The level aspect of Illinois topography has its explanation in the State's glacial history. As late as 25,000 years ago--a tick of the clock in geological time--there was still to be found in Illinois the last of the great ice sheets that had crept down from the North and with a leveling action comparable to that of a road-scraper, effaced hills and valleys carved by centuries of erosion. Ninety per cent of the State's surface was covered by ice; the only unglaciated areas are Jo Daviess County in the extreme northwest, Calhoun County in the west-central section, and the seven southernmost counties. In these areas the rugged terrain, sharply dissected by valleys, indicates the probable appearance of the whole of Illinois before the ice age. Elsewhere, save for sporadic outcrops, the uneven relief lies beneath a mantle of drift averaging 75 feet in depth.
The four ice-sheets that invaded the United States are definitely known to have reached Illinois. The next to last of these covered so great a portion of the State that it has been named the Illinoisan by geologists. Occurring approximately 150,000 years ago, it pushed south to the northern edge of the Ozark Range, and there, halted by increased melting and the barricade of hills, piled up rock debris 20 feet deep on the hillsides. This was the greatest southern penetration of any of the North American glaciers.
The Wisconsin Glacier, which moved into Illinois 50,000 years ago and receded 25,000 years later, covered only the northeast quarter of the State., but because of its geological lateness its effects are more obvious to the layman. The great central portion of the State which was covered by the older Illinoisan sheet, but not overlaid by the Wisconsin, is much more nearly even in relief and mature in drainage. The terminal moraines--ridges of drift piled up where the glacial front stopped--are low and inconspicuous. Those of the last glacier, however, are among the largest known to geologists. Sharply defined and extensive in length, they comprise the chief topographical relief of the northeast portion of the State. The major ones are named for cities that have been built upon them; the Shelbyville, Bloomington, Marseilles, and Valparaiso moraines are four of the most important.
Marked with the characteristics of recent glaciation, the land bordering Lake Michigan near the Wisconsin State line is poorly drained, with many lakes and marshes formed by the melting Wisconsin glacier. Thus was created the lake region of Illinois, major recreational area for the metropolis of Chicago. At the time of recession, the waters of the glacier were impounded between the Valparaiso moraine and the receding edge of ice, forming Lake Chicago, ancestor of Lake Michigan. The site of Chicago lay deep beneath the surface of this ancient lake, and deposition from its waters accounts for the table-top flatness of the city today. In successive stages the water receded north and east.
Glaciation and climate largely explain the agricultural distinction of the Illinois country. The average growing season varies from 160 days in the north to 211 days at Cairo, in the south. The drift laid down by the ice had been gathered from so great a variety of bedrock that an ample percentage of essential minerals was assured. Lying at the southernmost reach of the ice-sheets, Illinois was not strewn with the boulders and heavy débris that pock-mark the land further north. Much of the State is veneered with a layer of loess, the finer particles of drift that were sorted out by the wind and spread across the land. Enriched by prairie grasses during thousands of years, it possesses an even texture which, with the regular terrain, fits Illinois admirably for mechanical cultivation.
Buried beneath the glacial drift, the rock strata of Illinois effect little influence upon the topography, but their minerals yield to the State an income placing it tenth in the country in mineral output. All of the substructure that has been explored by geologists is sedimentary in nature, with the exception of a deep-lying mass of red granite encountered at 3,700 feet near Amboy, in the northern part of the State. At an unknown depth, the entire State is underlain with igneous rock, mother-rock of all formations, but vast processes of sedimentation have buried it beyond reach.
Of the five geological eras, the third, the Paleozoic, was by far the most important both geologically and economically. Beginning some 600 million years ago, it was characterized by repeated submergences and uplifts. What is now Illinois was then covered by a series of shallow seas. In great cycles, the seas advanced, covered the land for millions of years, and then retreated to expose the surface again to weathering and erosion. The strata laid down during each submergence differ sharply from each other, the degree depending upon the depth of the sea and the nature of the land at its shoreline.
