appalachia beneath the Atlantic. From this mysterious continent much of the Atlantic seaboard may have been built up including much of New York State.

The Tertiary Period

The Cretacic uplift made the rivers active by the steeper grade of their watercourses. The Mohawk Valley's present physiography dates from the Cretacic rise. Prior to this time the streams of the present area of the Mohawk Valley, rising in the Adirondacks, generally flowed southward into the sea. Some of these were streams now existent, which probably followed the ancient channels, such as the Chuctanunda, Cayadutta, Schoharie, Sacandaga, Garoga, East Canada, and West Canada (through the channel of Nine Mile Creek).

[3 Photos: The Cohoes Mastodon.]

Since the close of the Cretacic period, the present Mohawk Valley below Little Falls has been carved out of the upraised Cretacic peneplain by the Mohawk River and its tributaries along a weak belt of Ordovicic shales, which lie between the Adirondack granites and the Helderberg limestones.

In the Tertiary period, prior to the great Ice Age, the present eastern Mohawk River had its source probably in the East Canada Creek, and sluggishly flowed eastward over the Nose, into the lower Mohawk and thence into the Hudson. The Sacandaga then joined the Mohawk near Fonda instead of flowing into the Hudson River as it does today.

Fall Hill was a mountain ridge, probably considerably higher than at present. On its western slopes all the streams flowed westward into a westward flowing watercourse (generally following that of the present Mohawk) now called by geologists the "Rome River". West Canada Creek was then tributary to the Rome River, flowing into it through the channel of present Nine Mile Creek. This was the lower preglacial course of the West Canada, which was stopped up during glacial times, by drift, following which the postglacial West Canada formed its present channel from Prospect to its outlet into the Mohawk at Herkimer.

The headwaters of "Rome River," rising at the west side of Fall Hill formed the most easterly source of what is known as the Dundas River. Its waters flowed southwestward into a stream corresponding to the present Mississippi and the Fall Hill ridge of that distant day, formed one of the headwaters of this mighty river.

Few, if any, lakes, waterfalls and gorges existed. There were no lakes where Lake Erie and Ontario now are, the basins of which were drained by the westward flowing Dundas. The St. Lawrence had its source at the Thousand Islands region.

Catskills and Helderbergs Created

The Helderbergs and Catskills were produced by erosion in the Tertiary period and all the main present day topographical features of the State, at the end of the Tertiary, were very similar to those of today. Plants and flowers were then developed in their present forms. The Tertiary is the Age of Mammals. Birds, reptiles and fishes then reached their present general form and development.

The Quaternary period may be called the modern times of geological history. The periods of the earth's physiographic development, which precede the Quaternary, are so inconceivably long, covering millions of years, that the Quaternary period seems a present day time by comparison.

Quaternary or Glacial Period

Just as the Tertiary period made its beginning by a great continental uplift, so did the Quaternary period open with the spreading of great ice sheets over northern North America, Europe and Asia.

No period had a more vital influence upon the history of the Mohawk Valley, the State of New York and the world's greatest city on Manhattan Island than did the ice sheet of the Quaternary period, for it created the great present-day New York to Buffalo railway, waterway and highway transportation line route, and made possible our present water-level railroad between these two cities.

It is interesting to note that the present, general popular acceptance of the existence of the great Ice Age shows the youth of modern science, because it was not discovered until 1837 by Louis Agassiz and not publicly announced until 1840. Like all great scientific discoveries, it was the subject of ridicule at first but gradually gained the support of scholars and geologists, and it has now been long accepted by the general public.

We know that the great glacier of North America existed, because the rock surfaces, where it lay, show exactly the same conditions as exist today in rocks from which modern glaciers have receded. Only the great Greenland glacier affords any comprehensive idea of the ice cap of North America at the height of its existence.

Similar to the action of present day glaciers, the glacier of the great Ice Age has left us polished and striated rock surfaces, glacial boulders or erratics (which are often transported from long distances), glacial moraines and terminal moraines (like the hills of Long Island) which make the southernmost limit of the great ice sheet, glacial debris, both stratified and unstratified, which cover all of Canada and a considerable belt of the northern United States.

At the maximum time of the great Ice Age an area of four million square miles of North America was covered by the ice cap. This is an extent of land very considerably larger than the present day area of the continental United States.

The great ice sheet of the Quaternary period had three centers from which the ice flowed and these glaciers are called the Labradorean, which had its center in central Labrador; the Keewatin, with its center west of the central west shore of Hudson Bay and the Cordillerian with its center at the northern limit of present British Columbia. The ice sheet which covered the Mohawk Valley and New York State was part of the Labrador glacier.

