Geological Survey Bulletin 611 Guidebook of the Western United States: Part A

Like most of the other valleys of this region, this one has not been carved by the stream that occupies it but is merely a chain of low places along which the water finds an outlet. Such valleys have no definite shape or plan; and consequently at one place the railway may be in a fine rolling country that is well farmed and prosperous, as it is at Verndale, and at another place it may be in the most dismal expanse of swamps and shallow lakes.

In a general way the country becomes more rolling toward the west, and about the town of Wadena (see sheet 3, p. 32) there are fine farms on both sides of the railway. When the crops wave green in the breeze or take on the golden tints of harvest time this country affords the traveler a pleasing contrast with the swamps and scrub oaks of the region to the east. Just east of the station at Wadena the Northern Pacific is crossed by a line of the Great Northern which runs from Sauk Center to Cass Lake, and about 2 miles west of Wadena a branch line of the Northern Pacific turns to the left and runs to Fergus Falls and Breckenridge.

SHEET 3. (click on image for an enlargement in a new window)

Near milepost 169¹ the railway approaches Leaf River on the right, and near the valley there is more decided evidence of morainic topography than there is between this point and Staples. The hills are not high, but they have the peculiar conical or sugar-loaf shape that characterizes morainic hills, and they are separated in many places by marked kettles or depressions. The hills in this region are formed of material that the ice brought in from the Red River valley. A brief history of the several invasions of Minnesota by the ice and a description of the drift deposited by them is given below by Frank Leverett.²

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¹Mileposts on the Northern Pacific are numbered from division points and not from the ends of the system.

²Before the glacial epoch, or Great Ice Age, Minnesota presented a very different appearance from that which it presents to-day. Where there are now flat plains there were then rocky hills and ridges, separated by deep valleys. In the central and western parts of the State, from the Minnesota Valley northward, the bedrock is deeply buried. Deep drilling shows that it has an uneven surface and is composed chiefly of old crystalline rocks in which there are differences of altitude of at least 500 feet. In the northeastern part of the State the iron ranges and their associated rock formations stood out much more prominently than they do to-day. This old surface is now so deeply buried under glacial material in the greater part of the State that it is not possible, with our present knowledge, to outline the position and courses of even the principal streams of that time. Of the eastern and southern parts, however, enough is known to warrant the statement that the positions of the preglacial stream courses were not widely different from those of to-day. The Mississippi flows locally in a new course past St. Anthony Falls, at Little Falls, and at Sauk Rapids; but drilling has shown that a deeply buried valley, which is 200 feet or more below the present stream, lies near the river and in places crosses it.

The glacial epoch did not consist simply in the growth and disappearance of a single great continental glacier; there were stages of great extension of the ice, separated by stages in which it was greatly reduced if not entirely melted away. There were also several centers of exceptionally great snowfall and snow and ice accumulation, from which the ice radiated or flowed outward. From three of these centers of dispersion the ice spread into Minnesota in the Wisconsin stage. (See map on sheet 3, p. 32.) The western and southern parts of the State were covered by ice (western ice sheet) which came from central Canada. The eastern part as far south as the vicinity of St. Paul was covered by ice (middle ice sheet) from the region south of Hudson Bay, and a small area on the border of the Lake Superior basin was covered by ice (Superior ice sheet) which came in from the east through that basin. The western sheet brought in fragments of limestone and shale, the middle sheet carried southward much material from the iron ranges and also red sandstone from the west end of Lake Superior, and the eastern or Superior sheet transported to the limits of its advance large amounts of the red sandstone bordering that basin.

The effect of these invasions was to fill up and obliterate the valleys or to block them in such a manner as to produce chains of lakes along their courses. Large moraines or irregular, hummocky ridges of drift mark successive positions of the border of each of the ice sheets. Sand and gravel were spread out by water escaping from the ice front, fringing the moraines in extensive plains termed outwash aprons. In places where the ice border melted back rapidly no moraines were formed, but instead a nearly level surface, composed of bowlder clay or till.

The moraines of the Superior sheet encircle the west end of the Lake Superior basin in a series of concentric ridges, each ridge being later than the one without and earlier than the one within. Those formed by the western ice sheet lie in the high country along the valleys of Red River and Minnesota River. These streams are bordered by broad plains which owe their form to the fact that they lay under the deep part of the ice sheet and along its axis of movement.

