A STUDY OF LAKE BASINS

Freshwater and saline lakes.—Lakes require for their existence a basin within which water may be impounded, and a supply of water more than sufficient to meet the losses from seepage and evaporation. If there is a surplus beyond what is needed to meet these losses, lakes have outlets and remain fresh; their content of mineral matter is then too slight to be detected by the palate. If, on the other hand, supply is insufficient for overflow, continued evaporation results in a concentration of the mineral content of the water, subject as it is to continual augmentation from the inflowing streams.

As we have seen, there are in areas of small rainfall special weathering processes which tend to bring out the salts from the interior of rock masses, these concentrated salts generally first appearing as a surface efflorescence which is ultimately transferred through the agency of wind and cloudburst to the characteristically saline desert lakes.

Lake basins may be formed in many ways. Depressions of the land surface may result from tectonic movements of the crust; they may be formed by excavating processes; but in by far the greater number of instances they result from the obstruction in some manner of valleys which were before characterized by uniformly forward grades. In relatively few cases loose materials are heaped up in such a manner as to produce fairly symmetrical basins.

Newland lakes.—On land recently elevated from the sea, basins of lakes may be merely the inherited slight irregularities of the earlier sea floor, in which case they may be assumed to be largely the result of an irregular distribution of deposits derived from the land. Lakes of this type are especially well exhibited in Florida, and are known as newland lakes (Fig. 430). Such lakes are exceptionally shallow, and are apt to have irregular outlines and extremely low banks. Under these circumstances, they are soon filled with a rank growth of vegetation, so that it is sometimes difficult to properly distinguish lake and marsh.

Basin-range lakes.—Newland lakes may be said to have their origin in an uplift of the land and sea floor near their common margin. A lake type dependent upon movements of the earth’s crust but within interior areas has been described as the basin-range type and is exemplified by the Warner Lakes of Oregon. In this district great rectangular blocks of the earth’s crust, which in their upper portions at least are composed of basaltic lavas, have undergone vertical adjustments in level and have been tilted so that the corresponding corners of neighboring blocks have been given a similar degree of down-tilt (Fig. 431). Lakes formed in this way are of triangular outline, are bounded on the two shorter sides by cliffs, but have extremely flat shores on their longest side. From this shore the water increases gradually in depth and attains a maximum depth at or near the opposite angle. Such lakes naturally betray a tendency to appear in series (Fig. 432), and are unfortunately much too often illustrated on a small scale after a shower by the tilted blocks of imperfectly made cement sidewalks.

Rift-valley lakes.—Another type of lake basin which has its origin in faulted block movements is known as the rift-valley lake, and is best exemplified by the great lakes of east Central Africa. In this type a strip of crust, many times as long as it is wide, has been relatively sunk between the blocks on either side so as to produce a deep rift, or what in Germany is known as a Graben (trench). Such a basin when occupied by water yields a lake which is long, straight, deep, and narrow, and is in addition bounded on the sides by steep rock cliffs. At the ends the shores are generally by contrast decidedly low. If the hard rock at the bottom of the lake could be examined, it would be found to be of the same type as that exposed near the top of the side cliffs. The valley of the Jordan in Palestine is a rift of this character and was at one time occupied by a long and narrow lake of which the Dead Sea and the Sea of Galilee are the existing remnants (Fig. 433).

One of the most striking examples of a rift valley lake is Lake Tanganyika, while Albert Nyanza, Nyassa, and Rudolf in the same region are similar (Fig. 434).

Earthquake lakes.—The complex adjustments in level of the surface of the ground at the time of sensible earthquakes are many of them made apparent in no other way than by the derangements of the surface water. This is at such times impounded either in pools or in broad lakes, which inasmuch as they date from known earthquakes have been called “earthquake lakes”, even though in a strict sense any lake which has originated in earth movements might properly be regarded as an earthquake lake. To avoid unnecessary confusion, the term must, however, be restricted to those lakes which are known to have been formed at the time of definite earthquakes (Fig. 435). Reelfoot Lake in Tennessee, which in late years has acquired undesirable notoriety because of the feuds between the fishermen of the district and the constituted authorities, is a lake more than twenty miles across and came into existence during the great earthquake of the lower Mississippi valley in 1811.

