A Geomorphological Study on Byobusan Sand Dune Region, Aomori Prefecture

Abstract

In this paper, the writer attempts to make clear both the history of the formation and the morphological features of the Byóbusan sand dune region in the northernmost part of the Honshu Island.
The following results are obtained.
The Byobusan region consists of two terraces, about 10 meters and 20 meters higher than the present sea level. The latter is called the Yamadano terrace, which was formed during the stage of the higher sea level in the Shimosueyoshi transgression (in the Monanstrian age), and the former is called the Dekishima terrace (in Holocene age). On certain parts of the Yamadano terrace, the Old dune was formed in Pleistocene, and covered by the Iwaki volcanic ash layer. At that time, the prevailing winds were blowing from the west, just as at the present time.
The Younger dune in Holocene, covers about two-thirds the area of the Byobusan region. Most of it was formed since the Yayoi period. Some parts of it were formed since 1948, when strong prevailing winds blew sand grains to creep up the cliffs or gullies, and formed transverse dune, on both Yamadano and Dekishima terraces.
To the lee of transverse dunes, U-shaped dune and parabolic blowout dunes were developed and migrated downwind. Longitudial dune ridgs were developed finally by the erosion of parabolic blowout dunes. Sand dunes are commonly arranged in chains extending downwind from the source drifts. Thus the developement of sand dunes is related to the shifting speeds of sand dunes and the supply of sand grains.