NOTE ON 



THE MUTUAL RELATIONS OF LAND-ELEVATION AND ICE- 

 ACCUMULATION DURING THE QUATERNARY PERIOD. 



It is generally agreed that the Quaternary was characterized by remark- 

 able oscillations of land-level, and corresponding oscillations of climate and 

 of ice-accumulation in northern high-latitude regions. But the most op- 

 posite views are held regarding the time-relations of these two sets of phe- 

 nomena. Some hold that the land-elevation was coincident with the cold and 

 the ice-accumulation, and was at least one of its causes, and that the mod- 

 eration of temperature and removal of the ice was coincident with the de- 

 pression, and was its effect. Others, on the contrary, take exactly the 

 opposite view ; they hold that the ice-accumulation, which was the result of 

 entirely different and perhaps extra-terrestrial causes, produced crust de- 

 pression by its weight, and the subsequent removal of the ice and relief of 

 pressure caused the reelevation of later times. 



There is doubtless much to be said for both of these views ; there is in 

 both a mixture of truth and error. The error in the first is in neglecting the 

 undoubted eiSect of load and relief on crust-level : The error in the second is 

 in neglecting other causes of crust movement than load and relief; especially 

 in this case in neglecting the land-elevation, which commenced in preglacial 

 times. I believe that the two extreme views may be reconciled and all the 

 facts satisfactorily explained by supposing, (1) That the continental eleva- 

 tion which commenced in the Pliocene culminated in the early Quaternary 

 and was at least one of the causes of the cold and therefore of the ice- 

 accumulation ; (2) That the increasing load of ice was the main cause of 

 subsidence below the present level ; (3) That the removal of the ice-load by 

 melting was the cause of the reelevation to the present condition ; but (4) 

 That all these effects lagged far behind their causes. This lagging of effects 

 behind their causes is seen in all cases where effects are cumulative. For 

 example: the sun's heating power is greatest at midday, but the temperature 

 of earth and air is greatest two or three hours later ; the summer solstice is 

 in June, but the hottest month is July ; and in some cases the lagging is much 

 greater. The cause of sea breezes, i. e., the heating power of the sun, cul- 

 minates at midday, but the effects in producing air currents culminate late 

 in the afternoon and continue far into the night, long after the reverse 

 cause, i. e., the more rapid cooling of the land, has commenced. Now, in 

 the case under consideration, it is probable that the lagging would be enor- 



(329) 