Crater lakes.—The craters of volcanic mountains are natural basins in which surface waters are certain to be collected, provided only the supply is sufficient and seepage into the loose materials is not excessive. Some craters, still visibly more or less active, are occupied by lakes (Fig. 436).

In the larger number of cases in which craters become occupied by lakes, the evidence of continued activity is lacking, and it would appear in such cases that the lava of the chimney had consolidated into a volcanic plug, closing the bottom of the crater. Notable groups of crater lakes are the Caldera of the Roman Campagna (Fig. 437) and the so-called maare of the Eifel about the Lower Rhine. Crater lakes are easy to recognize by their circular plan, their steep walls of volcanic materials, and their considerable depth with a maximum near the center.

One of the most remarkable of these water-filled basins is Crater Lake in Oregon, which has a diameter of about six miles and is believed to have resulted from the incaving of a great volcanic cone in the latest stage of its activity. This remarkable feature has now been made a national park and will soon be conveniently reached by tourists and counted one of the greatest nature wonders of the Pacific slope.

CoulÉe lakes.—Far more important as lakes are those volcanic basins which arise from the flow of a stream of lava across the valley of a river so as to impound its waters (Fig. 438).

At the time of the great eruption under SkaptÁr JÖkull in 1783 the river SkaptÁr and many of its tributaries were blocked by the flow of lava, which it is estimated exceeded in bulk the mass of Mont Blanc.

Morainal lakes.—As we have learned, the obstruction of drainage, due to the distribution of rock dÉbris by continental glaciers, has yielded lakes in almost countless numbers. Probably ninety per cent or more of the known lakes have had this origin, and the type is so common within the once glaciated regions that it forms perhaps the best distinguishing mark of former glaciation. The hummocky surface of morainal deposits is so characteristic that the lakes of this type are never very large and are correspondingly irregular in outline. They have often numerous islands, and their banks are formed of the combination of rock flour and ice-worn materials known as till (Fig. 439). The smallest of the morainal lakes are mere kettles on the marginal moraine, and these rapidly become replaced by peat bogs. In contrast with pit lakes, morainal lakes lack the steep surrounding slopes and the encircling plain.

Pit lakes.—The so-called pit lakes have their origin in continental glaciation, and are found in groups within broad plains of glacial outwash (mainly sand and gravel), which are for this reason described as “pitted plains” (see p. 314). Those areas which lay between neighboring lobes of the ice sheet were subject to particularly heavy deposits of outwash material, and are, in consequence, particularly likely to be occupied by pit lakes. As has been pointed out in an earlier section, the water derived from surface melting within the marginal portions of a continental glacier descends to the bottom in the crevasses and thereafter flows in an ice tunnel under the same conditions as water flowing in a pipe. Having in most cases a considerable head at the outer margin of the ice, this water may rise and issue well above the lower ice layers and so cover a portion of the ice margin beneath sand and gravel (Fig. 440). Separated blocks, often of massive proportions, are thus buried beneath nonconducting materials by which they are long protected from further melting. Eventually, however, with the approach of still milder climates they disappear, thus causing the overlying sand and gravel to descend and form a pit of steep walls similar to the sawdust pits over melted ice blocks within our storehouses.

Pit lakes are thus easily recognized by their occurrence usually in groups within a plain of glacial outwash and by their characteristic banks inclined at the angle of repose of such materials (Fig. 441).

Glint or colk lakes.—It has been found to be true of existing continental glaciers that where their mass has been held back by a mountain wall, their current at the portals within this rampart becomes greatly accelerated. Though the upper layers of the glacier in the vicinity may move forward with a velocity of but an inch per day, the current within the outlet may be as much as seven hundred or a thousand times as great. In many respects these conditions are similar to those about the raceway of a reservoir where the near-by surface of the water is lowered by the indraught of the outlet and the current in the raceway is so accelerated that, unless protected, the bottom of the race is carried away and a basin excavated which extends a short distance both above and below the position of the dam. In Holland such basins hollowed out beneath breaks in the dykes are known as colks. Basins which were excavated beneath the glacier outlets by a similar process would not be open to our inspection until after the ice had disappeared from the region; but it is most significant that in Scandinavia, where the Pleistocene continental glacier, advancing westward from the Baltic, was held in check by the escarpment at the Norwegian boundary (the glint), lake basins have been excavated in hard rock whose walls show the abrading and polishing which are characteristic of glacial sculpture, and whose positions are such that they lie beneath the former outlets partly above and in part below the line of the escarpment. Their position in reference to the rampart and to the former outlets is brought out in Fig. 442. The largest of the glint lakes of this series is TornetrÄsk in northern Lapland (see p. 277 and Fig. 443).

