The general topography of Isabella county would be what is called level, with a general trend downward from the west to the east. This is indicated by the course of the rivers and smaller streams flowing through the county. The Chippewa river, which is the principal one in the county, enters the west line thereof about six miles south of the northwest corner. The upper part of the river and before it enters this county is made up of two branches the south branch and the north branch. The south branch has its .head in the Chippewa lake, in Mecosta county, in township 16 north, range 8 west, and from thence runs in an easterly direction until it intersects the north branch, which has its head in the lakes and swamps near Chippewa Station in township 17 north, range 7 west, and runs thence in a south direction till it joins with the south branch and is then the Chippewa. Entering the county at Sherman City, it runs south and some east through Sherman township, leaving the township on section 34; coming back across the line in section 35, it runs northerly about a mile and then takes a south and easterly course, leaving the township at the southeast corner. About two miles south of Sherman City it is fed by a group of four or five small lakes, from the west, and is also fed at Bundy, which is on section 3 in Broomfield township, by Indian creek, which also comes in from the west. As you come down the river and on the west of it, there is some considerable rolling land as you leave the river valley and go west. There is also some rolling land as you go east from the said valley, none of it, however, so steep or so-rough that it can not be utilized as farming lands.

As you enter the township of Deerfield there is something of a rise on both sides of the river, but not very abrupt, nor very high. The river runs south and some easterly to where it crosses the section line between sections 32 and 33, about sixty rods south of the north line, and there it turns to the east and a little north and goes out of the township on the north half of section 25, where it enters the township of Union and runs in a northeasterly direction through this township and passing through the city of Mt. Pleasant, thence north and east, leaving the township of Union and entering the township of Chippewa on the southwest corner of section 6 and thence in a general easterly course through this township to the east side of the county, leaving the county on section 6 of Chippewa. The eastern part of the county along the said river and reaching back from the river for a long ways is generally level, with a surface just rolling enough to make it drainable without too much outlay of money and labor. Where it makes its most southerly detour in Deerfield there is some quite rolling land, as if the waters had been retarded there and afterward had broken through and passed on to the east.

In the northwest portion of the township of Coldwater there is a small creek running, west to the north branch of the Chippewa, indicating somewhat of a dividing ridge and creating a water shed to the west. Then again about the middle of the said township several small streams join together and form what is known as Walker creek, which flows in a southeasterly course, emptying into the Coldwater river just above Weidman. Where these creeks form and come together it is some rolling, but nothing serious, and it also shows a general trend to the southeast. The Coldwater river has its source in Littlefield lake sections 17, 18 and 20 of the township of Gilmore and runs thence a southerly course to Weidman and then on to the Coldwater lake, through that lake on south till it empties into the main Chippewa on section 7 in Deerfield. The territory drained by the Coldwater is comparatively a level country. The course of the river being so nearly straight it would seem as if it had taken the shortest route possible. As you move on to the east three or four miles you encounter the North branch of the Chippewa in Isabella county. This stream comes into the county on the north side and on section 8 in Gilmore takes a southeast course to the southeast corner of section 24, where it receives the waters of Stevenson's lake and then makes a straight break south for the Chippewa, going almost due south for something over twelve miles. then turns a little to the east and enters the Chippewa in Union. All of the territory drained by the branch and its lesser branches is comparatively level and is first class farming land. It only has a gentle slope to the south. The only elevations found are on the south side of Stevenson's lake, where you can find a few small hills, but nothing to make it objectionable. Just north of Stevenson's lake there seems to be somewhat of a dividing line and a small part of the township drains north to the Tobacco river. The east part of Vernon, Isabella, and all of Wise and Denver, drain to the east; the waters are carried off by the little creeks and rivers, viz: The Little Salt, which arises at or near Loomis and takes a southerly and easterly course to where it crosses the railroad at Delwin, when it veers off to the east. This river is fed by several small creeks, one of which starts in section 7 in Wise and, running a little south of east, empties into the branch. Another, the Kinney, starting in Vernon, and running east and south, empties into the Salt; also another commencing about at section 27in Vernon known as the Killenbeck, running almost cast to the Salt. Another starting near the north line of Isabella township, known as Spring creek,. running east to the South branch of the Salt; also the South branch of the Salt, commencing about a mile north of Whiteville and running east to the Salt; and also one called the Jordan, commencing near Whiteville and running east to the Salt; and also another known as the Kneft, commencing on section 5, township 14 north, range 4 west, and running in a northeasterly direction to the Salt, all of these streams running into the Salt. All of the country drained by these creeks, embracing nearly one quarter of the county, is a level country with very little rolling or hilly land. It is substantially the same kind of a surfaced country drained by the Big Salt which rises in the west part of Lincoln township and runs east and north through Shepherd and on to the Chippewa. The country is some more rolling than that north of the Chippewa river, but not to make it objectionable.

