Formation of Ventifacts on the Backshore at West Coast of Wakkanai in Hokkaido

Abstract

Ventifacts are observed on the backshore at Lueran in west coast of Wakkanai. Ventifacts have smooth and polished faces on the upper side which were attacked by the wind abrasion. Two reasons for the formation of ventifacts in this area can be pointed out: 1) Most of gravels which were derived from Tertiary mud stone "Koetoi Formation" are very soft, and seem to accept easily the wind abrasion. 2) NW prevailing wind blows on the backshore in the dry season between May and June. The wind abrasion on the gravels can not work between December and March, because the backshore is covered with snow drift. After the winter season, the sand-charged wind forms the ventifacts on the backshore in a few months between April and September. In the autumn and winter seasons, the ventifacts are trasported from the backshore to offshore.