Ice-dam lakes.—Whenever a continental glacier, either in advancing its front or in retiring, lies across the lines of drainage upon their downstream side, water is impounded along the ice front so as to form ice-dam lakes. Such lakes are found to-day in Greenland and in the southern Andes, and similar bodies of water of far greater size and importance came into existence in Pleistocene times each time that the continental glaciers of northern North America and Europe advanced upon or retired from suitably directed river systems. Thus above the Baltic depression, when the ice front lay to the eastward of the main watershed, each easterly sloping valley was obstructed by the ice and occupied by an ice-dam lake (Fig. 444), the beaches of which may all be traced to-day (Fig. 445).

One side of each ice-dam lake is formed by an ice cliff at the glacier front, and if the region is relatively flat, the remaining shores are likely to be formed by a marginal moraine which the glacier has abandoned in its retreat. In their smaller stages, therefore, ice-dam lakes on prairie country have the form of a crescent, which is the more pronounced because the waves by their attack upon the ice front flatten the curvature of its outline (see Fig. 360, p. 330).

The life of an ice-dam lake is begun and ended in important changes of glacier outline, and after the draining of lakes by this process the land shores may be traced in beaches, and the ice margin by a water-laid moraine of low relief (Fig. 359, p. 330).

A much smaller but in many respects similar ice-dam lake is to-day to be seen at the side of the Great Aletsch glacier, a mountain glacier of Switzerland. The traveler who makes the easy ascent of the Eggishorn may look directly down upon this crescent-shaped lake with its ice cliff on the glacier side (see Fig. 446).

Glacier lobe lakes.—Upon the sites of the former lobes of the Pleistocene glacier of North America are found the basins of the Laurentian River system, the largest freshwater lakes in the world. There has been much controversy concerning the manner of formation of these lakes, but the view which has seemed to have the largest following is that they were excavated by the eroding action of the continental glacier over the drainage basins of former rivers. It is but one phase of the long controversy between opposing schools, which have advocated on the one hand the efficiency of glacier ice as an eroding agent, and upon the other its supposed protection from the weathering processes. The positions and the outlines of the several lakes of the series sufficiently proclaim their connection with the former glacial lobes, and the name which we have adopted leaves the exact manner of their formation a still open question. The recognition of the importance of the glacial anticyclone, in giving shape to the glacier surface and in effecting a transfer of snow from the central to the marginal portions, has had the effect of emphasizing the relative importance of erosion under the marginal and lobate portions. Thus the importance of ice lobes has been greatly accentuated, though this applies only to the shaping of the basins and not in any important way to the impounding of the present waters. The present Laurentian Lakes owe their existence to the elevation by successive uplifts of the country to the northward and eastward, since the glacier retired from the lake region. When the ice front lay to the northward of the Ottawa River, the discharge of the upper lakes was by a channel through Nipissing River and Lake and thence down the Ottawa River to a gulf in the lower St. Lawrence. The uplift of the land has had the effect of raising a barrier where the former outlet existed, and diverting the waters to a roundabout channel by way of Detroit and Lake Erie (see Fig. 365, p. 335).

Rock-basin lakes.—The reversed grades which develop in a valley deepened by mountain glaciers—the back-tilted treads of the cascade stairway (see p. 376)—furnish a series of basins hollowed in rock which are strung along the course of the valley like pearls upon a thread, or, far better, like the larger beads in a rosary (Fig. 447). This characteristic arrangement accounts for the name “Paternoster Lakes” which has sometimes been applied to them in Europe. Their positions in series within U-shaped mountain valleys, and their rock shores with characteristically smoothed and striated surfaces, make them easy of determination. In the higher portions of the valley, where the treads of the cascade stairway are relatively narrow, such lakes are often approximately circular in outline, but in the lower levels and upon wider treads they may be ribbon-like, though lakes of this type are to a large extent replaced in the lower levels by the valley moraine type or a combination of the two.