The only other river of note draining a portion of the county is the Pine. This river enters the west line of the county in section 6, township of Rolland, and, running nearly due east about four miles, is there intersected by the Poney, which traverses the south  half of Broomfield, crossing the south line thereof and then runs into the Pine. The Pine then continues in a southeasterly direction to the southeast corner of Rolland. It is fed on its way from the west side by a creek running through Blanchard and by another, known as Skunk creek, which is near the south side of the county. There is also a swamp lying south of Winn fed by springs; these finally form a creek known as the North branch of Pine river. This extends south to the main Pine. This part of the county is quite level, except on the west side of Rolland, which has some considerable hills. None of these hills are of such a nature as to make them worthless for farming purposes and there is scarcely an acre of land that can not be utilized for some profitable purpose.

Isabella county, Michigan, is, a tract of land situated approximately between eighty-four degrees and thirty-seven minutes and eighty-five degrees and four minutes west longitude and forty-three degrees and twenty-seven minutes and forty-three degrees and forty-eight minutes north latitude. It contains, five hundred and seventy-six square miles, being twenty-four miles square. It is divided into sixteen townships, each six miles square. Its population is twenty-two thousand seven hundred and eighty-four. It may be reached by the Ann Arbor and Pere Marquette railroads.

It is a prosperous farming county, and contains a diversity of soils, from boulder clay to coarse sand. The water supply is adequate, the average rain- fall being thirty-three to thirty-five inches. The region is drained by the Chippewa river and its branches. The ground water level varies from a few feet in the eastern part to one hundred and sixty feet below the surface in the western part. The region formerly contained some of the best cork pine in the state, and still contains some excellent hard wood timber. There are extensive deposits of marl around several of the lakes, notably Littlefield's.

The writer wishes to acknowledge the aid of Prof. R. D. Calkins, of the Central State Normal School, and of Mr. Clarence Tripp, in the collection of field data and for many helpful suggestions. Mr. Leverett's map of the region has also been of great aid as a check, and great care was taken in the survey of that particular locality, where an interpretation differing from his is suggested.

Work was commenced August 6, 1906, and the field work was completed September 1, 1906. The ground was covered for the most part on bicycles, though trains were used when necessary. Of course these means of conveyance were supplemented by excursions on foot where there were no roads and when it was found to be necessary to cross sections in order to get a sufficiently accurate view. The amount of ground necessary to be traveled depended, of course, upon the topography and upon the absence or presence of standing timber. Therefore where the relief was low and the land clear it was not always necessary to cover the ground so minutely. It seemed necessary also in many cases to approach a point from two sides in order to interpret the data correctly, so that over nine hundred miles were covered.

A compass, a clinometer, a soil auger, and an aneroid barometer reading to three thousand feet were found necessary. The accuracy of the barometer was preserved by frequent comparisons with the barograph in the Central State Normal School. Although there is no topographical map of the region, a field map was made and data located by means of sections. It has seemed advisable to locate the special parts here treated of by means of townships and sections, though reference has been made in a few cases to well known points.

Isabella county, situated as it is in the center of the Great Lakes district, presents in detail a small part of the problem of this interesting region. Its surface shows very plainly the work of the ice, and in the eastern part the shore and bed of the glacial lake Saginaw stand out distinctly.

It seems plain that those problems which involve the direction of ice motion and the relation of the terrace and beach levels cannot be definitely worked out without a detailed knowledge of the whole surrounding region, so that this report has been made largely descriptive, along with such theory as could be worked out by a study of the county itself.