The Glacier in the Mohawk Valley

Regarding the intrusion of the ice sheet into the present Mohawk Valley, Dr. W. J. Miller says:

"When the Labrador ice sheet spread out southward as far as northern New York, the Adirondack Mountains stood out as a considerable obstacle in the path of the moving ice, and the tendency was for the current to divide into two portions, one of which passed southwestward up the low broad St. Lawrence Valley, and the other due southward through the deep, narrow Champlain Valley. As the ice kept crowding from the rear, part of the St. Lawrence ice lobe pushed into the Ontario basin, while another part pushed its way up the broad low Black River valley and finally into the Mohawk. At the same time the Champlain ice lobe found its way into the upper Hudson Valley and sent a branch lobe up the (eastern) broad, low, Mohawk Valley. The two Mohawk lobes, the one from the west and the other from the east, met in the Mohawk Valley not far from Little Falls. As the ice sheet continued to push southward, all the lowlands of northern New York were filled; a tongue or lobe was sent down the Hudson Valley and finally almost the whole state was buried under the ice. The general direction of ice movements, at this time of the greatest ice extent, was southward to southwestward with perhaps some undercurrents determined by the larger topographic features."

The greatest depth of this ice sheet in the State must have been several thousand feet and the Mohawk Valley must have been deeply covered. Ice erosion was effective because the glacier carried with it in its movements, rocks and rock fragments of all sizes which scoured the valleys and gullies of the State. The steep eastern side of the Tug Hill Plateau, forming the western limit of the Black River Valley, is an example of ice erosion. The Fall Hill Ridge (at Little Falls) and the Noses, were probably considerably worn down by this glacial scouring. The Adirondack peaks were rounded and scraped off by the ice movements, while the St. Lawrence River bed is the result of glaciation, both by ice and water.

"During the very long preglacial time, rock decomposition must have progressed so far that rotten rock, including soils, had accumulated to considerable depths, as today in the Southern States. Such soils are called 'residual' because they are derived by the decomposition of the very rocks on which they rest. But now one rarely ever sees rotten rock or soil in its original place in New York because such materials were nearly all scoured off by the passage of the great ice sheet, mixed with other soils and ground up rock fragments and deposited elsewhere. Such are called 'transported soils'." (W. J. Miller.)

It can be generally stated that the erosive power of this great glacier produced but slight changes in the chief topographic features of the state, although there were some minor changes and some very radical changes in the courses of streams by the filling up of water-courses at certain points by glacial drift. The West Canada Creek and the Sacandaga are noted local examples of such marked changes of water-courses produced by glacial deposits.

Aside from the great terminal moraine marking the southernmost limit of the great glacier, there are several intermediate ones marking advances or recessions of the glacial front during the thousands of years of the great Ice Age.

Next to the southern terminal moraine in importance, is one which has been traced from Herkimer to Oriskany Falls, Cortland, Watkins, Bath, Portageville, Dayton and Jamestown, all in New York State.

The glacier produced "overwash plains" by depositing sediment upon a flat plain, when the glacier was at rest; "valley trains", which were deposits from glacial streams in valley bottoms; glacial boulders (the largest being 25 feet in diameter) which have been mentioned before; "ground moraines", which were deposits made by the glacier, generally during its melting ; "till", or boulder clay, being the finer material dropped by the glacier; "drumlins", being low rounded mounds of glacial drift. These exist along the New York Central from Syracuse to Rochester, and, extend west and north to Oswego, in which area these small hills are scattered all over the country. A "kame" is a stratified deposit, in the form of a low hill or hillock, reaching sometimes a height of 200 feet. The kames of the Oriskany Creek Valley are very numerous and form a striking feature of the landscape in the vicinity of Oriskany Falls, which lies in the watershed of the Mohawk.

Extinct Black Lake

The retreat of the ice margin resulted in the formation of the many lakes of New York State where deep valley outlets were blocked by glacial drift. Lake George and practically all of the Adirondack Lakes are creations of the glacier. There are also many extinct glacial lake basins. The largest one in the State is called Black Lake which filled the Black River Valley, with its first formation at present Forestport reservoirs, and an outlet into the Mohawk through Lansing Kill which is now the eastern upper headwater branch of the Mohawk. This large lake formed a considerable stream which deposited silt and formed a delta at what was the town of Delta, below the point where the Mohawk's east and west upper branches join and where the Delta Lake or reservoir of the Barge Canal is now located. With later changes Black Lake found its outlet into the St. Lawrence and, with the lowering of its outlet, it finally disappeared. Its flat lake bottom persists in the broad flatlands along the Black River.