Valley moraine lakes.—The recessional moraines which mark the halting stations of mountain glaciers, while retiring up their valleys, form dams in the later river and so produce a type of lake which is in contrast with the morainal lakes which result from continental glaciation. They may, therefore, be distinguished by the name valley moraine lakes. Their positions on the bed of a U-shaped mountain valley, and the glacial materials which compose the dams, are sufficient for their identification (Fig. 448). Moraine Lake and Lake Louise in the Canadian Rockies are typical examples. Rock basin and valley moraine lakes may occur in alternation or combined in mountain valleys.

Landslide lakes.—The sheer-walled valleys which are carved by mountain glaciers are too steep to long retain their perpendicularity when the support of the glacier has been removed. Aided by the ever present joint planes, which admit water to the rock, they succumb to frost action, and further give way in avalanches whenever the rock is of sufficiently porous material to become saturated with water. Landslides sometimes occur successively until the original valley wall has been replaced by a terraced slope. The treads of the steps in this terrace have generally a backward-sloping grade, so that basins are formed to be filled by relatively long and narrow lakes or by successions of small pools (Fig. 449 and plate 23 B).

When the avalanched material is so disposed as to dam the valley, much larger lakes of this type come into existence. During an earthquake which occurred on January 25, 1348, there was a landslide within the valley of the Gail, Carinthia, which destroyed seventeen villages and produced a lake which even to-day is represented by a great marsh.

Border lakes.—Whenever mountain glaciers push out their fronts beyond the borders of the mountain range by which they are nourished, they spread upon the foreland in broad aprons about which morainic accumulations are particularly heavy. This elevation of morainal walls about the margins of the aprons yields natural basins that are occupied by lakes so soon as the glacier retires its front within the valley. Because such lakes are found at the borders of upland districts they have been called border lakes. The beautiful Lakes Constance, Lucerne, Maggiore, Lugano, Como, and Garda (Fig. 450), on the borders of the Alpine highland, are all of this type.

Ox-bow lakes.—The cutting off of a meander within the flood plain of a river yields a lake which is of horseshoe (ox-bow) outline and lies generally with low banks within a plain composed of river silt. Before separating from the parent stream the meander had begun to silt up, especially at the ends. Ox-bow lakes are, however, relatively deep near the convex shore and correspondingly shallow toward the concave margin (Fig. 451).

Saucer lakes.—As we have learned, a river meandering in its flood plain has banks which are higher than the average level of the plain, for the reason that at flood time the main current of the stream still persists in the channel, thus allowing the burden of sediment to be dropped in the relatively slack water upon its margin. Because of these natural embankments or levees, tributary streams are often compelled to flow long distances in nearly parallel direction before effecting a junction. Between the trunk stream and its tributaries, likewise bounded by levees, and between streams and the valley walls, there thus exist low basins which are more or less saucer-shaped (Fig. 452). At flood time, when the levees are overflowed or crevassed, water enters these depressions, and an additional supply may be derived from the walls of the valley. Good illustrations of such lakes are furnished by the flood plain of the former river Warren near the banks of the present Minnesota River (Fig. 453).

Crescentic levee lakes.—As we approach the delta of a river, the size and importance of the levee increases, and here a new type of levee lake may develop in series (Fig. 454). At flood time the levee is breached near the point of sharpest curvature on the convex side (Fig. 454 a). When the waters are subsiding, the current is kept away from the old channel by the rising grade of the levee as well as by the inertia of the current, and an entrance to the old channel is first found below the next change in curvature of the meander, since here scour becomes effective in cutting through the levee. The new channel is thus established in the form of a loop inclosing the old one, and the process of levee building now erects a wall about the territory newly acquired by the meander. This territory has the form of a crescent, and when occupied by water produces a crescentic levee lake often joined to its neighbors in series. The abandoned channel now closed at both ends by levees may be occupied by water to produce a subordinate ribbon type of curving trench (Fig. 454 b, c).