The oldest period of the Paleozoic Era was the Cambrian, during which thick layers of sandstone and dolomite were deposited over the entire State. This, like the igneous rock, does not outcrop in Illinois, but slants upward from the south to come to the surface in Wisconsin. Rainfall in the latter area, seeping through surface soil to the sandstone layers, follows these to northern Illinois, where it serves as a reservoir for the wells of many municipalities.
The second period of the Paleozoic Era was the Ordovician, which saw a series of submergences of long duration. Its first deposits, the Prairie du Chien group, included a limestone which was the basis of Utica's natural cement industry, important in the last century but now abandoned. Another of the early Ordovician deposits is a layer of St. Peter sandstone, which outcrops in Ottawa and nearby in a remarkably pure form that has achieved national industrial importance as a source of silica sand used in glass-making and a hundred other processes. St. Peter sandstone also forms the picturesque bluffs that comprise Starved Rock State Park. Platteville limestone, likewise an Ordovician deposit, is used in the manufacture of Portland cement. Late in the period a layer of Galena dolomite was laid down. It bears the lead which gave Galena its name and its early mining boom. Related to this formation is the Kimmswick limestone, source of petroleum in the southwestern field at Dupo.
The third period, the Silurian, laid down several strata of dolomite and limestone. The latter is quarried extensively near Chicago and Joliet for road material, aggregate, and soil replenishment. The following period, the Devonian, is likewise chiefly important for its limestone. Among the Mississippian deposits are the sediments that store the southeastern oil pool, long a steadily producing field and lately the scene of a spectacular boom of revived activity.
Near the end of the Paleozoic Era occurred the Pennsylvanian period, when Illinois' great coal measures were deposited. The coal strata, but a small portion of the Pennsylvanian deposits, far outstrip all other geological periods in the wealth they have yielded. The land at this time was low and marshy, a few feet above sea level. A favorable climate encouraged the growth of giant trees and ferns that subsequent eons compressed into the coal veins that underlie two-thirds of the State. Despite a half-century of extensive mining operations, not more than 2 per cent, it is estimated, of Illinois' coal reserve has been tapped.
Following the close of the Pennsylvanian period, the greater portion of Illinois remained above sea level. Great land movements that raised the Appalachians in the east, folded the land of Southern Illinois into the present Ozark range. The work of the seas was done, and now rain and wind attacked the surface to erode and crease it with great valleys and ridges. But then, following a vast climatic change, snow began to fall in the northern region, year after year, deeper in the winter than the brief summer sun could melt.
So began the glacial period, the deus ex machina in the making of Illinois. Even as the curtain descended upon the State's geological drama, the ice sheets appeared, effaced the ruggedness, and retreated-so recently that Indian legends make awed mention of the Ice God that once came down from the North.
Showing posts with label Lake Michigan. Show all posts
Showing posts with label Lake Michigan. Show all posts
The land of Illinois reveals graphically the agricultural importance of the State
SEEN FROM THE AIR, the land of Illinois reveals graphically the agricultural importance of the State. Carved by intensive cultivation into an intricate mosaic of squares and rectangles, the level prairie resembles nothing so much as a vast stretch of modernistic linoleum. In the grainfields no land is wasted; pasture adjoins field, farm fits snugly against farm, and between them is nothing but the straight line of a fence or hedgerow of osage orange.
Lying between the Great Lakes and the Mississippi, Illinois enjoys a drainage system extraordinarily complete and extensive. Water from 23 of the 48 States crosses its surface and flows along its boundaries, eastward through Lake Michigan to the Atlantic Ocean and southward in the Mississippi to the Gulf. Although its topography presents no striking contrasts of surface contour, the State is separated into seven gentle but distinct basins, bearing the names of Lake Michigan, the Illinois, the Rock, the Kaskaskia, the Big Muddy, the Wabash, and the Ohio Rivers. The arteries and branches of these six great rivers serve 87.2 per cent of the 56,665 square miles of the State's surface. The largest, the Illinois, runs from northeast to southwest and drains an area 250 miles long and 100 miles wide, comprising 43 per cent of the State.
