DISINTEGRATING WORK OF FREEZING WATER. 443 



every mountainous region of the world the peaks of which extend above 

 the snow line. For instance, the top of Grays Peak, in the Front Range of 

 Colorado, is a mass of disrupted fragments, the solid rock being nowhere 

 exposed. Mount Dana, in the Sierra Nevada, furnishes an illustration of 

 the disintegration of a schistose rock. Here also the top of the mountain is 

 a mass of disrupted blocks, the solid rock protruding only here and there. 



As to latitude, it is certain that in the lowlands of the Tropics, where 

 the temperature does not fall to 0° C, the effect of freezing and thawing is 

 nil. But in the north temperate and frigid regions where there is a long 

 season of alternate freezing and thawing, the effect is very great. The 

 rapidity of the disintegration of rocks in areas like Greenland and Spitz- 

 bergen is largely explained by the alternate freeziug and thawing. Cushing 

 has described the argillites of the region of Glacial Bay as disintegrating 

 with amazing rapidity.* 1 



It is impracticable wholly to discriminate the above-described disinte- 

 grating work of freezing and thawing from that of insolation. Insolation 

 is everywhere at work, although, as has been explained, with variable 

 power. It is common to attribute the work of disintegration in temperate 

 and arctic regions wholly to freezing and thawing, but it is plain that the 

 disintegration in such regions is partly the result of insolation. 



A further effect of freezing and thawing, fully described by Merrill, is 

 the movement of materials already disintegrated. The movements may 

 affect pebbles and bowlders as well as fine material. As the soil below a 

 pebble or bowlder freezes it expands upward, this being the direction of 

 least resistance. When the soil thaws, the fine material falls back more 

 readily than the bowlders, and thus leaves the pebbles and the bowlders 

 slightly higher than before. 6 



Oftentimes in saturated tough clay soils, after the surface layer of water 

 and soil has frozen, and thus forms a congealed sheet, as the process of 

 downward freezing continues the necessary space required by the expansion 

 in the change from water to ice is obtained by the water breaking- through 

 the crust at very numerous points. As the water is slowly squirted up 

 through these pipes it congeals at the points of issue, just as it does when 



oCushing, H. P., Notes on the Muir Glacier region, Alaska, and its geology: Am. Geol., vol. 8, 

 1891, p. 224. 



b Merrill, George P., Rocks, rock- weathering, and soils, Macmillan Co., New York, 1897, pp. 

 393-394. 