The importance of levees in obstructing drainage to form lakes is only beginning to be appreciated. It has quite recently been shown that when trunk streams are greatly swollen and burdened with sediment while flowing from a receding continental glacier, they may build such high levees as to aggrade their tributary streams above the junctions, even producing reversed grades and so impounding the waters to form extensive lakes. During the “ice age” lakes of this type were formed in Illinois and Kentucky rivers just above their junctions with the Ohio. The old lake floor with its eastern shore line and its protruding islands is easily made out upon the new topographic maps of Kentucky.

Raft lakes.—Within humid regions the flood plains of our larger rivers are generally forested, and as the river swings from side to side in its perpetual meanderings, the timber which grows upon the convex side of each meander is progressively undermined by the river and felled upon its bank. The prostrate trees remain upon the banks during the low water of the summer season, to be gathered up at the time of flood in the next spring season. It is log jams thus acquired which so generally block the main channel of a river and turn the current across the neck of the meander when cut-offs occur with the formation of ox-bow lakes. When the mass of timber thus gathered up by the river is excessive, as, for example, within the flood plain of the Red River of Arkansas and Louisiana, huge log rafts are produced which dam up the river so effectively as to produce temporary lakes. The impounded waters soon find an outlet over the levee at some point higher up the river, and the waters flowing off through the timbered bottom lands, other logs are caught by the standing timber as in a weir. A second dam is thus formed which is separated from the initial one by open water, and in this way the driftwood dam acquires enormous proportions as it gradually moves up the river. After a period of perhaps a century or more, the lower sections of the jam become decayed and dislodged so as to float down the river.

In the lower Red River a great raft of alternating jams and open water reached a length of about one hundred and sixty miles and moved up the river at the average rate of something less than a mile per year. Within the limits of the dam all tributary streams were blocked, so that secondary lakes were formed in a double fringe about the main river (Fig. 455). The great raft which formed here in the latter part of the fifteenth century has now at the beginning of the twentieth been largely removed and measures have been adopted to prevent its re-formation.

Side-delta lakes.—It is characteristic of river drainage that the tributary streams enter the main valley on steeper gradients than the trunk stream at the point of junction. Wherever the difference in velocity of the two streams at the junction is large, and the side stream is charged with sediment, a delta will be formed at the mouth of the tributary stream. Such deltas push out from the shore and may eventually block the main channel so as to form a more or less sausage-shaped expansion of the river—a side-delta lake. Traverse and Big Stone Lakes in the valley of the Warren River in Minnesota have been formed in this way (Fig. 354, p. 326). Lakes Thun and Brienz in the Swiss Alps are of similar origin, the beautiful city of Interlaken being built upon the delta plain over the valley of the earlier river (Fig. 456). The Mississippi has similarly been expanded to form Lake Pepin above the delta at the mouth of the Chippewa River.

Delta lakes.—A somewhat different type of delta lake has been formed in Louisiana, where the “father of waters” discharges into the gulf. Here the various distributaries radiate from the main channel to produce the “bird-foot” delta type and the toes in this foot by their junction with the banks which outline the ancient estuary, have separated in succession a series of basins that before were in direct connection with the sea (Fig. 457). Lake Pontchartrain is the largest of this series, while the so-called Lake Borgne is in process of separation.

Where large deltas push out from the shore into the open sea, the levees which border the individual distributaries are attacked by the waves and their materials are transported by the shore currents and built into barriers. These barriers cut off the re-entrants between neighboring distributaries so as to produce lagoons or lakes (Fig. 458).

A type of delta lake, which more resembles the side-delta lake above described, has formed at the mouth of the Colorado River, where it enters the Gulf of Lower California. The Imperial Valley lying to the north of this delta is the desiccated floor of the earlier Gulf of Lower California which has been captured from the sea by the delta of the Colorado. The rampart of mountains, by which this valley is surrounded, has cut it off from any water supply derived from clouds, and its waters being no longer renewed from the sea, the region has passed through a period of desiccation which has left the Salton Sink as the only existing remnant of the earlier lagoon. It will be remembered that careless operations in diverting distributaries of the Colorado recently reversed this process so that the waters rose in the valley, and expensive emergency operations were necessary in order to again turn the waters of the Colorado into their accustomed channels.

