68 PROCEEDINGS OP THE WASHINGTON MEETING 



height and relative age agree with the fluctuations in the growth of the sequoia 

 trees 50 miles west of Owens Lake. The most notable strand appears to date 

 from the fourteenth century — a time at which the big trees made a peculiarly 

 rapid growth. It is remarkable for its size and strength. It could have been 

 formed only under the influence of unusually high winds. What seems to be 

 the same strand can also be recognized at Mono and Pyramid lakes, both by 

 its relative location and its evidences of peculiarly strong wave action. 



The fourteenth century period was also marked by climatic stress in other 

 regions. In central Asia the Caspian Sea and Lop-Nor expanded with great 

 rapidity, as is known from well authenticated historic records. In north- 

 western Europe storms of unusual severity afflicted the countries around the 

 North Sea. Floods were of frequent occurrence, and extraordinarily cold 

 winters caused the Baltic Sea to be frozen over completely. Norway suffered 

 great economic distress because of persistent failure of the crops. In England 

 the rains were so abundant that the average production of wheat per acre fell 

 off one-third and the agricultural population was in great distress. In Iceland 

 and Greenland similar occurrences took place. Petterson holds that increased 

 severity of climate and the crowding down of the ice were the cause of the 

 final abandonment of Greenland by the Norsemen. 



It is noteworthy that in both the eastern and western hemispheres the chief 

 evidences of climatic stress come from the semi-arid and desert regions, where 

 a subtropical climate prevails, or else from the northern border of the belt of 

 cyclonic storms. These are the regions where the Glacial period also produced 

 the most noteworthy results, either by the expansion of salt lakes or by the 

 production of ice-sheets. The conditions in the fourteenth century seem to 

 have been of essentially the same nature as those of the Glacial period, the 

 only apparent difference being in degree. It is possible that a study of such 

 climatic fluctuations during historic times may lead to a final solution of the 

 problem of the nature and cause of Glacial periods. 



Presented in abstract extemporaneously. 



PLEISTOCENE DEPOSITS OF MINNESOTA AND ADJACENT DISTRICTS 

 BY FBANK LEVERETT 



{Abstract) 



The extension of glacial investigations into Minnesota from districts farther 

 east has shown that in the last, or Wisconsin, stage of glaciation the Labrador 

 ice-sheet reached its culmination and began to wane before the ice which 

 spread over northern Wisconsin and neighboring parts of Minnesota reached 

 its culmination, and that this ice in turn began to wane before the Keewatin 

 ice-sheet, which lay still farther west, reached its culmination. It is suggested 

 in explanation of this westward wave of ice culmination that the highland of 

 Labrador Avas the natural starting point of glaciation, and that because of 

 storms coming to it from the southwest the ice-sheet grew westward to such 

 an extent as to eventually receive more snowfall in the region south of Hudson 

 Bay than in the Labrador district; so that there resulted a waning of ice 

 movement from ■ the latter district. Still later the ice-sheet grew westward 

 into central Canada and caused the culmination of the Keewatin ice movement 

 which spread into Minnesota and Iowa. 



