Ice features and ice-thrust shore forms at Luodonselkä, Gulf of Bothnia, in winter 1972/73

Abstract

Three major young ice pressure processess occurred on Luodonselkä in late December 1972. The forms of the rafted and hummocked ice and the ice‑thrust shore forms were studied in detail. A continual watch was kept on the movements of the ice by air photography, and direct measurements of the surface features were made immediately after formation. A zone of rafted ice with alternate overlaying and under­lying fingers about 80 m long was observed. In places this zone had been pushed and hummocked beyond the gently sloping beach, and some very long overthrust fingers reached almost 100 m up the shore. Longitudinal grooves and transverse rectilinear and parabolic terminal push ridges were formed. A type of finger rafting not described earlier in the literature was observed. Some new features and structures of hummocked and stranded ice are depicted and interpreted.