THE ARCH^AX FORMATION OF THE ABUKUMA PLATEAU. IQQ 



trend. The general aspect vividly reminded me of the Sambagawan 

 chain of Shikokii, as viewed from the Seto-nchi side. Below, down 

 the steep dec]i\'ity towards the plain, the precipitous wall is flanked 

 on the east by tlie palo3ozoic sandstones and clayslates, which grad- 

 ually submerge themselves under the tertiary and still later forma- 

 tions; the surface deposits of the lower plain, or rather of a raised beach, 

 bein«^)' a thick accumulation of D-ranitic blocks and coarse sand. 



The superficial covering of diluvial deposits, just referred to, 

 is mainly coniposed of sand and gravels, with little or no clay that 

 might keep hold of tlie percolating waters. P)eing of such a coarse 

 and porous texture, the dry soil is no better than the pumice 

 ground of Nasu, or the region around Volcano Bay in Hokkaido. 

 For this reason, we find here many lonely " haras," or prairie-like 

 ground, 2-4 km. in. I^readth, along the shore, such as the Hara of 

 Soma, Harano-niachi, and Chilka. 



These sterile flats, together with the underlying tertia.ry strata, 

 terminate al)ruptly at the water's edge, forming jtrccipitous bluffs, 

 interrupted only by occasioned indentations of alluvial depressions. 



The region lying to the west of these grassy deserts is the elevation 

 of A])ukuma-. It extends over the provinces of Flitachi and Iwaki, 

 stretchino' north and south for about 150 km. with an averao-e breadth 



O a 



of 45 km. It is separated from the backbone of Xorth fTapan by the 

 meridional valleys througli which the rivers Aljukuma and Kuji 

 make their way ; and its north and south sides are limited by these 

 streams, which, after making an easterly trend, finally discharge 

 their waters into the Pacific basin. The generrd outline of the plateau 

 thus defined is consequently elliptical. 



The jjliijsical a.'ipect of the elevation presents a typical -[»liysiog- 

 noniy (jf a plateau-chai'acter, with the mean height of 4t)lj m. It is a, 

 broad, gently undulating siuTace, relieved only by some few [)r(jmi- 