It has been impossible always to distinguish between "glacial wash," "out wash" and "river  wash," as the three are often blended.

The relief as well as the height above sea level increases toward the west, the eastern part being about seven hundred and sixty feet above sea level, while the western moraines reach nine hundred feet above, Bundy's Hill, in section 8 of Broomfield, rising to about one thousand three hundred and fifty feet above sea level, or four hundred feet above the surrounding country. .

There are many morainal lakes in the county, Coldwater lake, in section 30, Nottawa, the largest, being about two miles long and one mile in width. These are usually surrounded by wash, and drain into the Chippewa system.

The region has many artesian wells, always on the east side of a morainal ridge, which would indicate a general eastern dip of the gravel beds.

It is an interesting economic fact that the change of soil is nearly always shown by the condition and size of the farm buildings. On a rich clay soil may be seen a large stone residence, with two large barns, while less than half a mile away is a log shack with a tumble-down stable, the latter farm being situated on sandy wash. Moreover, a glance at the map will show that roads are lacking where the soil is sandy and unproductive.

The moraines have been distinguished as terminal and ground, though in many cases the line between them has been drawn only after much deliberation and in a few instances may be said to be a matter of personal opinion. The word "terminal" is used for all moraines where the ice paused long enough to leave a ridge or a thick hummocky moraine. The eastern moraines are more truly recessional than terminal.

The general trend of the terminal moraines is nearly north and south. There are five of them and, although they are broken by wash plains, they can be traced the whole length of the county, with the exception of the ridge at the extreme east.

Accompanying these terminal ridges, and usually parallel to them, there are irregular patches of ground moraine. In a few places these are totally surrounded by terminal, and some are seemingly in front of the terminal. This of course raises the question of ice motion.

The moraine farthest toward the east consists of a ridge beginning in a hummocky patch in sections 20 and 29, Chippewa, and extending southward through sections 28 and 33, Chippewa, and sections 4, 9, 15, 16,22, 27 and 35, Coe. It averages about one-fourth mile in width, though it widens to a mile or more in several places. It is about twenty feet higher than the surrounding country. It is composed largely of boulder clay, though there is a layer of gravel through it. This layer of gravel would seem to be of great importance, since cast of this ridge and along nearly its whole length there are artesian wells, some filling a two-inch pipe.

This ridge is a true recessional moraine and shows one of the various pauses during which the ice thickened the ground moraine and left a ridge. North of the end of this ridge, in sections 17 and 18, Chippewa, there is a ridge about a mile in length and one-forth mile wide. It stands alone amid the wash plain, and though it is of comparative low relief yet it shows the moraine characteristic.

Directly west of the village of Shepherd, in sections 7 and 8, Coe, and section 12, Lincoln, there are three almost parallel ridges which, though lower than the main ridge, show very plainly their recessional character.

The next moraine is much larger. On the north it enters the county in sections 1 and 2, Vernon, and extends south through sections 4, 14, 22, 27and 33, Vernon, 4, 8, 18, 19, 30 and 31, Isabella, 6, 7, 8, 20, 28 and 34, Union, and 2, 10,14, 24 and 25, Lincoln.

At its northern edge it is fully two miles wide and widens slightly until it reaches Isabella, where it narrows rapidly until at the point where the Chippewa river valley cuts across it it is scarcely a half mile in width. South of the Chippewa valley it continues as a narrow, irregular ridge, sometimes so low as to be confounded with the surrounding ground moraine. It widens somewhat at its southern end.

At its northern extremity it is somewhat hummocky, but does not lose its ridge character. West of section 10, Isabella, the moraine consists of a series of parallel ridges gradually growing higher toward the west. It is here very difficult to draw the line between ground and terminal since the terminal differs from the ground in degree only. As it enters Union it again assumes its ridge form and is easily distinguished from the somewhat lower ground moraine surrounding it. It is composed mostly of boulder clay, though it contains some sand and gravel.