The moraines of the middle ice sheet are well developed south and east of St. Paul and in central Minnesota. The Northern Pacific Railway traverses one of the most prominent moraines of this ice sheet, between Little Falls and Staples.

The three advances of ice, though occurring in a single glacial stage, did not take place at the same time. After the middle sheet reached its maximum and melted back nearly if not quite to the Canadian line, the other sheets advanced into the district it had occupied and there covered its drift with their deposits. The western ice in places extended 75 miles or more into the district the middle sheet had abandoned.

The map on sheet 3 (p. 32) is intended to show the several glacial invasions of Minnesota during the Wisconsin stage, but as the three glaciers did not invade the State at the same time it is impossible to represent them accurately on a single map. The extent of the middle sheet is known only from the drift it deposited, and as much of this is covered by material brought in later by the western sheet its limit on the west can be only conjectured, but it probably covered much of the northern part of the State.

The map is supposed to represent the State as it was when the western ice sheet extended southward along the Red River valley and deployed to the east into the open lands of Minnesota. Part of this great glacier found an outlet eastward into the upper Mississippi Valley and the valley of St. Louis River, but the main mass of the ice pushed southeastward along the valley of Minnesota River. A part overflowed northeastward, forming a lobe that covered much of the territory north of St. Paul. The main lobe swept on southward across the boundary of the State and as far as Des Moines, Iowa. After a time the melting at its front exceeded the supply of fresh ice coming from the north, and then the glacial margin began to retreat, and eventually the ice disappeared from the State.

When the ice of the Superior sheet melted back into that basin the ponding of water between the ice front and the highland bordering the basin formed a glacial lake, known as Lake Duluth, which discharged into the St. Croix Valley, in northern Wisconsin. Similarly, as the ice melted in the Red River valley, a lake known as Lake Agassiz (see p. 32) formed between the front of the glacier on the north and the high land to the south and discharged to the south through Browns Valley.

Over a large part of the surface of the drift of Minnesota there has been little change since the ice disappeared except the formation of soil and a slight leaching and weathering; but in some places notable changes have been wrought. Many of Minnesota's "ten thousand lakes" show beaches at higher levels than the present, their outlets having been cut down by the water at various stages. Many lakes have been so filled with sediment as to become marshes or even dry land, and many have been filled by the growth of peat. St. Anthony Falls, on the Mississippi, has retreated a few feet a year until recently checked by an artificial retaining wall. Minnehaha Falls, on a small tributary of the Mississippi, has retreated less than 400 feet in several thousand years. On the whole, the amount of stream erosion since the last glaciation is slight, and on many streams it is scarcely enough to be measurable.

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West of Bluffton the morainic character of the topography continues for some distance but gradually gives place to the rolling country about New York Mills. The less broken country here is well suited to agriculture, and fine farms may be seen on both sides of the track.

The railway is here on the divide between the Hudson Bay and Mississippi River drainage systems. It is not at all certain that before the glaciers covered this country the divide was at this place, as all the stream courses have been either materially modified or completely rearranged by the ice sheets that invaded the State. The present divide is not made evident by any well-marked ridge, and the appearance of the country will not probably show the traveler that he is crossing from one of the great drainage basins of the continent to another. The figures given for the elevation of the towns show that New York Mills is a little higher than the towns on either side and hence that the water parting is near that place.

At milepost 187 the railway crosses Otter Tail River, the first large stream passed in the Hudson Bay drainage basin. This stream has its origin in a number of beautiful lakes near the Northern Pacific line and flows southward through Rush Lake to Otter Tail Lake, the largest body of water in the region. Thence it flows westward and joins the Bois des Sioux at Breckenridge, forming Red River.

After crossing Otter Tail River, which meanders broadly in a swampy bottom about a mile in width, the railway traverses a rolling plain of rich agricultural land near the center of which stands the prosperous town of Perham, so named for the first president of the Northern Pacific Railroad Co. The surface of this plain is formed of sand and gravel washed out from the front of the western ice sheet as the big moraine to the west and north was being deposited. Pine, Little Pine, and Marion lakes lie a few miles from the track on the right, and the cottages and hotels along their shores offer many inducements to the sportsman or to the summer visitor who is in search of relaxation from the breathless hurry of modern city life.

The plain extends along the railway to a point 4 miles northwest of Perham, where it gives place to rough, hummocky land that marks an eastern point of the great morainic ridge on the west of the track. When this moraine was formed the ice had disappeared from the country to the east but covered all that part of the State lying to the west. From Luce to Frazee the ground is generally swampy or dotted by small lakes or ponds.

