THE VOLCANO ASO AND ITS LARGE CALDERA 



517 



Three samples of lava from Aso were examined by Dr. Albert 

 Johannsen of the U. S. Geological Survey, and the following descrip- 

 tion of these is based on the report which he kindly furnished. Speci- 

 men I is hypersthene-bearing basalt from the foot of the wall of the 

 caldera near the town of Takamori on the south-east side. It is 

 medium gray in color, compact, and highly porphyritic. The pheno- 

 crysts are about 55 to 60 per cent, labradorite, about 10 per cent. 



Fig. 10. — Stream channel on the east side of the modern cone. The Up of the 

 crater is immediately on the right, and the cliffs at the foot of the highest Aso peaks 

 on the left. The fine gray mud is fast eroded by rains. Looking south, parallel to the 

 long axis of the crater. Photo by Malcolm Anderson. 



augite, and the rest hypersthene, magnetite, and olivine in decreas- 

 ingly lesser amounts. The groundmass is made up, of plagioclase, 

 augite, and magnetite, with possibly a little glass. Specimen 2 is 

 basalt from the same locahty. It is mottled black and white, is some- 

 what vesicular, highly porphyritic, and strongly resembles specimen 

 I, especially under the microscope. The phenocrysts are about 

 80 per cent, labradorite, 15 per cent, augite, and the rest hornblende, 

 magnetite, and olivine in decreasingly smaller amounts. The ground- 