The next moraine toward the west is separated from the second one by a belt of wash and ground moraine. At the north it enters the county in section 1, Gilmore, and extends south to Stevenson's lake, where it is cut through by a wash belt. This part of the moraine is distinctly hummocky in form and has an irregular series of kettle holes. There are no definite ridges. It is here four miles wide and fifty feet high. In section 6, Vernon, was found a formation of Pleistocene sandstone into which were cemented several large striated boulders. The formation is apparently purely local

South of the wash belt the moraine continues through sections 26, 27 and 33, Gilmore; 4, 9, 16, 20, 27 and 32, Nottawa, and 5, 9, 16, 21 and 28, Deerfield. It is cut through by the wash belt in the Chippewa valley. This part of the moraine gradually assumes the ridge-like character, though it is irreg- ular both in width and height. It widens considerably near the wash belt.

South of the Chippewa valley it widens still more, and in section 2, Fremont, it divides, one tongue reaching the southern boundary of the county through sections 6, 7, 18 and 19, Lincoln, and 25 and 36, Fremont. The other tongue ends in a wash belt in section 22, Fremont. A belt of ground moraine separates the two.

About a mile east of Littlefield lake, in Gilmore, there appears a bit of terminal ridge extending from section 6 southward to section 32. It is entirely surrounded by wash and bordered on its eastern side by swamp. In shape it is an irregular ridge (or succession of ridges) and rises to a considerable height at its southern end. The only southern moraine which would seem to correlate with this isolated piece is in section 26, Sherman, five miles south. This, though cut by the valley of Indian creek, continues south to the edge of the county. In section 26, however, the moraine is composed mostly of clay and is very hummocky. It continues southeast and in section 33, Deerfield, is separated from the third moraine treated of by the Chippewa valley.

In the northwest corner of section 32, Deerfield, a small tributary of the Chippewa in draining a small lake has cut a deep V-shaped valley in the moraine, giving it the appearance of high relief. From this point it extends southward to section 7, Fremont, where it divides, one part ending in section 31, Fremont, the other cutting the southern boundary of the county in section 32 of that township. The material between those two parts has the character of ground moraine, though wash predominates in the valley between. The moraine varies in width and height, its width being from one-half to two miles. It,is impossible to say with certainty whether this rather irregular moraine belongs to the moraine toward the east or not, though at one place at least it nearly connects with it, there being only a narrow wash belt between.

The moraine, or group of moraines, farthest west presents the most interesting data. One patch occupies nearly the whole township of Coldwater and extends eastward into sections 9 and 19, Gilmore, and south into sections 7 and  10, Sherman. How far it extends north into Clare county and west into Mecosta county could only roughly be estimated. That part of the moraine in this county is very high, being two hundred feet higher than the wash in the valleys to the east. It is very hummocky in places and in sections 20 and 29, Coldwater, it assumes the form of ridges. In its southern portion in northern Sherman it has much the appearance of high ground moraine, yet near its edge it becomes higher and then drops off into a high wash terrace.
Nearly all the northern and northeastern portions are sandy and the soil  poor, but near Brinton the soil is clay. From the character and size of this  moraine it would seem to be more truly terminal than those farther east. The Chippewa valley cuts through sections 6, 7 and 17, Sherman, and south of this the moraine narrows, scarcely reaching the center of section 28. It again narrows, passing through the center of section 31 and gradually rising toward the south, till in sections 5, 6, 7 and 8, Broomfield, it reaches its highest point over thirteen hundred feet, in Bundy's hill . This is an irregular shaped hill, rising four hundred feet above the wash and having thin crests. These crests shape gently to the west and finally die out as ground moraine in Mecosta county. The eastern slopes are steeped, sometimes twenty and thirty degrees, and have a series of "foothills" or knobs, which do not seem to be entirely the work of erosion, for there are some undrained depressions.

At nearly the highest point there is a boulder of granite which measures forty feet in circumference and probably weighs twenty tons; there are several more, slightly smaller, near it, and others of the same type appear farther south.  None of these are found in the moraine farther east.

The hill proper is composed mostly of sand, though there is clay near its raine appears as borders. It slopes rapidly down until, in section 16, the low, narrow ridge, scarcely one-half mile wide. It slightly widens and dies out in section 26.

Between this and the next eastern moraine there appear three small, yet marked, ridges less than a mile in length; these are separated from the eastern moraine by wash, from the western ground moraine.

