BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 



VOL. 20, PP. 409-416, PLS. 38-42 DECEMBER 31, 1909 



STBIATIONS AND U-SHAPED VALLEYS PKODUCED BY 

 OTHER THAN GLACIAL ACTION 1 



BY EDMUND OTIS HOVEY 



{Presented orally before the Society December 29, 1908) 



CONTENTS 



Page 



Introduction 409 



Striations 410 



Sand-blast action on mount Pele 410 



Avalanche action on mount Pele 412 



Sand-blast action on the Souf riere 413 



U-shaped valleys 413 



Introduction 



Geologists and others are so much in the habit of considering striations 

 and grooves in rock surfaces, U-shaped valleys, and hanging valleys to be 

 conclusive proofs of glaciation that it will be of interest to cite some par- 

 ticularly striking instances of such features that have been in no way 

 connected with ice action. The illustrations accompanying this note tell 

 the whole story. They have been selected from the photographs taken 

 by me upon three expeditions to the Lesser Antilles undertaken for the 

 American Museum of Natural History in 1902, 1903, and 1908. The 

 conditions were either consequent upon or revealed by the 1902-1903 

 eruptions of Mount Pele of Martinique and the Souf riere of Saint Vin- 

 cent. Perhaps similar features may be known elsewhere, without an ex- 

 planation having been apparent. 



The eruptions of Mount Pele in 1902 and 1903 were characterized by 

 the emission of unnumbered, probably hundreds, of exploding steam- 

 clouds which were saturated with dust formed of comminuted lava (augite- 

 andesite). It is evident that an enormous excess of water vapor was con- 

 tained in the lava and that the vapor was under great pressure in the 



1 Published by permission of the American Museum of Natural History. 

 Manuscript received by the Secretary of the Society August 30, 1909. 



XXXVII— Bull. Gbol. Soc. Am., Vol. 20, 1908 (409) 