This deposition of drift has not changed any of the State's major topographic features. The drift deposits generally tended to fill depressions and to give us the rounded harmonious hills and flowing valley forms which we see in our Valley and State. Personally, the writer believes that glacial action on the surface of New York State was the cause of its varied and unusual landscape beauty.

Great Lakes Formed

The formation of the Great Lakes basin was probably largely due to the great deposition of glacial drift along the southern shores and a tilting of the land on their northern shores downward to the north, thus destroying the southern outlets of the lakes. This left basins which filled with water as the glacial wall receded, at which time the outlet of so-called Lake Chicago, Lake Saginaw, and Lake Wellesley was through the Illinois River into the Mississippi. It was somewhere in this period of the glacier's recession that the Mohawk Valley glacial lakes came into being.

Mohawk Valley Glacial Lakes

When the ice of the glacier moved gradually northward its waters formed a lake or lakes covering the Mohawk Valley at different levels as the outlets were lowered by water action. It is a very complex subject which has been explained by the theory of the retreat and advance of the glacial front, similar to that of modern glaciers on a smaller scale. The Mohawk glacial lake period was prior to the Glaciomohawk and Iromohawk which eroded the flats of the present Mohawk.

[2 Photos: The Noses and The Noses Near Sprakers.]

Concerning this interesting feature of the close of the glacial period, the reader is referred to "The Glacial Waters in the Black and Mohawk Valley," by Dr. Herman L. Fairchild, in the New York State Bulletin, No. 160, of May 15, 1912.

The writings on the subject were previously scanty and Dr. Fairchild's book gives an insight into the creation of many topographic forms and soil derivations. Investigation of this subject will doubtless give us further information.

Some of the beach lines, formerly attributed to the Glaciomohawk and the Iromohawk are now believed to be those of the glacial lakes. Characteristic glacial lake beaches are said to be in evidence four miles west of Little Falls. The proposed damming of the Sacandaga at Conklingville to form a large lake for power purposes, would almost exactly restore an original glacial lake. There are many such glacial lake beds in the Mohawk Valley and in New York State, the greatest of which, as previously mentioned, was the Black River Lake. Many valleys also show the effects of damming by ice and the fact that they were glacial lake drainage outlets by the perfectly flat character of the lowest level of these valleys.

Dr. Fairchild summarizes the glacial and postglacial drainage history of the Mohawk Valley as follows:

Summary of the Mohawk Glacial Lake Drainage History

Stage 1: — The axis of the Valley was occupied by a strait of ice connecting the two ice bodies in the Hudson and Ontario valleys. The water of the Adirondacks escaped across the ice, the overflow probably being into the Otsego-Susquehanna Valley. Sand plains through the Adirondacks, with elevation 1,450 feet and upward, probably correlate with this stage.

Stage 2: — The melting of the strait of ice in the Valley left a stretch of open water between the ice tongues, — the Herkimer lake. The water had two successive outlets, by Summit Lake (also called Mud Lake) pass to the Otsego-Susquehanna at 1,360 feet and by the Cedarville pass to the Unadilla-Susquehanna at 1,220 feet. Correlating sand plains of great expanse occur in the basins of the upper Mohawk, West Canada and East Canada Creek at 1,440 to 1,280 feet (elevation). The Black River Valley basin was flooded by the waters of this stage so far as relieved from the ice sheet.

Stage 3: — Waning of the Hudsonian ice lobe permitted escape of the water along the face of the Helderberg scarp, west of Albany, the later flow being across the divide between the Schoharie and Hudson valleys, at Delanson, 840 feet. Correlating sand plains exist in many localities with elevations, according to latitude, from 1,200 down to 820 feet. The Black River valley waters were now tributary to the Schoharie Lake, first through the Remsen outlet and later by the Boonville outlet.

Stage 4: — Amsterdam Lake. Further recession of the Hudson Valley ice lobe permitted outflow of the waters about the Rotterdam salient, west of Schenectady, at 800 down to 360 feet. The correlating delta plains are widely distributed, having altitude in the Rome district of 860 to 460 feet. The Black River waters were still tributary and two other tributary lakes were the Lansing Kill and the Sacandaga.

