近世以降のシラス台地開発に伴う鹿児島県の海岸砂丘形成 Formation of Coastal Sand Dunes Caused by Agricultural Landform Transformation since the Edo Era on the shirasu Plateau, Kagoshima
Coastal sand dune fields have been formed from large deposits of Shirasu ignimbrite sand such as volcanic glass and pumice from Shirasu plateau in Kagoshima Prefecture. In Fukiagehama dune field, dunes I and II were formed between 5, 200 and 1, 000yrs BP. Dune III was formed around the 18th century. Dune IV was formed artificially around the 19th century by sand arrestation work. Dunes I and II consist of large portions of quartz grains, while dunes III and IV consist of Shirasu sand (volcanic glass and pumice) originating from Shirasu ignimbrite. In Shibushi dune field, dunes I, II and III were formed between the late-Jomon period and the 18th century, and dune IV was formed between the late-Edo Era and early Meiji Era. Dune V was formed artificially by sand arrestation work after World War II. Dunes I, II, and III consist of large portions of quartz sand, while dunes IV and V consist of Shirasu sand. The abrupt changes in dune sand composition between the two dune fields may reflect the changes in the discharge of Shirasu sand from the Shirasu plateau to the coastal area caused by landform transformation due to agricultural development. The intensity of landform transformation increased beginning in the 17th century in Kagoshima (as all over the Japanese Islands). In Satsuma area, agricultural landform transformation was accelerated from 1651 to the end of the Edo Era. Agricultural development in the Ohsumi area was extensively carried out beginning in the early Meiji Era.<br>As a result of vegetational denudation due to agricultural landform transformation on the Shirasu plateau, soil erosion in the form of sheet flood and gully erosion occurred frequently. Construction of irrigation channels just under the Shirasu cliff, ended the gully erosion of Shirasu. Human-induced soil erosion, however, became prevalent around the 17th century on the Shirasu plateau. Agricultural land transformation on the plateau gave rise to great changes in the discharge of soil from the Shirasu plateau to coastal areas. The formation ages of sand dunes which consist of Shirasu sand coincide with the agricultural landform transformation of Satsuma and Shibushi.
第四紀研究 37(2), 107-115, 1998-05-31
Japan Association for Quaternary Research