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' 1 2 3 * ___; 32X > 4 6 ♦ 6 1 ,^*JMjSY i^ULLECTION 0/ CANADIANA %'^e„s (/,nversny a, K,ngs,o„ v-f £^f -"•'^^saBpfS' O [Fro/H r/i*' .lw6'>7>/iH Oeologut, Vol. XIV, November, 1S94.] *>• *■"> A REVIEW OF THE HISTORY OF THE GREAT LAKES.* By J. W. SpKNtER , Ph. 1)., K. (;:SS. (L. and A.). (Plalo VIII.) „ ,, ,„ CONTKNTS. I'age. I. I riiblenis and I'roBress 200 1. Kornior High ("ontiiiental Klevation. ...!.!...!! !.X!! .! 240 3. Cliaractor iif the Lake Hasins jor 4. (ilaciation of the Kevion [ 202 5. Hurled I.aurentlaii \ alley '. 20% h. Buried Tributaries W. 293 7. Hevcrsal ot the Drainage of the Ihiper Ohio and otiier rivers. 294 ><. Closing of tlie Valleys into Lake iSasins 304 I). Deserted Heaches in the Lake Region and their Deformation jqs 10. Warren Water ^ 11. Algonuu in and Lundy Waters jL, 12. Iroquois Water and Birth of the Modern Lakes..... .." 307 1.^. History of the Niagara River and Changes of the Outlets oftfie Lakes jq8 14 Recurrent Drainage of the (ireat Lakes into the Mississippi River by way of Chicago ' '300 *R»'ikI bffori' Hcction K of the AmtTioin Associiition for tiij' Adviincc- nn'iit of Hfitiiicf, III, lilt" Mrooklyn ni(), 18»4. / -d. % ] «-m»"i ^P M 290 The Americariijfeologist. November, MM vf i. Problems and Progress. "Problems settled in the rough and ready way by ru^e men, absorbed in action, de- mand renewed attention and show themselves to be still un- read riddles ; when men have time to think .... doubt . . . refuses to be cast out." In such a condition was our knowl- ^ edge" of the history of the Great Lake^ tributary to the St. Lawrence, when the writer commenced his fragmentary studies fifteen years ago. In these studies of the lakes some of the most interesting and important questions in dynamical, agri- cultural, and p,rtiBtic geology are involved. Even if the Great Lakes had attracted the attention due them, their study would have been impracticable at an early date, at least until after numerous soundings had revealed their character ; and until the railway surveys were made, ior these furnish data foi- / quantitative measurements. Many deep well-borings were needed to discover the buried valleys ; and the eurvejs of the deserted shores have delimited the boundaries of the shrink- ing lakes, and made known the deformation of the earth's crust, , From intimate familiarity witU the topographic features of the southern states, and by comparing them with those of the lake region, one can easily fee that there would be very little ditFerence between the features of the two arfias, if the super- ficial drift at the north were removed and the country were then compared with that at the south where there is no sucji mantle. Accordingly the meteoric origin of the great St. Law- rence basin suggests itself; but the basin has been obstructed and several great lakes now occupy what were once broad rolling plains. Before, men had tjme to study the lake history we were told that the lakes were valleys of erosion, but how they were made was hardly a question worthy of considera- tion. Later, it was an equally rough and ready method to tell us that the basins were excavated by glaciers. Their whole history is not yet written, but many chapters are now before us. Extracts of these will be giVen in their natural order {not in that of the discoveries), so that a short story of the lakes can be told. £. Former High Covtivental Elevation. As will be shown in the next paragraph, the basins of the lakes arfe more or less like erosion valleys. The deepest sounding of lake Ontario is . ^j.',' r* AWa* 5-. „4l* ''^^3^v5?E' ■': »■■ :-•r are; '-Hiirh Continental Elevation preceding the Pleistocene twri.xi," Bulletin Geol 8oc. Am vol I 188», pp. (J5-70; "Post-PJeistoceue Subsidence versus Olac.al Dams Id., vol. n 1«K), pp. 40.5-476; "Terrestrial Subsidence southeast of the American Continent,''' Id., vol. v, 18D3, pp. 19-'23 Each of these papers48 accomi)anied with a map. -''m Miiifciiiliiiilii utmtmitmm^lm ms 292 The Americati Geologist. NoTember, 1894 /^T- :4« "A ^" be shown to have been the drift filling the old valleys and the warping of the earth's crust. But the basins are river-like and broad submerged i^lleys. Lake Ontario is 247 feet above^ the sea, but its greatest depth is 788 feet ; and throughout a considerable portion of it, the southern side is bounded by high vertical but submerged walls, which for long ages formed bluffs along the ancient river.