Barrier lakes.—The Salton Sink illustrates a type of lake which is formed at the border of the sea through the erection of some kind of barrier which captures a small area of the ocean’s surface. Though such lakes may be properly described as strand lakes, it is usually at the mouth of a river that the process becomes effective. The common type of barrier lakes is found developed on most ragged coast lines where the shore currents have formed first bars and later barriers at the mouths of the estuaries (Fig. 459). Such embankments are usually gently curving or crescent shaped and are composed of sand or shingle which presents a steep landward and a gradual seaward slope.

Dune lakes.—Within the narrow strips of shore in which all the fine soil that could be available for plant life has been washed away by the waves, beach sand is exposed to the direct action of the winds. In time of storm the sand is picked up and after drifting in the wind is collected in long ridges parallel to the shore. Constantly traveling along shore, these dunes block the mouths of rivers and thus produce a series of lakes such as are indicated in Fig. 460.

Sink lakes.—Another class of lakes are due either directly or indirectly to the work of underground waters. In districts which are underlain by limestone, the surface water descending along the joints of the limestone may widen these passageways through solution of the rock and at lower levels flow on the floors of caverns eaten out by the same process on bedding planes of the formation. At the intersections of joints, more or less circular shafts known as “swallow-holes” go down to the caves from the surface. Locally, also the cavern roofs give way so as to choke the galleries with rubble and leave a basin at the surface which has an irregular but generally a more or less oval outline. If sufficiently clogged at the bottom by finer rock dÉbris, these basins become occupied by small lakes which are known as sinks, and constitute one of the best surface indications of a limestone country.

Karst lakes—poljen.—In the limestone country to the north and east of the Adriatic Sea—the so-called Karst region—there are many interesting features which are directly traceable to the solution of the country rock. Here all the surface water descends in certain districts along the widened joint planes so that the drainage is largely subterranean. The so-called dolines or sinks of very regular and symmetrical forms resembling deep bowls cover a large part of the surface.

The entire country is, moreover, faulted in the most intricate fashion into many rift valleys. The drainage being so largely subterranean, these downthrown blocks of crust, the so-called poljen, become flooded at certain seasons of the year when the subterranean passages become choked or are too small to carry away all the water. A seasonal lake of this character is the Zirknitz Lake (p. 189).

Playa lakes.—It is the law of the desert that the arid region be walled in by mountains. This encircling rampart forces the clouds to rise, and by robbing them of their moisture leaves the desert dry and barren. Those waters which fall upon the inner margin of the ranges drain toward the interior of this pan-like depression and are not returned to the sea—the desert is without an outlet. Infrequent though they be, the desert rains are of the cloudburst type and in the hills develop torrents whose waters, emerging upon the desert floor, develop lakes in the space of a few minutes or at most hours. In the hot and dry atmosphere the waters of these shallow basins may be sucked up in the space of a few hours but reappear in the same basins at the time of the next succeeding cloudburst. Such ephemeral lakes are known as playas.

Salines.—Desert lakes more favored in their supply of water may be relatively long lived and persist for periods measured in years or centuries. Such lakes are, however, extremely sensitive to climatic changes (see p. 198).

For the reason that they have no outlet the waters of desert lakes become salt through continued evaporation. They are, therefore, spoken of as salines. Lake Bonneville, so long as it discharged its waters over the sill of the Red Rock Pass, must have remained fresh; but when the level of its waters had fallen below this outlet, its waters became salt and the content increased as the volume diminished.

The shallow basins upon the floors of desert lakes may have come into existence in various ways; but it would appear that the irregular removal of the soil by the winds, modified as this is by differences in composition of the rock materials and by vegetable growth, and the deposition of sand by the same agent, are by far the most important. Many of the types of tectonic and volcanic lakes which have been described are characteristic of humid and arid regions alike.

