1957 Volume 66 Issue 4 Pages 231-236
As the result of the writer's survey on the erosion surfaces in the Haku-san mountain ranges and its adjacent areas, 19481954, the following main facts are known :
1) The Bessan erosion surface having about 2200 m. to 2300 m. in height lies near the peak of Bessen (2399.4 m. high) which is composed mainly of coarse grained sandstone and conglomeratic sandstone of the Tetori group of Mesozoic. Bessan, which lies to the south of the Haku-san volcanoes, and protrudes about 100 m. from the Bessan erosion surface, is seemed to be a monadnock on this surface.
2) The basement of the Haku-san volcanoes shows from 2200 m. to 2300 m. in height. Therefore it is thought that the surface on this basement is the northern extention of the Bessan erosion surface.
3) The Shira-kawa erosion surfaces having 1700 m. to 1800 m. in height are distinctly observed at Sarugababa-yama, Gozen-dake, Hideri-dake and other places, and these surface are about 300500 m. lower than those of Bessan district.
4) The flat plane west of Gankyoji mountain in the Koike area was formerly considered as an erosion surface by predecessors but it is now regarded as a deposited plane due to the volcanic activities of the Gankyoji mountain.
5) The Bessan and Shira-kawa erosion surfaces have been formed during from post-Miocene to the pre-Haku-san volcanic activities in Quaternary, and the former erosion surface seems to be more or less older than the latter in age.