* Besides the longitudinal trough, another deep channel crosses the basin east of Toronto. Lake Erie is 573 feet above tide, but it is generally less than 100 feet deep, except over a small area where it is 210 feet; but beneath the waters of the shallow basin there are many buried channels, the deepest of which, at Cleveland, Js 228 feet (Newberry). Lakes Michigan and Huron and Georgian bay, are at one altitude, 582 feet above the sea. Georgian bay is generally less than 200 feet deep, but at its southwestern side a channel reaches to a depth of 610 feet, in front of the foot of a very high escarpment, part of which is submerged. An- other submerged escarpment crosses lake Huron. This has a descent of more than 400 feet. The deepest sounding is 750 feet. The two basins of lake Michigan (respectively 864 and 576 feet deep) have vertical submerged escarpments adjacent to them. Also there are some deep channels and fjords, one of which is 612 feet deep. Lake Superior has been studied less. More or less drift is known to occur between the lake basins, like that filling the submerged channels under lake Erie. The buried valleys will explain the connection between the lakes. 4. Glaciation of the lieyion. The strite are nowhere par- allel to the direction of the escarpments, whether these be submerged or above the level of the lakes, where they form bold topographic features. Nor are the vertical walls of the limestone escarpments polished by lateral glaciation. In short, the stria; are at considerable angles, even at right angles, to the rocky escarpments. Thus it appears that the valleys were not shaped by glacial action. *> Proc. Basil Soc, London, vol XLVi, p. 523 (als^ pp. 86-97, with mapof the ancient Laurentian river system, and earlier papers. 1891); ■ J ^' ' K> ' * -■ - 'Jt ^' ^?. •'• * ^ f 7 r » . •- .1^ \ . Meoieio of History of the Great Lakes. — Spencer. 298 -* . .■.*•' • 6. Buried Lavrentian Valley. Below the outlet of lake Ontario, the valley is covered to some extent with drift, but the greater part of the barrier closing the lake-is rocky. Be- tween Georgian bay and lake Ontario, the writer discovered a- deep buried yfllTey (by a series of borings, for there was no superficial evidence of it, although parallel to thp> Niagara eg- carpment), beneath the great drift ridges ihtervening between the two waters. The full depth has not Been reached, although not less than 750 feet beneath the higher ridges, ^nd it is prob- ably very much deeper, as indicated by the fjords at both ends (in lake Ontario and in Georgian bay) ; so that hefre \^ the connecting valley between the submerged channels of thog upper lakes and lake, Ontario. The fjords of northern Mich- igan and the buried channel^ continue the evidence that from lake Michigan to the outlet of lake Ontario, the ancient Lau- rentian river flowed partly through the basins ^id partly across the country north of Toronto. The ancient river is thus named to distinguish it from the modern St." Lawrence river. The connection of the valley of Superior with the Lau- rentian river has not been determined; but judging from soundings in lake MichigaliS^' may suppose it to have been by way of the northern end of tlTM valley.