THi: GLACIAL LAKES 



would cut and build strong and pronounced beaches, shore 

 cHflPs and terraces. It is possible that many lakes once existed 

 of which we shall never have knowledge, for they left records 

 so weak and faint as to be now illegible. At any given level 

 of a lake the features of its shores and beaches must have been 

 horizontal and all related to that elevation. If the lake be- 

 comes smaller and remains long enough at a lower level, new 

 shore features will be made at that elevation; if it becomes 

 larger the rising waters wash over the older shore lines but do 

 not always destroy them. In fact, if the waters rise rapidly 

 and the lake becomes deep, old shore features of a lower level 

 may be well preserved; and if the new higher lake persists 

 long enough, these features may be buried by its varved clays. 

 Changes of lake level make all sorts of complications in the 

 records, but because shores are horizontal when made, most 

 of the records can be deciphered. 



It is from such records of glaciers, rivers and lakes, some 

 simple, others complicated, that we have been able to read 

 and learn of the development of the Great Lakes. 



Lake Maumee — The First of the Glacial Lakes 



When the ice had melted so far north that its front stood 

 north of the drainage divide and the land sloped toward the 

 ice, streams of melt water could no longer flow freely south- 

 ward, hence the water collected in front of the ice in long 

 narrow pools back of the bordering moraine. From the rec- 

 ords such as those described, we know that the earliest glacial 

 pools which formed along the edge of the ice lobe in the Erie 

 basin were in northwestern Ohio. When the ice had melted 

 far enough, several pools united to form a narrow crescent- 

 shaped lake around the front of the Erie ice lobe. Thus was 

 born the first of the great lakes — the ancestor of Lake Erie. 

 Faint beaches were made by these early pools of melt-water, 

 but the waters rose steadily and finally formed a strong beach 

 at the highest level the lake reached, about 230 feet above tlie 



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