172 STUDIES FOR STUDENTS 



latitudes has been pointed out by Walther/ by Russell,^ by Merrill, 3 

 and others, and reliance upon this action has been employed by 

 Oldham to reach the conclusion as to the existence of a period of cold, 

 but one not attended by glaciation during the deposition of the 

 Panchet group, early Mesozoic of India. ^ 



It has been thought by some that perhaps a rigorous winter climate 

 does not promote corresponding disintegration, since during a con- 

 siderable portion of the year there may be no thaw. Observation 

 seems to indicate, however, that with increase of altitude or latitude 

 the results of frost action become progressively more pronounced. 

 The explanation is apparently to be found in the fact that although 

 surface melting and refreezing may be absent, frost action is at such 

 times penetrating constantly deeper. The period of daily freezing 

 and thawing will in this case occur at the two ends of the winter 

 season instead of the middle and on account of the greater daily 

 insolation and nocturnal radiation the effects may be as pronounced 

 as during a somewhat longer period near the winter solstice. 



If the cold becomes so great, however, as to result in a perpetually 

 frozen substratum, the disintegrative action will presumably become 

 less instead of greater, but such a condition does not exist at present 

 except under polar climates. It is not oae which would, so far as 

 known, become widespread even at times of glaciation, and is the 

 consequence of a climatic extreme which need hardly be considered. 



The effects of increased cold in regions of no glaciation must 

 consequently be either one of two kinds, depending upon whether 

 frost action or snowfall is increased: frost tending to make more 

 rock waste ; snow tending to prevent frost action and by its melting 

 to carry waste away. 



In climates possessing but little snowfall, increased variations of 

 temperature and increased frost action will be the most marked 

 results of a change to a colder climate. In regions of exposed rock 



1 Einleitung in die Geologie, 1893-94, p. 559. 



2 Notes on the Surface Geology of Alaska, Bulletin of the Geological Society of 

 America, Vol. I, 1890, pp. 133-37. 



3 Disintegration and Decomposition of Diabase at Medford, Mass., Bulletin of 

 the Geological Society of America, Vol. VII, 1896, pp. 349-62. 



4 A Manual of the Geology of India: Stratigraphical and Structural Geology, 2d 

 ed., 1893, p. 201. 



