The lowest accessible rocks in Wisconsin consists of immense series of granites gneisses, syenites and homblendic, micaceous, chloritic chists and allied, crystalline rocks. These rocks bear within themselves decisive evidence that they were once sediments derived from the wear of earlier rocks. Nowhere are these earlier rocks exposed at the surface. These lowest accessible rocks are called "fundamental gneiss" and upon them are piled layer upon layer the rock formations of the state. First were deposited the St. Peter's sandstone, all together called the Potsdam period of the lower Silurian age (age of mollusks). Then in succession came the Trenton limestone, Galeria limestone and Hudson river shales of the Trenton period of the lower silurian age of the Paleozoic era. Then came the following strata:
All of the above strata were formed under the internal sea before any land in the present Wisconsin was above water except the famous "Isle Wisconsin," the only section of the state that was never under water. During the upper silurian age mollusks in enormous numbers flourished; their casts are found in the rocks of the county. Among them are crinoids, corals, protozoans, bryozoans, brachipods, cephalopods, crustaceans and others. At the close of the upper silurian age what is now Sheboygan county rose above the sea and was never afterward submerged ; but another agency deposited a vast amount of soil upon the upper silurian rocks of this county, namely, the quarternary age, or glacial period of epochs, thus:
The glacial period was remarkable in many particulars. That immense fields of ice should be pushed down from the north shearing off the soil and rocks of the older periods and carrying large portions southward to be dropped upon the surface of this county and elsewhere as the sun gradually melted the ice, seems an extraordinary event, but is well authenticated by indubitable testimony. The evidence is also clear that the tertiary age was warm to such an extent that animals and plants flourished almost to the north pole and certainly in Alaska and other sections even farther north.
But this age was succeeded by the quarternary age, which presented marked contrasts. It was intensely cold in northern latitudes and even in this section the heat of summer not being sufficient to melt the vast accumulations of snow and ice which thus formed immense glaciers which were forced slowly southward carrying the surface rocks and soil with them and depositing them where the ice melted. What is now Sheboygan county was thus covered with an immense glacier which flowed southward, digging out Lake Michigan and topping over until united with the glacier which likewise scooped out Green Bay and Fox river valley. These glaciers or others extended as far south as southern Illinois and southern Indiana. Of the material carried along there were thrown off at the sides great ridges now called terminal moraines which form many of the hills and elevations of this county. The material thus deposited is called "drift" and no doubt considerable deposited here was brought from Canada, the Lake Superior basin and the northern part of Wisconsin and Upper Michigan. No doubt all of the present Sheboygan county was swept by the ice of the first glacial epoch and subsequent glacial fields removed many evidences of the first glacial visitation.
The second glacial epoch is represented by a wide band of drift and moraines stretching across the county northeast and southwest, a little east of north and west of south. This band was the area where the Lake Michigan and the Green Bay glaciers joined and where in the meeting and the grinding of the two together there were deposited the drift and moraines of the second glacial band above described. Thus the direction of glaciation is as follows: In nearly the eastern half of the county the markings show movement from the Lake Michigan glacier in almost exactly a slightly southwest direction. In the west third of the county they show that the Green Bay glacier crowded in a southeast direction until arrested by the edge of the Lake Michigan glacier ; and there the hills of drift and the moraines were deposited in the band already described. The western margin of the Lake Michigan glacier is now marked by what is called the Kettle Range which in this county is about co-extensive with the second glacial area. This range is thus described by the state geologist:
The most striking result of the second glacial advance was the production along the margin of the ice sheet of a great moraine, the most gigantic and most remarkable yet known to characterize glacial action. It consists of a neat ridged belt of drift disposed in grand loops along what was the glacier's margin. Its re-entrant angles penetrated deeply between the adjoining lobes marking their line of contact. That portion of the moraine which lay between and was formed by the joint action of the Green Bay and Lake Michigan glaciers constitutes a succession of irregular hills and ridges, locally known as the Kettle Range from the peculiar depressions by which it is characterized. This ridged belt of drift is a true terminal moraine formed of the heterogeneous material accumulated as the margin of the ice and plowed up before it at the time of its greatest advance.
The intermediate portions of the Kettle Moraine lie along the face of two approaching ice sheets which may have met and antagonized each other to some extent, but did not coalesce; and furthermore they lie transverse to the glacial motion and are strictly marginal and are in real nature terminal moraines, differing from other portions simply in being formed by two glaciers pushing from opposite directions.
The characteristics of the Kettle Moraine are striking. It is not merely a simple ridge plowed up by the smooth edge of the ice, but consists of an irregular assemblage of drift hills and ridges, forming a belt usually several miles in width. The superficial aspect of the formation is that of an irregular intricate series of drift ridges and hills of rapidly, but often very gracefully, undulating contour, consisting of rounded domes, conical peaks, winding and occasionally genticulated ridges, short, sharp spurs, mounds, knolls and hummocks promiscuously arranged, accompanied by corresponding depressions that are even more striking in character. These depressions give rise to the various local names of potash kettles, pot holes, pots and kettles, sinks, etc. Those that have most arrested popular attention are circular in outline and symmetrical in form, not unlike the homely utensils that have given them names. However, some are irregular and shaped like a funnel, inverted bell, saucer, trough or even winding hollows. They vary in depth from a mere indentation to bowls sixty or more feet in depth. The kettles proper seldom exceed 500 feet in diameter. As a natural consequence of their forms many of the depressions are small lakes without inlet or outlet. Where there are depressions there also are hills and here they are the counterpart of the depressions, being inverted kettles or sharp ridges along trough-like hollows. As to material, clay, sand, gravel and boulders enter largely into the constitution of the Kettle Range, gravel being the most conspicuous element exposed to observation.
