768 



ABSTRACTS OF PAPERS 



GENETIC CLASSIFICATION OF ACTIVE VOLCANOES 

 BY T. A. JAGQAB, JB. 



(AJ)stract) 



The writer has studied seven active volcanoes in the last 8 years. Mer- 

 calU's classification by types of eruption and kinds of lavas is not genetic and 

 hence contains many overlaps. Volcanoes show kinship of origin and stages 

 of growth related to a common origin. It is believed that a classification 

 based on (1) the unity of all volcanic phenomena and (2) diversity of types, 

 measured by viscosity of lavas, will produce a rational and significant series. 

 This series was shown in tabular form. 



TARVMAI, A CUMULO-VOLCANIG ERUPTION IN JAPAN, 1909 

 BY T. A. JAGGAB, JB. 



i Abstract) 



This volcano is in southeastern Yezo. It became active January 11, 1909, 

 with a culminating eruption on April 12. Between April 12 and April 23 an 

 extraordinary hard lava dome, a phenomenon hitherto unknown in Japan, 

 rose within the crater. The volcano otherwise is a cinder cone. The size, 

 shape, and mechanism of the dome resemble Pel6 and Bogoslof. The writer 

 visited the volcano in May, 1909, accompanied by Japanese geologists. 



Discussion 



Prof. W. M. Davis : If it be intended that the seven types, beginning with 

 Kilauea and ending with Fuji, represent successive stages of development, is 

 it possible to find field evidence to show^ that the present Vesuvius has had a 

 previous Kilauea stage, and that the present Fuji has been preceded by the 

 various stages from the Kaluea through the Tarumai and Pele stages? In the 

 very nature of the case the evidence for Fuji would seem too difficult to re- 

 cover. I can not help fearing that, as more examples are brought into this 

 scheme, it will be found that the sequence of development is much more 

 irregular than is here suggested. 



Mr. F. L. Ransome pointed out that whereas Professor Jaggar's classifica- 

 tion of volcanoes is avoM^edly based on viscosity of the lavas erupted, this 

 basis of grouping is apparent in the first five only of his eight types. The 

 remaining three characterizations of primary rank in the classification, 

 namely, no lava extruded, ancient lava only, and laecolithic lava, are not 

 expressive or even suggestive of Increasing degrees of viscosity, but involve 

 classification on other bases than the one adopted in the first part of the 

 table. Mr. Ransome questioned, moreover, the validity of including laecolithic 

 Intrusions in a classification of volcanoes, suggesting that the laecolithic form 

 may be assumed by magmas of a wide range of viscosity and of varied 

 chemical composition. 



