THE JAPANESE VOLCANO ASO AND ITS LARGE 



CALDERA^ 



ROBERT ANDERSON 

 Washington, D. C. 



CONTENTS 



Brief description. 



Sources of information. 



Geology of Kiushiu. 



Approach to the caldera. 



The floor. 



The wall. 



The central range. 



The modern crater. 



Double rim of the modern crater. 



History of the modern crater. 



The outer slopes. 



Radiating lava flovfs. 



Character of the lava. 



A supposed former Mount Aso. 



Origin of the caldera. 



Origin of the central range. 



Origin of the barranco. 



List of large craters. 



Summary. 



BRIEF DESCRIPTION 



Aso-san is a volcano in the center of Kiushiu, Japan, within 

 twenty-nine miles of the western, and forty-five miles of the eastern, 

 coast of the island. It consists of a huge mound-shaped cone on the 

 summit of which is sunk an oval bowl measuring about ten miles in 

 width, fourteen miles in length, and i,ooo to 2,000 feet in depth, the 

 bottom being some 1,500 feet above sea-level. Within this bowl a 

 range of mountains, attaining an altitude above sea of 5,600 feet and 

 overtopping the rim more than 2,000 feet, runs from east to west across 

 its short diameter and divides it into 2 crescent-shaped basins. On 

 the summit of this dividing range is a low modern cone with active 



I Read before the Geological Society of Washington, January, 1907. 



499 



