MICHIGAN ACADEMY OF SCIENCE. 



19 



PHYSIOGRAPHIC SUCCESSION. 



A. Types of Lakes. 

 Chart I. Classification of Lakes of Temperate Regions. 



SMALL LAKES. 



Shallow Type I. Small lakes, 

 lakes. too shallow for ther- 

 mocline. S t a g n a nt 

 when frozen; good cir- 

 culation when not. No 

 abyssal depths. Shores 

 all of protected type. 



Deep Type IV. Small lakes 



lakes. deep enough for ther- 

 mocline. S t a g n a nt 

 when frozen, thermoc- 

 hne when not, except 

 spring and fall over- 

 turnings. Abyssal 

 depths with periodic 

 warming and aeration. 

 All shores of protected 

 type. 



LARGER LAKES. 



Type II. Larger lakes, too 

 shallow for thermocline. Stag- 

 nant when frozen; good circula- 

 tion when not. No abyssal 

 depths. Shores of both pro- 

 tected and unprotected types; 

 mostly the former. Rarely 

 beach pool formation. 



Type V. Larger lakes, deep 

 enough for thermocline, which, 

 however, is usually not very 

 sharp (14). Stagnant when fro- 

 zen, thermocline when not, ex- 

 cept spring and fall overturn- 

 ings. Abyssal depths with peri- 

 odic warming and aeration. 

 Shores of both protected and un- 

 protected types. Beach pool 

 formation on a small scale. 



VERY LARGE LAKES. 



Type III. Very large lakes, 

 too shallow for thermocline. 

 Stagnant when frozen; good cir- 

 culation when not. No abyssal 

 depths. Shores of both pro- 

 tected and unprotected types; 

 mostly the latter. Considerable 

 beach pool formation. 



Type VI. Very large lakes, 

 too large for thermocline. Rare- 

 ly completely frozen ; slow circu- 

 lation. Abyssal denths with 

 slow, but quite constant, warm- 

 ing and aeration. All shores of 

 unprotected types, except in 

 bays, behind spits, etc. Lakes 

 and large pools formed by cur- 

 rent and wave action. 



Lakes belong to the general series of physiographic successions known as 

 the lake-pond-swamp series. They tend to form ponds, by being filled in 

 with stream and wave sedimentation and by plant encroachment, while 

 ponds, in turn, become temporary swamps thru the action of similar agencies. 



Lakes have often been divided into three main groups based on their 

 adaptation for plankton life (See 8 and 9). These would be: (1 usually 

 small lakes too shallow to have a thermocline; (2) small or larger lakes, deep 

 enough to develop a thermocline; and (3) very large lakes, too large to allow 

 a thermocline. A classification based on the nature of the shores, and con- 

 sequently on their adaptability for shallow littoral forms would, on the 

 other hand, require a division into two different classes: (1) lakes too small 

 to develop wave and current action to the extent of building sandy, more or 

 less shifting shores; and (2) lakes large enough to prevent, by such action, 

 the fixation of the entire shore by vegetation. The second class would, of 

 course, include all of the lakes that would be able to develop pools to any 

 marked degree. 



The relationships of all of the different kinds, for temperate regions, might 

 be expressed about as shown in the accompanying chart (Chart I). Types 

 II, III, V, and VI, as shown in the chart, would be the only ones to develop 

 beach pools to any extent. Rush Lake in Huron County, Michigan, (5), 

 approaches the second type, while Lake St. Clair, between Lakes Huron 

 and Erie, is probably an example of the third. Types V and VI, however, 

 are the ones wi:h which this paper especially deals; Douglas Lake is an ex- 

 ample of the former, while the head of Saginaw Bay, off Lake Huron (5), 

 is an example of the latter. 



B. TYPES OF LAKE POOLS. 



In these types of lakes, with a portion of the shore-lines shifting and sandy, 

 another form, of the same series of physiographic succession as already 