Stage 5: — Lake Albany confined to the Hudson Valley, with outlet control southward. The Mohawk Valley now had free drainage, two phases being the Glaciomohawk, previous to Iroquois time, and the Iroquois-Mohawk, called for convenience the Iromohawk, the overflow of Lake Iroquois through the present Mohawk's course.

The Labrador ice sheet finally receded so that its Ontario lobe stood at the outlet of present Lake Ontario and the St. Lawrence Valley was still buried under ice. In geological nomenclature, Lake Ontario was then, "Lake Iroquois," covering a much greater basin than at present. Bodies of water approximating present Lakes Superior, Michigan, and Huron then formed one great inland sea known as Lake Algonquin, with outlets eastward through the present Detroit and Trent rivers. At this period the Niagara River and Niagara Falls were born.

The Mighty Iromohawk

"During this Lake Iroquois stage the waters of all the Great Lakes region discharged through the Mohawk-Hudson valleys and the volume of water which flowed past the present sites of Rome and Utica and across the preglacial divide at Little Falls must have been greater than that which now goes over Niagara Falls." (W. J. Miller.)

The Gateway to the West Created

It was at this time that this great Mohawk River finished the cutting of the gorge at Little Falls and wore down the Noses, giving us our Valley "water level route," from the Atlantic to the Great Lakes, and our famous "Gateway to the West".

Cohoes Falls

With the recession of the waters of Lake Albany and the erosion of the present lower channel of the Mohawk our river flowed over the rock rim of the ancient Hudson Valley and created the falls and gorge at Cohoes. The postglacial history of the lower Mohawk and that of Cohoes Falls is of such interest that it is given a separate chapter.

The Modern Mohawk

Glacial recession finally freed the St. Lawrence Valley of ice and the Great Lakes basin dropped its level. When this level fell below the Rome divide the Great Lakes ceased to flow through the Mohawk River and that famous postglacial stream dwindled to somewhat near its present volume. Several of the beaches of the postglacial Mohawk are in evidence along the river east of Little Falls.

Instead of the Mohawk outlet, the Great Lakes found their outlet through Lake Nipissing and Ottawa River, into the St. Lawrence. All the streams from north and south which entered the arm of Lake Iroquois (between Rome and Little Falls), were heavily charged with debris from the newly drift-covered regions and the current not being strong enough to carry away the debris, the valley from Rome to Little Falls was built up (aggraded) to such an extent that, after the disappearance of Lake Iroquois, the drainage from Rome was able to continue eastward. Thus we have here a very fine example of exact reversal of drainage directly due to glaciation, and by this means the upper waters of the Mohawk were added to the preglacial Mohawk. This made one river — the Mohawk — out of two, the lower, or eastward flowing, and the upper, or westward flowing one, of the days before the glacier.

The Mohawk Flats in the Making

The present Mohawk Flats are among the world's most fertile lands. These flats in a general way, lie on the channel made by the great Iromohawk. This channel has been filled level by silt deposited by the Iromohawk and the modern Mohawk which also by its freshets, has laid down the rich top soil of these flatlands — a dark earth which is from five to fifteen feet in depth.

[2 Photos: A Pothole and the Mohawk's Deep Spot — 150 Feet Deep.]

The World's Greatest Potholes

One of the most noteworthy evidences of the great postglacial cataract at Little Falls is the existence of potholes of varying sizes worn in the rocky sides of the gorge over which the waters of this tremendous falls once poured. They are from a few inches to thirty feet wide and the potholes in the Little Falls Gorge are the largest and most remarkable on earth. Some are fully thirty feet in depth and even deeper, as nearly all are filled with debris. These holes are cut in the Adirondack syenite. They were caused by round stones of varying sizes settling in a depression in the rock and then being whirled around until they had cut a circular hole or basin in the rock of varying depth. Most of these potholes are within a region of a half mile below the lowest falls, the largest examples being on Moss Island, between which and the mainland, the Big Lock of the Mohawk River Barge Canal is located. Some very fine examples are on the north shore a short distance east of the railroad bridge over the turnpike. They have been the subject of much study by geologists. During Indian Revolutionary forays, the red men frequently hid sheep and other loot, which they had stolen, in these holes and returned at night to remove them. They were also hiding places for the settlers during the Revolution. The largest of the potholes of the Little Falls Gorge is the basin just below the lower falls, with the water over 150 feet deep, at a point supposed to be where the last stage of the great cataract exerted its force during the process of wearing down the Gorge channel. In the Little Falls Gorge, evidences of powerful water action and even potholes are noted over 300 feet above the bed rock of the river.

