266 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1952 



there is no need here to describe the mechanism of geysers, it will suf- 

 fice to suggest the source of the water of these mud eruptions. Ac- 

 cording to the inhabitants of Hukaba, a group of springs formerly 

 existed at the village, the water of which was used in the hatching 

 ponds for salmon and trout, because of its constant temperature and 

 abundant supply throughout the year. There was also a fountain 

 that supplied drinking water to the farmers in the cornfield. Both 

 indicate an ample source of underground water in the area. 



Figure 2. — A sketch map of the newly formed mountain, Syowa Sinzan, on June 2, 1946. 



ASH EXPLOSIONS 



On July 2 tremendous explosions lasting about 5 hours spread a 

 large amount of ash over the surrounding terrain. The total amount 

 of ejecta for these explosions was estimated at 2,000,000 metric tons 

 and the energy expended at 1.4 X 10 20 ergs. This paroxysmal explosion 

 was, both in volume of ejectamenta and in intensity, more furious than 

 the numerous explosions that succeeded it. Another severe explosion 

 occurred the next morning, ejecting material estimated at 100,000 

 metric tons over a large area toward the southwest side of Usu. But 

 no new crater was opened by these two explosions. After these marked 

 outbursts, further strong explosions did not occur until July 10, al- 

 though columns of steam were intermittently observed from Sobetu. 



The abundant ash which fell upon the area did much damage to the 

 corn and potato fields, and the inhabitants of Hukaba were compelled 

 to abandon their homes and take refuge in other parts, carrying their 

 household effects with them. 