In sections 9 and 11, Sherman, there are two small oval hills. They are probably remnants of the large moraine, which have been isolated by erosion.

South of the Bundy moraine, and separated from it at its eastern end by the Pine river valley, lies a high moraine whose long axis is roughly east and west. It occupies sections 31 through  35, Broomfield, and is about one and one-half miles wide. It slopes down on the south to the Pine river valley. It is composed of a series of ridges, though at its eastern end and near its base it is quite hummocky. In composition it is clay, though some what mixed with sand. Its soil is generally good. It shows many of the characteristics of the Bundy and Coldwater moraines. South of the Pine river (which is tributary to the Chippewa) another high moraine occupies sections 7, 8, 9 and 15, Rolland. It is composed of one central ridge, though at its eastern end and alon its base it becomes hummocky. It slopes rather abruptly down into the valley of a tributary of the Pine, and on the south side of the valley there appear patches of a lower moraine having a very hummocky appearance.

At the western end of these moraines in Mecosta county the valley between then disappears and they join and form one.
Thus it would appear as though the Pine and its tributary had headed up into a moraine and dissected it, forming tongues. There is comparatively little wash in those Valleys and they present rather young characteristics.

South of Skunk creek, in sections 34 and 35, Rolland, there is a wide ridge of moraine, sandy on its northern edge, but good clay near the edge of the county. It runs southward for a considerable distance into Montcalm county.
 
 

The ground moraine usually occurs behind the terminal and next to it. In several cases, however, it has been necessary to designate areas which do not occupy this regular position as ground moraine. Again it is sometimes difficult to distinguish between terminal moraine and ground moraine on the one hand, and ground moraine and wash on the other, as sometimes the wash is but ground moraine rehandled slightly by running water.

There is a narrow belt of ground moraine east of the first terminal in Coe. Its surface is rather rolling and it is composed largely of boulder clay. It is bounded on the east by a very marked beach ridge.

Southeast of Mt. Pleasant there is a belt of ground moraine about four and one half miles wide situated between the two narrow terminal ridges. It is cut through near its southern edge by the narrow wash belt of the Salt River valley. It has a rolling topography and has several small swamps. It contains the three small morainal ridges already spoken of. The same belt apparently continues north of the Chippewa valley. It takes a northeasterly course and leaves the county at the north through sections 4, 5 and 6, Wise. It has a rolling topography and is composed of boulder clay.

South of Mt. Pleasant, and west of the second terminal, there is a belt of ground moraine about three miles wide. Towards its southern edge it is separated from the second and third terminals by wash. North of the Chippewa valley this belt continues, though dissected by the North Branch valley. In fact, it is entirely cut away from the second terminal north of section 1, Deerfield. It joins for a short distance north of Stevenson's lake, and leaves the county as a narrow belt about a mile wide. It is very irregular and apparently made more so by the wash belt cutting it lengthwise. .

In sections 11, 12 and 13, Deerfield, there is a peculiar ridge about a mile and a half long and thirty feet high. Its form is eskar-like, yet at its eastern end, in section 1, it is composed of boulder, clay for about a quarter of a mile. Then it assumes a true ridge-like character, though with several irregular off- shoots toward the north and west. From here westward it is composed of sand. and gravel, in many cases beautifully stratified as shown by sections in gravel pits. One of these especially showed a distinct dome-like character and the stones were rounded by water action. Although this ridge could not be called a true eskar, yet it showed the characteristic of a serpentine kame.

North of Stevenson's lake the ground moraine is quite level, though it is clay, even at the surface. In this moraine there are several flowing wells, one just north of the lake and several as far south as the Chippewa valley. The patch of ground moraine in eastern Fremont is a low belt of rolling country flashed on either side by the tongues of the terminals described above. Near its southern boundary it is bordered-on the west by a wash belt.

In sections 20 and 29, Fremont, there is an oval patch entirely surrounded by moraines, though a narrow wash belt has cut in on the west. It is rather rolling, yet it is not high nor hummocky enough to be classed as terminal. Its position is at least unusual.

In sections 11 and 12, Rolland, there is a narrow strip of moraine sloping from the terminal on one side to the wash on the other, yet it is composed of clay and has a rolling topography.

