]Q K. Yamasaki 



Another mountainous region, lying Letween the Pacific Ocean and 

 the tectonic valley of Abukuraa, is commonly called the Abukuma 

 Plateau. This is a broad mountain mass, and consists of an extensive 

 area of crystalline schists with narrow zones of Mesozoic and coal 

 bearing strata of Tertiary formation along the coast. Many collieries 

 working tlie so-called Joban coal-field are scattered there. The abra- 

 sion was raucli gi'eater here than in the Kitakami Momitainlaud. 

 The ancient niountain system with its complex strata was once reduced 

 to a ])eneplain, which was afterward ui)heaved to form what is now 

 an undulating plateau, whose greatest elevation scarcely exceeds 1000 m. 

 The southern extension of this plateau forms the small ranges of 

 Yamizo and Naka, which gradually sink into the plain of Kwauto. 

 At the extremity of the latter stands an isolated mountain called 

 Tsukuba. 



Another extension of the northern arc toward the southwest forms 

 the mountain blocks of Ashio on the one hand and Kwanto or 

 Chichibu on the othei', which constitute respectivel} the north and 

 northwest boundaries of the Kwauto plain. Hitachi, one of the well- 

 known copper mines of Japan, is located in the south end of the Abu- 

 kuma Plateau, while another, called Ashio, is in the mountain block 

 with the same name. The Kwanto mountain is a square block of the 

 older geological formations. On the west it terminates abruptly in 

 the tectonic valley of Chikuma and the basin of Kofu, and on the 

 east in the plain of Kwanto. Some celebrated mountains of this group 

 are Buko-zan, and Kimpu-zan. 



The inner zone of the northern arc consists of two ])arallel 

 ranges, separated from each other very distinctly by depressions forming 

 low plains. The central range, or the On Mountains, begins on the 

 shore of the Gulf of Mutsu. It runs south, forming the backbone of 

 northern Japan as well as the watershed between tlie Pacific Ocean 

 and the Sea of Japan. Geologically the range is made of liparitic 

 tuff and some other sediments of the later Tertiary period, accom- 

 panying a few exposures of older formation. Moreover, this range is 

 crowned with volcanic cones of the Nasu volcanic chain, one of the 

 most important volcanic chains of Japan. At the northern extremity 

 of it stands Osore-yama, 804 m., on tl\e north coast of the Gulf of 

 Mutsu. The chain runs south through such volcanoes as Yatsukoda- 

 san, 1584 m. ; Ganju-san, 2041 m., a gigantic volcanic cone of North 

 Japan; Koma-ga-take, 1130 m.; Sukawa-dake, 1628 m.; Zao-san, 