* * 6'. Buried -TribiUaries. A branch of the Laurentian river, now buried beneath 500 feet of drif^, extended from the southern basin of lake Michigan across the Michigan peniur suia and the southern end of the Huron basin. This large" tributary, which has been, named the Huronian river, is of the same age as the Laurd|||feil river. ' Through the Erie Hbtfin flowed the now buried and sub- merged Erigan river. Niagara river was not then in exist- , ence. But the Erigan passed iProm the Erie basin across the province of Ontario to the great canyon at the head of lake Onta;rio,""thus descending to the lower basin. Many branches and smaller tributaries are knowij to have joined these greater rivers, as revealed by the borings. In some cases there were no changes in the direction of the an- cient and modern drainage. In other cases the streams have locally left the original waterway s and again returned to the' *"()ri|Briii of tho Jlasins of tlie Great Lakes," cited before; also "Dis- coveryofthe Preglacial Outlet of the Basin of Lake Erie into Lake Ontario," by the writer, Proc Am. Phil. Soc, Philadelphia, l^8L A • if -va,-,! \ . ,/ 3: "^n;: T»%. ' '«aMi«4#.SMMA-.utM S- ^1. WM«» .K'. F?r, .y- 4>. \ \ 20i The American Geologist. 3- • *; November, 1894 old Valleys. A characteristic of the^. former drainage is the filling of the ancien^ channels, above which the modern streams flow upon the accnmulation of- drift. The ancient vatlleys are relathrely much shallower but broader than the modern, with sides more sloping and other marks of greater antiquity than tTie modern streams, where they have cut new channels^ in place of reopening the buried vallteys. ^ 7. Reversal of the Drainage of the Upper 0Ki6 and other rivers. Among the earlier studies on buried valleys were those of Dr. J. S. Newberry, Dr. T. Sterry Hunt, an^d Mr. J. F. Carll. Xo Mr. Carll belongs the credit of first^ working out the re- versal of the drainage of western Pennsylvania, wfiereiie dis- covered that the upper Allegheny and some other streams flowed into the Erie basin before the Pleistocene period. In ,1881 th6 writer,, following Carll, pointed out that there is ev- idence that' the whole upper' Ohio river, above the B.eaver tributary, flowed to th6 Erie basin. This hypothesis was am- plified by Dr. I*'. Max Fpshay, and later the observatipns have . been extended by Prof. T. C> Chamberlin and Mr. Frank Lev- ''erett, confirming the change in the direction of the drainage. ThB streams south of lake Erie generally drain a much smaller basin than formerly. So in New York, the upper waters of the Susquehanna, and of its tributaries, drained to the north into the Ontario basin, by way of t*he Finger lakes, which now-occupy the old river courses, partially closed up by drift deposits and by terrestrial warping or deforination towards the north. 8. C' losing of the V'aUei/s ijito Lake Bnnins. The old Lau- rentian valley Was more than a hundred miles wide, but it was interrupted by the deposition of drift in many places, most notably between Geo'rgian bay and lake Ontario. To some extent the modern St< Lawrence river is flowing over a drift- , filled valley. This obstruction has paused the modern drain- age to be changed from the old directions and often to pass over rocky barriers. But in addition to the drift obstruction, wo find that the Vecent terrestrial uplift hifls been greatest toward the n'octheast, producing barriers and forming basins. The warping has been measured and is found sufllicient to ac- count for all the ro^y barrier below the outlet of lake Onta- rio. Moreovfer this northeastern elevation has caused all tlie ^ .r •m V ^^ < *W fn , Mtf , . UH i h ii , i| lfcilj < .. k. -a ^iMRAwt > b/^yE^iMM*. «v ^ in^M \ K M^L'**^'^-'-' i^^^^^M^M^U^^k^Jtdd^^^St •mf^f mmsmmm '• I r/ S '} , , 1 Beviem'ff/ Hhtory of the Great -Lakea.^^Spencer. 296 B-' - '■-, / lakes to rise and nooditheip southern and western ends, since -the modern .lakes we're established". The quantitative charac- ter of this change will be expljtined in the v^l paragraph^ and the effects upoii the modern drainage beyond. J^ ^ 9. Deserted Beaches in the Lake Region and their Dfforma- ion. The Laurentian lake region abounds with, the remains b'f deserted beaches, terraces; sea-clitfe, and other evidences of •former shore Tines, '^i'he writer has made an extensive sur- vey of' these phenomena in Canada, across Mjchigan, in the Adirondacks, and in tlie Green and White mpun- ^tains.