﻿170 Nichols: The vegetation of Connecticut 



Geological Relations of Lakes and Swamps 

 The Effect of Physiographic Factors on the Distribution of Lakes 

 and Swamps. — In a general way it can be said that lakes and 

 swamps belong to the same family, and differ only in age.* Lakes, 

 however, "are temporary features of a landscape, and can only 

 exist where the land has been recently raised above the sea or 

 modified by some widely acting agent "f such as glaciers. Sooner 

 or later they are destined either to be drained through the activity 

 of streams cutting down their outlets, or else to be filled in through 

 the washing in of inorganic sediment from without and the ac- 

 cumulation of vegetable debris from within. 



Considered from the standpoint of their physiographic origin, 

 Connecticut lakes may be grouped under three heads: Glacial, 

 River, and Coastal. The term Glacial Lake is here used in 

 its broadest sense, to include lakes formed in any sort of a depres- 

 sion resulting from glacial activity. Glacial lakes may further 

 be subdivided as follows: (i) Morainal Lakes — those associated 

 with accumulated glacial debris of any description; and (2) Scoop 

 Lakes — those which occupy depressions scoured out of the under- 

 lying rock by the ice. Lake Saltonstall, near New Haven, affords 

 a striking example of a scoop lake. This lake is about three miles 

 long and has an extreme depth of 108 feet, more than eighty feet 

 below sea level; yet notwithstanding that the tides rise and fall 

 at its very edge, its water is fresh and constitutes part of the New 

 Haven water supply. J On the whole, however, scoop lakes are 

 far less abundant and of much less importance in Connecticut 

 than morainal lakes, and of the 1,026 lakes indicated on the topo- 

 graphic map of the state§ the great majority belong to this latter 

 class. Morainal lakes may originate under a variety of conditions. 

 Thus, (a) they may occupy depressions in the ground moraine; 

 ih) they may occur behind dams formed by the heaping up of 

 glacial till; {c) they may occupy depressions in stratified drift; or 

 {d) they may develop behind the ridges of stratified drift knowr 

 as eskers. Morainal lakes of the first two types here mentioi .rl 



* Possible exceptions to this statement are pointed out in later paragraphs, 

 t Rice, W. N., and Gregory, H. E. Manual of the geology of Connecticut, 

 Geol. and Nat. Hist. Surv. Connecticut, Bull. 6: 248. 1906. 

 t See Rice and Gregory, op. cU., p. 249. 

 § See Rice and Gregory, op. cit., p. 247. 