The Canajoharie Pothole

In the bed of the creek near the end of the Canajoharie Gorge, is a pothole about ten feet wide which is the original "Canajoharie" of the Mohawks — the name meaning, "the pot that washes itself" — with a popular interpretation of "the boiling pot". At medium high water the current flows in and out of the pothole in a way that justifies both names. The Mohawks named the entire region between Fall Hill and the Noses, "Canajoharie" and also so called several of their towns, which has been a cause of much historical confusion among historians who do not realize that it was a natural Indian trait to give one name to several locations. There is another pothole somewhat larger directly beneath Canajoharie Falls.

One of the most famous and deepest of the potholes of the Mohawk River is that which lay close to its outlet into the Hudson. It was sixty feet deep and here the famous Cohoes Mastodon was found in 1866. The Cohoes Falls, the Mohawk outlets and the Cohoes Mastodon are so important in their history that they are given description in the next chapter, which is devoted to these interesting subjects.

Change in the Sacandaga's Course

Both the Sacandaga River and the Kennyetto Creek were streams which in preglacial times flowed southward into the preglacial Mohawk. The Sacandaga now flows southeastward to Northampton where it makes a sharp turn and flows northeastward to the Hudson. This eccentric course is due to a glacial moraine blockade left by the glacier from Gloversville to Northampton across the preglacial Sacandaga Valley which made the old outlet impossible, and turned the Sacandaga northward and did the same to Kennyetto Creek at Broadalbin and to Hans Creek farther north.

West Canada Creek Changed

Closely associated with the postglacial example of the Sacandaga is the postglacial history of West Canada Creek and the famous chasm at Trenton Falls. The preglacial West Canada Creek flowed from Prospect (upper end of Trenton Chasm) past Holland Patent, through the valley of present Nine Mile Creek and into the Rome River opposite the Oriskany Battlefield. This channel was completely blockaded by glacial drift at Prospect so that the creek was forced to find a new course southward over the limestone at Trenton Falls and thence southeastward through its present course to its outlet into the Mohawk at Herkimer.

Trenton Falls Gorge

The gorge between Prospect and Trenton Falls villages is two and a half miles long and from 100 to 200 feet deep and has been cut into the Trenton limestone by the postglacial stream. It contains five or six waterfalls, ranging in height from 10 to 80 feet, the total drop of water in the two and a half miles of the gorge being 360 feet.

Postglacial Subsidence

At the beginning of the glacial period the region of New York particularly along its eastern side, was higher than at present. Toward the close of the Ice Age and shortly after, the land, perhaps because of the great weight of the ice cap, subsided to a lower level than the present one, the lower Hudson and the St. Lawrence channels became submerged (drowned rivers) and the Atlantic sea coast took on its present outline.

As the land was lower then than today, a narrow arm of the sea extended northward through the Hudson and Champlain valleys and joined a broad arm of the St. Lawrence estuary.

When Man First Saw the Mohawk River

In all this long story, through these aeons of time, and the passing of these countless myriads of years, there is no visible touch of human interest in the record of the rocks. We have witnessed the appearance of life even in the Precambric seas, while the curious water life forms of the Ordovicic and Siluric times have interested us, as shown in the sediments of those ancient seas. We have noted the curious plant life of the Devonic and Carbonic periods and the gradual development of fishes, reptiles, birds and mammals through long ages of time. However, it is not until the Quaternary period that we have signs of the life of human beings like ourselves in North America.

When did man first see the Mohawk? We do not know — neither do we know when the Indian first trod the forests which grew up on the Valley glacial soils and drift. There is a strong probability that the Eskimo were the first to enter our Valley as they gradually followed the border of the fading ice sheet northward. If so, they saw the great postglacial Mohawk River, and, along its shores, hunted the mastodon and other strange animals of that far distant day. Remains attributed to these most ancient dwellers along the Iromohawk are found on the beaches of that mighty river, which, of course, ran at a much higher level than the Mohawk of today, as well as upon the heights rising from those former shores of that once great ancestor of our present placid Mohawk.

The Rising and Subsidence of Today

The most recent development in the Quaternary period has been the gradual elevation of the land which probably is still proceeding around the Great Lakes.

And so we find our Mohawk Valley of today, the great "Gateway to the West," formed and moulded by Nature's mighty forces through the aeons of time since the dark rocks of our ancient Valley first rose above the surging waters of the primeval ocean.

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