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THE MARINE RECORD. LAKES. Before the Wagner Institute of Philadelphia W. B. Scott, professor of geology at Princeton University, re- cently lectured about the formation and life of lakes, from which the following interesting extracts are taken: “Lake” is a very comprehensive term, covering waters gathered and held from different sources. The smaller bodies of water. may be held securely above the general drainage level of the country; large bodies never are. Lakes are transitory and ephemeral—though not so in comparison with the events of human history. No one connected with the commerce of the great lakes need worry over the fact that they will some day disappear; such, however, must be their fate, ultimately. As moun- tains are short lived compared. with plains, so lakes are short lived compared with rivers. A very ancient topography is invariably marked by the absence of lakes. A lake map of the United States shows the northern states crowded with them, Wisconsin and Minnesota having them by hundreds. There are more lakes in Massachusetts than in the whole south, a differ- ence due to our northern topography being all young. Every bit of it has been remodeled by the great ice sheet lately covering it, while this ice sheet did not extend into the southern states. Consequently the southern topo- graphy is old, and with comparatively few exceptions, what lakes they had have disappeared. In most mountainous regions lakes abound; yet in an old range like the Apalachian they are wanting. ‘Lhey oc- cur in the Rocky Mountains, the Sierras, the Alps, the Himalayas—but these ranges are all of much later date. There are many methods of lake formation. There is the lake of a land surface recently upheaved, as in Florida, ‘which, geographically, is young. Such lakes are com- paratively rare—there being few surfaces which are youth- ful to this extent. Others arise from atmospheric weathering. Rock de- struction by aerial agents never take place uniformly; but always more rapidly along certain lines than others, so when any denuding agent comes along and sweeps clean the rock. surface of detritus, a very irregular surface will be left, and a lake basin is formed. Many lakes are merely extended river basins flooded. Usually some sort of a dam is thrown up at a point in the stream which will produce a lake. Sometimes this dam is the delta of a side stream, the tributary bringing in a good deal more debris than the main stream can carry off. Lake St. Peter, not far below St. Paul, is merely an expansion of the Mississippi river, three miles wide and five miles long. The lake was formed by the Chippewa river, which comes from the east and throws out a delta into the stream, which acts as a dam at a point where the valley is narrow. This dam shuts up the valley and the stream widens out into a great lake. When the Chippewa has cut down to the base level the Mississippi will be able to take away all that the Chippewa brings and to dig away part of what the Chippewa brought before. The Mississippi will eventually cut through that barrier and the lake will be drained away just exactly as you drain a pond. - Glacial erosion is one of the most important methods: of lake formation, and glacial deposition makes lakes on a smaller scale. A valley, having moraine material de- posited at its lower end, will, when the ice sheet has disap- peared, become the site of a lake if a stream flows there. With a glacier flowing past the end of a valley, the lat- eral moraines piled up will likewise form dams and thus lakes. . Periodical lakes are found through the Alps and in all ~ other glacial regions, where the great body of ice acts as adam. They melt a tunnel for themselves through the ice, and away under it, and often empty out with disas- trous results. Volcanic action makes what are called crater lakes, oc- cupying the crater of an extinct volcano. One of the most remarkable of these is in the Cascade Mountains, called Crater lake, and six miles in diameter. Another way in which volcartic agencies may produce lakes is by a lava stream damming up the mouth of a valley, as was done by ice in glacial days. Lakes of this kind abound in eastern Oregon, and the adjoining parts of Washington, Idaho, California and Nevada, where the whole country has been overwhelmed in great floods. Earthquakes produce lakes in two ways—one being that the lava, flowing in a deep, narrow valley, is dammed by having a fold of the earth thrust up across the mouth of the valley, a fold of a few feet being enough to produce a very effective dam, and thus convert a stream into a lake. A number of lakes of this character were formed by the Japanese earthquake of 1890. The earthquake may also do the same thing indirectly, by the landwaves or landslides. The great landslide of 1880 at Elm, Switzer- land, displaced 12,000,000 cubic meters of rock to an ayer- age distance of 2,000 feet. In mountainous regions a great many of the valleys are occupied by narrow streams, emptying through deep gorges. A landslide, by tumbling a huge mass of rubbish down the mouth of this gorge, would thus back the water up, producing a lake where there had formerly been a stream. The great Laurentian lakes (through the St. Lawrence to the Atlantic), the great lakes of Africa, the salt lakes of the interior of Asia (like the Black and Caspian Sea) are produced by the movements of the earth’s crust itself. An unequal movement of this crust will produce depres- sions, which, becoming filled with water, give rise to these vast lakes. The smaller lakes are those which are connected with glacial agency, one way or another. You can draw a line of the terminal moraine, showing the extension of the old ice sheet, and see a difference between the number of lakes in the region lying north of the terminal moraine and that lying at the south, which was not glaciated. In the other case there are lakes by the thousands; in the other none at all. In the whole south of the United States there are practically no lakes—one or two at New Orleans, like Lake Pontchartrain. There are more in a single county of Minnesota than in all the southern states. This is due to the fact that the glacier has rejuvenated the northern topography. The old topography is pre-eminently without lakes, which have disappeared by the cutting down of the bar- riers or by the filling up of their basins. Small lakes are removed in either way. A little bit of a lake, a few feet across in extent, is frequently chocked up by vegetable matter and thus converted from a lake into a peat bog. then into a swamp, and finally into a meadow. Some- what larger lakes are filled by the deltas of the