RECENT CHANGES IN LAKE LEVEIv 'JOi") 



L;ion," Tliis article advances evidence which indicates a soutliwest tilt- 

 iiiij^ of the re,ii;iou described. In the case of hike Saperk)r this tiltin<:; 

 movenient wouKl th)od the head of tlie lake, causing an aj)|)arent rise 

 of the lake level. One of the results of this rise would be the destruc- 

 tion of shore de})osits made while the hike stood at lower levels. The 

 destruction of the spits already noted tends to confirm the truth of 

 Gilbert's contention that the lake is invading the land because of a 

 southwest tilting of the lake region. The direction of tilting is assumed 

 by Gilbert to be south 27 degrees west — that is, the movement is more 

 to the south than to the west. This is undoubtedly true, and it may be 

 questioned whether the movement is not even more to the south than 

 he has assumed. It is within bounds to say that the maximum rate 

 of bar destruction takes place about Chequamegon bay; but if the tilting 

 were well to the west this would not be true, since under such circum- 

 stances the maximum attack would be on the bars at the head of the 

 lake. On the other hand, if the tilting is more southerly the tendency 

 would be to cause a maximum destruction anywhere on the south shore, 

 where wave action is most violent. Under the present conditions of ex- 

 posure, other things being equal, the bars and spits about Chequamegon 

 bay will suffer greater destruction than the bars at the head of the lake. 

 This is in part due to the fact that wave action has its effectiveness re- 

 duced by reason of the gradual contraction of the banks of the lake in 

 the neighborhood of Duluth and Superior. 



The second proof of apparent rise of the lake is the flooding of the 

 lower courses of streams. Some of the larger streams have true estuaries. 

 This is especially true of Saint Louis river at the head of the lake. In 

 a lesser degree the Bois Brule, the Kaukaugon, and the Bad rivers pos- 

 sess the same features. They are all broad and deep streams, when the 

 limited extent of their drainage areas is considered. As these streams 

 approach the lake, the current becomes more sluggish and they take a 

 meandering course to their outlet. The swamps through which they 

 pass in the lower ])art of their course are flooded in the vicinity of the 

 stream, though relatively dry and firm away from it. This is due to the 

 backing up of the lake waters into the river and the consequent flooding 

 of the region in the neighborhood of the river. All of the streams on 

 the south shore of the lake in Wisconsin show drowned features, though 

 there are differences in the degree of the drowning. If the tilting of the 

 land is to the southwest, an increasing amount of drowning should be 

 expected as the head of the lake is approached. The writer is unable 

 to find satisfactory evidence of such progressive increase of drowning^ 

 It is true that Saint Louis river exhibits the estuarine features on a larger 



* Eighteenth Ann. Kept. U. S. Geol. Survey. 

 XXX— Bull. Geol. Soc. Am., Vol. 12, 1900 