* Jffr. " G. K. (filbert 'didy- the first systematic wor'fe south TiT lakes Ontario arid*^ Erie.f Mr. F. B^ Taylor has more recentl^jj^ended the surveys north of lake Michigan and northeast of lake Huron;* and. Dr. A. C. LawSon, north of lake Superioi'.§ There has been very littk systematic work in the lake region upon these problems except by the named ojbservers. Sotne of these old shore lines, after form- ing highways known as ridge roads, have heen surveyed far hundreds of miles; others are broken pr interrupted. Gener- ally speaking, the northeastern extensions are unknown, owfhg to the want of surveys ; to t]>e changes in the topography, rendering their surveys difficult ?|to our ignorance of- the phe- nomena; to our ignorarico of\suspected ^nodern faultsj and to our further ignorance as toJjDw much th«' phenomena are 6b- ^"Ni>tc>s upon the Originjuiil History of thfi Orfal f^iikcs,." cited be- fortv, "Deformation of tbe Iroquois Reach and Hirth of Lalve Ontarior" Am. .Tour. ScK. HI, vol. xl. 18)>0, pp. 44:M31; "Deformation of (he M- Kon(iuin HesreU and Hirth of LakeHuron," id\, vol. xi,i, 1891, {>p. 12- il: "Hijrh Level Shores in the Ilegimi of the Great Lakes Jlftd their Deformation," id., pi^. 201-211; "Deformation of the Lundy Tleach and l5]rt"Ti of Lake P>ie," id., vol. x'tvii. 18i)4, pp. 207-212; "The Iroquois Shore north of the Adirondacks," Hulletin. (ieol. Soc. Am., vol. iir, 1891, pp. 4M8-491. Kdch of these papers, e.xceptinj^lheone lastcited, is accompan- ied with a map. ,- * f "The History of Nia;k'ara River,"*Sixth Annual Report (^ the Com- missioni^rs of the Slate Ilesej;vation at Nii Proc. A. A. A. S., vol. xxpi;-for 188(5, pp. 222, 223. X "Reconnaissances of -the Abandoned Shore Lines of Green Bay and of tlie South Coast of Lake Superior,"' American GEOiiOoisT, vol. xiii, pp.':nft-327.and :W5-:J83, M,ay and .June, 1894; "The Ancient Strait at Nipissing,'; Rulletin,'Geo\. Soc. Am., vol. v, pp^tJ20-r>20. Eacl\of these' papers has. a map. / ^ Vftketch of the Coastal Topography of^ievNtirth i^ideof Lake Sn- perior, wltJi-special rt?fei\Mice to the Abandoned Strands of Lake War- ren," Twentieth Annual Report, CSeol. Surv. Minnesota, for 1891, pp. 18»-289, with map and profiles, ^^ •a' /-• / 1-^ .^- it I mr V milUmtm* iiii'irwii;ii wr^ ' < * mr* k , I! -. h' •\ ,^ 296 TAe American Geologist." ^ November. 18M literated by ice action. Tliis la8t question involvep the prob- lems of subsidence of thcregion and of the character of ice dams. The writer regards the beaches as substantially farmed at sea-level (as some of the beaches unquestionably were), although the outlines may have been obstructed by glaciers, floe-bergs, or local ice accumulations, or periiaps the nortji- eastern coj^^tinuit}' of the beaches is obliterated by recent faults. . These are unsettled questions. Much is still to be done in the survey <>f the anctent lakes, yet we have some in- teresting contributions to recofd concerning them, even with- * out inquiry here as to the still unread histcrry. Fragments of beaches occur in the peninsula between -lakes Ontario, Erie and Huron, wp to altitudes of aWi^t 1,700 feet; and terraceg are found in the Genesee valley at a much » greater hight, besides others at high levels elsewhere in the lake region, lint wiien we descend to an altitude of 778 feet, at the head of lake Erie, we are at a beach of great extent (-to the northeast this rises several hundred feet); and one still \more extensive is reached by descending to 053 feet. All the higher shore developments are the remains of the first waters that covered the drift at the close of the Pleistocene '^lej-iod, whether they were i(!e-bound arms of the sea, or held by 'glacial dams, or by u-ndiscovered land barriers since lieform^d by terrestrial mf^ements. .The beaches were water-levels, but now they rise toward the north and east in increasing