Alluvial-dam lakes.—Within the mountains upon the desert borders, the alluvial fans which form at the mouths of valleys, because of the characteristic cloudburst, sometimes obstruct a main valley at the junction with its tributaries. By this process the waters of the main river are impounded in essentially the same manner as are the rivers of humid regions by the deltas of their tributaries.

RÉsumÉ.—The types of lakes which we have now considered are arranged below in tabular form so as to show their relationship to important geological processes. While not complete, the list includes the more important classes, as well as others which, while not of common occurrence, are yet of interest in giving further illustration to the processes which have been treated in earlier chapters.

By giving careful attention to criteria which have been above suggested, it should be possible in the greater number of instances at least to determine whether any lake which is visited has had its origin in one or another of the processes described.

CLASSIFICATION OF LAKES

Tectonic Lakes	Volcanic Lakes
Newland lakes Basin-range lakes Rift-valley lakes Earthquake lakes	Crater lakes CoulÉe lakes
Continental Glaciation Lakes	Mountain Glaciation Lakes
Morainal lakes Pit lakes Glint or colk lakes Ice-dam lakes Glacier-lobe lakes	Rock-basin lakes Valley moraine lakes Landslide lakes Border lakes
River Lakes	Strand Lakes
Ox-bow lakes Saucer lakes Crescentic levee lakes Raft lakes Side-delta lakes Delta lakes	Barrier lakes Dune lakes
Ground Water Lakes	Desert Lakes
Sink lakes Karst lakes—poljen	Playa lakes Salines Alluvial dam lakes.

Reading References for Chapter XXIX

General:—

I. C. Russell. Lakes of North America. Boston, 1895, pp. 125, pls. 23.

A. P. Brigham. Lakes, A Study for Teachers, Jour. Sch. Geogr., vol. 1, 1897, pp. 65-72.

N. M. Fenneman. The Lakes of Southeastern Wisconsin, Bul. 8, Wis. Geol. and Nat. Hist. Surv., 1902 (Rev. Ed., 1910), pp. 188, pls. 37.

A. Delebecque. Les Lacs FranÇais (with Atlas). Paris, 1898. (Work crowned by the Society of Geology of Paris.)

H. R. Mill. Bathymetrical Survey of the English Lakes, Geogr. Jour., vol. 6, 1895, pp. 46-73, 135-166.

A. Supan. GrundzÜge der Physischen Erdkunde. Leipzig, 1896, pp. 531-548.

H. Berghaus. Atlas der Hydrographie. Gotha, 1891, pl. 3.

R. D. Salisbury. Physiography. 1907, pp. 292-327.

Charles Rabot. Revue de limnologie, La GÉographie, Vol. 4, 1901, pp. 110-119, 172, 189.

I. C. Russell. A Geological Reconnaissance in Southern Oregon, 4th Ann. Rept. U. S. Geol. Surv., 1884, pp. 442-447. (Basin range lakes.)

Ed. Suess. The Face of the Earth, vol. 4, 1909, pp. 268-286. (Rift valley lakes.)

J. S. Diller. Crater Lake, Nat. Geogr. Mag., vol. 8, 1897, pp. 33-48, pl. 1; Geology of Lassen Peak Quadrangle, California, Geol. Fol. 15, U. S. Geol. Surv., 1895. (CoulÉe lakes.)

N. M. Fenneman. Lakes of Southeastern Wisconsin, l.c., pp. 4-6. (Pit lakes.)

Ed. Suess. The Face of the Earth, vol. 2, 1906, pp. 340-346, pl. 7. (Glint lakes.)

I. C. Russell. A Preliminary Paper on the Geology of the Cascade Mountains in Northern Washington, 20th Ann. Rept. U. S. Geol. Surv. Pt. ii, 1900, pl. 14. (View of a rock-basin lake.)

E. W. Shaw. Preliminary Statement concerning a New System of Quaternary Lakes in the Mississippi Basin, Jour. Geol., 1911, pp. 481-491. (New type of levee lakes.)

A. C. Veatch. Formation and Destruction of the Lakes of the Red River Valley, Prof. Pap. No. 46, U. S. Geol. Surv., pp. 60-62, pls. 29-33. (Raft lakes.)

M. Neumeyer. Erdgeschichte, vol. 1, pp. 595-596. (Poljen.)

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