At milepost 196 the railway crosses Otter Tail River, here flowing to the east. On account of the numerous ridges this stream wanders about from lake to lake, finding an outlet by an exceedingly round about course. Only a few of these lakes are visible from the train, but the map shows that great numbers of them lie on both sides of the road. The kettle-like depressions in a moraine, many of which are filled with water and become ponds or lakes, are due either to irregularities in the deposition of the drift along the front of a glacier or to the melting of detached blocks of ice.¹

FIGURE 3.—Diagram showing probable origin of many kettle holes. A, Block of ice recently broken from a glacier; B, same block after part has been melted and the remainder covered with sand and mud; C, depression resulting from complete melting of the ice.

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¹When a glacier reaches its greatest extension and begins to retreat, its pause and recession mean that the supply of fresh ice or snow back at the gathering ground, where it receives most of its material, is not sufficient to keep pace with the melting that goes on over its entire surface, but more particularly at its outer margin. The result is that the ice near the extremity moves forward very slowly and finally ceases to move at all. The edge of the ice sheet becomes thin and irregular, and, owing to more rapid melting along cracks or crevasses, masses of ice become separated from the main body.

Part of such a block, as shown at A in figure 3, above, may be uncovered, but possibly the larger part will be buried in sand and gravel washed out from the front of the glacier. In the course of time the part above ground melts and disappears, but if the deposition of sand and gravel continues the part below the surface may become completely covered, and being protected it persists, as shown at B in figure 3. Finally this also melts, and the surrounding sand and gravel fall into the hole left by the ice. This leaves such a depression as that shown in the diagram—a kettle, as it is generally called in a glaciated country.

If the material surrounding the kettle is open and porous, and if there is good underground drainage, the kettle may remain open and in much the same condition as it was when it was formed; but if the earth around the kettle is impervious, then most of the water falling into it or draining into it from the surrounding region is retained, and a lake or pond is the result. Some of the lakes of this region are many miles across, and if their basins were formed in this way the blocks of ice that caused the depressions in which they lie must have been correspondingly large.

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Near Frazee the surface is rough and broken and there are many deep valleys containing lakes, ponds, or swamps. A notable depression or old channel is crossed by the railway just southeast of the town. This channel extends northwestward from Murphy Lake, 2 miles southeast of Frazee, and it is swamps or
generally occupied by long, narrow lakes. The railway follows it for 3 miles beyond the town, and some of the views of the little lakes on both sides of the track are very pretty. Town Lake, close to Frazee, and Harold Lake, farther on, are in this channel on the left (south) of the track; and Chilton and Brink Lakes are irregular bodies of water on the other side.

Frazee is in the heart of a lake region, where large lakes abound on all sides of the town, but none of them are visible from the train for several miles beyond Harold Lake. It is also in a great morainic belt, which was formed by the ice sheet (western) that invaded this country from the Red River valley. The hills are steep and conical, and the depressions between them are very pronounced. To this glacier is largely due the lake region of central-western Minnesota, well known as a summer resort and as a paradise for sportsmen.

The largest and best-known sheet of water that is visible from the train in this vicinity is Detroit Lake, which can be seen on the left as the train skirts its banks between mileposts 208 and 209, a short time before reaching the station at Detroit. From Detroit Lake a river channel leads southward into and through a series of other lakes of equal beauty. This channel has been made navigable by a system of locks, and small steamers ply from lake to lake, passing the finest scenery of the lake region. The drinking water used on Northern Pacific dining cars comes from Pokegama Spring, on the shore of Detroit Lake.

Detroit is one of the most important towns in the lake region, and is a point of departure for many of its resorts. Just west of the town the Northern Pacific is crossed by a branch of the Soo Line (Minneapolis, St. Paul & Sault Ste. Marie Railway), which runs from Alexandria to Plummer.

The roughest part of the moraine seen from the railway, a part known as the Leaf Hills, lies east of Detroit, but west of that place the surface features become more and more subdued. As the morainic topography disappears farming becomes more general, and at Audubon field after field of grain stretches away over the rolling upland as far as the eye can see. Although the traveler may have enjoyed the ever-changing panorama of lakes, hills, and plains of the morainic belt, he may find it a relief to emerge into the fine farming region about Audubon and Lake Park.