The conception of Illinois as an unrelieved table-top admits pleasant and unexpected contradictions. A portion of the hilly Wisconsin driftless area projects into the northwest corner; there, at Charles Mound, is the highest spot in the State, 1,241 feet above sea level. An extension of the Ozark Range, with several hills exceeding a thousand feet in altitude, crosses southern Illinois. The Mississippi and its tributaries, especially the Illinois, have carved long ranges of bluffs, the more rugged portions of which have been enclosed in State parks.
Elsewhere is prairie, but its original extent and appearance have been greatly altered. The earliest settlers found almost half the State in forest, with the prairie running in great fingers between the creeks and other waterways, its surface lush with waist-high grasses and liberally bedecked with wild flowers. Here occurred the transition from the wooded lands of the East to the treeless plains of the West.
Since this was the pioneer's first encounter with the prairie, Illinois came to be known as the Prairie State, although westward lay lands more worthy of the title than the semi-wooded surface of Illinois.
The pioneers admired the grasslands, but clung to the wooded waterways. At the time of early settlement the fertility of the prairie was not known nor was it available until the invention of plows capable of breaking the tough sod. The waterways furnished timber for fuel and building, a convenient water supply, and protection for the settlers' jerry-built cabins from prairie fires and windstorms. Fires invariably swept the grasslands in the late summer, when the Indians burned off the prairie to drive out game. When the settlers at last began to venture cautiously out from the groves, they took the precaution to surround their homesteads with several plowed furrows as a fire check.
The fame of the great stretches of treeless grasslands spread eastward, even to England, and magazines carried articles of description, speculating upon their origin (which is still unexplained) and the possibilities of their cultivation. Dickens, while visiting St. Louis in 1842, especially requested that he be shown the "paroarer," as he noted it was pronounced locally. A rumbling, ancient coach took him out to Looking Glass Prairie, near Belleville, and he returned to write:
. . . . there lay, stretched out before my view, a vast expanse of level ground; unbroken, save by one thin line of trees, which scarcely amounted to a scratch upon the great blank . . . . a tranquil sea or lake without water, if such a simile be admissible . . . . and solitude and silence reigning paramount around . . . . I felt little of that sense of freedom and exhilaration which a Scottish heath inspires, or even our English downs awakens. It was lonely and wild, but oppressive in its barren monotony.
Lumbering activities and the pioneer's early preference for the woodland reduced the forests from their original extent, 42 per cent, to little more than 5 per cent. What is now commonly thought of as prairie is often the increment gained from the clearing of woodlands. Given over now almost wholly to farms, the prairies are constantly in flux as the landscape alters with the agricultural season. April transforms the Illinois country into a vast patchwork quilt of fresh color. Spring planting brings forth teams and tractors that comb and dress the land with geometric nicety. By summer the contours of the prairie are soft and round with ripening crops. July ushers in three months of intense industry. Crops are gathered, threshing machines build mounds of chaff, trucks and trains loaded with grain begin to move toward the cities. When autumn comes, the prairies, gashed by plows and stripped of their harvest, have a worn, desolate aspect that is heightened by the somber browns and yellows of the season. The prairies are dull throughout winter save for intermittent snowfalls, and then, in late March, the land stirs, splotches of green appear, and farmers turn again to the soil.
Lying between the Great Lakes and the Mississippi, Illinois enjoys a drainage system extraordinarily complete and extensive. Water from 23 of the 48 States crosses its surface and flows along its boundaries, eastward through Lake Michigan to the Atlantic Ocean and southward in the Mississippi to the Gulf. Although its topography presents no striking contrasts of surface contour, the State is separated into seven gentle but distinct basins, bearing the names of Lake Michigan, the Illinois, the Rock, the Kaskaskia, the Big Muddy, the Wabash, and the Ohio Rivers. The arteries and branches of these six great rivers serve 87.2 per cent of the 56,665 square miles of the State's surface. The largest, the Illinois, runs from northeast to southwest and drains an area 250 miles long and 100 miles wide, comprising 43 per cent of the State.