ratio. At the head of lake Erie they are nearly level ; at the eastern end of tills lake the northeastern rise is between three ii'nd two feet per mile, according as we take the uplift on the hi;^iieror lower beaches. East of (leorgian bay the deformation is foyr feet ; and near the outlet of lake Ontario it is fronr five to six feet per mile towards the northeast, but increases onward to seven and a hall" feet per mile. These rates of ascent ar«' re- corded in shores not t)ie highest; and there were many, lower stages of the lakes. ID. Worrell Wntc^r. The contracting waters of the Great Lakes region, -represented by the succession of be^iche^^ tin* writer named the Warren watj^r, — the ancestor of all these hiKes; aiidfcits lowest strand^ls the Forest beach, which at the Jiead. of the Erie basin has an elevation of 053 feet above the sea. This lake, during part of its history, covered 200,000 vt ■ ' /'il .i ii iin i fc* iii i MH«M«i|*Mil(||#r«MH»~l<^^ %iMj^ I'l'WW'liWPiHi Review of History of the Great Lakes. — Spencer. 297 square miles. But tb the east it has not been defined, and" its old margins have b^n very considerably tilted. With the <5ontinued rise of the land, the waters sunk to a lower level, dismembering Warren water and producing : — 11. Al(jon(iuin and Lundy Waters. When the level of the wate*r fell about 150 feet below the level of the Forest beach, ithe irpper three lakes v/ere enclosed within the Algonquin b«iach, and Erie within the Lundy beach, which latter extend- ed to the Ontario basin. At that time the waters of t^hp lakes did not reach to their western and southern boundaries of to- rtheast, the rims (tf the lakes were raised, backing the waters in tlie basins and extending the modern lakes as we see them. Xhi« rise was intermittent, but, for tile average of the secular episiules of movement and repose, the warping in the Niagara district appears to have been a foot and a (puirter in a century, and it was double that .;^i ?<^' -( / •* mitiimtmimmmmtm mmimimm MHIMMM r- -line I -•■■■ ^^ 298 The American Geologist. November, 1894 ■i-M : \ 4 < amount at the outlet of lake Ontario, but almost zero at the head of lakp Erie. 13. History of the Nlagnra River and Changes of the Out- lets of the Lakes. From a recently written paper I make the following extracts, coftcerning the changes and recession of Niagara falls (Plate VIII). Upon tlie dismemberment of Lundy water, the Niagara river came into existence, and for a time (taken as 1,000 years) drained the infant lake Erie without cascading over a fall. The waters of the lower lake ^ slowly sunk so that the total hight of the fall was 200 feet, with only the drainage of the Erie basin, or about ^^j of the modern volume of the water. The early falls are almost ex- actly j-eproduced in the magnitude of the American falls. The duration of the first episode is computed, at about 17,200 years. Again the waters subsided in the Ontario basin (80 feet lower than now) so that the total descent was 420 feet. At that time the falls receded by three cascades (like the Gen- esee of to-day), at first with only the discharge of the Erie basin and afterwards with the drainage of all the upper lakes. This condition is computed to have lasted 10,000 years. Then succeeded one uni-ted fall of 420 feet, which lasted 800 years. Finally the northea8t(;rn part of the Ontario basin rose so that the descent of the river waters was reduced to 365 feet and ji^rwards to about 320 feet (the downfall from the head of the rapids above the falls to the lake below). This adds 3,000 years to the age of the falls. Thus, it can be seen that the age of the Niagara river is computed to be 32,000 years. It is now well established that the three upper lakes have dis- charged (>nly a comparatively short time into the Erie basin, having formerly sent their waters to the Ottawa river. This change in the direction of the outlet is ealeulated at H,000 years ago, when the northeastern terrestrial tilting turned the. drainage intffthe