October 1, 1896.] 



KNOWLEDGE, 



223 



THE HISTORY OF THE GREAT LAKES AND 

 NIAGARA. 



By Andrew J. Herbertson. 



THE problem of the origin of the Great Lakes and 

 Niagara has always been an interesting one, and 

 various theories have been put forward to explain 

 it. Dr. J. W. Spencer, of the Geological Survey 

 of the Great Lakes, has recently published a set 

 of papers in which he attempts to reconstruct the past 

 history of the Great Lake Region of America. ' 



Dr. Spencer believes that between the middle Miocene and 

 early Pleistocene periods the region stood three thousand, 

 perhaps even five thousand or six thousand, feet higher 

 than at present. In support of this he appeals to the 

 evidence of soundings round the American coasts, which 

 reveal the existence of what appear to be ancient river 

 channels. For instance, were the water to sink sis hundred 

 feet below its present level the banks to the south of New- 

 foundland and Nova Scotia would be dry land ; but this 

 would be traversed by a deep fjord over three thousand 

 feet deep where it joined the sea, whose depth near its 

 mouth would be five thousand feet. This channel, sixty 

 miles wide at its mouth, follows for over eight hundred 

 miles the bed of the present St. Lawrence River, growing 

 narrower and shallower as it projects inland. Dr. Spencer 

 supposes that previous to the existence of the present lake 

 basins the continent was much higher, and was drained by 

 a great river, which he names the Laurentian River, which 

 excavated this deep channel. The depths of the various 

 lakes afford corroborative evidence, the floors of Ontario 

 and Superior being almost five hundred feet below the 

 present sea-level, that of Michigan three hundred feet, and 

 of Huron one hundred and fifty feet. The soundings of 

 the lakes and borings in various regions reveal the ancient 

 beds of this Laurentian River and its tributaries. Lake 

 Michigan was drained by two rivers, one in the northern 

 basin which flowed by the present outlet to Lake Huron, 

 in the middle of which it was joined by a tributary running 

 from the southern basin of Lake Michigan, across the 

 present State of Michigan, and through Saginaw Bay. The 

 united streams did not flow southwards towards Lake Erie, 

 but first north-westwards to the present Georgian Bay, 

 then south-eastwards near its western shore, and by Lake 

 Simcoe, turning to the eastwards at a point in Lake 

 Ontario nearer the southern than the northern shore, and 

 thence to the sea by the present course. The Lake Erie 

 basin was drained by another tributary which turned north- 

 wards by the Grand River and Dundas Valleys, and curved 

 eastwards again at the western end of Lake Ontario, joining 

 the Laurentian main stream at its bend opposite the mouth 

 of the present Niagara River. 



This river and its tributaries had eroded the region and 

 formed broad valleys just before the Pleistocene period, 

 and during that period, and particularly towards its end, 

 parts of the old valley were i^radually blocked. This 

 blocking of the valley may have been due to the accumu- 

 lation of glacial drift at some places, but i>r. Spencer 

 believes that terrestrial warpings are a more important 

 factor, and that these to a certain extent are measurable. 

 The absence of glacial markings in the direction of the 

 axis of the lakes goes to prove that they have not been 

 hollowed out by ice. 



Round the Great Ijakes are found traces of terraces 



• " The Duration of Niagara Falls ant) the History of the Great 

 Lakes." By J. W. Spencer, .\.M., Ph.D., F.O.S. .>-'i-eonil Edition 

 189). (Alhany; The Commissioners of the N.V. State Reservation 

 at -Viapaia.) 



composed of waterworn pebbles, the result of the action 

 of waves or of currents. These Dr. Spencer has examined 

 and surveyed, and concludes that they are of marine 

 origin at a time when there was a depression of the surface 

 to over two thousand feet below its present level. He does 

 not discuss the theory that they may have formed the 

 shores of lakes retained by moraines, but he points out 

 that glacial lakes retained by ice are neither large enough 

 nor sufficiently long lived to account for such beaches. 

 The depression of the continent at the time of the newest 

 till is no more impossible than the generally admitted 

 elevation of the pre-Pleistocene period, but the discon- 

 tinuity of the terraces and the absence of salt-water deposits 

 are difficulties in the way of the theory of their marine 

 origin. The first of these objections is met by the answer 

 that these terraces have not yet been perfectly explored, 

 that subsequent terrestrial movements may have deformed 

 them, and that erosive and other agents have been at work 

 modifying the topographical features. As to marine 

 deposits, these are found at a height of five hundred and 

 twenty feet, but their absence at higher levels is not 

 evidence of the non-marine character of these old shores, 

 since there are many marine beaches in which no fossils 

 are found. 



When the depression of the land was greatest the region 

 of the Great Lakes was then a huge ocean gulf, whose 

 shores formed one of the raised beaches Dr. Spencer has 

 surveyed. It is possible that at times the narrower parts 

 of the gulf may have been filled up from giant glaciers, 

 but these ice barriers could not retain a vast volume of 

 water for any lengthened time. 



But a close examination of the raised beaches leads to 

 other conclusions. Tliey do not lie parallel to the present 

 water surface of the Great Lakes, but are usually higher 

 above the kke level in the east than in the west, in the 

 north than in the south. This aflords important evidence 

 of terrestrial deformation having taken place since the 

 formation of these beaches ; and these alterations of levels 

 have resulted in the formation of the Great Lakes. 



The first uplift seems to have taken place in the region 

 to the south-east of the present Lake Huron, and when 

 the land had risen one hundred and fifty feet the upper 

 waters of the original gulf, covering Lakes Superior, 

 Michigan, Huron, and Georgia, were separated from the 

 lower waters which extended over the present Lakes 

 Ontario and Erie. This great lake was at first joined to ■ 

 the sea by a broad strait covering the present Lake 

 Nipissing and the Ottawa Valley. 



The nest event was the isolation of Lake Erie, and at 

 first its waters, too, flowed to the Ontario Gulf without 

 any perceptible fall. The upward movement of the land 

 continued until there were three huudred feet of difference 

 between the levels of the gulf and the lake, and the 

 Niagara Falls came into existence. But the water falling 

 over them was only that of Lake Erie, for the overflow of 

 the upper lake still took place by the Ottawa Valley. This 

 was the time when the beach round Lake Ontario (which 

 Dr. Spencer calls the Iroquois) was formed approximately 

 at the sea-level, and must have been after the uppermost 

 drift was deposited, as it rests on mud covering the till. 

 This beach is three hundred and sixty-three feet above the 

 sea (one hundred and sixteen above the lake) at the western 

 end of the lake, but it rises especially in the north, and at 

 the east end it is six hundred feet higher than at the west 

 end. 



As the uplift continued more rapidly in the east than in 

 the west the communication with tlie sea was gradually 

 closed, save by the present channel of the St. Lawrence, 

 and Lake Ontario was formed. The rising of the land 