The conception of Illinois as an unrelieved table-top admits pleasant and unexpected contradictions. A portion of the hilly Wisconsin driftless area projects into the northwest corner; there, at Charles Mound, is the highest spot in the State, 1,241 feet above sea level. An extension of the Ozark Range, with several hills exceeding a thousand feet in altitude, crosses southern Illinois. The Mississippi and its tributaries, especially the Illinois, have carved long ranges of bluffs, the more rugged portions of which have been enclosed in State parks.
Elsewhere is prairie, but its original extent and appearance have been greatly altered. The earliest settlers found almost half the State in forest, with the prairie running in great fingers between the creeks and other waterways, its surface lush with waist-high grasses and liberally bedecked with wild flowers. Here occurred the transition from the wooded lands of the East to the treeless plains of the West.
Since this was the pioneer's first encounter with the prairie, Illinois came to be known as the Prairie State, although westward lay lands more worthy of the title than the semi-wooded surface of Illinois.
The pioneers admired the grasslands, but clung to the wooded waterways. At the time of early settlement the fertility of the prairie was not known nor was it available until the invention of plows capable of breaking the tough sod. The waterways furnished timber for fuel and building, a convenient water supply, and protection for the settlers' jerry-built cabins from prairie fires and windstorms. Fires invariably swept the grasslands in the late summer, when the Indians burned off the prairie to drive out game. When the settlers at last began to venture cautiously out from the groves, they took the precaution to surround their homesteads with several plowed furrows as a fire check.
The fame of the great stretches of treeless grasslands spread eastward, even to England, and magazines carried articles of description, speculating upon their origin (which is still unexplained) and the possibilities of their cultivation. Dickens, while visiting St. Louis in 1842, especially requested that he be shown the "paroarer," as he noted it was pronounced locally. A rumbling, ancient coach took him out to Looking Glass Prairie, near Belleville, and he returned to write:
. . . . there lay, stretched out before my view, a vast expanse of level ground; unbroken, save by one thin line of trees, which scarcely amounted to a scratch upon the great blank . . . . a tranquil sea or lake without water, if such a simile be admissible . . . . and solitude and silence reigning paramount around . . . . I felt little of that sense of freedom and exhilaration which a Scottish heath inspires, or even our English downs awakens. It was lonely and wild, but oppressive in its barren monotony.
Lumbering activities and the pioneer's early preference for the woodland reduced the forests from their original extent, 42 per cent, to little more than 5 per cent. What is now commonly thought of as prairie is often the increment gained from the clearing of woodlands. Given over now almost wholly to farms, the prairies are constantly in flux as the landscape alters with the agricultural season. April transforms the Illinois country into a vast patchwork quilt of fresh color. Spring planting brings forth teams and tractors that comb and dress the land with geometric nicety. By summer the contours of the prairie are soft and round with ripening crops. July ushers in three months of intense industry. Crops are gathered, threshing machines build mounds of chaff, trucks and trains loaded with grain begin to move toward the cities. When autumn comes, the prairies, gashed by plows and stripped of their harvest, have a worn, desolate aspect that is heightened by the somber browns and yellows of the season. The prairies are dull throughout winter save for intermittent snowfalls, and then, in late March, the land stirs, splotches of green appear, and farmers turn again to the soil.
Wisconsin area topography rivers
Wisconsin's area of 56,066 square miles, in the north central portion of the United States, is defined by a ragged boundary. Lake Michigan lies on the east, Lake Superior and the Menominee, Brule, and Montreal Rivers on the north, the St. Louis, St. Croix, and Mississippi Rivers on the west. Only the southern border and some relatively few miles at the State's northern limits follow a line unsuggested by natural water courses.
