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Approximately 3300 words
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Rob F. Sanderson
724 Edgewater,
Portage, WIS

What Makes Lakes?
Rob F. Sanderson

Editor’s note: This article is informative, and may be of use to you if you think your readers are ever curious about how a lake is made by the forces of Old Mother Nature. It would explain the origin of the various types of lakes, what type of hunting and fishing is to be expected in each, and side-light information which may understand the water better. Effort has been made to refrain from complex physiographic terms, which might confuse or dis-interest the reader.

What Makes Lakes?

          In all the times you have been out on a lake - hunting, fishing or just boating --, has your curiosity every asked you, “I wonder what made this lake?”

          If you are like the rest of us sportsmen, most of the time you take nature’s work pretty much for granted. We know that trees growing make a woods, and that water makes a lake; and generally we let things go at that and confine our curiosity to why the fish aren’t biting today or why this blind isn’t as good shooting this year as last.

          But every once in a while when we see a beautiful sunrise over the water, or when in autumn we see the flamboyant foliage of the shore trees mirrored in the water with perfect color reproduction, we wonder “How did this all come about? Why is this lake here? Why are there thousands of lakes in some parts of the country and almost none in other parts?”

          Lakes are really an un-natural occurrence. Rivers are the natural way for the water to drain from the clouds to the oceans, and the rivers carve and erase our hills and mountains. Somehow the natural gravity run-off has to be interfered with. The result is imponded water and a lake, but a lake is a pretty impermanent thing, speaking geologically. Sooner or later the outlet will dig its bed lower and lower by washing away the earth and rock, and drain the lake just as a pitcher would be drained by lowering the spout. If the lake has no outlet, either it will fill with sediment settled out of the water and form a swamp or dry basin, or else streams will eat headward and eventually tap and drain away the water.

          So you see, if left to himself Old Man Weather will soon smooth out the wrinkles of he world. In a few million years all our lakes would be gone, if Mother Nature just sat back and did nothing to make new ones. If she loafed long enough, the wear from the clouds would wash away all our continents and all we could do then is fish. But just our as the land is rebuilt, lakes can be rebuilt or new ones can be fashioned to take the place of those that have lived their life cycle and are no more. Like trees, lakes live only so long and then they wither up and die. Only lakes don’t grow from drops of water like trees grow from seeds, and as they live much longer than trees we seldom see one born or dying.

          Just as there are different kinds of trees, there are different brands of lakes. Mother Nature uses many different methods and if you look closely you can usually tell how a particular lake happened to be made. After you are able to tell this by looking at a lake, you will appreciate it a great deal more just as you appreciate a good gun or reel more because you have an understanding of how it works. You will also be better able to appraise a lake or a lake area for its hunting and fishing prospects.

          Ice has made more lakes than any other one cause on our continent. Odd, isn’t it, especially now when we see ice made from lakes every winter? We would never think that the lake we are on could have been made by ice.

          But if you live north of a line roughly approximated by the Ohio and Missouri Rivers, chances are that your favorite hunting and fishing lakes are the handiwork of a great ice sheet that very slowly pushed and spread out from the Canadian snowfields which then accumulated faster than they melted. The climate was very cold then and there was no summer to speak of. This sheet of continental ice came down from Canada and then went home again on probably four different occasions, separated by inter-glacial epochs measured by tens and hundreds of thousand years. The ice last left about thirty thousand years ago and as the interglacial epochs were longer than this, and planed and animal remains tell us that at least one interglacial epoch was much warmer than the climate we have now, some people insist we are still in the ice age. Scientists believe that even for the earth’s pole to be ice capped, is very uncommon in the earth’s history.

          You can imagine the effect of a slowly moving sheet of ice several miles thick in places. It acted on the surface of the earth like a gigantic road scraper, gouging off the tops of hills ands filling in valleys and riverbeds. When the ice finally got too warm and tired and went back home, it left the land pretty well messed up.

          You can see the difference by a glance at the land once covered by the ice, compared to the land beyond the ice advance. Compare the flat-to-rolling Illinois and Southern Wisconsin farmland with an “island” in the ice sheet - the Drift less Area of Southwestern Wisconsin, which has high wooded ridges and steep abrupt valleys. Compare Northern Indiana, flat as a pool table, to hilly Southern Indiana, which the ice missed. The difference can also be seen in Missouri and other states only partly scoured by the ice.

          The reason the Ohio-Missouri valleys mark the approximate ice boundaries is not by chance but because these rivers with their tributaries used to flow north into Hudson Bay and the St. Lawrence River respectively, and the southward moving ice gradually dammed and backed up these rivers. As the Mississippi Valley was the lowest gap in the south, the ice progressed furthest here, and the waters from the east and west flowed along the edge of the ice from toward the low spot in the middle, down the ‘sippi valley to the Gulf. This is why the Ohio and the Missouri join the Mississippi within as short a distance from each other. This latter river was at this time many, many miles wide and perhaps a half a mile deep owing to the enormous discharge of melt water.

