XIII 

 SCIENTIFIC PAPERS 



lANDSLIDES IN UNCONSOLIDATED SEDIMENTS; WITH A 

 DESCRIPTION OF SOME OCCURRENCES IN THE HUDSON 

 VALLEY 



BY DAVID H. NEWLAND 



Introduction 



Landslides, or landslips, involving- bodies of soft materials like 

 the recent accumulations of clay and sand in many valleys of the 

 glaciated region, are not unfamiliar. They have been described 

 from time to time as individual occurrences having attracted atten- 

 tion by reason of some striking feature or incidental interest. Less 

 notice has been taken, however, of their relation to the processes of 

 degradation or surface leveling, which from a geological stand- 

 point is of first importance. 



The subject of landslides has been treated in a systematic manner 

 by Heim^ who gives a classification of the forms which they assume 

 under different conditions. His work, naturally enough, is con- 

 cerned rather with their occurrence and effects in mountain 

 regions, and especially such rugged regions as the Alps, the scene of 

 most of his observations. Howe^ in his monograph on the San 

 Juan landslides includes a broad study of the phenomena, adopting 

 the general conclusions of Heim with some modifications, but 

 giving more explicit reference to the kinds of disturbances that are 

 under present consideration ; his treatment is probably the best that 

 the subject has received in recent years. 



The observations upon which this paper is based relate mostly to 

 the Hudson valley and are such as have been recently collected by 

 the writer, supplemented by published data of an earlier date. The 

 valley is typical for the well-opened glaciated valleys of the north- 

 eastern part of the country, most of which were flooded during the 

 period of ice retreat. In the waters which reached well up the 

 slopes of the rock-walled valley were deposited clays, sands and 

 fine gravels in sorted beds of considerable thickness. With later 



1 Ueber Bergstiirze (Zurich, 1882). 



2 Landslides in the San Juan Mountains, Colorado. U.. S. Geol. Surv. 

 Professional paper 67 (Washington 1909) 



[79] 



