THE ORIGIN OF THE GULF OF ST LAWREXCEi 



BY JOHN M. CLARKE 



Present-day geography contemplates not only the surface of the 

 earth and its forms of land and water, but considers also the 

 physical and human causes that are modifying it. The geographer 

 sees these things and looks forward ; the geologist sees present con- 

 ditions and looks backward for their inception — and then again 

 forward in the perspective of cause and effect. It is hard to draw 

 the line between these two fields of scientific interest. Some have 

 tried to circumscribe each but it is a bootless effort. Each trenches 

 on the other. At all events every geographer is something of a 

 geologist. And this may be my justification in endeavoring here to 

 find a clue to the origin of a geographic feature of so deep interest 

 to us all as the Gulf of St Lawrence. W't are very apt to take such 

 a geographic fact for granted as it is and to let our geography end 

 with a knowledge of i^s outlines, the contours of its shores and its 

 bottoms. To unravel its history and to find the causes which have 

 brought it into being is a task that will be fruitless on the face of the 

 facts as they present themselves to the maker of charts. The key 

 lies in the geological birth and growth of the whole land mass by 

 which such a body of water is embraced. 



So to find the real factors in the making of this classical and 

 romantic body of water, we shall have to go well back to the early 

 events in the making of the land. 



Fundamental among these facts is the existence of the great 

 mass of crystalline rocks that sweeps from Labrador to the Lauren- 

 tides and northwestward to Alaska — the Canadian shield — as a 

 continental land mass rising above the waters of the primitive ocean. 

 Its shores were washed by the first sea whose life records have been 

 kept for us in the sediments which, now changed to shale, sandstone 

 and limestone, bound all its ancient shores. On the south coast 

 of this Canadian continent, in the ages of its independent existence, 

 lay, in the longitude of ^Montreal, a great tongue or peninsula which 

 forms the Adirondack mountains of Xew York; and still farther 

 south, perhaps, were long and narrow land masses that kept their 

 uncertain heads above water for no great time. About these con- 



1 Reprinted from Bulletin de la Societe de Geographic de Quebec, v. 7. 

 January 1913. 



132 