          The Great Lakes were the biggest lakes left by the ice. Before the ice came these lakebeds were lowland plains with sluggish rivers meandering through them. Gravitating to the lowest levels, the ice moved through these areas easier and thicker, scouring them much deeper than before. The ice pushed the old Lake Erie outlet full of rocks and dirt, and left the river to cut a new channel across the Niagara escarpment. This formed the present Niagara Falls, which date from the glacial retreat. As the falls eat backward the level of Lake Erie lowers and someday if not interrupted the gorge will drain the lake and leave a marshy basin as existed before the ice advance. Eventually all the Great Lakes basins will be drained and begin again as valleys for rivers.

          The Great Lakes are only a part of the ice engineering. Lake Winnebago, famous fish and waterfowl paradise in Eastern Wisconsin, is the largest fresh water body entirely within the boundary of one state, in the United States. This was formed by the ice-dumping till (glacial debris) in the valley and mouth of the Fox River, which flows north into Lake Michigan. When the later Lake is drained, the Fox River will soon dig down to the new level and drain Lake Winnebago.

          Not satisfied with some very big bathtubs, Mother Nature decided to make hundreds of thousands of small fingerbowls. You can see them today in Northern Wisconsin, Michigan, and Minnesota, as well as much of Canada. Now and then you find them in the more southern of the states and the ice frosted.

          Many of these are “kettle hole” lakes. These were made by large blocks of ice getting buried in the earth left behind by the ice. Some of the stones and earth were carried hundreds of miles frozen in the moving ice. When the ice blocks melted they left big holes in the earth. Some of these were too high to fill with water, and the smaller ones looked like the imprint a mammoth old-fashioned iron kettle leaves in a bean hole. So they were called “kettle holes” by the early pioneers who first saw them.

          When the depressions left by the large ice blocks are low enough to fill with water, they are called “kettle lakes”. Some of the buried ice blocks were huge. They left lakes several miles long. Some are round but many are very irregular as the larger masses of buried ice were not as symmetrical as the smaller ones. When big valleys were filled alternately with huge chunks of ice and dirt fill, we find “kettle chains” which often connect to form a chain of lakes.

          Sometimes a great many small, symmetrical lakes are found close together in level country. They were formed on an outwash plain a short distance from the ice front. Masses of ice became isolated from the main body and were buried by dirt and gravel washed out of the melting glacier. Sometimes it took many hundreds of years for the ice to melt away and leave the finished kettle. In Alaska today there are places where good-sized pine forests grow in a layer of soil several feet thick, beneath which is dark glacial ice of unascertainable age and depth.

          Many ice-age lakes are not kettle lakes. Sometimes the advancing ice with stones firmly frozen to the bottom layer would simply gouge out a trough, which later filled with water. But more often it interrupted the normal drainage pattern by filling the stream valleys, damming the normal flow of water to make it form higher, more meandering outlets. As a result the Missouri and other rivers were displaced from their natural bed and now flow through land considerably higher in places than their old beds but a few miles away.

          To show us that these glacial lakes are temperamental in existence, glacial geologists point to Lake Agazzis, which was the largest of America’s inland lakes, excepting the Great Lakes. Lake Agazzis covered the Red River Valley area in Northern Minnesota and Southern Manitoba. Its sediments form the now fertile wheat land there, but the lake itself long ago drained away to the north. Lake Calvin on the Upper Mississippi River is another ancient glacial lake that has drained away to the Sea. There were many other smaller lakes that are now dry.

          The nature of the ice lakes depends largely on the type of country they were formed in. Usually the water is clear and cool and often the beaches are sandy with a thin growth of rushes around the shallow shore water. Fishing is apt to be good for bass, pickerel, and smaller fish. Owing to many of the lakes being spring fed, the fish flesh is firm and tasty.

          Waterfowl hunters find good shooting over much of the glaciated country. Not only are the lakes plentiful, but the mixed-up drainage system spreads out over low areas to form immense marshlands with sluggish streams flowing through them. Some of these marshes are thousands of acres in extent and attract shooters from scores of miles away.

          The second most important area of concentrated lakes has nothing to do with ice. It is in the sunny state of Florida about as far as we could get from a potential ice threat in our country. These are the sinkhole lakes of Central Florida, where ten-pound black bass can almost jump in from Kentucky, Tennessee, and other states underlain by limestone formations.

          These lake basins are formed by the dissolving of the limestone underlying the surface. Geologists call them “solution basins” because the lime dissolves in the water and goes away in solution. Limestone is simply calcium carbonate that has precipitated from the sea and hardened to form rock. As chalk is largely calcium carbonate and you know how easily chalk dissolves in water, you can easily see how the lakes are made. Some limestones are more pure than others and there is considerable difference in the solubility.

