2t>4 S. Powers— Volcanic Domes in the Pacific. 



day; 110 on -Inly 23; 351 on the 24th; and 1G2 on the 25th, 

 the day on which the eruption began, with the accompanying 

 release of pis by explosions." The first explosions took place 

 on the north flank of Usu, about 1,300 feet south of Lake Toya 

 and opened craterlets from which ash and rock fragments 

 already at the surface of the ground were thrown out. New 



Fig. 2. 



LAKE TOYA 



Fig. 2. Map of Usudake showing the volcanic domes O-Usu and Ko-Usu and New 

 Mountain, which was tilted up in 1910. The old somma rim of the volcano is shown 

 by heavy dashes. Contour interval 20 meters. 



6 F. Omori, The Usu-San eruption and the earthquake and elevation 



craters continued to form until the end of the year, but on the 

 third day of the eruption smoking bombs of new hypersthene- 



phenomena, Bull. Imp. Earthq. Inves. Comm., Tokyo, vol. v, No. 1, 1911; 

 D. Sato, Eruption of Mount Usu, Bull. Imp. Geol. Surv., Japan, vol. 

 xxiii, 1910. 