Erie basin. About fifteen hundred years ago, the differential uplift in the Niagara district and the recession of the falls through the" Johnson ridge, a short distance below the present site of the falls, were competing for the mastery, and in the meanwhile • the four upper lakes rose so high as to commence to send their waters to the Mississippi river. But the ridge was cut through and the waters were lowered to the exclusive Niagara drain- \ ilWttiifei '■■^./■\'- rii ■... I it Hj i ft*im |jli ri mmmti^m^mmmatm rMlt . M w^^ "r.'tf'iMv' "■ir , ?C ^» ;^ A-,-' 'V' I'ji' 'Vi I i ■j /" -^ /O SMplMiMMp iiliiiiiililfitel -^.;«MipM - - " -'■r Beview of History of the Great Lakes. ^Spencer. 299 age. If the terrestrial elevation of the land shall.continue as foi' the last 1,600 years, the barrier across the outlet of lake Erie must rise so high as to turn the drainage of the lakes into the Mississippi, by way of Chicago; and it is computed th^t the end of the Niagara river and falls, under such conditions, will be about 5,000 years hence. All these estimates are based upon the rate of recession of the falls and the amount of work done in each episode, as dis, coveted in working out tfie history of the lakes. In 1842, Prof. James Hall made the first instrumental survey of the falls. The next was made in 1875 by the Coast Survey. In 1886, Prof. R. S. Woodward made the third ; and in 1890 Mr. Aug.' S. Kibbe made the last. From^ these four surveys, the mean rate of recession of the falls ( that is, the mean elonga- tion of the gorge) was found to be 1.17 feet a year. But the river in the region of the falls is now crossing a pre-Pleisto- cene viiUey, where the hard surface rocks have been removed for 80 or 90 feet in depth beneath the rocky ridge crossing the course of the canyon a short distance below the present site of the falls. Thus the amount of work now being done by the river is much less than the average demand upon the stream during the greater part of the life of the river. Before 1876 all statements as to the age of the river werepure conjectures, but that of Lyell was nearly correct. The estimates made upon the retreat of the falls alone have proved to be not even ^o accurate, although the method was better as far as it went; but it stopped short of the history of the falls. Again, spec- ulations as to the ancient Niagam, flowing down by the Whirl. pool-St. David's valley have been disproved by the rock which crosses that course hundreds of feet above the lake level; in- stead, the Niagara here touches a little buried tributary ()| an ancient stream t(» the west. ', In conclusion, the Niagara falls serve as a chronometer of geological time, as they -give some idea of the epoch of the. •lakes. J( the Icjs age ended with the birth of Warren water, Hien we can roughly estimate it to date back some 60,000 or .60,000 years., At the birth of the Niagara river and falls, and long before, there was no ice barrier in the Niagara district. Lastly, if we regard the Iroquois water as at any tinie ob- structed by ice, such conditions have not existed since the ?-..''• ^ W^ \ *>*- 300 The American Geologist NoTember.lSW close of the episode which ended 14,000 years ago. Whilst, however, the date of the decadence of the Ice age in this region is told, the falls do not necessarily record its termination in other and distant regions. - " ' U. Recurrent Drainage of the Great Lukes into the Mis- sissippi River by way of Chicago. Long ago, Dr. E. Andrews described the deserted beaches soAith of Chicago, and found that the highest reaches an elevation of 45 feet above the lake. For many miles around the head of the lake, the de- serted shores are. found far inland. There are other raised beaches near the lake. The different sets form an apparent "succession, but in reality there is confusion between the old water-margins and the very repent beaches. The low plain at ~ the head of the lake rises so gradually that at the divide be- tween it and the Mississippi drainage southwest of Chicago it is only eight feet above the lake, with a rocky floor a foot or two l^wer "(canal survey). In proceeding northward along ' the margin of the Michigan basin, beaches are found emerg- ing from beneath the waters. From the measured deformation of the various sets of deserted shores, the depth to which the tilted beaches are depressed beneath the lake can be calculated.