272 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1937 



and north of the shield. The Great Lakes basins are neither the 

 largest nor the deepest of these features. The Finger Lakes of New 

 York State and Lake Champlain are smaller than, but almost as deep 

 as, the Great Lakes. The Gulf of St. LawTence is comparable to the 

 Great Lakes and contains large, deep, rimmed depressions.^ Along 

 the coast of Labrador a few inlets, notably Lake Melville, are also 

 comparable, but in general the inlets or fiords are too small to warrant 

 consideration. 



North of Canada the series of straits and gulfs among the islands 

 have been charted only very crudely, and soundings are scarce. 

 Such information as is available, however, suggests that these bodies 

 of water are similar to the Gulf of St. Lawrence and probably con- 

 tain basins of a depth and size quite comparable to the Great Lakes. 

 Hudson Bay has been sounded sufficiently to show that it has basins 

 within it which compare in dimensions with the Great Lakes. Great 

 Bear Lake, Great Slave Lake, Lake Athabasca, Reindeer Lake, and 

 Lake Winnipeg are almost as large as the Great Lakes. Their depths 

 are not well known, but soundings in Great Slave Lake show a maxi- 

 mum of 826 feet and in Great Bear Lake of 4.50 feet * — depths not 

 unlike those of the Great Lakes. On the other hand, Lake Winnipeg 

 docs not have depths much in excess of 60 feet so far as is known. 



In the European glaciated area (fig. 3) there are various large 

 lakes, and the seas and gulfs contain many basin depressions. The 

 Skager Rack, south of Norway, has a deep, rimmed basin.® The 

 Baltic Sea, the Gulf of Bothnia, and the Gulf of Finland all contain 

 sizable depressions. Farther east in the Soviet Union are Lake 

 Ladoga and Lake Onega. The White Sea contains a deep basin, and 

 the continental shelf in the Barents Sea contains a series of deep, 

 rimmed depressions. 



All these examples of large basins in glaciated regions of relatively 

 low relief show that the Great Lakes are features characteristic of 

 continental glaciation. The areas unmediately outside the glaciated 

 regions, together with much of the area of marginal glaciated terri- 

 tory, where the glaciers were thin and of short duration, have few 

 basins both on the lands and on the continental shelves. Accord- 

 ingly, it appeai-s that the Great Lakes are in some way related to 

 glaciation. 



DIASTROPHISM IN GLACIATED TERRITORY 



The possibility must be considered that the abundance of basins in 

 the glaciated territory simply means that this territory has also been 

 very active diastrophically. Tests will be applied to see whether this 



' Shepard, F. P., The St. Lawrence (Cabot Strait) submarine trough. Bull. Geol. Soc. Amer., vol. 42, 

 pp. 853-64, 1931; se« also f5g. 6, p. 860. 



• From information kindly supplied by F. Anderson, hydrographer, Canadian Hydrographic Service. 



• Shepard, F. P., Glacial troughs of the continental shelves. Journ. Geol., vol. 39, flg. 9, p. 352, 1931. 