streams that flow into them. Great lakes are removed by the cutting of their barriers, which requires a very long period of time, because the streams flowing out.of lakes are remarkably clear. Lakes act as’settling basins, and clear, pure water has ‘very little power in the way of cutting out rock. Further, these lakes generated by movements of the earth’s crust are very apt to be below sea level. The bottom of Lake Su- perior is several hundred feet. below sea level, and no stream flowing out of Lake Superior is going to be able to saw its barrier below the bottom otf the lake, because it is already below base level. So Lake Superior is going to be a very long-lived lake. In the course of the cen- turies the barrier will be cut down to base level and the lake very greatly reduced in size. Eventually it will be filled up with material washed in from the banks and brought in by the tributary streams. That will be the end of Lake Superior. Salt lakes invariably imply an arid or dry climate. If you could bring the Great Salt Lake of Utah and set it down in eastern Pennsylvania, you couldn’t keep it any length of time. The basin in which you put it would grad- ually fill until it would rise to the level of some point in its banks, when, securing an outlet, it would freshen at once. Salt lakes are of two origins—those which are merely cut-off arms of the sea and which were salt from the be- ginning, and those which are due to the indefinite con- centration of river water by means of evaporation. River water contains a good many things in solution—carbonate of lime, sulphate of lime (gypsum), chloride of sodium (common salt), smaller quantities of chloride of magnesi- um, chloride of calcium, etc. Provided you keep on boil- ing these things down long enough, you would invariably get a salt lake. The water being distilled off all the time by the action of the sun, no matter how dilute the solu- tion with which you begir, you must eventually end up with a saturated one. Great Salt Lake and the Dead Sea are so saturated with brine that they are depositing salt all the time. | In Great Salt Lake the water is so dense that swimming in it is one of the most remarkable experiences imagina- ble. You can stand up straight with your shoulders up- ward and you are out of water. While it is impossible to drown there in the ordinary sense, it is very easy to get irto trouble in it, because the water is so intensely bitter, and if you get any of it in your eyes or throat, it is like a dose of liquid fire. Novices who don’t know how to swim turn the wrong way up. The head goes down and the feet goes up; and they suffocate and drown in that frightful stuff simply because they can’t keep the head up. Toa person who can swim it is a sensation of being ab- solutely without weight. It would be like flying, if one could move fast enough. The sensation is all due to’ the excessive density of the water. : Lake Agassiz is a very large body of water in Manitoba, adjoining parts of North Dakota and Minnesota. It had : north Oe south diameter of some 700 miles—yery much Oe ae Aint ve ice sheet which came down fre the pata A lie. of great glaciers. For these ie aN ee cre areas of etnbutiog The first = ae Wa ents ond in the highlands@ET UMMAUE Lap of the St. Lawrence river and south of Hudson Bay, the third the mountain ranges of Te mai a es glacier swept down over ace Taek ie Bei issippi valley, into Minnesota and eccballe docs Mes as Iowa; then it commenced te retreat; ie he oe : ; when it was retreating, the great Laurentian glacier from Labrador was coming in from the east. There came a time when the Riwatti glacier formed a northern dam and the Lauren- tian glacier an eastern dam, and two standing nearly at right angles; and in this great dammed up space was formed Lake Agassiz. It rose until it could overflow the the barrier to the south, and thus discharge into the Miss- issippi river by means of a river which now has entirely - disappeared, and was known as the River Warren, after the late Gen. George K. Warren, who first discovered it. This lake continued until the glaciers up there, retreating one to the northward and the other to the eastward, sepa- rated and left a space between them. Then the drainage way to Hudson bay was opened again, and the lake was very rapidly drawn in that direction. We cam find per- fectly well the old beach line and the old drainage of Lake Agassiz has completed. The old terraces, and beaches are there today, and the level bottom of the lake is clearly shown. The whole history of the lake has been made ou with perfect clearness and_definiteness. vs Lake Bonneville occupied nearly all of eastern Utah i the pleiocene period: This lake had about four periods in its history. In the first period of rainfall the lake grad- ually acquired an area of 19,000 square miles—filling the whole of the depression of eastern Utah with water to the maximum depth of 1,000 feet, until an outlet was found in the north in the Snake river valley, and through the Snake into the Columbia, and thus to the Pacific. Then the climate of the country changed and evaporation ex- ceeded rainfall, and the lake steadily shrunk until it be- came dry. That was the second period. The third was where the rainfall again increased until the lake assumed its old extent, and even exceeded it, and then had its out- let again in the north. After this came another period of minimum rainfall, when the lake again dried up, and Salt Lake is one of the remnants of old Lake Bonneville, but only one-twentieth its size. At the left hand side of the Wahsatch Mountains the lines of the old lake shore can be seen for many, many miles. The Yellowstone lake is a rock basin. Not very long ago, from a geological point of view, it had a drainage the other way. The old outlet led southward across to Ocean Pass, down through a comparatively insignificant river into the Pacific. Its traces are still clearly visible, whereas the present outlet is north by way of Yellowstone river into the Missouri, and thus into the Atlantic water- shed. This is due to a change in the movement of the earth’s crust, but the basin itself is partly due to atmos- pheric disintegration. —_— eet A waterway to connect Red river with Rainy lake is proposed by building a dam at the outlet of Red lake, thus creating a water line of transportation extending from Thief River Falls to the head of Red lake, a distance of 84.6 miles on the river and 50 miles on the lake. From the east end of Red lake a canal can be very cheaply cut through to Rainy river—a marsh covers the whole dis- tance—thus, it is said, opening a great stretch of country bordering a navigable river, includimg the Lake of the Woods.