Ancient beach

Muinaisranta: Pirunpellot are the old beaches of the Baltic Sea

As the continental ice sheet retreated, the exposed land was covered by the ancient Baltic Sea, or Baltic Ice Lake, that had opened up in front of the glacier. Only the tops of the highest hills were above the water surface. Such an untouched supra-aquatic area can be found, for example, at Riuttanmäki (143 mby). The rocky, probable ancient shore of the Baltic Ice Lake phase can still be seen in places on the slopes of Riutta today. When the water level of the ice lake that had been undulating in front of the glacier subsided about 11 years ago, a rocky shore zone was exposed in the lake, from which the waves washed away fine material. This ancient shore reflects the level of the shore zone at the time of the Baltic Ice Lake.

Ancient beaches are also called "devil's fields". In the reef, such a bare, boulder-strewn zone can be found 140 meters above the current sea level, near the lift of the ski slope. Muinaisranta is partially destroyed, because the mining track splits the formation.