CHAPTER I 



VARVE CLAY, AND THE METHOD OF 

 INVESTIGATION 



Formation of Varve Clay 



In the glaciated areas most of the soils were formed during 

 the disappearance of the last ice sheets. Part of the water from 

 the melting glacier, working down through fissures in the ice, 

 sought its way down to the ground. Here it formed a river and 

 dug a tunnel in the lower part of the ice. Under hydrostatic 

 pressure and with tremendous velocity the river rushed toward 

 the ice edge, carrying with it big boulders, stones, gravel, sand, 

 and mud. When it reached the ice border the pressure gave out, 

 and the transporting power was reduced to a trifle. Boulders 

 and gravel, consequently, were unloaded at the mouth of the 

 tunnel and just beyond it, forming eskers and outwash. The 

 annual deposition of coarse material was often very considerable. 

 If the glacial river discharged into standing water, coarse sand 

 was deposited in the direction of the current for some hundred 

 yards from the ice edge, while silt could be transported consider- 

 able distances and fine clay carried more than fifty miles. 1 



In North America large areas which now form fertile clay 

 lands were covered by water at the disappearance of the ice. 



1 i mile = 5,280 feet = 1.6093 kilometers. 1 kilometer = 0.6214 mile. 



1 yard = 3 feet = 0.915 meter. 1 meter = 1.1 yard = 3.28 feet = 



1 foot = 12 inches = 30.48 centimeters. 39-37 inches. 



1 inch = 2.54 centimeters. 1 centimeter = 0.3937 inch. 







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