Directly cast of the Bundy moraine there is a strip of ground moraine five miles long and one wide, which, though hounded on the east by wash, would seem to belong to the terminal east of the Bundy terminal. North of this the ground moraine does not appear in the county, though it probably appears a few miles west in Mecosta.

West and south of the Bundy moraine there is a wide tract of rolling ground moraine which fits snugly against the Bundy moraine on the north and the terminal moraine on the south. It is rolling and slightly sandy and contains some swamp land.

South of Blanchard there is a large tract of ground moraine which extends back into Mecosta and Montcalm counties. It is somewhat sandy, though as a rule the land is good. It is rather rolling, but is lower than the terminals on the east.

It can now readily be seen that the general trend of the moraines is north and south; that the terminals increase in height and dimensions toward the west, and that the eastern ground moraines cover a much larger per cent of the morainal area than the western ground moraines. It may also be re- marked that cast of the Chippewa valley the ground moraines are on the east side of the terminals, while, on the west side of the valley they are on the west side. Moreover, the character of the moraines west of the valley is different from that on the east. The western moraines are more sandy and contain very large boulders of granite and a quartzite conglomerate which were not found cast of the valley.

All the drainage is east or southeast with the exception of a small stream in northwest Coldwater. The streams have cut valleys across the moraines, and in most cases the valley narrows in passing across them. In nearly all cases the original trend of the moraine can be readily seen.

As before stated, the term "Wash" has been used for both glacial wash and river wash. In some parts of the region they are distinct, in others they are so intermingled that any line of separation is impossible. The wash is usually more or less stratified sand or rounded gravel. It usually follows the river valley, though there are notable exceptions. The swamps have been classed as wash, though the large ones have been differentiated. The lake bottom, flat in the eastern part, has been classed as wash, for it shows quite a depth of sand upon the clay beneath. In many cases the rivers come from the moraines in comparatively young valleys and distribute the wash in their lower courses. In a few cases, notably in front of the high terraces near Weidman, the lower flats are made from rehandled glacial wash.

Along some of the valleys the glacial wash terraces look much the same as the lower river terraces, though their surfaces are much more uneven than the river terraces and present the appearance of pitted plains.

The strip of Wash immediately around Littlefield lake consists of low, marshy land, and near the lake and somewhat farther south there are extensive marl beds. On the east side of the small strip of terminal the wash is some- what sandy, though close to the moraine there are a series of small swamps. A narrow strip of wash follows the valley -of North Branch eastward and combines with the Stevenson's lake wash.

Directly north of the Coldwater moraine, and fitting snugly against it, are a series of high glacial wash terraces. Near the moraine they are very little modified by erosion and form a very good example of,a pitted plain. About a mile north of Weidman these are dissected by erosion and from this point south neatly to Coldwater lake another lower terrace has been cut from the high one. Both terraces are, of course, dissected by erosion, and from this point south nearly to Coldwater lake another lower terrace has been cut from the high one. Both terraces are, of course, dissected by the important drainage lines.

The southern edge of the high terrace swings westward and joins the Coldwater moraine close to the Chippewa valley. Remnants of this high terrace can be noted in section 6, Nottawa. The land being dissected by erosion, it was impossible to note any remnants south of Coldwater lake, the lake itself being on the same level as Weidman. The lower terrace gradually blends into the wash in the Chippewa valley.

The wash in the valley of the Pine River system seems to be rehandled glacial material b'rought from the dissected moraines toward the west. It is a broad, rather flat valley, containing a good soil. In section 18, Fremont, there is a small swamp whose drainage is south through a wash belt into the Pine.

In the valley of the north branch of the Pine there is considerable wash, and north of Winn it assumes the character of swamp land. The wash in the southern end of the valley is rather sandy.

South of Stevenson's lake the wash belt narrows and swings through a narrow pass into the valley of the north branch of the Chippewa. This valley is apparently cut from the ground moraine and the inroads made by tributaries in the southern part of the valley show that the work is still in progress. How much of the terminal moraine on the cast has been cut away can only be judged from the evidence furnished by the existence of the remnant on the south end.