* These record the shrinking of the lake from the highest.Ievel south of Chicago to others even hundreds of feet beneath. • The Ridgeway beach extends from the Erie basin across soutliern Michigan, by way of Saginaw bay and the Grand river valley, and southeast of lake Michigan it descends and is lost in the sand dunes of that region ; but, with the meas- uied rate of deformaticyi, it is computed to pass about 40 feet beneath the surface of the water. The Forest beach, the last strand of Warren water, is about 100 feet lower. The still l.)wer Algonquin beach (the great shore line of the dismem- bered upper lakes) occurs well defined about the northern half .,f the lake (Andrews and Taylor); but if produced to the H(nitiiern end of the basin, it would be submerged between 260 and 300 feet. There are other lower and less important deserted shores ; but all these represent the subsiding of the lakes during the time of discharge of the waters of lake Huron ♦"Hijrli L.'v.'l Shori's in lh« n'>?iun of the Groat Lakes .iiid their Dc- rormiilioii, before citi-d. . mmmaiffmtififm IfVHMpMI NoTember. 18M ago. Whilst, in this region rmination in into the Mis- . E. Andrews ), and found Bt above the lake, the de- other raised an apparent ween the old low plain at ' le divide be- :)f Chicago it >or a foot or tiward along ound ertierg- deformation th to which ake can be ike from the ireds of feet • basin across the Grand escends and h the nieas- bout 40 feet ich, the last The still ;he disDiem- le northern )roduced to fed between » important iding of the lake Huron uid their I)p- ^ Review of History of the Great Lakes.— Spencer. 801 by way of the Ottawa river, which is found to have drained the Huron, Michigan and Superior basins for about 24,000 y^ars. The highest of the beaches ^bout the head of lake Michigali (at 45 feet) has been regarded as the equivalent of the Mau- mee beach, or not a lower strand, and therefore the oldest well' defined beach of the region, although it is only ^ few feet above the present and recently deserted shores. Owing to the terrestrial deformation, the Ottawa outlet of - the Huron basin was closed by the rim being raised so highas to turn the overflow into the Erie basin. This northeastward uplift also affected the outlet of the Erie basin, and on ac- count of the presence of the Johnson ridge, about a mile north of the present site of the falls of Niagara, caused, an actual ov.erflow of the drainage of all the upper lakes into the tribu- taries of the Mississippi. ' At that time the lacustrine silts upon the prairies at the head of lake Michigan were laffl down. But the Niagara falls were receding at the rate of about four' feet a year and completed the incision through the Johnson ridge about 1,500 years ago,* thus overcoming the terrestrial uplift of the Niagara district (which is about a foot and a quarter a century), And then the level of lake Erie was lowered to about 17 feet below the Chicago divide. The slightly raised beaches about the head of lake Michigan mark this late sub- siding of the wattTs. The lowering of the waters by the recession of the falls has preserved thepresent t^utlet of the lakes hn^ii further period, but if the late rate of terrestrial deformation shall continue in the future, the drainage of the upper lakes will be diverted from the Niagara into the Missis- sippi in perhaps 5,000 or (J,00() .years, so that this result will' be reached before the falls shall have receded to bulfalo. . »"l)<'f()rmrttii)n of llif Luinlv Hi-acli and l?irlh of Laki' Krif," bt-fort' oiled. -^-4^ ,'Jw. '«»l|6!M**.»*.'(*t*v> 'ii.Mik'^ : JMrn^^^^'^^ J^