          Sinkhole lakes are naturally very clear. Sometimes so much vegetation grows in the lake that the water is darkened and discolored, but the water is very seldom of a muddy nature. They are usually connected with other lakes and streams by means of underground streams flowing in tunnels dissolved in the rock. If you have been to Silver Springs, Florida, and taken a trip in the glass bottomed boats there, you will recall how a crystal clear, full-fledged river boils right out of a crevasse at the bottom of the pool; and how the water was so clear you saw huge fish swimming along the bottom in thirty or more feet of water.

          If the low state of Florida were suddenly elevated high above the sea, you would find these limestone regions honeycombed with caverns through which the underground rivers flowed. Mammoth Cave, Mark Twain Cave and countless others are but the former channel ways of ancient subterranean streams, now high and dry enough for sightseers. Carlsbad Caverns, Colossal and Wind caves, prove that our arid west once had abundant water and vegetation. Sometimes variations or whims in these underground channel ways will cause the connecting lakes to rapidly fluctuate or even disappear over night.

          A couple of years ago on a trip down the Mississippi River from Minnesota to Louisiana, I was surprised to find the large number of lakes lying just off the river. These were sometimes several miles long and their location and shape changed faster than the map. These are known variously as oxbow lakes, cut-offs, or sloughs, and furnished bass, pickerel, and other fish we did not find in the Mississippi herself.

          These lakes are simply segments of abandoned stream channel. Usually when a stream starts winding back and forth in too-long fishermen were nightly surprised to see the river flow upstream and then dry up. For two or three days kids rolled up their pants and plodded back and forth across the empty riverbed. Then suddenly the river resumed flow and the news came down that the quake had opened a huge rent in the ground and the mighty ‘sippi took time out to fill another of nature’s bathtubs. That lake is still there and residents and visitors are thankful for some mighty fine fishing.

          An unusual type of lake dots the sand hill region of Nebraska. The wind has worried the blow sand around, blowing some places deeper and drifting some places higher. The depressions are called “blowouts” and many have been filled with water. This is due to the streams having been backed up higher by dunes filling the channels, raising the water level and filling the depressions by underground seepage.

          In Eastern Africa, three very large lakes have been formed by faulting of the earth’s surface. Lakes Victoria, Tanganyika, and Nyassa are good examples of fault lakes. If the crust of the earth faults higher on the downstream side, a lake is formed. If, however, the land on the downstream side of the fault lowers, a waterfall is formed.

          Mountain making often results in large lakes. Flathead Lake in Montana is our largest example. Andes Mountains of South America contain many lakes resulting from unequal rise of the land surface. Volcanism is associated with mountain making and in Yellowstone Park sheets of flowing lava poured into a stream valley and hardened there to form a dam with an impounded lake behind it. Volcanic cones sometimes blow their peaks off, leaving a crater, which fills with water. Crater Lake in Oregon is an example of a lake basin in a volcanic cone.

          Sometimes river deltas make strange effects. On the Upper Mississippi is long, broad Lake Pepin. This lake is backed up as a result of a vast accumulation of gravel and stone being washed out of the Chippewa River and deposited in the bed of the ‘sippi, to form a deltaic dam.

          In a very arid climate, deltas can work a different effect. Near the of California, the Colorado River built out its delta into the Gulf until the delta extended all the way across to the other shore. Before long the entire channel ran off the south side of the delta deposit into the Gulf proper, leaving a land locked basin. The water gradually evaporated out of this basin until all the water that is left is the Salton Sea, in the center of the great Imperial Valley of California and at present almost 250 feet below sea level. In 1905-07 the Colorado River broke through an irrigation ditch and began to fill the valley but engineers stopped it.

          Most recent of our lakes are the man-made lakes such as have formed behind Boulder, TVA, Grand Coulee, FT. Peck and other dams. Many of these rivers are heavily loaded with silt, which settles out when the dams slacken the current. As a result some people have estimated that you and I will someday see these reservoirs completed silted in. Then we will have man-made swamps, just as natural lakes fill into form swamps.

          Even though lakes may come and go with as much rapidity in Geologic time, as mud puddles do compared to human time, as hunters and fishermen you and I won’t have to worry very much about whether or not our favorite lake has disappeared since we visited it last.

          But by knowing how lakes are made and un-made, we can tell a lot better just where the best lakes are for the purposes we want to use them for. And it’s a big thrill to look around at a big body of water and understand just how nature’s fingers sculptured them into the surface of the land.

          The next time you visit a lake, look around and see first hand how the natural engineers of the out-of-doors fixed up some good hunting and fishing for you and your partners!



© 2003 Chronicles of Bob