In section 17, Lincoln, there begins a large swamp which drains southward. It continues about two miles wide and still appears as markedly swamp on the southern edge of the county. In the eastern part of Lincoln a belt of wash a mile in width at its source gradually narrows as the river approaches the lake flat.

At Mt. Pleasant the wash widens rapidly and its southern boundary extends east to section 21, Chippewa, then nearly southeast to the southeast corner of the county. The northern boundary of the wash is rna,.rked only by the change from sand to clay, as the till plain is as level here as the wash. The line of separation is an irregular line passing through sections 31,29, 21, 16, 10 and 13 Denver.

The till plain has been mentioned and it does not seem out of place here to continue the discussion. The line of separation from the moraine on the west is not at all satisfactory, it being very marked in places and entirely dis- appearing in others. In a few places there appears even the sernbl:-ance of a beach ridge, yet it is only local and always dies out within a short dis- tanc,e. Yet the till plain is so level and grades so imperceptibly into the wash on the south that it is at least probable that the lake covered this also, at least for a time. The flat plain of wash proper is covered on top with a sandy loam, which varies in depth from a few inches to several feet. Its surface is almost level except where drainage lines have dissected it.

In section 36, Coe, there appears at the eastern edge of the lake flat a low ridge of sand and gravel, which extends along the lake border to section 21, Chippewa. It has an even crest and slopes with an even angle out into t e lake flat. In places it has been destroyed by erosion, but it is clearly traceable along the edge of the flat. At its. northern end it divides and forms two
projections, one behind the other. This would indicate a sort of spit formation. Moreover, about a quarter of a mile toward the cast there is a low ridge running out from the end of the terminal. It is apparently a spit formed when the waters of the lake at a slightly higher level were down as a littoral current northward off the end of the moraine and into deeper water, where the spit was deposited. Then the waters of the lake fell, due, probably, to the shifting of the ice, and the beach ridge was formed, the little spit first, then the eastern. one. The beach ridge seems at no place to have been a barrier, though modifications since may have destroyed the evidence.

As stated earlier in this report, no attempt has been made to give more than a descriptive statement of the surface geology of the region. There are a few conclusions which might, however, be suggested.

It was probably in the western part of the county that the Michigan lobe and the Saginaw lobe of the ice sheet came together. Perhaps the only legitimate evidence of the point of contact is the fact that the Chippewa valley separates the moraines by a comparatively wide wash basin, and that west of this basin the ground moraines are west of the terminals, while cast of the valley they are east of the terminals. Moreover, the terminals east and west differ in material and in the size and number of the large boulders. The fact that the whole valley near Weidman was filled with high wash sloping eastward would tend to indicate wash from the west. Then in many cases the lower terraces fit into the uneven edge of the dissected terrace and slope westward. There is a probability that the Michigan lobe advanced and deposited the western moraine, and that the wash was formed in front and sloped toward the east, and that then there was cut and formed a high terrace. Later the Saginaw lobe advanced to the position of the terminal east of Weidman and, its wash sloped away from its front and fitted into the erosion lines of the high wash.

Lake Saginaw was formed when the ice had retreated from the recessional moraines farthest east, and the water was held between the moraine and the retreating ice. How far it extended westward at Mt. Pleasant is only a matter of conjecture, for the, wash from the Chippewa has destroyed the ridge if there ever was any. The absence of the beach north of Mt. Pleasant may be explained by the fact that the lake remained only a short time, and that it had washed over very little material is shown by the absence of sand on the till plain.

The question of river terraces and the correlation of levels would be an interesting problem, but would require a careful study of all'the Surrounding rivers and of the lake shore both north and south. It is probable, however, that the terraces in the valleys correspond to the fluctuations in lake level, which were in turn caused by the advance and retreat of the ice.

It is hoped that the work done in this county will be some small aid in the solution of the more general problem of the Great Lake region.

[The above article on the geology of Isabella county is entirely the production of Fabian Bouton Dodds, and to him is to be given all credit for his thorough and painstaking labor, as well as his knowledge of the subject]

I. A. FANCHER
 
 

© 1999 - 2009 by Donna Hoff-Grambau
ALL RIGHTS RESERVED