The topography today is essentially the same as it was immediately following the Ice Age. Broadly, it may be described as a composite of large areas of plains, smaller areas of stream-cut plateaus, and large areas of erosion-worn mountains. Elevations above sea level range between 581 feet where Wisconsin's eastern border edges Lake Michigan to a highest point of 1,940 feet at Rib Mountain near Wausau. The mean altitude for Wisconsin is 1,050 feet. Generally speaking, the elevation of the north is higher than that of the rest of the State.
Streams to the west of Wisconsin's major watershed, a broad land arch extending north and south through the middle of the State, empty by way of the Mississippi River into the Gulf of Mexico. Chief among these streams are the St. Croix, Chippewa, Black, and Wisconsin Rivers, the latter the State's largest interior waterway. Each joins the Mississippi at some point along Wisconsin's western border. The Rock River and some few small streams flow through Wisconsin into Illinois, where they join the Mississippi system. Streams to the east of the watershed. empty into the Atlantic Ocean by way of Lake Superior or Lake Michigan. The St. Louis, Brule, Bad, Nemadji, and Montreal Rivers find their way to Lake Superior; the Menominee, Peshtigo, Oconto, Wolf, Sheboygan, and Milwaukee Rivers, together with numerous smaller waterways, are a part of the Lake Michigan system.
Wisconsin is bordered by more than five hundred miles of Lake Michigan and Lake Superior; the State Possesses close to 4,000 mapped interior lakes. To the northeast, chiefly in Vilas, Oneida, and Iron Counties, are the hundreds of small waters of the highland lake district. In the northwest, especially in Sawyer, Barron, Polk, Burnett, and Washburn Counties is a second group of small, closely set lakes. Eastern and southeastern Wisconsin have a generous number of moderatesized, scattered lakes. Lake St. Croix, an interruption the St. Croix River, and Lake Pepin, a widening of the flow of the Mississippi, are both long narrow bodies associated with hundreds of small flood plain lakes within the bottom lands that line these rivers. Of all Wisconsin lakes, Winnebago, in the Fox River Valley, is largest, covering 215 square miles.
The topography today is essentially the same as it was immediately following the Ice Age. Broadly, it may be described as a composite of large areas of plains, smaller areas of stream-cut plateaus, and large areas of erosion-worn mountains. Elevations above sea level range between 581 feet where Wisconsin's eastern border edges Lake Michigan to a highest point of 1,940 feet at Rib Mountain near Wausau. The mean altitude for Wisconsin is 1,050 feet. Generally speaking, the elevation of the north is higher than that of the rest of the State.
Streams to the west of Wisconsin's major watershed, a broad land arch extending north and south through the middle of the State, empty by way of the Mississippi River into the Gulf of Mexico. Chief among these streams are the St. Croix, Chippewa, Black, and Wisconsin Rivers, the latter the State's largest interior waterway. Each joins the Mississippi at some point along Wisconsin's western border. The Rock River and some few small streams flow through Wisconsin into Illinois, where they join the Mississippi system. Streams to the east of the watershed. empty into the Atlantic Ocean by way of Lake Superior or Lake Michigan. The St. Louis, Brule, Bad, Nemadji, and Montreal Rivers find their way to Lake Superior; the Menominee, Peshtigo, Oconto, Wolf, Sheboygan, and Milwaukee Rivers, together with numerous smaller waterways, are a part of the Lake Michigan system.
Wisconsin is bordered by more than five hundred miles of Lake Michigan and Lake Superior; the State Possesses close to 4,000 mapped interior lakes. To the northeast, chiefly in Vilas, Oneida, and Iron Counties, are the hundreds of small waters of the highland lake district. In the northwest, especially in Sawyer, Barron, Polk, Burnett, and Washburn Counties is a second group of small, closely set lakes. Eastern and southeastern Wisconsin have a generous number of moderatesized, scattered lakes. Lake St. Croix, an interruption the St. Croix River, and Lake Pepin, a widening of the flow of the Mississippi, are both long narrow bodies associated with hundreds of small flood plain lakes within the bottom lands that line these rivers. Of all Wisconsin lakes, Winnebago, in the Fox River Valley, is largest, covering 215 square miles.
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