INTERESTING PHENOMENA ON THE ERUPTION OF USU 283 



eruption the cone Nishimaruyama could be seen from the village 

 of Nishikohan, but as a result of the elevation which took place 

 the view was obstructed. The area of elevated land is about 2 km. 

 in length by 1 km. in width to the edge of the lake, and, judging 

 from soundings made, it extends another kilometer under the 

 water (Fig. 23). The maximum height of the elevation measured 

 about 120 m. (Figs. 24, 25, 26). x 



Fig. 24. Mountain slope in the beginning of eruption. Taken July 29, 1910 



Mr. Ito, of the Sapporo Meteorological Observatory, found a 

 lowering of 36 m. on the top of the new mountain in April, 1911, 

 while Mr. Iizuka, of the Imperial Geological Survey, recorded 43 m. 

 lowering in July, 191 1, by an aneroid barometer. 



When the gases involved in the lava are expelled in a great 

 quantity, a decrease of volume will take place, and the lowering 

 of the mountain should result from this shrinkage. 



1 This measurement was made by comparing graphically and to scale the photo- 

 graph taken before the elevation with that taken afterward. This checked well with 

 the reading of the aneroid barometer which nearly coincides with the map of the 

 Imperial Geological Survey of Japan. 