The great core of the range consists of a confused commingling of clay, sand, gravel and boulders of the most pronounced type. Thus the range is essentially unstratified. It is undeniable that the agency which produced the range gathered its material all along its course for at least three hundred miles to the northward and its largest accumulations were in the immediate vicinity of the deposit. Thus the material of the range changes along its whole course and is quite often more or less stratified.
The glacial period was succeeded by an epoch when the southward flow of the water was checked and much of this northern country was submerged beneath the lakes and it was at this time that the red clay, beach deposits and other soils were left upon a considerable portion of the surface. The forest trees so often found buried no doubt grew between the glacial periods when warm weather prevailed, the change from heat to cold occurring every 10,500 years, due to the precession of the equinoxes.
The retreat of the glaciers left spread over the surface subjected to their action a sheet of confused and commingled earthy and rocky material scraped from the surface of the areas lying northward and partaking of the diverse natures of the parent sources. This contained ingredients from a large variety of rocks of various mineral composition and therefore furnishing a substratum remarkably well fitted to yield a soil rich in all requisite mineral constituents. Since then the sun, rain, air and frost have developed there from a deep, rich and enduring soil, to which vegetation has added humic products." (Geology of Wisconsin, Vol. 1.)
At the close of the second glacial epoch elephants, mastodons, mammoths and other giant animals roamed over Wisconsin; among them were buffaloes, deer, wolves, raccoon or species closely related to these animals.
How were the Kettle Hills formed? The answer would be by one of two ways: One by removing the land from around the hills and leaving them as is the case with clay hills, a part of the clay undisturbed deposit. The ridge east of the Rock mills at Sheboygan falls is of this kind, also the hill directly east of the same village on the river road, where the river formerly ran on both sides of it. This is the theory of J. H. Denison, in his interesting article which was made a part of Joerns Atlas of the county published in 1902. Mr. Denison goes on to say in the article that he is inclined to think the Dr. Seeley hill, near Sheboygan city, and every elevation that is clay and hard pan down to the smooth rock, belong to this class.
The other kind he says, is the gravel hills, mostly in the western part of the county, that are of later formation and are built by piling up the material brought together often from a distance and consisting of limestone, gravel and sand, sometimes mixed with clay. This material in what are called Kettle hills is the same that is found all along the Sheboygan river down to its mouth. A good example of it may be seen along the railroad track where it is used as ballast. That the Kettle hills belong to the same epoch as the formation of the river valleys, Mr. Denison concludes from the fact that the gravel hills and gravel beds are alike all covered with a deposit six inches to two feet of clay loam. There is not a gravel bed in the country that was not originally covered with a sedimentary deposit.
The gravel hills and ridges in the county are found in the western and southern part of Rhine, the western and northern part of Plymouth, the southeastern portion of Greenbush, the western of Lyndon, and the eastern and central part of Mitchell and Scott. The major portion of the land is tillable.
The Kettle Range of hills which traverse the eastern border of the state, crosses the western portion of the county obliquely, abruptly breaking the generally undulating surface. Several small lakes dot the landscape at different sections of the county, the principal ones of which are Sheboygan, Elkhart, Cedar and Random lakes. These have become attractive places as summer resorts, not only for the people living close by but are visited yearly by many people in the state, Chicago and other places.
The county is abundantly supplied with streams of water, the most important of which are the Sheboygan, Mullet, Onion and Pigeon rivers, with many tributary creeks. The courses of these streams are generally very circuitous, flowing in all directions, but many of them supply good water power which is utilized for manufacturing purposes. The county was originally covered with timber, both of fine pine and hard woods. The best of this has been used for many manufacturing purposes. Most of the soil is rich and fertile and adapted to almost any kind of a crop in this latitude. The cultivation of the cereals yields liberal returns and this section of the state cannot be surpassed for the development of dairy products.
Sheep-raising is also quite an industry, while by reason of the peculiar quality of soil and conditions along the shore of Lake Michigan, a superior quality of green peas were grown, which were eagerly sought by the markets of the east and west and of which thousands of barrels were put up in local canneries and large quantities were shipped both by land and water. This industry is no more. Worms finally got into the peas and the planting of them has long since ceased. Beautiful cream colored brick of fine quality are made of the red clay in certain localities, and in other localities a fine commercial limestone is quarried and burned into lime.
The geological formation of the county was accurately shown a number of years ago by the boring of an artesian well in Fountain Park, which was sunk to a depth of 1,475 feet. The borings displayed a surface drift reaching 92 feet in depth, which was underlaid by 719 feet of Niagara limestone, 240 feet of Cincinnati shale, 213 feet of Trenton and Galena limestone and 212 feet of St. Peter sandstone. Water of a strongly saline character, tinctured with various mineral substances, was found here in abundance.
Information gathered and adapted from History of Sheboygan County, Wisconsin, Past and Present
Carl Zillier, Editor
Pubished by The S.J. Clarke Publishing Company, 1912, Chicago, IL